Synthesis and characterization of graphene quantum dots-silver nanocomposites M. Vandana, S. P. Ashokkumar, H. Vijeth, M. Niranjana, L. Yesappa, and H. Devendrappa
Citation: AIP Conference Proceedings 1942, 050046 (2018); doi: 10.1063/1.5028677 View online: https://doi.org/10.1063/1.5028677 View Table of Contents: http://aip.scitation.org/toc/apc/1942/1 Published by the American Institute of Physics
Synthesis and characterization of graphene quantum dotssilver nanocomposites M Vandana, SP Ashokkumar, H Vijeth, M Niranjana, L Yesappa , H Devendrappa* Department Of Physics, Mangalore University, Mangalagangothri 574199, India *Corresponding author:
[email protected]
Abstract.A facile microwave assisted hydrothermal method is used to synthesise glucose derived water soluble crystalline graphene quantum dots (GQDs) andcitrate reduction method was used to synthesized silver nanoparticles (SNPs). The formation of graphene quantum dots-silver nanocomposites (GSC) was synthesized through a simple refluxing process and characterised using Fourier Transform Infrared (FT-IR) to study the chemical interaction, Surface morphology using FESEM, Optical properties were studied using UV-Visible spectroscopy. The absorption band shows at 249, 306 and 447 nm confirms the formation of GQDs and GSC. The electrochemical performance of GSC tested to determine the oxidation/reduction processes by cyclic voltammetry and linear sweep voltammetry.
INTRODUCTION Graphene quantum dot (GQDs) is one of the most significant zero dimensional material because of their electronic, optical and electrochemical properties induced by quantum confinement and edge effect. They exhibit strong photoluminescence, coupled with other properties like heavy metal free, biocompatible and good solubility in water, suitable for various devices fabrication LED, photovoltaic, bio-imaging, photo detectors and optoelectronic applications in low cost.A metal nano particle like gold, platinum, silver, and copper has good electronic, thermal, optical and catalytic properties as well as they are now being developed for various biological applications.
EXPERIMENTAL METHODS Materials Glucose (99%) purchased from Merck, silver nitrate (AgNO3) from National chemicals India, triosodium citrate (C6H5Na3O7.2H2O) from Merck India.
Synthesis of Graphene Quantum Dots A microwave - assisted hydrothermal method is used to prepare highly luminescence graphene quantum dots using glucose solution prepared by dissolving distilled water [1]. Then solution is taken in 50ml of Teflon lined autoclave heated by microwave oven with high pressure and temperature is about 180oC for 3 hours. In this experiment it is noticed that the heating time, microwave power, solution volume, source concentration, and pressure parameters are affects the growth of GQDs and its size. After completion of experimental process the solution undergo changes the colour from transparent to pale yellow indicates formation of graphene quantum dots
DAE Solid State Physics Symposium 2017 AIP Conf. Proc. 1942, 050046-1–050046-4; https://doi.org/10.1063/1.5028677 Published by AIP Publishing. 978-0-7354-1634-5/$30.00
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Synth hesis of Silveer Nano parrticles and GQDs-SNP G s Composites A Turkkevich method d (Citrate reduuction method)) [2] is used to t prepare a coolloidal silver nanoparticles.. Here AgNO3 soolution was heaated and stirreed till it attain boils. Then trriosodium citrrate solution was w added dropp wise about 1 droop/sec into solution. This proocess is continuued until the soolution turned yellowish brow wn colour indiicating the formatiion of AgNPs colloidal c solutiion. Mechanism m of the reactio on is, 4Ag+ + C6H5O7Na3 + 2H2O---------------→ 4Ag+ + C6H5O7H3 +33Na+ +H+ +O2 ↑ The grapheene quantum dots-silver d com mposites (GSC)) are synthesizeed through a siimple refluxingg process. Typpically, drop wise addition of sillver colloidal solution to thee GQDs solutioon with vigoroous stirring at a room tempeerature about 24 hours, then centtrifuging, the reesultant solutioon is GSC.
CHARAC CTERIZAT TIONS P Elmer Lamda 350 UV/Visible U sppectrometer. Fourier F UV-Visible spectra were obtainedd by using Perkin o Bruker Alppha ATR FT--IR spectrometter. Electrocheemical transform infrared (FT-IIR) spectra were recorded on performancce carried outt CHI 660E ellectrochemicall workstation. Field Emissioon Scanning Electron E Microoscopy (FESEM) was w conducted d by using Sigm ma Zeiss FESE EM.
R RESULTS A AND DISCU USSION UV-Visib ble spectrosscopy The UV V-Visible abso orption spectruum of GQDs, SNPs, S GSC shhown in a Figuure 1(a). GQDss shows, absorrbance peak at 2449nm is due to o the π → π* transition t of C=C C and 306 nm n is due to thhe n →π* trannsition of C=O O. This functional group present in the GQDs speculates s the graphitic struccture. UV-absorption of collooidal AgNPs soolution where triosodium citratee serves as both reductant and a stabilizer. The yellowishh brown colouur of colloidal silver shows absorption peak at a 447nm in thhe visible regiion (390-700 nm) is attribuuted surface plasmon resonannce of AgNPs. Heence, broad SP PR peak obserrved at approxiimately 447nm m confirms the formation of AgNPs. A The peak p at 249, 306 annd 447nm show ws typical absoorption in bothh UV and Visibble region repreesents the form mation of GSC.
FIGURE 1. UV-Visible absorption a of a) GQDs, G SNP, GS SC and b) colourrisation photograaphs c) FT-IR sppectra of GQD, SNPs, S and GSC
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FTIR Spectroscopy The FTIR spectra of GQ QDs, SNPs, GS SC shown in a Figure 1(c). The peak obseerved at 1687 cm-1 is due too C=C stretching which w is imporrtant elementarry unit of GQD Ds core. The peeak at 3437 cm m-1revealed thaat O-H stretchinng and -1 1687cm is i due to the deformational d v vibration of –N NH2 group on the t surface of GQDs [3].Thee peaks at 1698cm-1, -1 -1 1505cm reveals r that ben nding vibrationn of amide. A sharp s band at 1741cm 1 indicates that phenool hydroxyl grooup on + -1 the surfacee serving reducction of Ag too elemental silvver. The absorrption peak at 3556cm 3 attribbutes O-H streetching 2 vibrations. A stable GSC C was obtained by hybridizatioon between SN NPs and SP daangling bonds of o GQDs.
Ellectrochemiical Characcterisation Cyclicc voltammettry The eleectrochemical performance p c be tested by can b cyclic voltam mmetry using three electrodee systems conssisting of glassy carbonas c workiing electrode inn the presence of suitable eleectrolyte, platinnum wire is auxiliary electrodde and Ag / Agcl reference r electtrode.
FIG GURE 2. Cyclic voltammetry meeasurement of GQDs, G SNPs, GS SC respectively.
The ovverall oxidation n/reduction recoorded at variouus scan rates frrom 0.5 to 0.1vv/s and potentiaal range from -2.5 to +2.5V.Thee anodic current increases liinearly with square s root off the scan ratee therefore thee oxidation potential shifting to positive directtion with increaasing the scan rate [4].
Linear sw weep voltam mmetry
FIGURE 3. Linear sweepp voltammetry of GQDs, SNPs, GSC
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The I-V V measuremen nt performed foor GQDs, SNP Ps, GSC shownn in a Figure 3.. All three exhhibiting charactteristic curves withh increasing biias from 0V to 5V with differrent scan rate 0.5 0 and 0.3v/s with w sensitivityy 1e-002. As thhe bias voltage inccreases 0 to 5V V the positive photocurrent p is observed. If bias voltage frrom -5 to +5 first f there is neegative photocurreent is persisted d then after 0V V positive phootocurrent willl be achieved [5]. The negaative photocurrrent is reverted too positive when n the bias is redduced back. Thhe origin of chaange in the chaarge trapping scenario in the GQDs at higher bias b is mainly due d to the change from neutraal to charged suurface functionnal group at higgher bias.
Fiield Emissioon Scanningg Electron Microscopy M (FESEM)
FIG GURE 4.FESEM M images of GQD Ds, SNPs, GSC
A well dispersed SNP Ps deposited onn the graphenee quantum dot there t is a curleed and wavy morphology m obsserved. ment of AgNPs aree randomly disstributed on thee graphene quaantum dots maaintaining a surrface facilitatinng the attachm nanoparticles to GQDs [6]. [ A Well diispersed SNPs with the size 78.55nm deposited on grapphene quantum m dots, ucture. which conffirms their stru
CON NCLUSIONS In this work, highly y luminescencee graphene quuantum dots suuccessfully syynthesized by Microwave asssisted mal method using natural gluucose powder and silver nannoparticles are synthesized byy Turkevich method m hydrotherm (chemical reduction meth hod) and theirr nano compossites can be preepared by simpple refluxing method m respectively. V-Visible, FTIIR, FESEM, CV, C and LSV which demonsstrated The syntheesized compossites are characterised by UV AgNPs aree well dispersed d in GQDs maatrix. The synthhesized nanocoomposites can be b used as variious applicationns and fabricationn of electrochem mical sensors.
ACKNOW WLEDGEM MENT The autthors are also grateful g to the PURSE P LAB Mangalore M Uniiversity for prooviding FESEM M facilities.
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