Nanoelectronics and Sensors

Nanoelectronics and Sensors

Nanoelectronics and Sensors

Editors V. Rajendran K. Thyagarajah K.E. Geckeler

© KSR Group of Institutions, 2015 First Published, 2015 All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage or retrieval system, without prior permission in writing from the copyright holder. No responsibility for loss caused to any individual or organization acting on or refraining from action as a result of the material in this publication can be accepted by Bloomsbury India or the author/editor. BLOOMSBURY PUBLISHING INDIA PVT. LTD. New Delhi London Oxford New York Sydney ISBN: 978-93-85436-94-9 10 9 8 7 6 5 4 3 2 1 Published by Bloomsbury Publishing India Pvt. Ltd. DDA Complex LSC, Building No. 4, 2nd Floor Pocket 6 & 7, Sector – C Vasant Kunj, New Delhi 110070 Typeset by fortune graphics, Naraina, New Delhi Printed at anvi composers, Paschim Vihar, New Delhi

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Foreword The past few decades have seen unprecedented advancements in the field of nanotechnology with spectacular developments in a wide area of Material Science. Currently, nanotechnology is a fast growing field with a broad spectrum of applications and it is appreciated that the Centre for Nano Science and Technology (CNST) of the K.S. Rangasamy College of Technology (KSRCT) has undertaken an initiative to organize an International Conference on Nanomaterials and Nanotechnology (NANO-15) with a special topic on ‘Research to Innovations to Technology Transfer’ in India, especially at Tamil Nadu. Based on its good infrastructure and human resources, CNST develops R & D activities with international standards by many funded projects and research publications. KSRCT collaborates with academic institutions and national and international research laboratories/ industries of high reputation. The conference features many plenary and key note addresses presented by invited speakers and more than 1100 delegates from around the world are participating, interacting, and discussing the exciting and rapidly developing aspects of Nano Science and Technology. I trust that this conference will be an ideal platform for the presentation and discussion of new concepts and developments of new functional nanomaterials and their applications in new devices and sensors. NANO-15 provides a forum to discuss eco-friendly technologies and promote interactions and collaborations between the delegates. I appreciate that the organising team publishes peer reviewed papers in six independent books. The articles therein will describe new ideas in a rapidly developing field and so stimulate further progress. I am pleased to write a foreword for these books to be published during NANO-15 and wish the Conference participants a fruitful and enjoyable stay in India and I want to thank the organizing team for the their kind helpfulness and hospitality. 20.11.15

Dr. H.C. Mult Robert Huber FMRS Noble Laureate

Message MeSSage

Date : 21.11.2015

I am happy to note that our Centre for Nano Science and Technology (CNST) of K. S. Rangasamy College of Technology (KSRCT) is organising an International Conference on Nanomaterials and Nanotechnology (NANO-15) with a special topic on Research to Innovations to Technology transfer during December 07-10, 2015 at our campus. The CNST established with good infrastructure facilities to meet the Scientists and Academicians to an advanced level in the field of nanotechnology. It also focuses in organising such International conferences and workshops to recognize the research outcomes of the young researchers. NANO-15 is organized in KSRCT with plenary lectures by Noble laureates and distinguished scientists, Key note address, invited talks and more than 550 contributed papers. The plenary talk by Nobel Laureates and invited talks from reputed organizations of India and abroad would bring out the current status in material science and technology. I ensure that the participants will have effective deliberations through this conference. I thank Dr. K. Thyagarajah, Principal, KSRCT and Dr V. Rajendran, Director R&D, Organising Chair and his team to organise this event as a successful. The kind support from the various government and private organisations/agencies for the successful conduct of the conference is highly acknowledged. I extend my warm greetings to all the participants and best wishes for the success of the Conference.

Dr. K. S. Rangasamy MJF

Sponsors Science and Engineering Research Board, Department of Science and Technology, New Delhi

Defence Research and Development Organisation, New Delhi

Board of Research in Nuclear Sciences, Mumbai

Indian Council for Medical Research, New Delhi

Tamilnadu State Council for Science and Technology, Chennai

Indian Society for Technical Education, New Delhi

Axis Bank Limited, India

Co-Sponsors National Institute for Nanotechnology (NINT) Innovation Centre, Alberta, Canada NanoCanada, Canada

Silver Sponsor Shimadzu India Pvt. Ltd, Chennai

x Sponsors

The Professor Venkatachalam Rajendran Research Foundation

Exhibitors

CSIR - Central Glass and Ceramics Research Institute, Kolkata

Tekna Plasma India, Chennai, India Lark Innovative Fine Teknowledge, Chennai

Industrial Partners Exigo Knowledge Ventures Private Limited, Bangaluru

Global Connect Inc., Saskatoon, Canada

Higginbothams Private Limited, Chennai, Tamil Nadu

Samraj Constructions, Tamil Nadu

Talent2Success Learning Pvt. Ltd, India Zealtech Electromec India Private Limited, Tamil Nadu

Sponsors xi

Publication Partners Bloomsbury Publishing India Pvt. Ltd, New Delhi The Higher Education Review, Bangalore

Journal Partners Polymer International

Nano System : Physics, Chemistry, Mathematics

Synthesis and Reactivity in Inorganic, Metal Organic and Nano-Metal Chemistry IET Nanobiotechnology

Media Partner The Hindu

Hospitality Partner Radisson 5 Star Hotel, Salem

xiv International Organising Committee

Editors’ Profile Dr. V. Rajendran FUSI, FASI, FInstP, is Director, Research & Development, K S R Group of Institutions and Centre for Nano Science and Technology, K.S Rangasamy College of Technology, Tamil Nadu, India. Under his able guidance, 20 scholars have completed and 09 scholars are pursuing their Ph.D. degrees. He has published more than 200 research papers in reputed international and national journals, 60 papers in conference proceedings, 32 refereed books, 4 R&D books and 11 patents. He has won many awards including the UNESCO visiting Scientist Fellowship, South Africa (2016), Fulbright Fellowship (2015), USA, PSN National Award for Excellence in Science (2013), Prof. K. Arumugam National Award in 2011, Best faculty award in 2010, Raman-Chandra Sekhar silver medal (2010), Tamil Nadu Scientist Award, NDT Man of Year 2004, Indo-Australia Senior Scientist Science and Technology visiting fellowship (2013), DAAD from Germany (2002), INSA, TNSCST Young Scientist, DAE/ BRNS Visiting Scientist, Best paper award from MRSI, ASI, ASA and USI and Outstanding Organiser Award for the 7th National Symposium on Ultrasonics, 1996. Dr. K. Thyagarajah, an erudite academician, an able administrator and outstanding scholar has the distinction of receiving his doctoral degree in power electronics & AC motor drives from the world renowned Indian Institute of Science, Bangalore in 1993. He has 31 years of rich teaching, research and industrial experience. He has produced 6 Ph.Ds so far, and is currently guiding 6 Ph.D scholars. His areas of interest include higher performance motor drives, insulating materials and industrial automation. He has authored 24 research papers in international and national journals and attended many conferences. He is a member of the Board of Examinations of various universities in Tamil Nadu and neighboring states. Currently, he is the Principal of K.S. Rangasamy College of Technology, Tiruchengode. Dr. K.E. Geckeler is affiliated with the Gwangju Institute of Science and Technology (GIST), South Korea. and is a Professor at the School of Materials Science and Engineering. He has been the Founding Chair of the Department of Nanobio Materials and Electronics, World Class University (WCU), Gwangju, South Korea. In addition, he serves as Vice Director of the Gruenberg Center for Magnetic Nanomaterials (GCMN). He received his Ph.D. and M.D. degrees from the University of Tuebingen, Germany (both degrees: “magna cum laude”) and spent sabbatical leaves at Harvard University, University of Montana, Clemson University (USA), and at the University of Montpellier (France). He received a series of prestigious awards including the “Fonds of the Chemical Industry”, the “Fritz-Ter-Meer Award”, and the “Science Prize of the President of Korea”. The biannual international IUPAC symposium series on “Macro- and Supra¬molecular Architectures and Materials (MAM)” has been initiated and coorganized by him. Prof. Geckeler is Editor-in-Chief of the journal “Polymer International”, published by John Wiley & Sons, and is also on editorial boards of a series of other international journals. He has published more than 350 research articles and short communications, 12 book chapters, 15 books, and over 130 patents. His recent books cover different aspects of nanomaterials including the two standard references: “Advanced Nanomaterials” and “Functional Nanomaterials” published by Wiley.

Preface The International Conference on Nanomaterials and Nanotechnology (NANO-15), third in this series with a special topic on Research to Innovation to Technology transfer is organised by Centre for Nano Science and Technology (CNST) of K.S. Rangasamy College of Technology, Tamil Nadu, India during December 07-10, 2015. This conference is jointly organised with World Class University, Gwangju Institute of Science and Technology (GIST), South Korea. Having established the state-of-the-art experimental facilities at the CNST, the centre is offering undergraduate (B.Tech.), post-graduate (M.Tech.) and research (Ph.D.) programmes and looking for industrial collaboration and partners for the need based development of products in nanotechnology. NANO-15 has been received tremendous supports and overwhelming responses worldwide. More than 950 abstracts have been received from 33 countries. Out of 600 full papers, 450 have been selected and peer reviewed by the expert committee for the publication in conference books. All the received papers are classified under six titles namely Synthesis and Fabrication of Nanomaterials, Advanced Nanomaterials: Synthesis and Applications, Nanoelectronics and Sensors, Applications of Nanostructured Materials for Energy and Environmental Technology, Bio-nanomaterials for Biomedical Technology and Industrial Applications of Nanostructural Materials. Out of total 450 full papers accepted for NANO-15, a total of 56 have been identified for the inclusion in the book entitled Nanoelectronics and Sensors after peer review. This book contains the contributed papers discussing about the range of sensors developed from metal/metal oxides including electrochemical, optical, mechanical, thermal, magnetic and biological sensors. Nanoelectronic design, fabrication and optimization of hybrid functional nanostructures based devices and its applications. All the contributed authors are extended by our sincere thanks for their timely submission and cooperation in carrying out suggestions by the referees. Our sincere thanks are to the members of technical committee for peer review of contributed papers. We are sure that the outcome of NANO-15 open up new avenue between the researchers and industrialists for the development of nano products. The various committee chairs and members are highly acknowledged for making this event a grant success. The various government funding agencies, private organizations and industries are thankful for their munificent support and sponsor for the successful conduct the conference. The support extended by Bloomsbury Publishing India Pvt. Ltd in bringing out this book on time is highly appreciated. V. Rajendran K. Thyagarajah Kurt E. Geckeler

Contents Foreword v Message vii Sponsors ix International Organising Committee xi Editors’ Profile xiii Preface xv

Plenary Speakers 1. Understanding and Applications of Ferrofluids Baldev Raj and John Philip

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Keynote Speakers 2. Polymeric Nano-Electro-Mechanical Sensor Systems V. Ramgopal Rao 3. Molecular Nanoscience at Surfaces Rasmita Raval 4. Probing Nano Precipitates in Radiation Resistant Steels C.S. Sundar

Invited Speakers 5. Electrically Conductive Inks with Nanotechnology Anuj Shukla

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6. High Frequency Devices for Defence 14 Poornendu Chaturvedi 7. Graphene and Carbon Nanotube Nano-Composite Sensors for Glaucoma Ocular Pressure Measurements 15 D. Jenkins, M. Mane, A. Deepak, P. Davey, D. Oehring and P. Shankar 8. Investigation of luminescence properties of color tunable aluminosilicate nanophosphors for pc-LEDs 16 S.J. Dhoble 9. Ferroelectric Properties and Offset Polarization in Polycrystalline BNdT Thin Films for the Application of RAM Devices 17 Khalid Mujasam Batoo 10. Affinity-Specificity Augmentation for Molecular Imaging and Therapy Using Nano-Probes (ASAMIT-NP) 18 Anil K. Mishra 11. Electron-Positron Annihilation Spectroscopy to Highlight the Defect Characteristics of Nickel Oxide Nanocrystals 19 Anjan Das, Atis Chandra Mandal, Soma Roy and P.M.G. Nambissan

xx Contents 12. Thermoelectric Properties of Spark Plasma Sintered Lead Telluride Nanocubes S. Neeleshwar, B. Khasimsaheb, M. Srikanth, Sivaiah Bathula, Bhasker Gahtori, Ajay Dhar, S. Amrithapandian, B.K. Panigrahi, Sriparna Bhattacharya, Ramakrishna Podila and A.M. Rao 13. Quest of Nanomaterials for Field Emitter Devices R.B. Sharma

Contributed Papersy 14. Studies on the Synthesis and Characterization of Nano Phosphors for Field Emission Devices H. L. Vishwakarma and Anju Singh

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24

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15. Synthesis and Characterization of Novel Siloxane Based Transparent and Flexible Substrate for Oleds 31 D. Shanmuga Sundar, A. Sivanantharaja, C. Sanjeeviraja and D.Jeyakumar 16. Electrochemical Sensing of 4-nitrophenol Using CeO2@SiO2 35 A. Padmanaban, T. Dhanasekaran, K. Giribabu, R. Manigandan, S. Praveen Kumar, G. Gnanamoorthy, S. Munusamy, S. Muthamizh, A. Stephen and V. Narayanan 17. Electrochemical Determination of Uric Acid by Using Tris-(1,10-Phenanthroline) Copper(Ii) Complex Modified Gce 39 S. Praveen Kumar, K. Giribabu, R. Manigandan, S. Munusamy, S. Muthamizh, A. Padmanaban, T. Dhanasekaran, R. Suresh and V. Narayanan 18. Nanocrystalline Tin Oxide Synthesized by Co-Precipitation Method for Highly Selective Ammonia Gas Sensor 43 Shrabani Mondal, Rashmi Madhuri and Prashant K. Sharma 19. Multi-Walled Carbon Nanotubes for Sensor Applications 47 Khurshed A. Shah, Feroz A. Najar and M. Shunaid Parvaiz 20. Synthesis and Characterization of Tin Nano Metal Particles Doped Conducting Polymer Composite 51 G. Sowmiya and G. Velraj 21. CaSiO3: Pr3+ Nanophosphors: Propellant Combustion Synthesis, Photoluminescence Properties for Wled’s 57 R.B. Basavaraj, H. Nagabhushana, S.C. Sharma and B. Daruka Prasad 22. Colorimetric Sensing of Dopamine Using L-Histidine Capped Luminescent Mn Doped ZnS Quantum Dot 61 Printo Joseph, S.C.G Kiruba Daniel and M. Sivakumar 23. Nanophase Separation in Ge-Se-Pb Glasses Near the Charge Carrier Reversal Threshold 65 K. Ramesh, Sharona Thomas Horta, Pumalianmunga, R. Venkatesh and E.S.R. Gopal 24. Pt–Pd Nanoparticle Decorated Graphene Oxide on Screen Printed Carbon Electrode for the Nonenzymatic Sensing of Glucose in Neutral Medium 69 Basil Paul K and T.G Satheesh Babu

Contents xxi

25. Investigation of Graphene-On-Metal Substrates for Spr-Based Sensor Using Finite Difference Time Domain 73 Fairus Atida Said, P. Susthitha Menon, Sahbudin Shaari and Burhanuddin Yeop Majlis 26. Temperature and Size Dependence of Structural Anisotropy in Presence of Magnetic Field – A Study to Control Light Transport 77 Keyur G. Khatsuriya and Hem Bhatt 27. Synthesis, Characterization and HF Technique to Reduce Multiplicative Noise in Nano-dispersed LC Compounds 81 R.K.N.R. Manepalli, P. Pardhasaradhi, B.T.P. Madhav, K. Pandian and V.G.K.M Pisipati 28. Synthesis, Characterization, Electrical and Magnetic Properties of Ni Doped ZnO Based Diluted Magnetic Semiconductors 85 C.M. Barretto, I.A. Shaikh, P.P. Naik and R.B. Tangsali 29. Studies on Effect of Nano-Grains of Sm0.5Sr0.5CoO3 Film on Transport Properties of Sm0.5Sr0.5CoO3/Sm0.2Ce0.8O2 (Cathode/Electrolyte) Planar Interface 89 S.S. Pawar, R.S.Pawar, V.K.Chaudhari and S.H.Pawar 30. Dielectric Relaxation and Charge Transport Process in PrCrO3 Nano-Ceramic 93 Sujoy Saha, Alo Dutta, P.K. Mukhopadhyay and T.P. Sinha 31. Preparation of Poly (Vinyl Alcohol)-In(III)-Pt (IV) Coordination Polymer: Direct Deposition on Sensor Structure, Thermolysis and Oxygen Sensing Properties 97 D. Selvakumar, P. Rajeshkumar, N. Dharmaraj and N.S. Kumar 32. Effect of Molar Concentration on Structural, Morphological and Optical Properties in Nanostructured Zinc Oxide Thin Films 101 A. Sales Amalraj, V. Sivakumar and G. Senguttuvan 33. A Study of Various Vibrating Modes in Nonlinear Coupled Interdigitated Polymer MENS Resonators 107 S. Sathya, M. Pavithra and S. Muruganand 34. Enhancement of Transmission Efficiency in an Optical Fiber Coated with LEEH Capped PBS Quantum Dots on Cladding 111 Bijendra Thakur, Shilpa Patel and Sukanta K. Tripathy 35. Mesomorphic Behavior of Nanoparticles Doped Cholesteric Liquid Crystal 115 Rita A. Gharde and Jessy P. J 36. Effect of Substrate Temperature on Microstructure and Properties of Nanocrystalline Titania Thin Films Prepared by Pulsed Laser Deposition 119 G. Balakrishnan, S. Manavalan and R. Venkatesh Babu 37. Bistable Electrical Switching and Performance of a Pentacene Based Write Once Read Many Memory Device 123 A.G. Gayathri and C.M. Joseph 38. Simulation of Conductance Change in Graphene Nanoribbons on Adsorption of NO2 Molecules 125 Neeraj Jain, Ahsana Sadaf and P.K. Chaudhary

xxii Contents 39. Ultrasonic Parameters of Polymer Dispersed Cholesteric Liquid Crystals Doped with Ferroelectric Nanopowder 129 Gharde Rita and Bhave Manisha 40. Zno/Sno2/Zn2Sno4 Nanocomposite: Preparation and Characterization for Gas Sensing Applications 135 M. Chitra, K. Uthayarani, N. Rajasekaran, N. Neelakandeswari, E.K. Girija and D. PathinettamPadiyan 41. Low Temperature Sensors using Cerium and Tungsten Doped Tin Oxide Nanostructures 139 Anima Johari and M.C. Bhatnagar 42. Optical Modulation of Dispersed Nanoparticles in Polymer Liquid Crystal 145 Rita A. Gharde and Krishnakant Mishra 43. An Investigative Study on Application of Carbon Nanotubes for Strain Sensing 149 M.R. Khodke and Satishchandra V. Joshi 44. Implementation of Robust Acoustic Echo Cancellation in the Short Time Fourier Transform Domain using Adaptive Filter 153 Gopalaiah and K. Suresh 45. Strain Sensor Based on Multi Walled Carbon Nanotube/Poly (Dimethylsiloxane) Composite Film 157 Zeeshan K. Shaikh, M. R. Khodke and Satishchandra V. Joshi 46. Cfd Analysis of Heat Transfer Aspects in Auto Infotronics Towards Balanced Control Over Nanoelectronics by Using Wireless Sensor Development 161 V.K. Reshma, G. Kalivarathan 47. Controlled Functionalization of Graphene Oxide-TIO2 Nanocomposite 165 Arvind Kumar, Chanchal Maheswari, Babita Behera, Ankushi Bansal and Siddharth S. Ray 48. Virus Imprinted Polythiophene Nanofilms: Electrochemical Synthesis and in-situ Sensing 169 Shashwati Wankar, Reddithota J. Krupadam 49. A Graphene-Organic Composite as a Fluorescent Chemosensor for Ag+ 173 N. Bhuvanesh, K.Velmurugan, S. Suresh and R. Nandhakumar 50. Optical and Electrical Properties of Polyaniline Thinfilm Synthesized by Aniline Vapour Polymerization 179 A. Bera, K.L. Bhowmik, K. Deb and B. Saha 51. Bio-Mediated Combustion Synthesis and Photoluminescence Studies of Y2O3 : Tm3+ Nanoscale Superstructures 183 Venkatachalaiah. K.N., R.B. Basavaraj, Daruka Prasad and B.H. Nagabhushana and S.C. Sharma 52. Structural and Electrical Studies of Nanocrystalline Mn3O4 187 Raghavendra Sagar, Sujaya C, Nayana Acharya and Anthoni Praveen

Contents xxiii

53. Optical Properties of Sodium Niobate Thin Films 191 Vijendra Lingwal, Alok Singh Kandari and N S Panwar 54. Porphyrin Functionalized Single Walled Carbon Nanotubes: Chem fets for Alcohol Detection 195 Arti D. Rushi and M.D. Shirsat 55. Investigations on Magnetodielectric Properties of LSMO–BCZT Composites 201 S.D. Chavan, S.G. Chavan, A.N.Tarale, P. B. Joshi and D. J. Salunkhe 56. Atomic Scale Modeling of Adenine Based Hydrogen Sensor 205 Debarati Dey, Pradipta Roy and Debashis De 57. Synthesis and Characterization of Formaldehyde Cured Cashew Nut Shell Liquid Based Nano Composites for Integrated Circuit Encapsulation Applications 209 Abhishek Benni, Shashikant Pawar, Aniket Patil, Padmanabhan K, Girish M. Joshi, Vijayaraghavan R. Arunmetha S. and Rajendran V. 58. Synthesis and Characterization of Acid Cured Cashew Nut Shell Liquid Based Nano Composites for Electronic Packaging Applications 213 Sayali Shinde, Prajakta Satpute, Aparna Nelluri, Padmanabhan K, Girish M Joshi, Vijayaraghavan R., Suriya Prabha R. and Rajendran V. 59. Synthesis of Nanocrystalline Bismuth Oxide and its Visible Photocatalytic Activity in the Degradation of an Organic Dye 217 Saranya Ramachandran and A. Sivasamy 60. Finite Element Method Based Design and Simulation of a Doubly Clamped Accelerometer with Integrated Silicon Nanowires 221 S. Vetrivel and A. Ravi Sankar 61. Atomistic Scale Modeling of Single Strand Dna Logic Gate 225 Pradipta Roy, Debarati Dey and Debashis De 62. DFT and TD-DFT Investigations of Organic Dye Sensitizers for Dssc: Effects of Different Acceptor 229 M. Prakasam, V. Sangeetha and P.M. Anbarasan 64. Manganese Oxide Nanofibers Based Sensor for Ammonia Gas Sensing 233 Alankar Tripathi, Ayush Agarwal, Neelam Kushwaha, Robin Kumar and Ranjit Kumar 65. Resonant Behaviour Due to Wavy Structure of Single Walled Boron Nitride Nanotube: A Mass Sensor System 237 Mitesh B. Panchal 66. Ammonia Vapor Sensing Performance of ZnO/Cu Bi-Layer Nanofilm 241 S. Fairose, Jithin Narayanan and S. Suhashini Ernest 67. Polyaniline – Titanium Dioxide Composite as Humidity Sensor at Room Temperature 245 S. Kotresh, Y. T. Ravikiran, S. C. Vijaya Kumari and H.G. Raj Prakash 68. Effect of Rashba Spin-Orbit Interaction on the Specific Heat of a Parabolically Confined Quantum Dot 251 Sanjeev Kumar D, Soma Mukhopadhyay and Ashok Chatterjee

xxiv Contents 69. Synthesis, Characterization and Application of Cadmium Sulfide Nanostructures as Hydrogen Sulfide Sensing Agent Amanullakhan A. Pathan, Kavita R. Desai & C. P. Bhasin 70. Zinc Doped Cadmium Sulfide Nanoparticles For Gas Sensing Measurement L. Arunraja, P.Thirumoorthy, A. Karthik and V.Rajendran Author Index

253 257 261

Plenary Speakers

Understanding and Applications of Ferrofluids Baldev Raj and John Philip1 National Institute of Advanced Studies, Bangalore, India. National Institute of Advanced Studies IISC Campus, Bangalore, Karnataka 1 Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu E-mail: [email protected]

Ferrofluid has emerged as a new class of ‘smart material’ with several fascinating applications in the fields of biomedicine, mechanical and optics. Over the last few decades, several new strategies have been developed for the production of stable aqueous and non-aqueous ferrofluids. E.g., Production of particles with well tailored sizes and morphologies have been achieved by varying the solvent polarity and reaction conditions, highly monodispersed particles are produced using micellar reactors and aggregation of particles are prevented by using special functional groups. Besides, ferrofluid based sealant technology for sodium pumps, we have also developed several new applications for ferrofluids and their emulsion, which include ‘smart coolants’ for electronic device cooling, optical filters, cation and defect sensors. In those applications, the response of ferrofluid to an external magnetic field is exploited to achieve the desired response. We have used magnetic fluid as a model system to probe the underlying mechanism of heat transport, heat propagation through percolating nanoparticle paths, probing of intermolecular forces and orderdisorder transitions, field assisted zippering transitions and formation of colloidal crystals. For example, using an in-house developed force measurement facility we probed the weak forces (10-13 N to 10-11 N) between individual colloidal droplets “in-situ” with a sensitivity in the inter-spacing of 0.1 nm. The force apparatus have been extensively used to probe the forces between colloidal particles in the presence of neutral polymers, polyelectrolytes, ionic and non-ionic surfactants. These studies enabled us to provide the first experimental evidence for the stretching and collapse of neutral polymer layers adsorbed at an oil-in-water interface. Using this force measurement tool, we have obtained several new insights into the associative behavior of polymer-surfactant complexes and colloidal stability. The tunable thermal properties of ferrofluids are achieved by controlling the aspect ratio of linear chains. These studies revealed that the Brownian motion has a less important role in thermal conductivity enhancement in nanofluids. During my talk, I would give an overview of our research activities on ferrofluid with an emphasis on current and futuristic applications.

V. Rajendran, K. Thyagarajah and K.E. Geckeler (eds.) Nanoelectronics and Sensors, pp. 1-1 (2015)

Keynote Speakers

Polymeric Nano-Electro-Mechanical Sensor Systems V. Ramgopal Rao P. Kelkar Chair Professor for Nanotechnology, Department of Electrical Engineering, IIT Bombay, Powai, Mumbai E-mail: [email protected]

Abstract Polymers enable fabrication of MEMS/NEMS devices with superior electro-mechanical characteristics as compared to the traditional silicon MEMS [1]-[7]. These technologies are ideally suited for low cost disposable sensor applications, as well as for applications that require high surface stress sensitivity. The applications for polymer MEMS range from healthcare to homeland security [8]-[15]. There are however multiple issues that need to be addressed in order to make the polymer MEMS a mainstream technology. One of the issues is related to the electro-mechanical transduction sensitivity, which requires integration of novel materials and process techniques. The other issue concerns the stability of polymer materials in atmosphere, when used as sensors. CMOS compatibility of these materials processing is another issue. In this talk, we will look at some of the approaches for addressing these concerns using a variety of processes & materials. The approaches for enhanced transduction sensitivity in polymer MEMS devices include integration of a highly strain sensitive organic transistor with a polymer microcantilever (CantiFET) [10], integration of nanoparticles and nanowires into the polymer layers [11], as well as use of graphene as a transduction material with polymer micro-cantilevers [13]. The stability issues are addressed using a range of low-temperature deposited materials for passivation purposes. The polymer device processing and packaging also needs to be CMOS compatible in order to enable eventual integration of these technologies into the CMOS platforms for the Internet of Things (IoT) applications. This talk discusses the current status of research with polymer MEMS using real world applications.

Keywords: MEMS, Polymer MEMS, Transduction, Piezoresistive, Packaging

REFERENCES [1] Sangita Chaki Roy, T. Kundu, V. Ramgopal Rao, “Polymer based MEMS photodetector with spectral response in UV-Vis-NIR and Mid-IR region”, IEEE Journal of Lightwave Technology, Vol. 33, No. 15, August 2015 [2] M adhuri Vinchurkar, Anjali Joshi, Swapnil Pandey, and V. Ramgopal Rao, “Polymeric piezoresistivemicrocantilevers with reduced electrical variability”, (IEEE/ASME) Journal of Microelectromechanical Systems (J-MEMS), Vol. 24, No. 4, August 2015


8 Nanoelectronics and Sensors [3] Prasenjit Ray, Rashi Nathawat, Prakash R Apte, V. Ramgopal Rao, “Plastic deformation study of vertical Zinc oxide nanowires for polymer cantilever based sensor applications”, IEEE Transactions on Nanotechnology, Vol. 13, No. 4, July 2014 [4] Sheetal J. Patil, Arindam Adhikari, Maryam Shojaei, V. Ramgopal Rao, “An Ultra-sensitive Piezoresistive Polymer Nano-composite Microcantilever Platform for Humidity and Soil Moisture Detection”, Sensors & Actuators B: Chemical (Elsevier), Volume 203, November 2014, Pages 165-173 [5] Rajul S Patkar, Prakash R. Apte and V. Ramgopal Rao, “A Novel SU8 Polymer Anchored Low Temperature HWCVD Nitride PolysiliconPiezoresitive Cantilever”, IEEE Journal of Microelectromechanical Systems, Vol. 23, No. 6, December 2014 [6] Sheetal J. Patil, Nikhil Duragkar and V. Ramgopal Rao, “An Ultra-sensitive Piezoresistive Polymer Nano-composite Microcantilever Sensor Electronic Nose Platform for Explosive Vapor Detection”, Sensors & Actuators B: Chemical (Elsevier), Volume 192, March 2014, Pages 444-451. [7] M. Kandpal, A.K.Bandela, V.K. Hinge, V. Ramgopal Rao, and C.P. Rao, “Fluorescence and piezoresistive cantilever sensing of trinitrotoluene by an upper rim tetra-benzimidazole conjugate of calix[4]arene and the delineation of the features of the complex by molecular dynamics”, ACS Appl. Mater. Interfaces, 2013, 5 (24), pp 13448–13456 [8] P. Ray, V. Ramgopal Rao, “ZnO Nanowire Embedded Strain Sensing Cantilever: A New ultra-sensitive Technology Platform”, IEEE Journal of Microelectromechanical Systems, Vol. 22, No. 5, October 2013 [9] P.Ray, V. Ramgopal Rao, “Al-doped ZnO thin-film transistor embedded micro-cantilever as a piezoresistive sensor”, Applied Physics Letters. 102, 064101 (2013) [10] Seena, P.Pant, S.Mukherji and V.Ramgopal Rao, “Organic CantiFET: A Nanomechanical Polymer Cantilever Sensor with Integrated OFET”, IEEE Journal of Microelectromechanical Systems, Vol. 21, No. 2, April 2012 [11] Seena, A.Rajorya, P.Pant, S.Mukherji and V.Ramgopal Rao, “Polymer microcantilever biochemical sensors with integrated polymer composites for electrical detection”, Solid State Sciences (Elsevier), Volume 11, Issue 9, September 2009, Pages: 1606-1611 [12] N.S. Kale, S. Nag, R. Pinto and V. Ramgopal Rao, “Fabrication and Characterization of a Polymeric Microcantilever with an Encapsulated Hotwire CVD PolysiliconPiezoresistor”, IEEE Journal of Microelectromechanical Systems, Vol. 18, Feb. 2009 , Pages: 79-87 [13] Seena, A. Fernandes, P.Pant, S. Mukherji, V. Ramgopal Rao,”Polymer nanocompositenanomechanical cantilever sensors: material characterization, device development and application in explosive vapour detection,” IOP Nanotechnology 22 (2011) 295501 (11pp) [14] Prasenjit Ray, Swapnil Pandey and V. Ramgopal Rao, “Development of GrapheneNanoplatelet embedded Polymer Microcantilever for vapour phase explosive detection applications”, Journal of Applied Physics, 116, 124902 (2014); doi: 10.1063/1.4896255 [15] K. Prashanthi, M. Naresh, V. Seena, T. Thundat, and V. Ramgopal Rao, “A Novel Photoplastic Piezoelectric Nanocomposite for MEMS Applications”, IEEEJournal of Microelectromechanical Systems, Vol. 21 , Page(s): 259- 261, April 2012 [16] M. Kandpal, C. Sharan, P. Poddar, K. Prashanthi, P.R.Apte, V. Ramgopal Rao, “Photopatternable nano-composite (SU-8/ZnO) thin films for piezo-electric applications”, Applied Physics Letters, 101, 104102 (201

Molecular Nanoscience at Surfaces Rasmita Raval The Surface Science Research Centre, Department of Chemistry, University of Liverpool, L69 3BX, UK

Molecules represent the most versatile, functional entities available in Nature and are central components in the machinery of life. Fascinating insights into molecular behaviour may be obtained by placing them on surfaces and using powerful microscopes and spectroscopies to observe them. From this, the nanoscale details of how complex molecular organisations and architectures are nucleated, controlled and propagated have begun to emerge.1-5 The forces that drive these assemblies range from weak, supramolecular interactions1-7 to strong intermolecular covalent bonding8-11. From these organised molecular units arise complex functions like molecular recognition and sensing4,6,7, chirality1-4,6, adaptive behaviour4,5, on-surface synthesis8-11 and directed molecular motion12 that are important in nanoscience and new materials. Importantly, the fact that these molecular phenomena can be captured at surfaces, and are directly addressable, makes these systems highly relevant for 21st century nanotechnology.

Reference

[1] M.Ortega-Lorenzo, C.J.Baddeley, C.Muryn and R.Raval, Nature, 404 (2000) 376. [2] M. Forster, M. Dyer, M. Persson and R.Raval, J. Am. Chem. Soc., 131 (2009) 10173. [3] M. Forster, M. Dyer, M. Persson and R.Raval, Angewandte Chemie Int. Ed., 2010 (49), 2344. [4] S.Haq, N. Liu, V.Humblot. A.P.J.Jansen, R.Raval, Nature Chemistry, 1 (2009) 409. [5] J. Carrasco, A.Michaelides, M. Forster, S. Haq, R. Raval and A. Hodgson, Nature Materials, 8 (2009) 427. [6] P. Donovan, A. Robin, M. S. Dyer, M. Persson, R. Raval, Chemistry, A European Journal, 16 (2010) 11641. [7] N. Liu, S. Haq, G. R. Darling and R. Raval, Angewandte Chemie Int.Ed., 46 (2007) 7613. [8] S. Haq, F. Hank, M. S Dyer, M. Persson P. Iavicoli, D. B. Amabilino and R. Raval, J. Am. Chem. Soc. 133 (2011) 12031 [9] M. In’t Veld, P. Iavicoli, S.Haq, D. B. Amabilino and R. Raval, Chem. Comm., 2008, 1536. [10] F. Hanke, S,Haq, R.Raval and M.Persson, ACS Nano, 5 (2011) 9093. [11] S. Haq, F. Hanke, J. Sharp, M. Persson, D. B. Amabilino and R Raval, ACS Nano, 8 (2014) 8856–8870. [12] S Haq, B Wit, H Sang, A Floris, Y Wang, J Wang, L Pérez-García, L Kantorovitch, D B. Amabilino, R Raval, Angewandte Chemie Int Ed. 2015, DOI: 10.1002/anie.201502153


Probing Nano Precipitates in Radiation Resistant Steels C.S. Sundar J.C. Bose Fellow, Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam , Tamil Nadu

Incorporation of nano precipitates in steel matrix results in the improvement of high temperature mechanical properties and in enhancing the radiation resistance of structural materials in a nuclear reactor. In this lecture, I shall present the results of our investigations on the thermal and radiation stability of nano-dispersoids in steels that are incorporated to suppress void swelling under irradiation. The systems investigated include Ti modified austenitic steels containing nano TiC precipitates, and oxide dispersion strengthened steels containing and Y-Ti-O nano particles in Fe. The simulation of neutron damage has been carried out using ion beams, and the characterization of nano precipitates has been carried out using the techniques of positron annihilation spectroscopy, transmission electron microscopy and atom probe tomography. Results from computer simulation studies, encompassing ab-initio calculations, molecular dynamics and kinetic monte carlo simulations, that provides insight on the structure and stability of oxide nanoparticles in steel will also be presented.


Invited Speakers

Electrically Conductive Inks with Nanotechnology Anuj Shukla Defence Lab, Jodhpur

Abstract Recently, it has been shown that printing methodologies can be used to print electrically functional devices on a variety of substrates. The requirements for printing electrically functional devices are much more demanding than graphic printing applications due to the additional requirement of easy electron flow. This additional requirement increases the need for print uniformity and layer-to-layer registration to a much higher degree. The proposed printing approach is a simple low cost additive manufacturing process that can be used to realize metamaterials, frequency selective surfaces, and EMI protection devices. There has been extensive research for the last few years on process improvement of electrical conductive inks, as well as the advances of nano-filler such as nanoparticles, nanowires, or carbon nanotubes, conducting polymers and graphenes. In this lecture, recent research trends on electrically conductive inks and their related nanotechnologies are discussed, with the particular emphasis on the emerging nanotechnology, including synthesis and characterization of nanomaterials and characterizations.


High Frequency Devices for Defence Poornendu Chaturvedi Scientist E and Centre Head Centre for Advanced Semiconductor Technology (ASemiT), SSPL, DRDO, Ministry of Defence, Delhi

Supremacy in any future warfare will be critically dependent on the state of device technology of the warring nations. High frequency devices are one of the most crucial elements of any weapon or communication platform. They are required for radars, missile seekers, telemetry, control, telecommunication, etc. Unlike, the breathtaking pace of Moore’s law which predicts doubling of transistor counts at every 18 months, development of device technology requires much longer gestation periods. Thus, it is imperative to forecast upcoming technologies that could be of interest to defence and timely direct adequate resources for their development. This talk will give an overview of defence applications and recent developments in field of high frequency devices.


Graphene and Carbon Nanotube NanoComposite Sensors for Glaucoma Ocular Pressure Measurements D. Jenkins, M. Mane1, A. Deepak1, P. Davey, D. Oehring2 and P. Shankar1 School of Computing, Electronics and Mathematics, Plymouth University, UK. 1 Saveetha School of Engineering, Saveetha University, Chennai, India 2 Faculty of Health and Human Science, Plymouth University, UK.

Abstract A long standing area of eye health care concerns the reliable assessment of the intraocular pressure for monitoring glaucoma, especially in it early stage. One standard test involves delivering a puff of air to the cornea and using a Schiempflug camera to detect the deformation induced at the cornea. A significant issue in this area is mapping of the spatial and temporal properties of the pressure wave with that of the cornea. The paper will present some initial results on measurement of the average pressure received at the cornea using a commercially available MEMS pressure sensor. In order to measure the required spatial and temporal properties of this pressure wave, compliant nanocomposite thick film have been fabricated. The films are based upon PVDF, a piezoelectric polymer, but with functionalized carbon nanotubes or functionalized graphene added at up to 10 weight %. Nanocomposite films have been prepared using both the solvent casting method and by spin coating. The paper will present the initial results of this study, which are very encouraging for this application.


Investigation of luminescence properties of color tunable aluminosilicate nanophosphors for pc-LEDs S.J. Dhoble Department of Physics, R.T.M. Nagpur University, Nagpur E-mail : [email protected]

ABSTRACT The last decade witnessed remarkable exploration of nanophosphors, due to their potential application for various high performance and novel displays and devices. Their high quantum yields and spectral tunability, achieved through synthetic control, has helped them to emerge as attractive alternatives to several existing phosphors. Chemical methods such as colloidal, capping, cluster formation, sol-gel, electrochemical etc. can be employed for efficient synthesis of nanophosphors. A number of aluminosilicate nanophosphors were successfully prepared by chemical methods and their luminescence properties were investigated along with a phenomenological analysis of structure-property relationship. The present work is emphasized on structural, morphological, thermal stability and luminescent properties of aluminosilicate nanophosphors [1-4] were investigated as a function of sintering temperature and the variation of rare earth ion (Eu, Ce, Dy) concentration, by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermo-gravimetric analysis (TGA) and photoluminescence (PL) spectroscopy. These nanophosphors, with high thermal stability and high efficiency, may be potential candidates for phosphor converted light emitting diodes (pc-LEDs).

References

[1] Kumar Ashwini, Dhoble S J, Peshwe D R, Bhatt Jatin, J.Alloys and comp., 2013;578:389-393. [2] Pawade V B, Dhoble N S, Dhoble S J, Solid State Sci.,2012;14:607- 610. [3] Pawade V B, Dhoble S J, J. Lumin., 2014; 145:626-630. [4] Kumar Ashwini, Dhoble S J, Peshwe D R, Bhatt Jatin, J.Alloys and comp., 2014;609:100-106.


Ferroelectric Properties and Offset Polarization in Polycrystalline BNdT Thin Films for the Application of RAM Devices Khalid Mujasam Batoo King Saud University, Riyadh, Saudi Arabia.

Abstract The current surge of interest in multiferroic materials showing magneto-electric coupling due to the presence of both magnetic and ferroelectric ordering is fuelled by both the potential technological applications and the underlying new physics [1-3]. The magneto-electric coupling (ME) provides an additional degree of freedom in the designing of actuators, sensors, and data storage devices [3]. From the fundamental physics point of view, the coexistence of ferroelectric and magnetic order is contra-indicated [1], as the former requires empty ‘d’ orbitals for the off-centre displacement of cations responsible for ferroelectricity [4] while the latter results from partially filled d orbitals. The coexistence of such mutually exclusive phenomena in some compounds has been attributed to new mechanisms of ferroelectricity, such as lone pair stereochemical activity of the ‘A’ site cation [1-3,], loss of inversion symmetry due to spiral magnetic ordering [1-3], and change in geometrical arrangement of ions [1,2] After an introduction of the basic ideas and how the work relates to other work, providing some relevant References in short format [1, 2], present detailed descriptions of methods, device structures, and examples of specific results, whether experimental or theoretical. If absolutely necessary, these results can be supported by figures and/or tables, but only in strict compliance with space limits and preserving clarity. Multiferroic materials simultaneously present both ferroelectric and spin orders, which enable them to have potential applications in both magnetic and ferroelectric devices. So, the development of such type of material, which has magneto-electric properties in same phase at room temperature, is the milestone for modern technology. These materials have potential applications in memory devices where one can write ferroelectrically and read magnetically or vice versa. We report the multiferroic properties of polycrystalline homogeneous Bi4-xNdxTi3O12 (BNdT) ferroelectric thin films sandwiched in Pt electrodes by chemical solution deposition. Dense and uniform BNdT films were achieved by rapid thermal annealing the spin-on films at 700 °C for 3 min in oxygen environment. All the samples exhibited well-saturated hysteresis loops with remenant polarization (2Pr) increasing from 36.22 μC/cm2 (x = 0.0) to 109.86 μC/cm2 (x = 0.1), respectively, while the coercive field (2EC) = 64.6 kV/cm remained unchanged for all compositions at room temperature after exposing the films using Swift heavy ion irradiation . Polarization offset was observed in the compositionally graded ferroelectric thin films as a function of temperature. Polarization offset was notable after 100 °C and increased with increasing temperature which may be related to thermionic charge injection, which is asymmetric to top and bottom electrodes V. Rajendran, K. Thyagarajah and K.E. Geckeler (eds.) Nanoelectronics and Sensors, pp. 17-17 (2015)

Affinity-Specificity Augmentation for Molecular Imaging and Therapy Using Nano-Probes (ASAMIT-NP) Anil K. Mishra Division of Cyclotron and Radiopharmaceutical Sciences, Molecular Imaging Research Centre, Institute of Nuclear Medicine and Allied Sciences, Lucknow Road, Timarpur, Delhi E-mail: [email protected]

Imaging molecules always requires accumulation of probes at target site, often achieved most efficiently by steering with affinity probes specific to the target. This entails accessing target molecules hidden behind tissue barriers by using affinity amplification entities (NPs) to enrich imaging modalities having low sensitivity and high resolution and at the same time with imaging modalities having high sensitivity but low specific activity. To achieve excellent visualization and delivery of requisite quantity of drug or drug like molecules hybrid nano-particles are must. To achieve affinity and specificity enhancement are possible by utilizing selective transporter like, increase in amino acid uptake is one of the earliest events associated with in vivo transformation which induce up regulation of the amino acid transporter expression to enhance the facilitated transport. The LAT1 transporter is highly expressed in malignant tissue, involved mainly in the transport of amino acids to support continuous growth and proliferation of the abnormal tissue across some endothelial and epithelial barriers. The potential advantage of amino acid based tumor imaging NPs is that they confer predominantly higher uptake in proliferating tumor cells, with low nonspecific uptake in macrophages and other cells. Moreover, amino acids are the most popular building blocks to design NP for selective uptake in the diseased lesions compared with normal tissue, small viable tumors, and recurrence as well as for therapy monitoring. Keeping this in view we have designed several types of system with excellent affinity and specificity for targeted imaging and therapy.

Eu-MDM NPs V. Rajendran, K. Thyagarajah and K.E. Geckeler (eds.) Nanoelectronics and Sensors, pp. 18-18 (2015)

Electron-Positron Annihilation Spectroscopy to Highlight the Defect Characteristics of Nickel Oxide Nanocrystals Anjan Das, Atis Chandra Mandal1, Soma Roy2 and P.M.G. Nambissan2 Department of Physics, A.P.C. Roy Govt. College, Siliguri, Darjeeling 1 Department of Physics, University of Burdwan, Golapbag, Burdwan 2 Applied Nuclear Physics Division, Saha Institute of Nuclear Physics, Kolkata

ABSTRACT Nickel oxide samples of nanocrystallites of different average sizes were synthesized by sol-gel method. Another set of nanoparticulate samples of manganese-doped nickel oxide (Ni1−xMnxO, x = 0-0.35) were also prepared. They were characterized by X-ray diffraction and high-resolution transmission electron microscopy. The crystallites were face-centred cubic (NaCl-type) in shape and the lattice parameter varied with annealing temperature and doping concentration. The band gap energies, estimated from UV-Vis absorption spectra, increased with decreasing sizes of the nanocrystallites and increase in Mn-doping. The defects in the nanocrystalline samples were investigated through positron annihilation spectroscopy and the results are discussed in this paper.

INTRODUCTION The wide band gap semiconductors like the sulfides and oxides of transition elements exhibit several useful physical properties, which have made their studies especially at the nanocrystalline compositional levels interesting and informative [1]. Conventional techniques are convenient in dealing with them but novel methods are employed in understanding certain special aspects such as the nature and distribution of the vacancy-type defects and structural and phase transformations during external treatments. We used positron annihilation spectroscopy for characterizing the defects in nickel oxide (NiO) nanoparticulate samples of different crystallite sizes and doped with Mn ions in different concentrations. A number of review articles on the subject are available in literature [2,3]. EXPERIMENTAL DETAILS Nickel nitrate hexahydrate dissolved in 120 ml distilled water and 25% ammonium hydroxide are used as starting reagents. The precipitate formed after continuous stirring is taken out, washed in distilled water and then mixed with 120 ml ethanol (CH3CH2OH) and stirred again. 18 ml 1.01N acetic acid is then added. The final precipitate is then pre-heated at 70oC and annealed in air at different temperatures in the range 200–275oC for different hours. For the preparation of the Mn-doped samples, 50 gm of V. Rajendran, K. Thyagarajah and K.E. Geckeler (eds.) Nanoelectronics and Sensors, pp. 19-22 (2015)

20 Nanoelectronics and Sensors nickel nitrate hexahydrate and calculated amounts of manganese acetate tetrahydrate are separately dissolved in a mixture of ethyl alcohol and double-distilled water in the ratio 1:2. The pH of the solutions was kept in the acidic range by adding nitric acid and acetic acid. The individual solutions were stirred for 1 hour, mixed together and further stirred for 2 hours with a magnetic stirrer. The solution was then allowed for gelation for two days and the precipitate is taken out, washed and dried at 80oC and heated at 300oC for 2 hours. The characterization of the samples was done using X-ray diffraction and high resolution transmission electron microscopy (HRTEM). Optical band gaps were obtained from UV-Vis absorption spectroscopy. The details of experimentation and data analysis of positron annihilation measurements are given elsewhere [4,5].

RESULTS AND DISCUSSION Fig. 1(a) shows the positron lifetime spectra of two samples of pure undoped NiO with different mean sizes of the nanocrystallites. It clearly illustrates the sensitivity of positron lifetime spectroscopy for the characterization of vacancy-type defects in nanocrystalline materials. The spectra shown in Fig. 1(b) are capable of demonstrating the effects of doping and the modifications of the defects brought in by the introduction of the Mn2+ ions. The resolved positron lifetimes and their intensities, obtained from the analysis of the spectra using the program PALSfit [6], and the mean lifetime tm are listed in Table 1. Nanocrystalline NiO Bulk NiO

104 10

(a)

3

102 101 100

0

100

200

300

400

500

Channel number (25 ps per channel)

600

NiO Ni0.7Mn0.3O

105

Coincidence counts

Coincidence counts

105

(b)

104 103 102 101 100

0

100

200

300

400

500

600

700

Channel number (25 ps per channel)

Fig. 1. Peak-normalized positron lifetime spectra of (a) bulk and nanocrystalline (size ~ 6 nm) NiO samples and (b) pure and Mn-doped nanocrystalline (size ~ 6 nm) NiO samples.

The obtained shortest lifetime component t1 is larger than 110 ps, the lifetime of positrons annihilating in pure and defect-free NiO. It hints at positron trapping in the crystalline defects. The second component t2 is proof for the presence of large extended defects within the samples. The thermal diffusion length of positrons is typically 50-100 nm in oxide semiconductor materials. From the X-ray diffraction data and the HRTEM images, we estimated the crystallite sizes and they varied from 3.3 to 13.1 nm in the two sets of samples [4,5]. It is therefore expected that a significant fraction of positrons would diffuse out to the nanocrystallite surfaces and get annihilated there. This is one of the reasons that the magnitudes of the lifetime t2 are very large (Table 1). The component t2, however, also has in it the lifetime of positrons trapped in the vacancy type defects within the nanocrystallites. In ionic solids and semiconductors, the absence of an ion will result in a virtual opposite charge at the vacancy created by it. Thus, Ni2+ vacancies in NiO are negatively charged and positrons will be strongly trapped by them whereas the O2- vacancies will be repelling the

Electron-Positron Annihilation Spectroscopy to Highlight the Defect Characteristics ... 21

positrons due to the positive charge. A divacancy formed by the simultaneous absence of a neighbouring pair of cation and anion will result into mutual cancellation of their charges and the divacancy will be neutral. It can still trap positrons, which will experience an attractive potential due to the absence of the atomic nuclei. In the case of trivacancies, there are two possibilities. A trivacancy formed by two cationic and one anionic monovacancies will have a resultant negative charge and can trap positrons. The other type of trivacancy formed by two anionic and one cationic monovacancies will be having excess positive charge and hence cannot trap positrons. Positrons are thus highly defect-specific and can be used as probes in the investigation of defects of diverse nature and features. The longest lifetime t3 and intensity I3 are results of orthopositronium (o-Ps) formation in the intercrystallite regions. o-Ps is a metastable bound state of an electron and a positron of parallel spins and exists in that form till the positron in it is ‘picked off’ by an electron with opposite spin from the material. A reduced probability of formation of parapositronium is also there with the spins of the two particles aligned antiparallel but is not considered in the discussion due to the very low intensity (one-third of I3), quite often less than 1%. Table 1. The positron lifetimes and relative intensities resolved from the spectra of the samples. The figures in parentheses indicate the standard deviations.

Sample Bulk Nano. Pure Doped

t1 (ps) 175(2) 138(1) 194(1) 189(3)

t2 (ps) 444(3) 378(1) 450(5) 419(9)

t3 (ps) 2797(076) 2534(104) 2644(062) 1116(167)

I1 (%) 78.4(0.7) 41.5(0.4) 67.8(0.8) 54.2(1.6)

I2 (%) 20.4(0.7) 57.8(0.4) 30.5(0.8) 44.7(1.0)

I3 (%) 1.2(0.2) 0.8(0.1) 1.6(0.1) 1.1(0.1)

tm (ps) 260(8) 294(6) 311(6) 299(6)

From CDBS data, ratio curves are generated by dividing the projected Doppler shifted energy spectra of the Ni1−xMnxO samples by an identical spectrum of a reference sample [7]. While the magnitudes of the positron lifetime t2 are indicative of positron trapping in trivacancy-type defect clusters (VNi+O+Ni)2-, the CDBS ratio curves imply that the doped Mn2+ ions in large numbers occupy these clusters, reducing them to Mn-decorated neutral divacancies (VNi+OMnNi)0. The arrows in Fig. 2 indicate a shift in the peak that is characteristic of positron annihilation with the 2p electrons of oxygen. It indicates that a fraction of positrons are annihilated by the electrons of Mn2+ also. A marked deviation of the spectrum of Ni0.65Mn0.35O implies that the sample is on the verge of losing the phase stability and additional phases like NiMn2O4 are being formed. NiO/Al Ni0.9Mn0. 1O/Al Ni0.8Mn0. 2O/Al Ni0.65Mn0. 35O/Al

Ratio of normalized counts

2.0 1.8

Ni/Al

1.6 1.4 1.2 1.0 0.8

0

5

10

15

20

-3

pL (10 m0c)

Fig. 2. The ratio curves of some of the samples and elemental Ni with respect to the spectrum of pure (99.999%) and annealed (900K for 2 hours in high vacuum) Al single crystalline samples.

22 Nanoelectronics and Sensors

SUMMARY AND CONCLUSIONS In the study of wide band gap semi-conductors like transition metal oxides, the electronic structure and properties at nanocrystallite sizes can be investigated through positron annihilation spectro-scopy. NiO nanocrystals are investigated in this case, both as functions of the crystallite sizes and substitution by Mn2+ ions. The band gap energies estimated from the optical absorption spectra (not shown), indicated weak, intermediate and strong quantum confinement effects at finite sizes, in agreement with theoretical predictions [8].

REFERENCES [1] Rao, C.N.R., and Raveau, B., Transition Metal Oxides: Structure, Properties, and Synthesis of Ceramic Oxides, 2nd ed., pp. 1–392, Wiley, NJ, 1998. [2] Krause-Rehberg, R., and Leipner, H.S., Positron Annihilation in Semiconductors – Defect Studies, pp. 1–379, Springer, Berlin 1999. [3] Nambissan, P.M.G., Defects Characterization in Nanomaterials Through Positron Annihilation Spectroscopy, in Nanotechnology: Synthesis and Characterization, Shishir Sinha, N.K. Navani and J.N. Govil, Eds., Vol. 2, pp. 455-491, Studium Press LLC, Houston, USA, 2013. [4] Das, Anjan, Mandal, Atis Chandra, Roy, Soma, and Nambissan, P.M.G., Positron annihilation studies of defects and fine size effects in nanocrystalline nickel oxide, J. Exper. Nanosci. 10, 622-639 (2015). [5] Das, Anjan, Mandal, Atis Chandra, Roy, Soma, and Nambissan, P.M.G., Mn-Doping in NiO Nanoparticles: Defects-Modifications and Associated Effects Investigated Through Positron Annihilation Spectroscopy, J. Nanosci. Nanotech. (2015) in press. doi:10.1166/jnn.2015.10963 [6] Olsen, J.V., Kirkegaard, P., Pedersen, N.J., and Eldrup, M., PALSfit: A New Program for the Evaluation of Positron Lifetime Spectra, Phys. Stat. Sol. C 4, 4004-4006, 2006. [7] Asoka-Kumar, P., Alatalo, M., Ghosh, V.J., Kruseman, A.C., Nielsen, B., and Lynn, K.G., Increased Elemental Specificity of Positron Annihilation Spectra, Phys. Rev. Lett. 77, 2097-2100, 1996. [8] Brus, L.E., A Simple Model for the Ionization Potential, Electron Affinity, and Aqueous Redox Potentials of Small Semiconductor Crystallites, J. Chem. Phys. 79, 5566-5571, 1983.

Thermoelectric Properties of Spark Plasma Sintered Lead Telluride Nanocubes S. Neeleshwar, B. Khasimsaheb, M. Srikanth, Sivaiah Bathula1, Bhasker Gahtori1, Ajay Dhar1, S. Amrithapandian2, B.K. Panigrahi2, Sriparna Bhattacharya3, Ramakrishna Podila3 and A.M. Rao3 University School of Basic & Applied Sciences, GGS Indraprastha University, New Delhi, , India CSIR-Network of Institutes for Solar Energy, Materials Physics and Engineering Division, CSIR-National Physical Laboratory, New Delhi, India 2 Materials Physics Division, Materials Science Group, Indira Gandhi Center for Atomic Research, Kalpakkam, , Tamil Nadu, India 3 Departments of Physics and Astronomy, Clemson Nanomaterials Center, Clemson University, Clemson, South Carolina, SC 29634, USA 1

Abstract In the present investigation, we report the cost-effective, surfactant-free and scalable synthesis technique for Lead Telluride (PbTe) nanocubes by chemical precipitation method followed by spark plasma sintering (SPS). The synthesized nanocubes were characterized by X-Ray Diffractometer (XRD), High Resolution Transmission Electron Microscope (HRTEM) and X-Ray Photoelectron Spectroscopy (XPS). The HRTEM studies clearly indicate that the nucleation centers (spherical) evolve into nanocubes by addition of the Pb and Te atoms. The thermopower measurement performed on as sintered PbTe nanocubes exhibited an enhancement of 420 µV at 400 K, which is higher than the reported values at this temperature. This enhancement could be attributed to the potential barrier scattering at the grain boundaries. Further, significant reduction in thermal conductivity was observed due to its higher surface area with many facets effectively scattered various length scales of phonons for PbTe nanocubes and thus leading to an increase in ZT. The dimensionless figure of merit (ZT) was found to be ~ 0.45 at 300K, which is higher than the reported values at this temperature with similar chemical composition. Moreover, thermoelectric compatibility factor with respect to the temperature has been calculated and it is quite comparable with similar material synthesized employing different processing routes. Enhanced thermoelectric properties coupled with moderate compatibility factor makes PbTe nanocubes as a potential candidate for green energy generation.


Quest of Nanomaterials for Field Emitter Devices R.B. Sharma DRDO Headquarters, DRDO Bhawan, Rajaji Marg, New Delhi

Abstract The bright and stable emission of electrons is desirable for a field emitter for its use in the development of field emission devices such as field emission displays, high power microwave tubes, power efficient miniaturized x-ray tubes and compact high-resolution electron microscopes. The efforts are, therefore, being made to design and develop new materials with better field emission properties. The nanostructured materials, namely, carbon nanotubes1-2 and graphene nanosheets3 showed promise with their improved field emission properties. The analysis of atom probe mass spectra helped in successful evaluation of the surface composition of carbon nanotubes at the atomic level4. The electron emission mechanism is clarified with qualitative and quantitative analysis of field emission and field ion images from carbon nanotubes and graphene nanosheets.

References [1] Field emission from carbon nanotubes grown on a tungsten tip, RB Sharma, VN Tondare, DS Joag, A Govindaraj and CNR Rao, Chem. Phys. Lett. 344 (2001) 283. [2] Field Emission from Boron and Nitrogen doped carbon nanotubes grown on tungsten and Silicon substrates, RB Sharma, DJ Late, DS Joag, A Govindaraj, CNR Rao, Chem. Phys. Lett. 428 (2006) 102. [3] Field Emission from Graphene Nanosheets, Takahiro Matsumoto, Tomonori Nakamura, Yoichiro Neo, Hidenori Mimura and Makoto Tomita, in Graphene Simulation (Ed: Jian Ru Gong), August 1, 2011, pp 139. [4] 3D atom probe studies of carbon nanotubes and Smart materials, RB Sharma and GDW Smith, a report submitted to Department of Science & Technology (DST), India and the Royal Society, UK, Mar 2007.


Contributed Papers

Studies on the Synthesis and Characterization of Nano Phosphors for Field Emission Devices H. L. Vishwakarma and Anju Singh1 Department of Physics, Surguja University, Ambikapur (C.G) Department of Applied Physics, Rungta College of Engg & Tech, Kohka Road, Kurud, Bhilai, Durg

1

Abstract Nano phosphors were synthesized by chemical precipitation method with mercaptoethanol as the capping agent. Manganese doped ZnS nano phosphors (ZnS: Mn) with varying concentration of capping agent as well as of Mn2+ were synthesized at room temperature. The optical absorption studies show that the absorption edge shifts towards blue region as the capping agent concentration is increased indicating that the effective band gap energy increase with decreasing particle size while with the change in doping concentration no variation was observed in the absorption spectra. The nano phosphors obtained were characterized by XRD. It was found that as the capping agent concentration is increased, there is reduction in particle size.

Keywords: Nano phosphors, characterization, Luminescence, Optical properties.

Introduction ZnS is a direct transition semiconductor with the widest energy band gap among the group II- VI compound materials.The most striking feature of ZnS nanocrystallites is that their chemical and physical properties differ dramatically from those of bulk solids. ZnS is a semiconducting material, which has a wide band gap material of 3.70 eV [1], [2]. Among these, luminescent semiconducting nano phosphors, also termed as nanophosphors, were paid much attention particularly for their life time shortening and enhanced emission efficiencies [3], [4]. Bhargava et al. first reported luminescent properties of Mn doped ZnS nano phosphors prepared by a chemical process at room temperature, which initiated investigation on this topic [5], [6]. Depending on the capping molecules present on the ZnS: Mn, particles passivate surfaces. ZnS doped with Mn2+ nano phosphors are having high quantum efficiency and luminescence intensity [7]. The band structure of the semiconductor changes with decreasing in particle size. Zinc sulphide doped with manganese (ZnS: Mn2+) show interesting luminescence properties for application as phosphors [8]. In 1994 Bhargava et al. reported that the luminescence efficiency increases with decreasing particle size and life time of Mn2+ emission was shortened from milliseconds to nanoseconds due to quantum confinement effect. This result has led to a new class of luminescent material finding applications in displays, sensors, lasers etc. As far


28 Nanoelectronics and Sensors as display is concerned the resolution depends greatly on the size of the pixel and improves with a reduction in the size of the pixel that is in turn determined by the size of the phosphor particles. Zinc sulphide is an important semiconductor and has many optoelectronic applications including solar cells, photodiodes, light emitting diodes, nonlinear optics and heterogeneous photo catalysis. In the present study we have synthesized ZnS nano phosphors with varying concentration of capping agent using chemical precipitation technique. The particles are characterized using XRD.

Experimental Method All the reactants and solvents used in this study were analytical grade and used without any further purification. The synthesis was carried out in water for its inherent advantages of being simple and environment friendly. All steps of the synthesis were performed at room temperature and under ambient conditions. In the present investigation chemical route synthesis technique has been adopted. Nano phosphors of ZnS are synthesized in aqueous medium through chemical precipitation technique starting from analar grade zinc salt and sodium sulphide, and using mercaptoethanol as capping agent. The nano phosphors are separated from the reaction medium by centrifugation at 3500 rpm and finally air dried. Different samples were prepared by changing the capping agent concentration. Special care has to be taken to maintain the same physical condition during the synthesis of the samples. Absorption of the samples prepared with various concentrations of capping agent and dopant were studied. Perkin Elmer λ-12 spectrometer was used to obtain the absorption peak of ZnS nano phosphors. The lambda-12 UV/ VIS spectrometer features in all reflecting optical system. All the samples were characterized at IUC - Indore. The morphologies and sizes of the mercaptoethanol capped ZnS: Mn was determined by X- ray diffraction studies with CuKα radiation (λ = 1.5418 A0). XRD data were collected over the range 50 - 750 at room temperature. X- ray diffraction patterns have been obtained by Bruker D8 Advance X- Ray diffractometer. The particle size was calculated using Debye- Scherer Formula. The finite three- dimension crystal lattice diffracts Xrays in manner analogous to the reflection of visible light from a ruled grating. When the particle size is of the order of the wavelength of incident beam, the diffracted beam becomes diffused. The width of the X-ray diffraction line is able to give the crystallite size. The relation between crystallite size and diffracted ray line broadening was given by Scherer [9] D=

Kλ

β ⋅ Cosθ Where K is a constant which depends on the crystalline shape and diffractometer setup, λ is the wavelength of monochromatic radiation, β is full width half maxima (FWHM) in radians, θ is Bragg’s angle. The value of K and λ are equipment parameters and the value of β and θ can be obtained from the diffraction pattern. Figure shows the X- ray diffraction pattern prepared with different mercaptoethanol concentrations. Three different peaks are obtained at 2θ values of 29, 47 and 57.50 for all the samples. This shows that the sample has zinc blend structure and the peaks corresponding to diffraction at (111), (220) and (311) planes respectively [10]. Lattice parameter ‘a’ can be determined using equation (2), substituting the value of sin2θ and corresponding h, k and l. a=

λ 2 ⋅ Sinθ

h2 + k 2 + l 2

The lattice parameter has been computed as 5.33 A0, which is very close to the standard value of

Studies on the Synthesis and Characterization of Nano Phosphors for Field Emission Devices 29

ZnS zinc blend structure (5.42 A0).

Results and Discussions Absorption spectra of ZnS nano phosphors at various concentrations of capping agent as well as for doped ZnS have been studied in the present investigation. The samples were prepared with capping agent concentration of 0.005 M, 0.01M, 0.015M, 0.02M, and 0.025 M respectively. It is clear from the spectra (Fig: 1) that there is practically uniform absorption in the visible range (800nm – 390nm).

Fig. 1: Absorption spectra of ZnS nano particles at various concentration of capping agent

Fig. 2: Absorption spectra of ZnS Mn nano particles

The absorption increases suddenly in the visible range. Sudden increase in absorption occurred at 240nm, 235nm, 230nm, 225nm, and 220nm respectively. The absorption edge was found at shorter wavelength with decreasing particle size. As the capping agent concentration increases the optical band gap is found to increase which was calculated using the absorption edge. It is observed that no optical absorption occurs at surface states and therefore these do not affect the absorption spectra. A typical X-ray diffractogram (XRD) of nanocrystalline ZnS doped with Mn2+ is shown in fig.2. XRD study reveals that ZnS nano phosphors have zinc- blende crystal structure. For all the samples three peaks are observed corresponding to diffraction from (111), (220) and (311) planes. Due to the size effect, the XRD peaks tend to broaden and their width increases as the size of the crystal decreases. The crystallite size has been estimated from the broadening of the first diffraction peak using Debye – Scherrer formula. The crystallite size has been found to decrease from 1.54nm to 0.91nm with increasing the capping agent concentration from 0.005M to 0.025M. From the XRD

30 Nanoelectronics and Sensors patterns of undoped and doped ZnS nano phosphors it is observed that the presence of Mn increases the broadening of peaks. The broadening of peaks in Mn doped samples is indicative of small crystallite size.

Fig. 3: X-Ray Diffraction study of Mn

2+

doped ZnS nanocrystalline

Conclusions Optical excitation of electrons across the band gap is strongly allowed transition, producing an abrupt increase in absorptivity at the wavelength corresponding to the gap energy. The studies have revealed that capping agent restricts the growth of crystals and by increasing its concentration; the small crystals can be obtained. Optical absorption studies show that the absorption edge shifts towards blue region as the capping agent concentration is increased indicating that effective band gap energy increases with decreasing particle size. XRD study reveals the zinc blend structure for ZnS crystals. The lattice parameter has been obtained as 5.24 A0 which is approximately same as for bulk. The crystalline size computed from the XRD peaks comes out to be of the order of few nanometers. Acknowledgment This work has been partially supported by IUC, Indore (M.P). The authors are thankful to the management of Rungta College of Engineering and Technology, Bhilai (C.G.) and KITE, Raipur for providing financial assistance and research facility to carry out research work. References

[1] D. Denzler, M. Olschewski and K. Sattler, J. Appl. Phys. 84, 2841 (1998). [2] B.S. Zou, R.B. Little, J.P. Wang and M.A. EL- Sayed, Int. J. Quantum Chem. 72, 439 (2002). [3] R.N. Bhargava, D.Gallagher, X.Hong and A.Nurmikko, Phys. Rev. Lett. 72, 416 (1994) [4] T. Igarashi, T. Isobe and M. Senna, Phys. Rev. B 56, 6444 (1997). [5] I.I. Yu and M. Senna, Appl. Phys. Lett. 66, 424 (1995) [6] M. Konishi, T. Isobe and M. Senna, J. Lumin.93,1 (2004). [7] H. Hu, W. Zhang, Opt. Mater. 28, 536 (2006) [8] G. Becker and A. J. Bard, J. Phys. Chem. 87, 4888 (1983). A. Guinier, X-ray diffraction, W.H. Freeman, San Francisco (1963). [9] S.Mahamuni, A.A.Khosravi, M.Kundu, A.Kshirsagar,A.Bedekar, D.B. Avasare, P.Singh and S.K. Kulkarni, J. appl. Phys., 73, 5237 (1993)

Synthesis and Characterization of Novel Siloxane Based Transparent and Flexible Substrate for Oleds D. Shanmuga Sundar, A. Sivanantharaja, C. Sanjeeviraja1 and D.Jeyakumar1 Alagappa Chettiar College of Engineering & Technology, Karaikudi, Tamil Nadu 1 CSIR-Central Electrochemical Research Institute, Karaikudi, Tamil Nadu E-mail: [email protected]

ABSTRACT In this research, we have synthesized a novel flexible and transparent substrate with the help of organic materials such as Polydimethylsiloxane (PDMS) and Tetra ethoxy orthosilicate (TEOS). Characteristics such as transmittance (T), absorption (A), refractive index (n) and extinction coefficient (k) are calculated. Optical band gaps for both direct and indirect transitions are also calculated. The average transmittance of about 85-95% is obtained in the visible region (400-700nm) and the synthesized substrate show better thermal characteristics and withstands temperature upto 200oC without any color and weight loss.

Keywords: Organic light emitting diodes (OLEDs). Flexible substrate; Polydimethylsiloxane (PDMS) INTRODUCTION Organic light-emitting devices (OLED) have attracted researchers due to its delightful advantages such as ultra-thin thickness, light weight, and environment protective nature which insist to use them in flat panel displays and interior lighting source [1]. OLEDs also plays a major role as a transmitter in the field of Visible light communication, a recent trend in the field of communication in which the information is transferred by use of visible lights [2]. In order to achieve the efficient data communication in the field of VLC, flexible panel OLED displays with high efficiency are identified as a perfect candidate [3]. Generally OLEDs works on the principle of electroluminescence which states that by applying bias the device emits light and it was first reported by Pope et al. in 1963 [4]. Though the first practical OLED was reported by Eastman Kodak in 1987 [5]. Recently literature review on flexible candidates has been expanding. It now includes a book on flexible flat panel displays written by Crawford [6] and a special edition of the Proceedings of the IEEE on flexible displays [7].The scenarios for flexible displays are auspicious, although the timing still depends on technical and manufacturing developments [8, 9].


32 Nanoelectronics and Sensors Though plastic substrates such as poly (ethylene terephthalate) (PET) and polycarbonate (PC) are used as the flexible substrates [10, 11] but due to their limitations such as high gas permeability and low temperature withstand make these substrates not suitable for flexible displays applications. Another major drawback of plastic as flexible displays is its refractive index mismatch with the Indium Tin Oxide (ITO). But this can be overcome by using anode stack which will increase the efficiency of the device [12]. In order to overcome these drawbacks, Polydimethylsiloxane (PDMS) based flexible substrate with improved properties is reported. Due to delightful advantages such as transparent, light weight, flexible and robust, polymers are considered to be a very promising material as substrate for flexible displays [13-15]. In this work, we have synthesized a novel highly transparent and flexible PDMS based substrate which withstand high temperature upto 200oC without any structural and color changes. Also reported substrate has a transparency of about 85-95% in the visible region (300-700nm) and has a low thermal coefficient of expansion, better surface smoothness and resistance to both chemical and moisture with better rigidity which will make ease of commercializing the flexible displays soon in market.

EXPERIMENTAL In this work, a thin flexible film with improved thermal and optical characteristics is synthesized by means of using high viscous Polydimethylsiloxane (PDMS) of molecular weight around 1,10,000 from sigma aldrich with 99% assay. A few grams of PDMS is taken in a beaker and allowed to dissolve in toluene for few minutes. After uniform dissolution, then the cross linker tetraethylorthosilicate (TEOS) from sigma aldrich with 99% assay is added to the mixture and it is sonicated for few minutes then finally curing agent is added and once again it is sonicated for few minutes and it is coated on Teflon sheet or glass using doctor blade method to obtain a uniform thickness of 0.5mm. Then it is allowed to dry at room temperature for few hours and a free standing film of 0.5mm thickness is peeled off from the glass. Figure 1 show the photographic image of the as-prepared film.

Fig. 1: Photograph of synthesized transparentsubstrate

RESULTS AND DISCUSSION Figure 2 (a) and (b) shows the changes of transmittance and absorbance with respect to the wavelength of the substrate using UV 3000+ UV-VIS spectrophotometer from LABINDIA. Transmittance of about 85-95 % is obtained in the region of 300-700nm (visible region) which indicates that the film can be used for OLED and OPVs application as a substrate.

Synthesis and Characterization of Novel Siloxane Based Transparent and Flexible Substrate for Oleds 33

Optical parameters such as refractive index (n), extinction coefficient (k) are calculated for the film using the following equations (1 + R) 4R n= + − k2 (1 − R ) (1 − R)2

... (1)

k = αλ/4π) (2) where R is a reflectance, α is an absorption coefficient and λ is the wavelength. The refractive index of the substrate is found to be 1.5 throughout the entire visible region which is approximately close to glass makes it to be suitable for opto-electronic device applications.

Fig. 2: (a) Transmittance (b) Absorbance spectra of the PDMS film

Figure 3 (a) and(b) shows the DSC and TG-DTG curve (thermal characteristics) of the substrate respectively. TG-DTG curve of films shows that there is only 0.2% weight loss upto 100oC and there is a loss of 0.7% and 2% in the range of 150oC and 200oC respectively and finally at the temperature of 300oC there is a weight loss of around 5% is noted which states that the PDMS based film has better thermal stability compared to flexible plastic substrate which has temperature withstands of 150oC. Hence the synthesized film can be used for the fabrication of the OLEDs and OPVs which requires high processing temperature for the fabrication process.

Fig. 3: (a) DSC-DDSC curve (b) TG-DTG curve of the PDMS film


CONCLUSION Due to large-size applications, portability as well as low-cost production through RTR processes, flexible displays will be the ultimate choice in future. However there are many drawbacks are still there in commercialization of Opto-electronics in market due to low processing temperature, temperature dependent transparency and high gas permeability. In this paper, it is concluded that, we had reported the flexible substrate with high transparency of 85-95% in the region of 300-700nm and with improved thermal properties which make this substrate suitable for high processing opto-electronic devices. REFERENCES [1] T.-H. Han, Y. Lee, M.-R. Choi, S.-H. Woo, S.-H. Bae, B. H. Hong, J.-H.Ahn, and T.-W. Lee: Extremely efficient flexible organic light-emitting diodes with modified graphene anode, Nat. Photonics 6 (2012) 105. [2] StanislavZvanovec, PetrChvojka, Paul Anthony Haigh, ZabihGhassemlooy, Visible Light Communications towards 5G, Radio Engineering, Vol. 24, No. 1, April 2015 [3] Paul Anthony Haigh, ZabihGhassemlooy, SujanRajbhandari, IoannisPapakonstantinou, Visible Light Communications using Organic Light Emitting Diodes, IEEE Communications Magazine, (2013) [4] W. C. Tang and S. A. VanSlyke: Organic electroluminescent diodes, Appl. Phys. Lett. 51 (1987) 913.J. Van der Geer, J.A.J. Hanraads, R.A. Lupton, J. Sci. Commun. 163 (2000) 51–59. [5] M. Pope, H. P. Kallmann, and P. Magnante: Electroluminescence in organic crystals. J. Chem. Phys. 38 (1963) 2042. [6] W. C. Tang and S. A. VanSlyke: Organic electroluminescent diodes, Appl. Phys. Lett. 51 (1987) 913.J. Van der Geer, J.A.J. Hanraads, R.A. Lupton, J. Sci. Commun. 163 (2000) 51–59. [7] Crawford GP. Flexible flat panel display technology. New York: Wiley; 2005. [8] Nathan A, Chalamala BR. Special issue on: flexible electronics technology. ProcIEEE 2005;93(7–8). [9] Gasman L. OLED and paper-like display markets. Veritas et Visus, Flex Substr 2006;2(6):22–5. [10] Allen KJ. Reel to real: prospects for flexible displays. ProcIEEE 2005;93:1394–9.J. van der Geer, J.A.J. Hanraads, R.A. Lupton, The art of writing a scientific article, J. Sci. Commun. 163 (2000) 5159. [11] Z. B. Wang, M. G. Helander, J. Qiu, D. P. Puzzo, M. T. Greiner, Z. M. Hudson, S. Wang, Z. W. Liu, and Z. H. Lu: Unlockingthefullpotentialoforganiclight-emittingdiodesonflexibleplastic, Nat. Photonics 5 (2011) 753. [12] S. Kim, Y. J. Lee, K. N. Byun, B.-S. Lee, S.-Y. Jung, and J. S. Yoo: ECS Trans. 1 [35] (2006) 7. [13] Dhanapalan Shanmuga sundar and A.Sivanantharaja, High efficient plastic substrate polymer white light emitting diode, Opt Quant Electron DOI 10.1007/s11082-012-9604-x [14] Cristina I, Marc JM, Abadie. EurPolym J 2000;36:2115. [15] Sheng SH, Yen PC, Cheng KC. J Polymer 2000;41:3263. [16] Iskender Y. In: Henri B, editor. Advances in polymer science, vol. 86. Berlin: Springer-Verlag, Heidelberg Press; 1988. p. 5.

Electrochemical Sensing of 4-nitrophenol Using CeO2@SiO2 A. Padmanaban, T. Dhanasekaran, K. Giribabu, R. Manigandan, S. Praveen Kumar, G. Gnanamoorthy, S. Munusamy, S. Muthamizh, A. Stephen1 and V. Narayanan Department of Inorganic Chemistry, University of Madras, Chennai 1 Department of Nuclear Physics, University of Madras, Chennai

ABSTRACT CeO2@SiO2 nanoparticles were synthesized by thermal decomposition method. The synthesized CeO2@ SiO2 was characterised by X-ray diffraction. The morphology of the sample was investigated by (FESEM). The morphology of the CeO2@SiO2 nanoparticles was found to be in spherical shape with uniform size. CeO2@SiO2 nanoparticles were used to modify the glassy carbon electrode (GCE) and the modified electrode was used to detect 4-nitro phenol by voltammetric techniques.

INTRODUCTION The redox and catalytic properties of CeO2 are strongly influenced when it is combined with other transition metals or rare earth oxides [1]. Ceria (CeO2) is ability to shift easily between reduced and oxidized states (Ce3+/Ce4+) and to accommodate variable levels of bulk and surface oxygen vacancies [2] . In 2002, Nishikawa et al. demonstrated high performance CeO2 dielectrics because of their good interfacial properties on Si substrate [3]. The phenol and substituted phenol compounds have toxic effect on humans, animals and plants and they give an undesirable taste and odour to drinking water, even at very low concentration[4]. EXPERIMENTAL Synthesis of CeO2@SiO2 nanoparticles Ceric ammonium nitrate (Qualigens), Tetraethyl orthosilicate(TEOS) (Qualigens), Polyethylene glycol 600 (Merk), Ammonium hydroxide, Ethanol and Double distilled water. CeO2@SiO2 nanoparticles were prepared by thermal decomposition method. Ceric ammonium nitrate (1.5 mmol) and 2 mL of PEG-600 was dissolved in 30ml of double distilled water and stirred for 10 min. To the mixture, 10 mmol of tetraethyl orthosilicate was added dropwise and the pH was adjusted to10 by addition of ammonium hydroxide. The obtained precipitate was heated at 70 oC for 2 h. The resulted product was washed with water and ethanol several times. The obtained product was calcined at 750 oC for 2 h. Fig.1 shows the XRD pattern of CeO2@SiO2was determined by Rich Siefert 3000 diffractometer with Cu-Kα1 radiation (λ=1.5406Å). The observed XRD pattern compared and well matched with the V. Rajendran, K. Thyagarajah and K.E. Geckeler (eds.) Nanoelectronics and Sensors, pp. 35-38 (2015)

36 Nanoelectronics and Sensors standard JCPDS data (65-5923) confirms the formation of CeO2 phase having cubic fluorite crystal structure. Four distinct peak observed at (28.5), (33.0), (47.4), (56.3) respectively, corresponding to the reflections of (111), (200), (220), (311) plane. No reflection peak of SiO2 is observed in the pattern of CeO2@SiO2 and may be due to the formation of CeO2 over the SiO2. No other phase is observed. The FESEM image of CeO2@SiO2 was analysed by HITACHI SU6600 shown in Fig 2. The morphology of the CeO2@SiO2 is uniform spheres can be observed and the particle size is ~10 nm. CeO2 is decorated on the surface of the silica nanosphere.PEG may act as a capping agent and also inhibit theiragglomeration, forming the individual SiO2

Fig. 1: XRD pattern of CeO2@SiO2

Fig. 2: FESEM images of CeO2@SiO2

Electrochemical Sensing of 4-nitrophenol Using CeO2@SiO2 37

Fig. 3: DRS UV spectrum of CeO2@SiO2

Fig. 4: CV of bare and modified CeO2@SiO2/GCE

sphere to grow up below 10 nm.Fig. 3. shows the DRS UV vis spectrum of the CeO2@SiO2was recorded using Perkin-Elmer 650 spectrophotometer. CeO2 has a strong absorption band in the UV region 200 to 350 nm which is due to the band gap transition from valence band to the conduction band [5]. Fig.3. shows a strong absorption band at 312 nm can be attributed to the inter-band transitions.

ELECTROCHEMICAL PROPERTY Fig. 4. show cyclic voltammograms of bare and modified GCE in presence of 0.1 mM4nitrophenol in 0.1 M PBS at the scan rate of 50 mVs-1. The potential range is from -1 V to

38 Nanoelectronics and Sensors 1 V. A reduction peak at -0.81 V was observed at bare GCE in the presence of 4-nitrophenol but there is no oxidation peak. The modified CeO2@SiO2/GCE in presence of 4-NP exhibit both reduction and oxidation peaks at -0.79 V and 0.25V respectively. The reduction peak is due to the combined form of p-(hydroxyamino)phenol-p-nitrosophenol and oxidation peak is due to the formation of p-quinoamine.[6]

CONCLUSION The CeO2@SiO2 nanoparticles were prepared by a thermal decomposition method. The synthesized CeO2@SiO2 was confirmed by XRD analysis and the morphology was found to be in spherical shape with uniform size. The modified CeO2@SiO2/GCE was successfully fabricated for the determination of 4-nitrophenol. REFERENCE [1] B. M. Reddy, A. Khan, et.al., J. Phys. Chem B.,107 (2003) 11475.2. A. Trovarelli (Ed), Catalysis by Ceria and RelatedMaterials, Catalytic Science Series, vol. [2] , ImperialCollege Press, London, 2002. [3] Y. Nishikawa, T. Yamaguchi, et.al., Appl.Phys.Lett.81 (2002)4386. [4] F. Grasset, R. Marchand, et al, J. Colloid Interface Sci. 299 (2006) 726. [5] Q. Fang, X. Liang., RSC advances, 2 (2012)5370. [6] K. Giribabu, R. Suresh, et al., Analyst. 138 (2013) 5811.

Electrochemical Determination of Uric Acid by Using Tris-(1,10-Phenanthroline) Copper(Ii) Complex Modified Gce S. Praveen Kumar, K. Giribabu, R. Manigandan, S. Munusamy, S. Muthamizh, A. Padmanaban, T. Dhanasekaran, R. Suresh1 and V. Narayanan Department of Inorganic Chemistry, University of Madras, Chennai 1 Department of Chemistry, SRM University, Ramapuram, Chennai E-mail: [email protected]

INTRODUCTION More than five decades 1,10-Phenanthroline (phen) has been extensively used as a ligand. Phen, a hetero aromatic bidentative chelating ligand, forms stable complexes with various transition metal ions through the nitrogen hetero atom. The stability may be attributed by rigid planarity of phen [1]. Copper is an important biological element among the essential trace elements, It plays a fundamental role in the structure and function of a number of metalloenzymes for multiple biochemical processes in human body. Copper has better redox transformation, the ability to undergo redox transformations between two stable oxidation states [2]. Uric acid (UA) is the major nitrogenous compound in urine, it is primary excreted via for UA. The abnormal level of UA levels is a sign of various diseases like gout, hyperuricemia, or Lesch–Nyhan syndrome. Similarly, elevated level of UA is related with some other conditions such as obesity, kidney disease, diabetes, high cholesterol, high blood pressure, heart disease and including increased alcohol consumption. Thus, screening of UA is much more important in clinical process to know several diseases. SYNTHESIS OF tris-(1,10-PHENANTHROLINE) COPPER(II) COMPLEX. An absolute methanolic solution of 3 mmol, 1,10-phenanthroline (0.540 g) was taken in a beaker and it was stirred by using magnetic stirrer. To the stirred phenanthroline solution, 1 mmol methanolic solution of copper(II) chloride (0.171 g) was added by drop wise and stirred about 2 hrs. Then the reaction mixture was employed for the microwave irradiation at 320 W, for 2 min. A sky blue colour precipitate was obtained, it was collected and washed with methanol at several times.



Scheme-1 Synthesis of tris-(1,10-phenanthroline) copper(II) complex.

RESULTS AND DISCUSSION Characetrization of Copper Complex The copper complex shows three absorption peaks in electronic spectrum at 290, 450 and 750 nm due to π→π* transition, metal-to-ligand charge transfer transition and d-d transition respectively. The FT-IR spectrum shows an important characteristic band at 590 cm-1, corresponds to the stretching vibration of metal nitrogen bond. This peak conforms the complex formation between phen ligand and copper(II) metal ion (N····Cu+2). The C=N stretching frequencies of phen ligand was reported in the region of 1700 - 1650 cm-1, it exhibit at 1640 cm-1 in the copper complex. The C=N stretching frequency is generally

Fig. 1: (a) UV-Vis, (b) FT-IR, (c) Emission spectra and (d) cyclic voltammogram of copper(II) complex

Electrochemical Determination of Uric Acid by Using Tris-(1,10-Phenanthroline) ... 41

shifted to a lower frequency, indicating that bond order of C=N is decreasing due to the coordination of copper metal with the nitrogen lone pair electron. Tris-(1,10-phenanthroline) copper(II) complex shows the emission at 600 nm for the irradiation of 400 nm wave length. The emission arises due to electron transition in d-orbitals. Electrochemical activity of copper complex was examined by cyclic voltammetry (CV) at the potential range of -0.8 V to 0.8 V. The voltammogram shows an anodic peak at 0.058 V and its corresponding cathodic peak at -0.211 with the potential difference of 270 mV. It exhibit that copper complex has electrochemical activity [3, 4].

Sensing of Uric Acid by Copper Complex The glassy carbon electrode (GCE) was modified by the electrochemical polymerization of 0.1 M tris-(1,10-phenanthroline) copper(II) complex in acetonitrile solution. The copper complex modified GCE (poly-Cu-phen/GCE) was used for sensing of UA. The electrochemical behaviors of Uric acid (UA) at GCE and poly-Cu-phen/GCE were investigated by CV in phosphate buffer as background electrolyte. In the voltammogram the oxidation peak of UA at pH 7 was appears at 0.626 V (vs SCE) for bare GCE and for modified electrode it exhibit at 0.530 V, which is about 96 mV more negative than that of GCE. It must be pointed out that the oxidation peak current of UA observed on modified GCE has increased than that of bare GCE. These results indicated that poly-Cu-phen/GCE has an excellent selectivity towards UA, and the fabricated modified electrode might be applied to determine UA in real samples [5, 6].

CONCLUSION Tris-(1,10-phenanthroline)copper(II) complex was prepared by microwave irradiation method. The synthesized copper(II) complex was characterized by different spectral techniques such as FT-IR, UV-Vis and emission. Further, we developed poly-Cu-phen/GCE as a UA sensor by electrochemical polymerization method. The proposed p-Cu-phen/GCE exhibited high electrocatalytic activity towards UA.

Fig. 2: (A) Electrochemical polymerization of copper complex and (B) Sensing of UA at (a) bare GCE without UA (b) bare GCE (c) modified GCE presence of 0.1 mM UA in 0.1 M PBS

ACKNOWLEDGMENT One of the authors (S.P.K) wish to thank Department of Science and Technology (DST), Government of India for the financial assistance in the form of INSPIRE fellowship (Inspire Fellow no: 130032) under the AORC scheme.


REFERENCE

[1] L. A. Summers, Adv. Heterocycl. Chem., 22, 1, 1978. [2] W. Kaim, J. Rall, Bioelement, Angew. Chem. Int. Ed. Engl. 35, 43, 1996. [3] K. Inoue, T. Namiki, Y. Iwasaki, Y. Yoshimura, H. Nakazawa, J. Chromatograph. B, 785, 57, 2003. [4] S.P.Kumar, R.Suresh, K.Giribabu, R.Manigandan, S. Munusamy, S. Muthamizh, V. Narayanan, Spectrochim. Acta A, 139, 431, 2015. [5] A. Safavi, N. Maleki, O. Moradlou, F. Tajabadi, Anal. Biochem., 359, 224, 2006. [6] G. Dryhurst, N.T. Nguyen, M.Z. Wrona, R.N. Goyal, A. B. Toth, J.L. Owens Jr., H.A. Marsh, J. Chem. Educ., 60, 315, 1983.

Nanocrystalline Tin Oxide Synthesized by Co-Precipitation Method for Highly Selective Ammonia Gas Sensor Shrabani Mondal, Rashmi Madhuri1 and Prashant K. Sharma Functional Nanomaterials Research Laboratory, Department of Applied Physics, Indian School of Mines, Dhanbad 1 Department of Applied Chemistry, Indian School of Mines, Dhanbad E-mail: [email protected]

ABSTRACT In the present work nanostructured SnO2 with different Na doping concentration was synthesized by simple co-precipitation route followed by heat treatment at 600°C for 2h. Ammonia sensing characteristics of the prepared samples at various temperatures were examined for a wide range (10-100 ppm) of gas concentration. Sn0.90Na0.10O2 exhibited far better response compared to pure SnO2. Developed Sn0.90Na0.10O2 sensor showed lower detection limit of 10 ppm with response ∼20%. Comparative sensing response for other common gases like ethanol, butane in presence of NH3 was also investigated at optimum operating temperature; 150°C. Sn0.90Na0.10O2 sensor has 3 times better selectivity than ethanol and 5 times than butane. Response and recovery time for 10 ppm of NH3 is 39s and 104s. This study suggests that Na incorporation in SnO2 was beneficial for sensing performances.

Keywords: SnO2, Nanostructures, X-ray diffraction, Gas sensor.

INTRODUCTION Metal oxide (MOS) gas sensors have shown great impact in environmental monitoring as well as human safety. After accomplishing so many efforts to facilitate advance devices it has been accepted undoubtedly that nanostructured MOS are far superior in comparison to solid state MOS gas sensors in terms of responsivity, selectivity, dimensionality, weight, recovery time and cost [1]. Nanostructured MOS gas sensors such as TiO2 [2], ZnO [3] etc. have been investigated extensively as sensing materials in last decade. In 1962, T. Seiyama et al. have first proposed SnO2 as a gas sensing material [4]. Since that period, eco-friendly nature and high sensitivity at low gas concentration has established SnO2 the favorable one among other MOS. It is well known that gas sensing is a surface dominated adsorption phenomenon. So the key factor of tailoring high quality sensing material is to optimize the surface morphology, decrease in grain


44 Nanoelectronics and Sensors size, controlling surface defects or pores, promotes high surface area etc.. Till date a huge amount of research has been devoted on SnO2 to improvise its sensing responses. Addition of different transition metal ions like Cu2+, rare earth ions such as Tb3+, Eu3+ has been performed to enhance the reaction speed of the SnO2 material [5]. In case of n-type MOS low oxygen vacancy [6] always restricts the rate of reaction resulting poor sensor response. We have preferred alkali metal (Na) as dopant aiming to appreciably increase the adsorption sites on the sensor surface in order to promote the gas diffusion process further. To the best of our knowledge so far no experiment has been conducted on Na doped SnO2 for gas sensing application. In this work we have investigated the NH3 sensing properties and also the operating conditions are optimized. The developed sensor has shown excellent selectivity towards NH3 gas.

SAMPLE PREPARATION Na doped SnO2 sensing materials were prepared by simple chemical route. To start with, required amount of sodium hydroxide for 0 to 10 mol% of Na doping is dissolved in 100 ml of stannic chloride (1 gm) aqueous solution under continuous stirring for 15 min. Next ammonia solution was added drop wise under vigorous stirring until pH of the entire solution became neutral. The final milky white solution was centrifuged, washed and the filtrate was oven dried for 6h at 100°C followed by calcination at 600°C. Samples were named as S0, S1 and S10 which corresponds 0, 1 and 10 mol% Na content, respectively. Prepared samples were characterized by XRD and FESEM. RESULTS AND DISCUSSION XRD patterns of the synthesized powder samples are shown in Fig. 1a. Intense and quite sharp diffraction peaks at the 2q positions are well matched with the JCPDS file no 88-0287 and confirms the polycrystalline nature of the samples. Meanwhile, there is no trace of dopant related peaks which concludes that Na doping in SnO2 precursor has not affected the crystal structure at all. JCPDS data indicates the formation of tetragonal structure of SnO2 with lattice constants a = b = 4.737 Å, c =3.187 Å, a= β = γ, space group P42/mmm. Fig. 1b represents the FESEM image of the S0 sample surface. The morphology of all 3 samples is same (So only one of them is shown here). Spherical shaped with average diameter of 600 nm is observable. Another noticeable thing is that the surfaces of the spheres are not totally smooth but there is a distribution of tiny particles. SAED pattern of S0 is displayed in Fig. 1b inset. Diffraction spots arranged in a manner of circular rings indicates the formation of polycrystalline nature of the samples. This observation is consistent with the results of the XRD analysis. Gas sensing responses of the prepared samples has been carried out in a homemade set up using four different reducing probe gases viz. ammonia, methanol, ethanol and butane. Samples are taken in the form of pellet (Fig. 1f (inset)). To start with, the response of S0, S1 and S10 towards 100 ppm ammonia is checked at a fixed temperature, 100 °C (Fig. 1c). S10 sensor shows maximum response so further tests have been performed using this sensor only. Fig. 1d shows the response of S10 sensor for different ammonia concentration (10-100 ppm) in the temperature range 50-500°C. Graph shows increment-maximum-decrement type behavior and at 150°C the sensor exhibit maximum response. Hence the next all experiments are conducted at this optimum operating temperature, 150°C. Also the response increases with the increase in gas concentration however this increase is non-linear with temperature. This observation is quite expected. Because an increase in gas concentration allows larger number of gas molecule to interact with the surface and accordingly the response rises. Response time

Nanocrystalline Tin Oxide Synthesized by Co-Precipitation Method for Highly Selective ... 45

for 10 ppm ammonia is found to be 39 sec (Fig. 1e). Selective detection of a particular gas is the challenging issue for any oxide gas sensor. The selectivity is estimated as the ratio of maximum response of interfering gas to maximum response of test gas. In order to investigate the ammonia selectivity of the developed sensor, we have tested S10 against the mentioned probe gases for 100 ppm at 150°C (Fig. 1f). Studies shows that S10 sensor has highest response for ammonia and for other test gases response is few times lesser, (ammonia/ethanol)res=3, (ammonia/methanol)res=5, (ammonia/butane)res=5.1.

Fig. 1: (a) XRD spectra of SnO2 samples (b) FESEM and SAED (inset) image of S0. (c) Response of SnO2 samples with varying doping concentration. (d) Response at different operating temperature, (e) transient response curve and (f) selectivity of S10 sensor. Inset of (f) represents the schematic diagram of SnO2 palette.

This improved response of S10 sensor can be understood easily by considering the sensing mechanism which is particularly based on the modulation of electrical resistance in presence of test gas and ambient atmosphere. At elevated temperature the sensor surface is covered with a number of adsorption sites specifically different oxygen species. Consequently a space charge layer is developed which hinders the conduction mechanism/electron mobility. As soon as the reducing gas ammonia is exposed to the surface, the gas molecule is trapped by these adsorption sites and releases the electrons to conduction band of the sensor material. Accordingly the resistance is regulated. The number of electrons taken part in the solid-gas interface for different gases might have played an important role behind this selective nature of S10 sensor.

CONCLUSIONS Na doped SnO2 based ammonia sensor is developed by simple chemical process from stannic chloride precursor. Structural and sensing properties of the prepared materials are analyzed. 10 mol% Na doped sample has shown highest sensing response at relatively lower operating temperature, 150°C. Lowest detection limit of the fabricated sensor is 10 ppm of ammonia. Selectivity of the sensor towards ammonia in presence of 3 interfering gases is examined. The response for ammonia is almost 3-5 times greater than ethanol and butane. Present work concludes that Na incorporation in SnO2 has effectively enhanced the sensor performance.


ACKNOWLEDGEMENT Financial support from DST-SERB (Ref. No.: SR/FTP/PS-157/2011, Ref. No.: SB/FT/CS-155/2012), DAE-BRNS (Ref. No.: 34/14/21/2014-BRNS) and ISM (FRS/34/2012-2013/APH, FRS/43/2013-2014/ AC) are thankfully acknowledged. REFERENCES [1] Hsueh, T.J., Hsu, C.L., Chang, S.J., Chen, I.C., Laterally grown ZnO nanowire ethanol gas sensors, Sens Actuator B., 126, 473-477, 2007. [2] Han, Z., Wang, J., Liao, L., Pan, H., Shen, S., Phosphorus doped TiO2 as oxygen sensor with low operating temperature and sensing mechanism, Appl Surf Sci., 273, 349-356, 2013. [3] Shinde, S.D., Patil, G.E., Kajale, D.D., Gaikwad, V.B., Jain, G.H., Synthesis of ZnO nanorods by spray pyrolysis for H2S gas sensor, J Alloy Compd., 528, 109-114, 2012. [4] Seiyama, T., Kato, A., Fujiishi, K., Nagatani, M., A new detector for gaseous components using semiconductive thin films, Anal Chem., 34, 1502-1503, 1962. [5] Elhouichet, H., Othman, L., Moadhen, A., Questali, M., Roger, J. A., Enhanced photoluminescence of Tb3+ and Eu3+ induced by energy transfer from SnO2 and Si nanocrystallites, Mater Sci Eng B., 105, 8-11, 2003. [6] Morrison, S.R., Selectivity in semiconductor gas sensors, Sens Actuators B., 12, 425- 440, 1987.

Multi-Walled Carbon Nanotubes for Sensor Applications Khurshed A. Shah, Feroz A. Najar and M. Shunaid Parvaiz Nanomaterials Research Laboratory, Department of Physics, Govt. Degree College for Women, Anantnag (J&K) E-mail: [email protected]

ABSTRACT In this study Multi-Walled Carbon Nanotubes (MWCNTs) were chemically treated in order to investigate the structural and chemical changes in them and to use them for sensor applications. Raman spectroscopic analysis reveals that the chemically treated MWCNTs are useful for chemical and gas sensor applications.

Keywords: Multi-Walled Carbon nanotubes, Chemical treatment, Raman Spectroscopy, Sensor Applications.

INTRODUCTION The last decade has witnessed vigorous research activity in the field of Carbon nanotubes (CNTs) due to their extraordinary properties. There are various structures of carbon nanotubes (CNTs) depending on how the tube is rolled up and it is defined by the chiral index (n, m) and its quantum properties depend on the diameter and chirality [1,2]. It exists both in single and multi-walled form. Isolated single-wall carbon nanotube normally does not occur. Mostly group of SWNTs led to formation of bundles of tubes, so-called nanoropes containing between 20 to hundred individual tubes [3, 4]. There are various applications of CNTs which includes sensors as well [5, 6]. The CNTs as produced by the various synthesis techniques contain various impurities [7] and for many applications these impurities have to be separated from the carbon nanotubes before they can be used for sensor applications. Purification techniques include air oxidation, acid treatment, annealing, micro filtration, sonication, ferromagnetic separation, functionalization, and chromatography techniqueshave been devised in order to improve the quality and yield of carbon nanotubes[8]. Among these methods in this study the chemical method has been chosen inorder to attach functional groups to CNTs. The results show that carboxylic groups are attached with the carbon nanotubes after chemical treatment by using Raman spectroscopy. These carboxylic groups are very useful for chemical and gas sensing applications.



EXPERIMENTAL DETAILS As produced multiwall carbon nanotubes (MWCNTs) were treated in a mixture of H2SO4, HNO3 under a refluxing condenser with magnetic stir for a time period of 5hr. After refluxing, the mixture was cooled to room temperature, diluted with methanol andfiltered through whatman filter paper.The dried sample wasthen studied by Raman Spectrometer. RESULTS AND DISCUSSION Figure 1 shows Raman spectra of treated CNTs excited with the 532.8nm laser line.

Fig. 1: Raman spectra of chemically treated carbon nanotube sample with excitation wavelength 532.8nm.

In case of CNTs defect induced band (D band) and graphitic band (G band) are usually found in the range of 1332-1365cm-1and1516-1585cm-1respectively. From Figure 1 it is seen that the twopeaks were observed at 1356 cm-1 (D band) and at 1577 cm-1 (G band) showing the characteristics of CNTs, when the acid treatment of CNTs was conducted Furthermore it is seen that the peak position does not change indicating that the acid treatment does not destroy the structure of CNTs [9].The intensity ratio of D-to G-mode (ID/IG) values of chemically treated and as-grown MWCNTs increases. As observed from Raman spectra the ratio between the intensity of the D band and the G band is 0.68.The ratio between the intensity of G’ band to G band is 0.43. These results are generally attributed to the presence of more structural defects [10]. The adsorption of functional groups increases the number of

Multi-Walled Carbon Nanotubes for Sensor Applications 49

defects in the structure of nanotubes, increasing the ratio ID/IG and providing the early decomposition of CNTs. These results indicate certain insertion of defects and/or break on the structure of nanotubes and attach some functional groups which are useful for chemical and gas sensor application as many researchers studied[11].

CONCLUSION As produced MWCNT sample was characterized by Raman spectroscopy after chemical functionalization. The analysis of Raman spectra indicated the modification of structure of CNTs after chemical treatment and increase in defect sites.Some carboxylic groups are attached with these defect sites which are very useful for chemical and gas sensing applications. ACKNOWLEDGEMENTS This work has been financially supported by the Department of Science and Technology, Science and Engineering Research Board (DST-SERB), Govt. of India (Project grant No.SB/S2/CMP36/2013). REFERENCES [1] Ebbesen, T.W., Carbon Nanotubes : Preparation and Properties, CRC Press, Boca Raton, Florida, 1997. [2] Rao, A.M., Richter, E., Bandow, S., Chase, B., Eklund, P.C., Williams, K.A., Fang, S.,Subbaswamy, K.R.,Menon, M.,Thess, A., Smalley, R.E., Dresselhaus, G., and Dresselhaus, M.S., Diameter-Selective Raman Scattering from Vibrational Modes in Carbon Nanotubes, Science,275, 187-91, 1997. [3] Iijima, S., and Ichihashi, T.,Single-Shell Carbon Nanotubes of 1-nm Diameter, Nature, 363, 603-605, 1993. [4] Journet, C., and Bernier, P.,Production of Carbon Nanotubes, Appl. Phys. A, 67, 1-9, 1998. [5] Liu, J.H., Liu, J.Y., Yang L.B., Chen, X., Zhang, M.Y.,Meng, F.L., Luo, T and Li, M.Q.,NanomaterialAssisted Signal Enhancement of Hybridization for DNA Biosensors: AReview, Sensors, 9, 7343-7346, 2009. [6] Balasubramanian, K., Burghard, M., Biosensors Based on Carbon Nanotubes, Anal. Bioanal. Chem., 385, 452-468, 2006. [7] Koshio, A., Shiraishi, M., Kobayashi, Y., Ishihara, M., Koga, Y., Bandow, S., Iijima, S., &Kokai, F., Modification of Carbon Nanotubes by Laser Ablation of Copper, Chemical Physics Letters, 396, 410-414, 2004. [8] Agboola, A.E., et al.,Conceptual Design of Carbon Nanotube Processes, Springer-Verlag, 9, 289-311, 2007. [9] Osorio,A.G., Silveira,I.C.L., Bueno,V.L. & Bergmann,C.P.,H2SO4/HNO3/HCl-Functionalization and Its Effect on Dispersion of Carbon Nanotubes in Aqueous Media, Applied Surface Science, 255, 24852489, 2008.

50 Nanoelectronics and Sensors [10] Tian, Z.Q., Jiang, S.P., Liang, Y.M. &Shen, P.K., Synthesis and Characterization of Platinum Catalysts on Multiwalled Carbon Nanotubes by Intermittent Microwave Irradiation for Fuel Cell Applications, J. Phys Chem.B, 110, 5343-5350, 2006. [11] Bekyarova, E., Davis,M., Burch,T., Itkis, M.E., Zhao, B., Sunshine,S., and Haddon,R.C.,Chemically Functionalized Single Walled Carbon Nanotubes as Ammonia Sensors,J. Phys. Chem. B, 108, 1971719720, 2004.

Synthesis and Characterization of Tin Nano Metal Particles Doped Conducting Polymer Composite G. Sowmiya and G. Velraj1 Department of Physics, Periyar University, Salem, Tamilnadu Department of Physics, Anna University, Chennai, Tamilnadu E-mail: [email protected]

1

ABSTRACT In the present study, Sn nanoparticles doped Polypyrrole (NPs) were synthesized using chemical oxidation polymerization method. The physical characterization of the synthesized PPy and n-SnPPy nanocomposite were studied by FT-IR, XRD, FESEM with EDX and electrical conductivity methods. The FT-IR analysis confirms the chemical structure of Polypyrrole and n-SnPPy nanocomposite. XRD pattern shows that the PPy and the n-SnPPy nanocomposite are amorphous and the latter case it becomes crystalline in nature. Sn NPs were of spherical morphology having crystallite size of 35.68 nm as obtained from Scherrer’s formula using most intense peak of XRD. The FESEM micrographs indicate the morphological modifications due to doping. The A.C electrical conductivity of pure PPy and n-SnPPy nanocomposite has been studied using two probe method. The results obtained are found to be n-SnPPy nanocomposite had better electrical conductivity than the PPy. The enhancement in the electrical conductivity of the n-SnPPy nanocomposite indicated the incorporation of nano tin particles in the sample.

Keywords: Polypyrrole, FT-IR, XRD, FESEM with EDX and A.C. electrical Conductivity

INTRODUCTION In recent years, conducting polymers such as polypyrrole, polythiophene and polyaniline have received much attention because of their potential applications in chemical and biological sensors, electronic devices, as well as efficient and low cost solar cells, due to their remarkable mechanical and electrical properties such as low operating temperature, low cost, flexibility and easy processability and so on [1–7]. In the recent years, synthesis and application of conducting polymer nanocomposite with various inorganic nanoparticles such as TiO2[8], MnO2[9], Cu2O [10], ZnO[11] have been reported. The present paper reports the synthesis of polypyrrole nanocomposite by the incorporation of nano tin particles in the polypyrrole matrix. To achieve this goal, ppy and n-SnPPy have been synthesized by chemical oxidation method. These polymer hybrid nanocomposite have been characterized using various techniques. The structural properties were analyzed by FT-IR and XRD. The interaction of nano tin composite with


52 Nanoelectronics and Sensors the polypyrrole has been visualized using the field emission Scanning electron microscope (FESEM). The electrical conductivity measurement was studied using two probe technique.

EXPERIMENTAL METHODS Synthesis of Polypyrrole The Polypyrrole was prepared by using chemical oxidative polymerization method. H2SO4 is used as a dopant. K2Cr2O7 is used as an oxidant. The Pyrrole monomer solution was stirred at ice temperature and the H2SO4 solution was added drop wise into this Pyrrole monomer solution one by one. The reaction mixture was stirred one hour at constant rpm value. The solution of 0.5 M of K2Cr2O7 was added drop wise into the mixture.This reaction mixture kept under the ice temperature and stirred constant RPM value at 24 hours continuously. The black precipitate was separated out by filtering. The final product was dried in Laboratory oven at 100ºC for 90 minutes. Finally the product was ground into fine powder using mortar and pestle. Synthesis of n-SnPPY Nanocomposites The 200mg of PPy powder was mixed with 100ml of distilled water and the mixture was added to 200mg of Nano tin particle and stirred constant RPM value at 12 hrs continuously. Then the precipitate was separated out by filtering. The final suspension was dried in laboratory oven at 100ºC for 60 m.

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RESULTS AND DISCUSSION FT-IR Analysis The FT-IR spectra of synthesized PPy and n-SnPPy are shown in the Fig: 1 & 2. The very strong band of 3124cm-1 is due to C-H stretching in PPy. The medium band around 1697cm-1corresponds to PPy is attributed to in plain and out-of-plain bending vibration. The characteristic peak at 1541cm-1 corresponds to PPy ring vibration. The vibration peak at 1457cm-1 attributed to the C-N and C-C symmetric and asymmetric stretching vibration in the pyrrole ring vibration [12]. The strong bands in the 1200-1000cm-1 region can be referred to over tone bands of Sn-O-H structure units in polycrystalline structures, but they could be ascribed also anti symmetrical stretching vibrations. The peaks at very strong band at 1179cm-1 corresponds to C-N stretching vibration. The very strong peak at 1056cm-1 is attributed to (=C-H) in plane vibration. The strong band at 932cm-1 region could be assigned to symmetrical and anti symmetrical stretching vibration [13]. The very strong peak at 883cm1 is due to the C-H out of plane bending in PPy. A week band around 421cm-1 reflect vibrations of Sn(IV)-O and Sn(II)-O bonds in mixed Sn(II) Sn(IV)oxides. The peaks observed in the present work match well with the previous literature [12, 13] confirming the formation of PPy and n-SnPPy.

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Synthesis and Characterization of Tin Nano Metal Particles Doped Conducting Polymer Composite 53

XRD ANALYSIS 1600

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X-ray diffraction pattern of Polypyrrole (PPy) and Nano tin composite of polypyrrole (n-SnPPy) are shown in Fig 3 and 4. The XRD spectra showed that the PPy is amorphous in nature. The broad amorphous diffraction peak which appears at 2Ɵ = 22.85º. In Fig: (4) shows that the XRD pattern of n- SnPPY. The sharp peaks are at about 30.49º, 31.90º, 43.73º, 44.76º and 55.33ºcan be associated with (200), (101), (220), (211) and (301) respectively, which attributed clearly Sn nano particle are existing in PPy matrix. XRD spectra showed that the n- SnPPy is crystalline in nature. This matches well with JCPDS, tin file No. 89-2958. The n-SnPPy product shows tetragonal body centerted, which are in good agreement with the literature. The average crystalline size for this n-SnPPy is found to be 35.68 nm.

FESEM WITH EDX ANALYSIS The morphology of the obtained PPy & n-SnPPy nanocomposites has been studied through FESEM and the images are shown in Fig 5(a) & (b) respectively. The high maginification FESEM image reveals the presence of nano tin particles uniformly distributed throughout the composite sample and nano tin Particles were found to be spherical in shape and there is some agglomeration also observed in the image, which may be due to annealing of Polypyrrole (PPy) was analyzed using


EDX analysis. The weight percentage of each element is given in Table 1& 2. Fig: 6(a) & (b) shows the EDX spectra of PPy & n-SnPPy. While the EDX result proved the existence of Sn nano particles. The elemental concentration of

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Fig: 5: FESEM image of (a)PPy and (b) n-SnPPy cps/eV

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Element SK OK KK

Weight% 53.59 37.21 9.20

Atomic% 39.49 54.95 5.56

Table 2: Elements present in n-SnPPy

Element Weight% Atomic% SnK 53.92 13.96 OK 43.52 83.59 SK 2.56 2.45 n-SnPPy particle shows the presence of tin and oxygen elements and it confirms the stoichiometry of Nano Particles. The average size of spherical Sn nano particles is in the range of 1µm.

Synthesis and Characterization of Tin Nano Metal Particles Doped Conducting Polymer Composite 55

ELECTRICAL CONDUCTIVITY ANALYSIS Conductivity measurements have been performed by a typical two probe technique. The A. C electrical conductivities of PPy and n-SnPPy are shown in Fig 7 and 8. The A.C conductivity of pure PPy is found to be 8. 2090 × 10-9 S/cm, where as the conductivity of n-SnPPy is 1.9655 × 10–7 S/cm. When we compare the A.C conductivities of pure PPy with n-SnPPy, the conductivity has been increased by two order increase in A.C conductivity is there when we compare pure PPy with n-SnPPy. The result shows that nano composite posses better electrical conductivity than pure PPy. This enhanced conductivity of n-SnPPy is due to incorporation of metal particles into the polymer matrix. “After doping, the increase in the A.C conductivity of n-SnPPy may be due to the even distribution of nano particles and increase in crystallite density in unit space which is evidenced by the XRD Fig.4 & 5. 6.0x10-6

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The combination of amorphous and crystalline structure in the composite material may also be the reason for improved conductivity [14].”

CONCLUSION Polypyrrole (PPy) and nano tin doped Polypyrrole composite (n-SnPPy) were synthesized by adopting a facile chemical oxidation polymerization method. The synthesized Polypyrrole (PPy) and n-SnPPy were characterized using FT-IR spectroscopy. The electrical conductivity measurements were investigated by two probe method using graphite for ohmic contact. The XRD figure shows that the PPy and n-SnPPy are amorphous in nature and crystalline in nature respectively. The average crystalline size of n-SnPPy was found to be 35.68nm. The FESEM morphology showed that the PPy and n-SnPPy has the morphological modification due to doping and EDX study reveals that the Sn nanocomposites is evenly distributed through the polymer matrix. The electrical conductivity of both the sample PPy and n-SnPPy was discussed in detail. The achieved results showed that the n-SnPPy had better electrical conductivity than pure polypyrrole (PPy) indicated the incorporation of tin nano composite in the polypyrrole sample. ACKNOWLEDGEMENTS The author is very much thankful to instrumentation center, Bharathiyar University for the instrumentation facility of FESEM with EDX. One of the authors is thankful to the Periyar University for the financial assistance through University Research Fellowship. REFERENCES [1] B. Adhikari, S. Majumdar, Polymers in sensor applications, Progress in Polymer Science 29 699–766 (2004).

56 Nanoelectronics and Sensors [2] M.A. Chougule, et.al. Facile and efficient route for preparation of polypyrrole-ZnO nanocomposites: microstructural, optical and charge transport properties, Journal of Applied Polymer Science 125 1418–1424 (2012). [3] M. Woodson, J. Liu, Guided growth of nano scale conducting polymer structures on Surfacefunctionalized nanopatterns, Journal of the Amer-ican Chemical Society 128 3760 – 3763 (2006). [4] D. K. Bandgar, D. M. Jundale, G. D. Kuspe, V. B. Patil, Facile and novel route for preparation of nanostructured polyaniline (PANI) thin films, Journal of Applied Nanoscience (2013), http://dx.doi. org/10.1007/ s13204-012-0175-8. [5] G.D. huspe, D. K. Bandgar, ShashwatiSen, V. B. Patil, Fussy nanofi-brous network of polyaniline (PANi) for NH3 detection, Synthetic Metals 162 1822 – 1827 (2012). [6] Q.H. Li, J. H. Wu, Q.W. Tang, Z.Lan, P. J. Li,et.al, Application of Microporous polyaniline counter electrode for dye-sensitized solarcells, Electrochemistry Communications 10 1299 – 1302 (2008). [7] S. G. Pawar, S. L. Patil, A. T. Mane, B. T. Raut, V. B. Patil, Growth, characterization and gas Sensing properties of polyaniline thin films, Archives of Applied Science Research 1 (2) 109 –114 (2009). [8] Babazadeh, M.; Rezazad Gohari, F.; Olad, A. J. Appl. Polym. Sci. 123, 1922-1927 (2012). [9] Ni, W.; Wang, D.; Huang, Z.; Zhao, J.; Cui, G. Mater. Chem. Phys. 124, 1151-1154 (2010). [10] Wang, X.; Chen, G.; Zhang, J. Catal. Commun., 31, 57-61(2013). [11] Batool, A.; Kanwal, F.; Imran, M.; Jamil, T.; Siddiqi, S.A. Synth. Met. 161, 2753-2758 (2012). [12] Arora k, chaubey A. Singhal R, Singh R.P, Pandey M.K, et.al, Application of electrochemically prepared polypyrrrole- polyvenlsul-phonate films to DNA:biosensors, Bioseens Bioelectron;21:1777-83(2006). [13] S. Ram, K. Ram, IR and Raman studies and effect of γ radiation on crystallization of some lead borate glasses containing Al2O3,J.of Material science, 23, ,4541- 4546(1989). [14] Straumal B.B, Protasova S.G, Mazilkin A.A, Baretzky B, Myatiev AA, et al. Amorphous interlayers between crystalline grains in ferromagnetic ZnO films. Mater Lett 71:21–4; 2012.

CaSiO3: Pr3+ Nanophosphors: Propellant Combustion Synthesis, Photoluminescence Properties for Wled’s R.B. Basavaraj, H. Nagabhushana, S.C. Sharma1 and B. Daruka Prasad2 1

C.N.R. Rao Centre for Advanced Material Science, Tumkur University, Tumkur Dayananda Sagar University, ShavigeMalleshwara Hills, Kumaraswamy Layout, Bangalore 2 Department of Physics, B M S Institute of Technology, Yelahanka, Bangalore

ABSTRACT CaSiO3:Pr3+nanophosphors were prepared by low temperature solution combustion method. The X-ray diffraction results evident that CaSiO3 phosphor shows pure single monoclinic phase. The average crystallite size was estimated using Scherer’s formula and W-H plots were found to be in the range of 25-35 nm. The SEM micrographs show high porosity and irregular shaped particles. Photoluminescence studies for all the samples under investigation shows the spectra mainly consists of manifolds arising from the emission of the 3P0 state to the 3H4,5,6 and 3F2 states in the visible region near 550, 606, and 650 nm respectively and a weak peak at 530 nm due to 3P1 → 3H4 transition. Nanophosphors show an intense yellow-orange emission with CIE coordinates (0.54, 0.45) with average correlated color temperature value 2152K. The present study demonstrates that the prepared samples are quite useful for display applications.

Keywords: CaSiO3: Pr3+nanophosphors; Combustion method; Photoluminescence.

INTRODUCTION There is a huge demand of phosphors of high performance displays and lamps with great energy saving capability. The phosphors can be used in various applications namely light emitting diodes (LEDs), field emission displays (FEDs) and plasma display panels (PDPs) [1–3]. The doping of rare-earth (RE) ions in a suitable host has always remained the most popular way to achieve excellent luminescence properties [4–6]. Self-quenching of the luminescence from the1D2 or 3P0 emitting levels of Pr3+ is a commonly observed phenomenon. That can be used in different types of light emitting devices. In the present work CaSiO3:Pr3+has been prepared by solution combustion route and the final product was well characterized.



EXPERIMENTAL CaSiO3:Pr3+(1-11mol %) nano phosphors were synthesized by solution combustion technique using Oxalyl di-hydrazine (ODH) as a fuel. Calcium nitrate (Ca (NO3)2.6H2O), silica fumes (SiO2), Praseodymium nitrate (Pr(NO3)3) and ODH (C2H6N4O2) were used as the starting materials. The stoichiometry of the composition was calculated based on the total oxidizing and reducing valencies of oxidizer and the fuel then they were dissolved in double distilled water.The mixture was introduced into a pre-heated muffle furnace maintained at 500 ± 10 °C. The reaction mixture liberates gaseous products and then the final product was calcined to 950 °C for 3h. RESULTS AND DISCUSSION Fig. 1 shows the PXRD patterns of undoped and Pr3+(1-11 mol %) doped CaSiO3 NPs. All the diffraction peaks of CaSiO3 sample has perovskite structure belonging to monoclinic system (JCPDS No. 84-0655)[6].The crystallite size was estimated by Scherer’s method and it was found to be in the range of 30 – 40 nm. JCPDS CARD NO 84-0655

11 mol% 9 mol%

Intensity(a.u)

7 mol% 5 mol% 3 mol% 1 mol%

10

15

20

25

30

35

40

45

50

Undoped

(122)

(522) (040) (421)

(402) (122) (601) (621)

(002) (202)

(400)

(320)

55

2θ (degree)

60

65

70

75

80

Fig. 1: PXRD patterns of CaSiO3:Pr3+ (1-11 mol %).

Fig.2 (a, b) shows the surface morphology of 3 mol % Pr3+ doped CaSiO3 nanophosphor was studied using SEM. It was clearly observed that, phosphor containing spherical shaped agglomerated particles having various sizes. The structural information of the CaSiO3: Pr3+ (3 mol %) NPs are further investigated by TEM, HRTEM and Selected Area Electron Diffraction (SAED) shown in Fig.3 (a, b and c). It was evident from the Fig.3a that, the particles are agglomerated in nature with average particle size was found to be in the range of 25 – 30 nm. Fig.3b shows HRTEM with d-spacing found to be 0.3972 nm. Fig.3c shows the selected area electron diffraction (SAED) image, reflects a distinct ring pattern which was an evidence for the polycrystalline behavior of the as-prepared nanoparticles.

Casio3: Pr3+ Nanophosphors: Propellant Combustion Synthesis, Photoluminescence Properties for wled’s 59

a

Fig. 2 SEM micrographs of Pr3+ (3 mol %) doped CaSiO3nanophosphors.

a

b

c

d = 0.3972 nm

Fig. 3 TEM (a), (b) HRTEM and (c) SAED image of CaSiO3:Pr3+ (3 mol %) NPs.

Photoluminescence Studies 6x106

λexi = 447 nm

3

P0

3

a- 1 mol% Pr b- 3 mol% Pr3+ c- 5 mol% Pr3+ d- 7 mol% Pr3+ e- 9 mol% Pr3+ f- 11 mol% Pr3+

5x106 6

4x10

3x106 2x106 1x106

H6 PL Intensity(a.u)

PL Intensity(a.u)

3+

3 mol%Pr3+ λexi = 612 nm

3.5x106

P0

H4

3

P2

447 nm

3.0x106

2.5x106 430

440

450

460

Wavelength(nm)

a bc de f 3

3

3

P0

3

H4

3

3

F2

P0

3

F3

0 500

550

600

650

Wavelength(nm)

700

750

Fig. 4: PL emission spectrum of CaSiO3:Pr3+ (1-11 mol %) (Inset: the excitation spectra).

The excitation spectra of Pr3+:CaSiO3 consist of peak centered at 447 nm (3H4 → 3P2) (Inset Fig.4) [8]. Fig. 4 shows the PL emission spectra excited at 447 nm. According to the energy level positions of Pr3+ions, the emission bands observed around 550, 612, 650 and 733 nm were attributed to the 3P0→3H4,

60 Nanoelectronics and Sensors P0→3H6, 3P0→3F2 and 3P0→ 3F4 transitions respectively [9].It was observed that maximum emission intensity of CaSiO3:Pr3+ phosphor appears at 3 mol %. At higher concentration, the luminescence intensity reduces contrarily owing to concentration quenching effect due to the energy transfer from one activator to the neighboring ion. The emission color of CaSiO3:Pr3+nanophosphors were investigated by using the 1931 CIE (Commission Internationale de L’Eclairage) system. The CIE coordinates ofCaSiO3:Pr3+located in orange-red region (Fig. 5a). Further, the calculated average CCT value ofnanophosphorswere found to be ~ 2152 Kwhich was within the range of vertical daylight (Fig. 5b). The phosphor might be a potential candidate for display applications. 3

0.6

CaSiO3:Pr3+ (1-11 mol %)

0.5

~ 2152 K

V'

0.4 0.3 λexc- 447 nm

0.2

mol % 1 3 5 7 9

0.1

11

0.1

0.2

0.3

0.4

U' 0.28105 0.28309 0.28293 0.2929 0.31113 0.34378

V' 0.5530 0.5527 0.5527 0.5514 0.5489

CCT 2342.4 2313.7 2315.9 2184.0 1983.0

0.5446 1772.50

0.5

0.6

U'

Fig. 5: CIE and CCT diagrams of CaSiO3:Pr3+ (1-11 mol %).

CONCLUSIONS CaSiO3:Pr3+ (1-11 mol %) nanophosphors were synthesized by a solution combustion method using ODH as fuel. The diffraction patterns of the nanophosphors were indexed to monoclinic single phase with average crystallite size in the range 30-40 nm. The emission peaks ascribed to 3P0→3H4, 3P0→3H6, 3 P0→3F2 and 3P0→ 3F4. Based on CIE and CCT coordinates, the phosphor materials can be a good candidate for the display device applications.

ACKNOWLEDGEMENTS Authors HN and BRB thanks to the DST-SERB (FAST TRACK) SR/FTP/PS -135/2010, New Delhi, India, for providing financial assistance. REFERENCES

[1] W. N. Wang, F. Iskandar, K. Okuyama and Y. Shinomiya, Adv. Mater., 2008, 20, 3422. [2] F. Du, R. Zhu, Y. Huang, Y. Tao and H. Jin Seo, DaltonTrans, 2011, 40, 11433. [3] J. Choi, T. K. Tseng, M. Davidson and P. H. Holloway, J. Mater. Chem., 2011, 21, 3113. [4] C. Feldmann, T. Justel, C. Ronda and P. Schmidt, Adv. Funct. Mater, 2003, 13, 511. [5] T. Justel, Nano scale, 2011, 3, 1947. [6] R.B. Basavaraj et al. / Materials Science Forum Vols. 830-831 (2015), 612-615. [7] Rai, V. K.; Kumar, K.; Rai, S. B. Opt. Mater. 2007, 29, 873–878. [8] Y. Pan et al. / Journal of Solid State Chemistry, 2003, 174,69–73. [9] R.S. Yadav et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2015, 142, 324–330.

Colorimetric Sensing of Dopamine Using L-Histidine Capped Luminescent Mn Doped ZnS Quantum Dot Printo Joseph1,2, S.C.G Kiruba Daniel2,3 and M. Sivakumar2,3 Department of Physics, Bharathidasan Institute of Technology, Anna University, Tiruchirappalli Nanoscience and Technology, Bharathidasan Institute of Technology, Anna University, Tiruchirappalli 3 Department of Chemistry, Bharathidasan Institute of Technology, Anna University, Tiruchirappalli E-mail: [email protected] 1

2

ABSTRACT In this work we synthesized Mn doped ZnSQD which is highly luminescent and non toxic comparing to other organometallic QDs by chemical co-precipitation method. We observed a better size confinement effect using L-histidine amino acid as capping agent by comparing with polymers such as PVA, PVP and chitosan.Colloidal solution of QD prepared using L-histidine as capping agent provides better sensing owing to its inherent attraction towards dopamine.Sensing of dopamine is essential for early diagnosis of Alzheimer’s and Parkinson disease.Colorimetric detection of solution from transparent to dark brown has been observed within few seconds after the interaction of dopamine with amino acid capped QD.

Keywords: Quantum dot, Mn doped Zinc Sulfide, Luminescent, Colorimetric sensing, Dopamine

INTRODUCTION Semiconductor nanocrystals like quantum dot are fascinating materials due to its optical and electrical properties. They exhibit fluorescence property due to the confinement of the particle in all direction as per the quantum mechanical principle. Mn: ZnS QD can be used for detection of E. coli bacteria and for sensing of DNA [1, 2]. In this work we describe unique detection method based on visible sensing of dopamine using amino acid capped QD. One step aqueous synthesis of Mn:ZnS quantum dots are done by using coprecipitation method. The size of the QD obtained will be around 5 nm range. Dopamine oxidise to quinine forms a brown colour precipitate while reacting with nucleophilic species. Sensing of dopamine was possible due to reduction of the functional group on the surface of Mn: ZnS QD which triggers colour change. MATERIALS AND METHODS 0.1M of Zinc acetate and 0.01M Manganese acetate is used as precursors and 0.1M Sodium sulfide is used as the reducing agent, NaOH is added to adjust the pH to 12 V. Rajendran, K. Thyagarajah and K.E. Geckeler (eds.) Nanoelectronics and Sensors, pp. 61-64 (2015)


Results and discussions UV Visible and Photoluminescence Spectral Analysis

Fig. 1: UV-Visible absorption spectrum (a) and photoluminescent spectrum (b) of Mn doped ZnS

Mn: ZnS quantum dots exhibits a broad absorption spectrum [1-2] as shown in the Fig.1(a).Blue shift in the absorption peak as we move from PVA capped QD to Histidine capped QD. An absorption

Colorimetric Sensing of Dopamine Using L-Histidine Capped Luminescent Mn Doped ZnS Quantum Dot 63

maximum of 290 nm is obtained from L-His capped Mn:ZnS quantum dot. The emission peak of QD Fig.1(b) appears at 580nm for polymer capped Mn: ZnS quantum dot [1-2]. The emission peak at 380 -420 nm is typical luminescence of undopedZnS Emission peak at 580nm is due to Mn+2 ions in ZnS crystal as trap site.

High Resolution Transmission Electron Microscopy

Fig. 2: HRTEM images of L-His capped Mn:ZnS QD at 10 nm and 5 nm scales

L-histidine capped Mn:ZnS QD exhibit excellent size confinement property and is colloidal in nature. So further studies were carried out only for L-His capped Mn:ZnS QD, and also due to its application such as sensing of dopamine. Size and shape analyses were done using HRTEM as shown in Fig.2. The particle size was found to be 4.77 nm average values.From that d spacing and (h k l) value is calculated and matched with the standard JCPDS no.77-2100.

DOPAMINE SENSING BY L-HISTIDINE CAPPED Mn:ZnS

Fig. 3: UV-Vis absorption spectrum of different concentration of dopamine (a) and their colour change (b)

The solution of Mn:ZnS turns to light yellow and then to brownish black colour after the addition of different concentration of dopamine. UV-Vis spectroscopy has been carried out..Sensing of dopamine at different concentration can be observed by colorimetic change in the solution. The characteristic

64 Nanoelectronics and Sensors peak for Mn:ZnS with different concentration of dopamine are 277nm, 279nm, 280nm, 284nm for 10μM , 15μM, 20μM, 25μM concentration of dopamine respectively.

CONCLUSION Colloidal QD with L-Histidine as capping agent shows excellent properties and Also colorimeteric sensing possible and the colour change with different concentration was observed with in few seconds. ACKNOWLEDGEMENTS This work was supported by TEQIP II funding in BIT campus, Anna University, Tiruchirappalli, India for student project proposal scheme. REFERENCE [1] Baruah, S., Ortinero, C., Shipin, O. V., & Dutta, J. (2012). Manganese doped zinc sulfide quantum dots for detection of Escherichia coli. Journal of fluorescence, 22(1), 403-408. [2] Zhu, Dong, et al. “Glutathione-functionalized Mn: ZnS/ZnO core/shell quantum dots as potential time-resolved FRET bioprobes.” RSC Advances 4.18 (2014): 9372-9378.

Nanophase Separation in Ge-Se-Pb Glasses Near the Charge Carrier Reversal Threshold K. Ramesh, Sharona Thomas Horta, Pumalianmunga, R. Venkatesh and E.S.R. Gopal Department of Physics, Indian Institute of Science, Bangalore E-mail: [email protected]

ABSTRACT Melt quenched chalcogenide glasses are generally p-type semiconductors. The equilibrium between the positively charged C3+ and negatively charged C1- defect states called the valence alternation pairs (VAPs) pins the Fermi level at the centre of the energy gap and prevents doping in these glasses. However, when Bi and Pb atoms are added to Ge-Se and Ge-Te glasses alters the balance between the charged defect states and unpins the Fermi level leading to a conduction type rversal(CTR). The structural models explain the CTR based on the phase separation PbSe micro clusters at the microscopic level in the Ge-Se-Pb glass. Though there are many reports on CTR in Ge-Se-Bi and Ge-Se-Pb glasses, the mechanism is still poorly understood. In the present work, we address this issue in PbxGe42-xSe58 glasses by carrying out thermal and microstructural studies. Thermal crystallization of these glasses indicates a new phase formation for composition with x > 9. Microscopic studies shows a nano phase separation at x = 9 at which the conduction type reversal occurs. From the XRD spectra the new phase is found to be the n- type PbSe. Based on this, we speculate that, at the critical composition, PbSe crystallites forms at nano scale level, and then it grows to a larger size for higher concentration of Pb.

INTRODUCTION Melt quenched chalcogenide glasses are generally p-type semiconductors and insensitive to doping[1]. Generally, the constituent elements of chalcogenide glasses obey ‘8-n’ rule, where ‘n’ is the column in the periodic table to which the element belongs [1]. However, when metal atoms are added, this rule is violated and the metal atoms are found to be in higher coordination state [2]. It is also believed that the presence of charged impurities pins the Fermi level at the centre of the energy gap and hence doping is not possible. However, when Bi and Pb atoms are added to Ge-Se and Ge-Te glasses, unpinning of the Fermi level occurs and these glasses exhibit a conduction type reversal from p- type conduction to n- type occurs [3,4]. There have been many structural and electronic models proposed to explain the CTR in chalcogenide glasses[5,6]. The structural models explain the CTR based on the


66 Nanoelectronics and Sensors phase separation of Bi2Se3 and PbSe microclusters at the microscopic level in Ge-Bi-Se and Ge-Se-Pb glasses respectively Another interesting aspect of chalcogenide glasses is the observation of topological phase transitions in composition dependence of physical properties[6,6]. At an average coordination number Zav = 2.4, the covalently bonded chalcogenide glass network undergo a floppy-to-rigid transition at which the glass has the highest stability and the rigid region begin to percolate. Another transition called chemical ordering also observed which usually occurs at higher coordination numbers (Zav = 2.67). The chemically ordered glass has a maximum ordering in the structure at which only hetero polar bonds are preferred. Beyond this chemically ordering, the structural network phase separate into molecular species which are in nano size and deploymerizes the network. In the present work, CTR in melt quenched bulk PbxGe42-xSe58 glasses has been studied. The microstructural studies reveal the nano scale phase separation at the composition corresponding to the critical threshold.

EXPERIMENTAL Bulk PbxGe42-xSe58 glasses were prepared by conventional melt quenching method. Appropriate amounts of high purity elements (99.999%) were sealed in a quartz ampoule under a vacuum of better than 10-5 torr and heated in a resistive furnace. The ampoule is heated to 600 ºC and kept for 6 hours and then the temperature is slowly raised to 950 °C and kept for 48 hours. The melt was continuously rotated to ensure homogenization and then quenched in ice water + NaOH mixture. The melt quenched samples were confirmed to be amorphous in nature by X-ray diffraction (XRD). Modulated Differential Scanning Calorimeter (TA Instruments: MDSC 2920 system) in normal DSC mode has been used to measure the Tg and Tc of the prepared glasses at heating rate of 10 °C/min. Fig.1 shows the DSC thermograms of the prepared glasses. Morphology of the samples was examined with the Quanta FE-200 SEM.

Fig. 1. DSC spectra of Ge42Se58Pbx glasses recorded at a x heating rate of 10 oC/min.

RESULTS AND DISCUSSIONS The stressed rigid glasses (lower concentrations of Pb) show pahse separation which is also reflected in the glass transition (Tg). For x ≤ 5, two glass transitions are observed which is a direct indication of the macroscopic phase separation in the glass network. For x > 5, only single glass transition is observed. To understand the phase separation, these glasses were annealed at their Fig. 2. XRD pattern of repective crystallization tempeartures annealed samples for 5 hours and subjected to X–ray diffraction. Fig.2. shows the XRD of the representaive annealed samples in PbxGe42-xSe58. It can be seen Fig. 3: SEM pictures of melt that the all the samples in the composition range shows the formation quenched Ge42-xSe58Pbx glasses of Pb2GeSe4 and GeSe2 crystallites upon annealing. The as prepared

Synthesis and Characterization of Novel Siloxane Based Transparent and Flexible Substrate for Oleds 67

glasses show the nanophase for x = 0 and 9. Ge42Se58 ( x= 0) parent glass is stressed rigid structure and the network is beyond the chemically ordered netork. In binary GexSe100-x glasses the chemical ordering occurs at x = 33.33 (Zav = 2.67). For Zav > 2.67, Ge-Ge homopolar bonds forms and also moelcular units Ge2(Se1/2)6 and GeSe involving Ge and Se forms. They pase separate at a nanoscale level. This has been clearly seen in fig.3. When Pb is added, it releives the stress and the molecular units rearrange to help in the formation of the ternary Pb2GeSe4 phase. Correspondingly, the nano phase disspaeras for x > 0. For x > 9, the binary PbSe crystallites are seen. Interestingly, the microstructure of the annealed samples studied by SEM shows the nano Fig. 4: SEM pictures Ge42phase formation at x = 9. Nanoscale phase separation observed at x = xSe58Pbx samples annealed at their respective Tcs. 9, in both glass and thermally crystallized samples shown in figures 3 and 4 indicates the formation of ionic Pb-Se phase.This nano phase grows and transform to microscopically phase separated Pb-Se phases as shown in the XRD patterns (fig.2). It should be mentioned that x= 9, is the critical composition at which the conduction reversal occurs. Pb-Se is a n-type conductor and its appearance and growth in percolative manner may be reason for the CTR in the PbxGe42-xSe58 glasses for x ≥ 9. The variation of the concentration of different types of bonds as a function Pb is shown in fig.5. The increase of Pb decreases the Ge-Ge, Ge-Se and bridging Se (b-Se) bonds and increases the Pb-Se and non-bridging Se (nb-Se) bonds. The decrease of the b-Se in turn the angular constraints suggests that the progressive reduction of stress and progressive increase of Fig. 6. The variation of the concentration of deploymerization in the network which results in the overall different types of bonds as a function Pb. decrease in the Tg [7].

CONCLUSIONS Nano phase separated Pb-Se, the increase in ionic Pb-Se bonds and the decrease in the degree of covalent character of the network for x ≥ 9, alter the balance between the charged defects and changes the conduction type from p- to n- type in Ge42-xPbxSe58 glasses.

REFERENCES 1. N. F. Mott and E. A. Davis, Electronic Process in Non-Crystalline Materials (Clarendon, Oxford, 1979). 2. K.S. Liang, A. Bienenstock, C.W. Bates, Structural studies of glassy CuAsSe2 and Cu-As2Se3 alloys, Phys. Rev. B 10, 1528 – 1538, 1974. 3. N. Tohge, Y. Yamamoto, T. Minami, M. Tanaka, Preparation of n-type semiconducting Ge20Bi10Se70 glass Appl. Phys. Lett. 34, 640 - 641, 1979. 4. N. Tohge, H. Matsuo, T. Minami, Electrical properties of n-type semiconducting chalcogenide glasses in the system Pb-Ge-Se, JNCS, 38-39, 809 - 816, 1987.

68 Nanoelectronics and Sensors 5. J. C. Phillips, Constraint theory and carrier-type reversal in Bi-Ge chalcogenide alloy glasses, Phys. Rev. B 36, 4265 – 4270, 1987. 6. L. Tichy, H. Ticha, P. Nagels, Is the n-type conductivity in some Bi-doped chalcogenide glasses controlled by percolation? Solid State Commun. 53, 399 - 402, 1985. 7. B. Vaidhyanathan, S. Murugavel, S. Asokan, K. J. Rao, Origin of Carrier-Type Reversal in Pb-GeSe Glasses: A Detailed Thermal, Electrical, and Structural Study, J. Phys. Chem. B, 101, 9717-9726, 1997.

Pt–Pd Nanoparticle Decorated Graphene Oxide on Screen Printed Carbon Electrode for the Nonenzymatic Sensing of Glucose in Neutral Medium Basil Paul K and T.G Satheesh Babu1 1

Department of Electronics and Communication Engineering Department of Sciences, Amrita Vishwa Vidyapeetham, Amritanagar P.O., Coimbatore E-mail: [email protected]

INTRODUCTION In recent years a great amount of effort has been dedicated towards overcoming the problems associated with the enzymatic glucose sensors. The use of nonenzymatic electrodes based on the direct electrooxidation of glucose holds promise as the fourth generation in glucose sensing. It has been well established that the nonenzymatic electrochemical glucose sensors have excellent sensitivity, selectivity and long term storage stability [1,2]. Choosing the right catalyst for the direct electrochemical oxidation of glucose is the key step involved in the fabrication of nonenzymatic sensors. Most of the nonenzymatic sensors reported earlier function in alkaline pH which is much higher than the physiological pH. The use of platinum and palladium nanoparticles for the direct electrochemical oxidation of glucose has been tried earlier. Pt based alloys Pt-M (M = Pd, Pb, Au, Ni) [1-4] show numerous advantages and uniqueness in sensor applications due to the electron coupling and ligand effects that exists between the two metals [2,3]. The integration of another metal reduces Pt loading and thereby increases the surface adsorption of glucose due to the changes happening in d band structure of Pt [4]. Incorporation of the electrocatalysts on materials such as graphene and carbon nanotubes that have high surface to volume ratio further enhances the electrocatalytic response. In this work, a non-enzymatic electrochemical glucose sensor was developed using an activated screen printed carbon electrode (SPCE) modified with platinum-palladium nanoparticles supported on graphene oxide. The fabricated electrode exhibits linear response to glucose with excellent selectivity and sensitivity in neutral medium. EXPERIMENTAL Reagents and Instruments β-D-(+)–glucose (ACS reagent), L-ascorbic acid (AA), dopamine (DA), uric acid (UA) (≥99 %), graphite powder (

Nanoelectronics and Sensors

Nanoelectronics and Sensors

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