Silver Nanoparticles: Green Synthesis & Optical Properties

IJSRD - International Journal for Scientific Research & Development| Vol. 4, Issue 11, 2017 | ISSN (online): 2321-0613

Silver Nanoparticles: Green Synthesis & Optical Properties Jeevan Jyoti Mohindru1 Umesh Kumar Garg2 1 Department of Applied Sciences 1 Punjab Technical University, Kapurthala Punjab, India 2 Guru Teg Bahadur Khalsa College of IT, Malout, Punjab, India Abstract— The present study reports a novel green synthesis of Silver nanoparticles using environmentally benign reducing agent (ascorbic acid) and identifies their main physical and optical properties. The stabilization of Silver nanoparticles was done with capping agents like starch and gelatin. The pH of the solution was adjusted to alkaline. Heating was done using a kitchen microwave .Formation of Silver Nanoparticles was indicated by change in color which is supported by the UV absorption at 570nm. Their structural and optical properties were reported. The characterization of Nanoparticles was done by TEM and XRD. In addition to the X-ray diffraction investigations and infrared spectroscopies confirmed the single phase of the copper nanoparticles. Optical studies were carried out by depositing silver nanoparticles on glass substrate using spin coating technique. The optical properties depend upon absorption of radiations which in turn depends upon ratio of electrons and holes present in the material and also on the shape of the nanoparticles. In the present investigation it was observed that optical absorption increases with increase thickness of the film which in turn depend upon speed of spin rotor and amount of silver sol added. The optical band gap for the Nanoparticles was obtained from plots between hv vs. (αhv)2 and hv vs. (αhv)1/2.The value of Band gap came out to be around 4.2 eV which is in close agreement with the earlier reported values. Key words: Silver Nanoparticles, Optical Properties I. INTRODUCTION Silver nanoparticles have attracted the interest of a large no of researchers due to their unique optical properties which are totally different from their bulk counterparts. Synthesis of silver nanoparticles has been carried out in recent past by a large no of research workers. It is always an area of concern to consider environment factors while developing a synthesis method for various materials. The development of an environmentally benign, low-cost method of nanoparticle synthesis is the need of the hour as these particles are required on commercial scale due their unique properties. Green chemistry provides an opportunity to improve upon the synthetic strategies in such a way that they have less detrimental effects on environment. Silver nanoparticles found incredible applications as antimicrobial agents, diagnostic agents, micro electronics and therapeutic usage [1-5]. Now a day’s most of the beauty products have silver nanoparticles due to strong inhibitory and bactericidal effects and also the ingredients of certain drugs due to their broad spectrum of antimicrobial activities. Silver nanoparticles have also been reported to possess antifungal, anti-inflammatory and antimicrobial activity. Silver nanoparticles have been synthesized in recent past by a variety of methods such as Chemical reduction method, electrochemical method, thermal decomposition, laser ablation, microwave irradiation and Sono-chemical

synthesis [6-10]. All these method require some refinement so as to become commercially viable as well environmentally clean route to synthesize silver nanoparticles. We are reporting the green synthesis of silver nanoparticle by using environmentally benign reducing agents like ascorbic acid with microwave irradiation technique. The optical properties of nanoparticles depend largely upon size shape and concentration of these particles in the distribution medium. Controlling these parameters, it is possible to develop nanomaterials with unique optical properties. The size of the nanoparticles lies in the range1100nm; which is far below UV Visible and Infrared region wavelength range. The sub-wavelength dimension is necessary for detention of charges and separation of energy levels, thus imparting to the nanoparticles distinct optical properties that move away substantially from the properties of bulk. The most important ones include the plasmonic effects with metals, the quantum confinement effects with semiconductor nanoparticles (quantum dots), and photo thermal effects, which make nanoparticles a strong contender for numerous applications in the allied field of optics. Metals are generally considered as good light reflectors due to the large number of mobile electrons. But as the size of metal particles decreases down to sub-wavelength range, this generalization does not hold any more since the electrons are restricted within the small volume. Optical properties of silver nanoparticles have been studied both in colloidal and thin film deposition forms on various solid substrates. The electrical conductivity of silver metal is (6.3 × 107 S/m) which is highest among all the metals, so silver nanoparticles are most suited candidates nano-electronics [11-13]. Silver nano-films have been prepared previously by techniques, such as vacuum coating, drop casting and air-spraying from NW suspension and spin coating. The vacuum coating method produces highly transparent films with excellent conductivity [14]. Using drop casting method always shows circular rings and discontinuous film on the substrates [15-16]. The film obtained from air-spraying coating is much better, but still forms sparse and non-uniform networks. In the present study we are using spin coating technique which is fast, easy and convenient method for making thin films of colloidal suspensions. Moreover in this method we can easily add any other material as dopent which may affect the properties of the thin film. II. EXPERIMENTAL A. Materials: All the materials used were obtained from Merk and Ranbaxy chemical division and were of analytical grade. Silver nitrate (A.R.), Starch(capping agent) and Ascorbic acid(reductant) were used as such with no further purification. For the preparation of mixture solution, deionized water was used.

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Silver Nanoparticles: Green Synthesis & Optical Properties (IJSRD/Vol. 4/Issue 11/2017/122)

B. Methodology: The silver sol was prepared by reduction of Ag+ ions using Ascorbic acid as a reductant. In this method water is used as the medium for reduction and stabilization of silver Nanoparticles was carried out with starch. The weight ratios of AgNO3 metal salt to starch were1:2,1:4, 1:8. The reaction mixture was heated using a kitchen microwave for about 5 minutes and the pH of the solution was adjusted to alkaline using NaOH solution. (Fig-2) Formation of Silver Nanoparticles was indicated by change in color of the solution from blue to yellowish black which is supported by the UV absorption at 570nm.the synthesized particles were washed with water and alcohol. [12-14]. The silver sol is applied on the glass substrate with a glass rod and a drop of silver sol is applied on the substrate mounted on a spin coater. After some time it is removed and dried and the coated films are ready for analysis. The speed of the spin coating machine and concentration of sol determines the thickness of the coating. A high concentration of sol and low spin speed gives a thicker coating of film on the substrate. The glass substrate is placed in vacuum oven for drying the film at 60 °C. Similar procedure is adopted for making thin films of silver sol containing Dicinnamalacetone.

size distribution of copper nanoparticles. Optical studies involved the mathematical treatment of UV absorption data using standard equation to find out the binding energy of the synthesized copper nanoparticles, the variation in size of copper nanoparticles can be correlated with variation in the binding energy of the copper nanoparticles A. Characterization of Silver Nanoparticles: Batch experiments were performed by varying the concentration of copper ions, reducing agents, capping agents and pH regulators at room temperature. Heating was done by using kitchen microwave oven. The Characterization of nanoparticles would be done by UV, XRD and SEM analysis. (Fig. 3(a), (b) & (c))

Fig. 1: Green Synthesis of Silver Nanoparticles (AgNP)

Fig. 2: Deposition of Silver nanoparticle sol by spin coating method. Ratio(Ag+ ion : Ascorbic Starch Geraniol reducing agent) Acid 1:2 48min 42min 54min 1:4 37min 35min 43min 1:8 25min 22min 31min Table 1: Time taken for the formation of silver nanoparticles with different ration of silver ions and reducing agent III. RESULT AND DISCUSSION Characterization and optical studies of stabilized copper nanoparticles were carries out and it was found that the concentration of copper ions in the starting solution effects

Fig. 3: (a) UV spectra of Silver Colloidal Solution Prepared showing Absorption Maxima-560nm(b) Fig.-XRD of stabilized silver nanoparticles(c) SEM Images of Silver Nanoparticles B. Optical Properties of Silver Nano-films: X-Ray diffraction:

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Silver Nanoparticles: Green Synthesis & Optical Properties (IJSRD/Vol. 4/Issue 11/2017/122)

XRD can be used to characterize the crystallinity of nanoparticles. The XRD Pattern were obtained using analytical’s Xpert-pro powder diffractometer employing Cu – Kα radiations in the 2θ range. where d = average particle size, β is full width at half maxima (FWHM), θ is the Bragg angle, λ is the wavelength of Cu Kα in radians [17-21]. The broad peak indicates that the silver nanoparticles thin film on glass substrate is amorphous in nature. UV-VIS. Spectroscopy: The formation of silver nanoparticles was monitored using UV-VIS absorption spectroscopy [22-28]. For analyzing the band gap of synthesized nanomaterials, the absorption spectrum is recorded through Double beam UVVIS absorption spectrometer in the range of 200-800 nm. Fig. 3 shows UV-VIS absorption spectra of as prepared silver nanoparticles on glass substrate.. The UV- VIS. spectroscopy revealed the formation of silver nanoparticles by exhibiting the typical surface plasma on absorption maxima at 290 nm for UV-VIS. spectrum. A sharp peak is observed near 290 nm, after which there is sharp decrease in absorption. Then there is sharp increase in absorption and a bump appears on 340 nm in the ultraviolet region and then it start decreases linearly up to visible region. Cut off wavelength in case of silver nanoparticles thin film on glass substrate is 290 nm. Ag Nanoparticles thin films on glass substrate have been confirmed using SEM, XRD and UV-VIS. spectroscopy. The thickness of silver nanoparticles thin films carried out by ellipsometry spectroscopy on glass substrate was 246.4nm.Silver nanoparticles on thin film on glass substrate were amorphous in nature. In UV-VIS. spectra, there is decrease in absorption in visible region. The band gap of silver thin film on glass substrate were 4.2 eV and films with Dicinnamalacetone it showed a band gap of 4.78ev IV. CONCLUSION Green synthesis of Silver nanoparticles has been arried out successfully. Optical properties were analyzed which gave a band gap value of 4.2-4.78eV.Band gap is found to depend upon factors such as particle size, nature of impurity added and initial concentration taken. Thin films of silver nanoparticles were deposited on glass substrate by spin coating technique. The structural and optical properties of the prepared Ag Nanoparticles thin film on glass substrate have been confirmed using SEM, XRD and UV-VIS. spectroscopy. The thickness of silver nanoparticles thin films carried out by ellipsometry spectroscopy on glass substrate was 246.4nm.Silver nanoparticles on thin film on glass substrate were amorphous in nature. In UV-VIS. spectra, there is decrease in absorption in visible region. The band gap of silver thin film on glass substrate were 4.2 eV and films with Dicinnamalacetone it showed a band gap of 4.78ev ACKNOWLEDGMENTS The authors are thankful to Punjab Technical University, Kapurthala and Guru Nanak Dev University, Amritsar for their support in analyzing the data. The authors are also thankful to Principal DAV College, Amritsar for providing the necessary lab facilities. A special thanks to University Grants Commission (New Delhi) for funding

REFERENCES [1] Jeevan Jyoti Mohindroo and Umesh Kumar Garg Optical Properties of copper nanoparticles, AIP ConferenceProceeding,1728,020534 (2016); http://dx.doi.org/10.1063/1.4946585 Conference date: 30–31 October 2015 [2] V.M. Shalaev, S Kawata, Advances in Nano-Optics and Nano-Photonics.(Elsevier,UK, 2007)pp2003-06 [3] M L. Brongersma, P G. Kik, Surface Plasmon Nanophotonics; 131(Springer: Berlin, DE, 2007)pp5573 [4] J.Tominaga,D.P. Tsai: Optical Nanotechnologies, Topics in Applied Physics,88(Springer ,Berlin 2003)pp5-15 [5] M Raghini, C Girard, R. Quidant, J. Opt. A: Pure Appl. Opt. 10 (09), 1-15(2008) [6] J Wang,., W.J Blau, J. Opt. A: Pure Appl. Opt. 11, 3-12 (2009) [7] K. A. Willets and R. P. Van Duyne, Annu. Rev. Phys. Chem. 58,267-297(2007) [8] U. Kreibig,, M. Vollmer,: Optical Properties of Metal Clusters, 25( Springer, Berlin 1995)pp1-532 [9] S. Asano and G. Yamamoto, Appl. Opt. 14(1), 29– 49(1975) [10] M. A. Mahmoud, B. Snyder and M. A. El-Sayed, J. Phys. Chem. C 114, 7436–7443 (2010) [11] E. M. Perassi, L. R. Canali and E. A. Coronado, J. Phys. Chem. C 113, 6315–6319 (2009) [12] A.Rastar, M.Esmail, A.Rashidi, S.M.Bidoki. Journal of. Engineering of fibre and fabrics 8(2) , 85-96 (2013) [13] Y Jian-guang et al, Trans. Nonferrous Met. Soc.17 ,1181-118(2007) [14] S. Panigrahi, S. Kundu S.K Ghosh., S. Nath and T. Pal ,(Journal of Nanoparticle Research* 6 ,411–414 ( 2004) [15] Z. Yin, D. Ma.* and X. Bao *, Chem. Comm 46, 1344– 1346 (2010) [16] X. YANG, S. CHEN, S. ZHAO, D. Lia and Houyima, J. Serb. Chem. Soc 68(11),843–847(2003) [17] A.U. Ubale and M.R. Belkhedkar, J. Mater. Sci. Technol. 31(1), 1-9 (2015) [18] S. Schultz , D. R. Smith, J. J. Mock, D. A. Schultz, 2000, PNAS 97, pp.996-1001. 10.1073/pnas.97.3.996 [2] M. Rai, A. Yadav, A. Gade, Biotechnol, 27 (2009) 76-83. 10.1016/j.biotechadv.2008.09.002 [19] J. L. Elechiguerra, J. L. Burt, J. R. Morones, A. Camacho-Bragado, X. Gao, H. H. Lara, M. J. Yacaman, J. Nanobiotechnol. 3 (2005) 6-12. 10.1186/1477-3155-36 [20] D. I. Gittins, D. Bethell, R. J. Nichols, D. J. Schiffrin, J. Mater. Chem. 10 (2000) 79-83. 10.1039/a902960e [21] D. V. Goia, E. Matijevic, J. Chem. 22 (1998) 1203-1208. 10.1039/a709236i [22] C. Taleb, M. Petit, P. Pileni, Chem. Mater. 9 (1997) 950958. 10.1021/cm960513y [23] K. Esumi, T. Tano, K. Torigoe, K. Meguro, Chem. Mater. 2 (1990) 564-573. 10.1021/cm00011a019 [24] Henglein, Langmuir 17 (2001) 2329-2334. 10.1021/la001081f [25] L. Rodriguez-Sanchez., M. C. Blanco, M. A. LopezQuintela, J. Phys. Chem. B 104 (2000) 9683-9686. 10.1021/jp001761r

All rights reserved by www.ijsrd.com

452

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[26] D. Azulai, T. Belenkova , H. Gilon , Z. Barkay, G. Markovich, Nano Lett. 9 (2009) 4246-4249. 10.1021/nl902458j [27] Y. Sun , Nanoscale 2 (2010) 1626-1642. 10.1039/c0nr00258e [28] S. De, T. M. Higgins, P. E. Lyons, E. M. Doherty, P. N. Nirmalraj, W. J. Blau, J. J. Boland, J. N. Coleman, Acs Nano 3 (2009) 1767-1774. 10.1021/nn900348c [29] J. Y. Lee, S. T. Connor, Y. Cui, P. Peumans, Nano Lett. 10 (2010) 1276-1279. 10.1021/nl903892x [30] T. Robert, M. B. Teresa, D. B. Jeremy, J. F. Andrew, T. Bobby, M. G. Lynn, J. H. Michael, L. B. Jeffrey, Adv. Mater. 21 (2009) 3210-3216. 10.1002/adma.200803551 [31] M. Epifani, C. Giannini, L. Manna, Materials Letters 58 (2004) 2429-2432. 10.1016/j.matlet.2004.02.024 [32] Y. Godowsky, A. E. Varfolomeev, A. E., Zaretsky, J. Mater. Chem. 11 (2001) 2465-2469. 10.1039/b103048p [33] Y. Kayanuma, Phys. Rev. B 85 (1998) 9797-9805. 10.1103/physrevb.38.9797 [28] L. Brus, J. Phys. Chem. 90 (1986) 2555-2560. 10.1021/j100403a003

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