ISSN 2347-3487 Optical Properties of Phthalocyanine and its Metal Complexes Thin Films Prepared by Nd-YAG Laser Deposition Technique R. Seoudia,b, M. G. Khafagia, A. Abouelsayeda, A. R. Lashina,c, D. A. Saidb,d, M. Boustimib a
Spectroscopy Department, Physics Division, National Research Centre, 33 El Bohouth st. (fromer El Tahrir st.) -Dokki - Giza - Egypt - P.O. 12622 b Department of Physics, College of Applied Science, Umm Al-Qura University, Makkah, Saudi Arabia c Department of Physics, Faculty of Science, Mansoura University, Egypt d Physics Department, Faculty of Girls for Art, Sciences and Education, Ain Shams University.
ABSTRACT In this work, thin films of phthalocyanine and its metal complexes were prepared by Nd-YAG pulsed laser deposition -1 technique. The transmission measurements were performed over a very broad frequency range (400-30000 cm ). The N-1 H vibrational mode appeared at 3289 cm in phthalocyanine film disappeared in its complexes film due to the replacement of the hydrogen by the metal cation. Two broad excitation bands were observed in the Vis-energy range at about 1.6 and 2.06 eV. This excitation was attributed to the contributions from bonding and anti-bonding molecular orbital. The strong absorption band at about 3.5 eV (B-band) is corresponds to the electronic transition from ππ (b2u - eg) orbital. The refractive index n ( ) and the extinction coefficient k ( ) have been illustrated by fitting the absorption spectrum with Lorenz model. There is a weak change of the refractive index n below 1.55 eV.
KEYWORDS Phthalocyanine; Thin Films; Laser Deposition Techniques; SEM; FTIR; Uv-Vis. Corresponding author E-mail address:
[email protected] (A. Abouelsayed).
Council for Innovative Research Peer Review Research Publishing System
Journal: JOURNAL OF ADVANCES IN PHYSICS Vol.8, No.3 www.cirjap.com,
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ISSN 2347-3487 1. Introduction Extensive studies have been made on the structural, thermodynamic, optical and electrical properties of phtahlocyanine thin films due to the technological interest [6, 7]. Thin film of phthalocyanines is relatively easy in preparation, and possess a great potential for applications including photodetector, magnetic, optical devices, sensors and in electronics [1, 2, 3, 8, 9, 10]. Thin film of phthalocyanines used as a solid-state solar cell and can be work in the same principle as silicon solar cell, but its energy conversion efficiency is rather poor [4]. These devices have been investigated for a long time due to very low cost but it is required some effort from the scientists to improve the solar power conversion efficiencies [5]. Nombona et al [11] investigated the optical properties of monocarboxy magnesium and zinc phthalocyanine and found the fluorescence quantum yields of MgPc is higher than pure phthalocyanine and zinc phthalocyanine thin films. Zhang et al [12] investigated the hydrogen nitrogen stretching and bending vibrational modes in phthalocyanine (Pc) and its complex. Rajesh [13] and coworkers studied the absorption and reflectance spectra of magnesium phthalocyanine thin film and calculated the absorption coefficient, extinction coefficient as well as the optical band gap, refractive index, real and imaginary parts of the dielectric constant. Fernandes et al. [14] prepared ultrathin films of silicon (IV) phthalocyanine bis (trihexylsilyoxide) and studied the thermal optical polarized spectroscopy. Several studied were carried out on the silicon phthalocyanine in visible region for photodynamic tumor therapy [15, 16]. Many techniques can be used for the preparation of phthalocyanines the thin films, such as, spin coating technique, ionimplantation, proton exchange, liquid phase epitaxial growth, RF-sputtering, DC-sputtering, flash evaporation and thermal evaporation [17-23]. Among the known preparation methods pulsed laser deposition (PLD) is one of the very promising techniques for the deposition of the thin film [24, 25]. In this paper phthalocyanine and its metal complexes by (Mg, Si and Zn) thin films have been prepared using Nd-YAG pulsed laser deposition technique on KBr belt and quartz substrate. We present the results of the UV-Vis and the IR absorption measurement to understand the underlying physics of the optical properties.
2. Experimental Phthalocyanine (Pc) was prepared by the reaction of o-phthalic acid with naphthalene and teteachloronaphthalene by nitric acid. Magnesium phthalocyanine, Zinc phthalocyanine and Silicon phthalocyanine dichloride are purchased from Sigma- Aldrich. Thin films of Pc, MgPc, ZnPc and SiPc were evaporated onto KBr belt and quartz substrates to measure the vibrational modes, the microstructure and the optical properties. The samples were evaporated using Nd: YAG laser (8 ns pulse, 5 watt, 10 Hz repetition rate at frequency doubled 523 nm) at 10-5 Torr. The quartz substrates were cleaned with dilute nitric acid followed by liquid detergent, rinsed well in distilled water and acetone, and dried in hot air before used. The thickness was monitored at 250 nm by a quartz crystal monitor during deposition processes. The scanning electron microscope images (SEM) was measured using a JEOL JSM-5400 and all specimens were gold coated. The infrared spectra were measured at room temperature in the frequency range 400-4000 cm-1 using A Jasco Model 6100 Fourier transform infrared spectrometer. The ultraviolet and visible spectra were recorded with spectrophotometer Model Jasco UV/VIS/NIR V-570 at room temperature.
3. Results and discussion The scanning electron microscopic (SEM) images of phthalocyanines films are shown in Figure 1. The morphological differences between the films is clear from Figure 1 (a - d). We notice that phthalocyanine film has cluster-like particles while the complexes phthalocyanine films are more clean. It is clear that, there is a difference in the amount of impurities in all films but the volume fraction appears to be the same. The changes of the films morphology and the particle sizes are due to the variation in the chemical structure. The area fraction of the agglomeration in the film was increased with increasing the atomic number of central metal. The higher porosity of (Mg, Zn and Si) complexes than phthalocyanine may be due to the multigrain agglomerations with the fracture surface. The infrared spectra of the thin films are shown in Figure 2. It is clear that the band appeared at 3434 5 cm -1 , which is related to the O-H vibration of adsorbed water, is observed in all samples. The band at 3289 cm-1 is assigned to the N-H stretching vibrations. This band is disappeared from the complexes due to the replacement of hydrogen by metal cation. The two bands observed at 3050 5 and 3030 5 cm -1 in all films are assigned to the C-H asymmetric and symmetric stretching vibrations in the ring. The absorption bands at 2925 5 and 2854 5 cm assigned to the C-H -1 symmetric and asymmetric stretching vibrations of alkyl. The band at 1609 5 cm refers to the C-C stretching vibration in pyrrole. The two bands at 1542 and 1455 cm -1 interpreted to the C-H in plane bending vibration. The three bands at -1 -1 1517, 1490 and 1474 cm assigne to the C-H bending of aryl. The bands at 1428 5 and 1332 5 cm interpreted C-C stretching in isoindole. The C-N in isoindole in plane band in pyrrole are illustrated by the absorption bands at 1284, 1162 and 1070 cm -1, respectively [26]. The two bands appeared at 1118 and 1085 cm -1 assigne to C-H bending in plane deformations and the three bands at 909, 882 and 728 cm -1 are related to the C-H bending out of plane deformations. The -1 band at 625 cm is related to the C-C macrocycle ring deformation. This films of phthalocyanine complexes shows three peaks in the spectral region (1000-1200 cm -1) that depends strongly on the molecular structure of the complexes as well as atomic structure for the metal cations. The middle peaks are originated from the vibration mode of a pyrrole ring and the other two peaks are related to C-H bending in the ring [26]. The middle bands indicates the molecular symmetry and this is agreement with our previous work [27]. -1
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Figure 1: Scanning electron microscope images of phthalocyanine (Pc), Magnesium phthalocyanine (MgPc), Zinc phthalocyanine (ZnPc) and silicon phthalocyanine (SiPc) thin films prepared by laser deposition techniques.
Figure 2: Fourier Transform Infrared spectra of (Pc, MgPc, ZnPc, SiPc) thin films deposited on KBr pellet. Figure 3 shows the UV-Vis spectra of thin films in transmission and absorption mode. The optical absorption features for phthalocyanine are assigned according to the band-to-band transitions originate from the molecular orbital within the
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ISSN 2347-3487 aromatic 18 electron system and from overlapping orbital on the central metal. Figure 3 reveals the interband transitions corresponding to the known Q band [28, 29]. The labels E1, E2 refer to the band to band transitions at about 2.06 and 1.6 eV, respectively. It has a doublet due to Davydov splitting Q and it is representing by [30, 31]. The absorption band at about 3.5 eV corresponds to the B-band or Soret band.
(b1u-eg)
Figure 3 : Ultraviolet-visible spectra of (Pc, MgPc, SiPc and ZnPc) thin films of (a) transmission mode and (b)absorption mode. The labels E0, E1 and E2 denote the doublet Q band transitions between π and π (b1u - eg) due to the excitation between bonding and antibonding molecular orbital and the B-band due to the electronic transition from
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ππ (b
2u
- eg) orbital.
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Figure 4: The absorption spectra of the (a) Pc, (b) MgPc, (c) SiPc and (d) ZnPc thin films at ambient condition together with the Lorentz function fit and the fit components. The typical energy regimes of the optical transitions in the doublet Q band transition and in the B band transition are illustrated by the labels E0, E1 and E2, respectively. The energy of the interband transitions can be extracted in the following way: the absorption spectra were fitted using Lorentz model to obtain purely the energy of the band-to-band transitions. Quantitative information was obtained by fitting the absorption spectra with Lorentz functions.
Nj 4 e2 ( ) m j ( 2j 2 ) i j where
j
and
(1)
N j are the width and the density of electrons bound with the central frequency j . Figure 4 (a-d) shows
the absorption spectra of thin films at ambient conditions together with he fitting curve and its components. The different components of the principle transitions correspond to the various contributions from the doublet splitting of the (b1u - eg) at about 1.6-2.06 eV due to the excitation between bonding and anti-bonding molecular orbital. The B-band at
about 3.5 eV arises due to the electronic transition from
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(b2u - eg) orbital [30, 31].
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Figure 5: The refractive index of the Pc, MgPc, SiPc and ZnPc thin films. Obviously, the spectral weight of the absorption band at about 2.06 on the macrocycle of ZnPc is lower than the spectral weight of the band at about 1.6 eV. This is due to excitonic vibration or vibrational interval indicating a typical
features the form structure [33, 34]. In case of the SiPc and MgPc compounds the and form crystal structure for free metal of the phthalocyanine are observed [35, 36]. The absorption band at about 3.5 eV nearly shifted to lower energy in the complexes due to the metal coordinated with nitrogen in phthalocyanine. This is in a good agreement with the previous studied by Collins et al. [37, 38]. Figure 5 (a, b) the refractive index To obtain
n( )
and
k ( )
n( )
and the extinction coefficient
k ( ) of the phthalocyanine thin films.
(real and imaginary part of the complex refractive index), we have fitted the absorption
spectrum with Lorenz model. This has been achieved by first modeling the refractive index
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nˆ n ik as follows [32]:
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ISSN 2347-3487 1 ( ) n k 2
2
j
2 ( ) 2nk j
where
j , Tj
and
j
T j2 ( 2j 2 ) ( 2j 2 ) 2j 2
T j2 j
(2)
(3)
( 2j 2 ) 2j 2
are the width, the oscillator strength, and the central frequency, respectively. In Figure 5 (a),
there is weak changes of the refractive index n below 1.55 eV and no significant changes at higher wavelengths due to the changes of the metal coordinated. Above 1.55 eV the refractive index varies sharply near the band edge. The extinction coefficient
k
values of all thin films demonstrated a peak at 1.6 and 2.06 and 3.5 eV (see Figure 5 (b)).
4. Summary The optical properties of the Pc, MgPc, SiPc and ZnPc thin films which has been prepared by laser deposition technique using Uv-Vis and infrared spectroscopy over a broad energy range. The surface morphology was studied and the porosity of (Mg, Zn and Si) complexes was higher than phthalocyanine. The change of the molecular structure due the complexation with metal cation was illustrated from FTIR results. Absorption were measured in UV-Vis spectrum and the crystal form was clarified. Another interesting observation is that the bands appeared at high and low wavelength was characteristic by Q-band and B-band and those assigned by refractive index
transition. The optical parameters such as the
n( ) and the extinction coefficient k ( ) were calculated.
Acknowledgements The team worker in the Femtosecond laser unit in the National research center is gratefully acknowledged for helping us for the films preparations.
5. References [1] A. K. Soteris, Prog. Energy Combust. Sci. 30, 231 (2004). [2] M. Shahid, M. Hamid, A. A. Tahir, M. Mazhar, M. A. Malik, M. Helliwell, Ind. Eng. Chem. Res. 51, 16361 (2012). [3] M. Ritala, M. Leskel, Vol. 1. (HS Nalwa, Ed.); Academic press: San Diego, 2002. [4] S. S. Ardestani, R. Ajeian, M. N. Badrabadi, M. Tavakkoli, Sol. Energy Mater. Sol. Cells. 111, 107 (2012). [5] N. Asim, K. Sopian, S. Ahmadi, K. Saeedfar, M. A. Alghoul, O. Saadatian, S. H. Zaidi, Renew. Sust. Energ. Rev. 16, 5834 (2012). [6] M. Hanack, M. Lang, Adv. Mater. 6, 819(1994). [7] F. Yang, M. Shtein, S. R. Forrest, Nat. Mater. 4, 37(2005). [8] B. J. Prince, B. E. Williamson, R. J. Reeves, J. Lumin. 93, 293 (2001). [9] S. Karan, D. Basak, B. Mallik, Chem. Phys. Lett. 434, 265 (2007). [10] A. Chowdhury, B. Biswas, M. Majumder, M. K. Sanyal, B. Mallik, Thin Solid Films. 520, 6695 (2012). [11] N. Nombona, W. Chidawanyika, T. Nyokong, J. Mol. Struct. 1012, 31 (2012). [12] X. Zhang, Y. Zhang, J. Jiang, Spectrochim. Acta, Part A, 60, 2195 (2004). [13] K. R. Rajesh, C. S. Menon, Mater. Lett. 5, 329 (2002). [14] A. N. Fernandes, T. H. Richardson, D. Lacey, J. Hayley, Dyes Pigm. 80, 141 (2009). [15] R. Decreau, M. Richard, P. Verrando, M. Chanon, M. Julliard, J. Photochem. Photobiol. B, 48, 48 (1999). [16] Jiang, X.; Huang, J.; Zhu, Y.; Tang, F.; Ng, D.; Sun, J, Bioorg. Med. Chem. Lett.,16, 2450 (2006). [17] I. zcesmecia, I. Sorarb, A. Gl, Inorg. Chem. Commun. 14,1254 (2011). [18] F. Aziza, K. Sulaiman, M. R. Muhammad, M. H. Sayyad, K. Karimov, World Academy of Science, Engineering and Technology (WASET) 56, 852 (2011). [19] H. Benten, N. Kudo, H. Ohkita, S. Ito, Thin Solid Films, 517, 2016 (2009).
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ISSN 2347-3487 [20] K. Shinbo, K. Onishi, S. Miyabayashi, K. Takahashi, S. Katagiri, K. Kato, F. Kaneko, R. C. Advincula, Thin Solid Films 438, 177 (2003). [21] Zucolotto, V.; Ferreira, M.; Cordeiro, M. R.; Constantino, C. J. L.; Moreira, W. C.; Oliveira, O.N. Jr, Synth. Met., 137, 945 (2003). [22] J. Locklin, K. Shinbo, K. Onishi, F. Kaneko, R.C. Advincula, Z. Bao, Chem. Mater. 15, 1404 (2003). [23] H. Ding, X. Zhang, M .K. Ram, C. Nicolini, J. Colloid Interface Sci. 290, 166 (2005). [24] M. D. Shirk, P. A. Molian, A. P. Malshe, Journal of laser applications (JLA). 10, 64 (1998). [25] Z. P. Zhang, P. A. Van Rompay, J. A. Nees, P. P. Pronko, J. Appl. Phys. 92, 2867 (2002). [26] F. H. Moser, A. L. Thomas, Van Nostrand-Reinhold, Princeton, NY, 1963. [27] R. Seoudi, G. S. El-Bahy, Z. A. El Sayed, J. Mol. Struct. 753, 119 (2005). [28] S. S. Mali, D. S. Dalavi, P. N. Bhosale, C. A. Betty, A. K. Chauhanc, P. S. Patil, RSC Adv. 2, 2100 (2012). [29] L. Edwards, M. Gouterman, XV. Porphyrins, J. Mol. Spectrosc. 33, 292 (1970). [30] P. Kumar, K. Santhakumar, P. K. Shin, S. Ochiai, Jpn. J. Appl. Phys. 53, 01 Ab 06 (2014). [31] M. Hara, H. Sasabe, A. Yamada, A. F. Garito, Jpn. J. Appl. Phys. 28, L306 (1989). [32] M. Dressel and G. Grner, Electrodynamics of Solids (Cambridge University press, UK, (2002). [33] A. T. Davidson, J. Chem. Phys. 77, 168 (1982). [34] S. Senthilarasu, R. Sathyamoorthy, S. Lalitha, A. Subbarayan, K. Natarajan, Sol. Energy Mater. Sol. Cells. 82, 179 (2004). [35] R. E. Menzel, Chem. Phys. Lett. 72, 522 (1980). [36] J. Janczak, R. Kubiak, Polyhedron, 20, 2901 (2001). [37] R.A. Collins, A. Krier, A. K. Abass, Thin Solid Films, 229, 113 (1993). [38] O. Stenzel, S. Wilbrant, A. Stendal, U. Beckers, K. Voigtsberger, C. von Bor-czskowski, J. Phys. D., 28, 2154 (1995).
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