EFFECT OF EXTRACT CONCENTRATION AND AGEING ON OPTICAL PROPERTIES OF BIOLOGICAL SILVER NANOPARTICLES

Transcription

1 Original Research Article Biotechnology International Journal of Pharma and Bio Sciences ISSN EFFECT OF EXTRACT CONCENTRATION AND AGEING ON OPTICAL PROPERTIES OF BIOLOGICAL SILVER NANOPARTICLES PATIL SUNITA AND MUTHUSAMY PALANISWAMY* Department of Microbiology, School of Life Sciences, Karpagam University, Coimbatore- 21, Tamil Nadu, India. ABSTRACT Biological synthesis of silver nanoparticles is an emerging trend in nanotechnology. The size, shape and optical properties of the silver nanoparticles can be controlled using plant extract concentration. A characteristic feature of noble metal nanoparticles is the strong color of their colloidal solutions, which is caused by the surface plasmon absorption. This size dependent electronic and optical property is possibly suitable for many electronic and photoelectronic applications. The UV-vis absorbance is used characterize the kinetics of formation, final colloid stability and to study the structural and morphological features. This article describes the synthesis of silver nanoparticles using five different concentrations (2 ml to 10 ml) of Aegle marmelos fruit pulp extract to study the property of surface plasmon absorption during the process of synthesis and aging using UV-Visible spectroscopy. As extract concentration increases surface plasmon absorption and rate of synthesis increased with decrease in particle size by giving narrow absorption peak. During ageing silver nanoparticles synthesized from 8-10 ml extract concentration have shown slight change in peak position at higher wave length. The biological reducing agent and silver nitrate ratio can affect the rate of synthesis, surface plasmon properties and ageing process of biological silver nanoparticles. KEYWORDS: Silver nanoparticle, Biological synthesis, UV-Visible spectrum, surface plasmon resonance MUTHUSAMY PALANISWAMY* Department of Microbiology, School of Life Sciences, Karpagam University, Coimbatore- 21, Tamil Nadu, India. Received on: Revised and Accepted on: DOI: B-686

2 INTRODUCTION Nanoparticles have optical properties that are sensitive to size, shape, concentration, agglomeration, and refractive index. 1 The dispersions of nanoparticles display intense colours due to the plasmon resonance absorption. The surface of a metal is like plasma, having free electrons in the conduction band and positively charged nuclei. Surface plasmon resonance (SPR) is a collective excitation of the electrons in the conduction band; near the surface of the nanoparticles. 2 Electrons are limited to specific vibrations modes by the particle s size and shape. Therefore, metallic nanoparticles have characteristic optical absorption spectrum in the UV-vis region. 3 The surface properties of nanoparticles make UV/Vis/IR spectroscopy a valuable tool for identifying, characterizing, and studying these materials. Nanoparticles made from certain metals, such as gold and silver, strongly interact with specific wavelengths of light and the unique optical properties of these materials is the foundation for the field of plasmonics. 4 Metal colloidal nanoparticles are becoming increasingly important in the field of science due to their analytical, electrical and optical properties. 5 The physical, chemical and optical properties of metal nanoparticles are highly influenced by its size, shape method of synthesis, capping agent. Silver nanoparticles continues to be of great current interest in various fields like medicine, cosmetics, food industry, fabrics due to their desirable optical, electronic, biological and chemical properties. 6 Size dependent optical and surface plasmon properties of silver nanoparticles have been explored in sensing biological molecule. Nowadays biological silver particles have been synthesized by using biological agents such as bacteria, fungi, plants, etc. 6-9 The controlled synthesis of biological silver nanoparticles is one of the most challenging tasks for novel nanotechnology. For effective application of biological silver nanoparticle, it is very important to control particle size, shape and morphology as well during nanoparticle synthesis. Biological synthesis of silver nanoparticle is an easy, simple and reliable technique for preparing metal particles in the nanometer range. In the present investigation, the silver nanoparticles were synthesized by biological route. Five different concentrations of Aegle marmelos fruit pulp extract were used to prepared silver nanoparticles. Silver nanoparticles Maturation and aging effect have been analyzed using UV/Vis absorption spectroscopy. MATERIALS AND METHODS Fruit pulp extract preparation The half ripen A. marmelos fruits were collected from the area of Coimbatore. Washed them thoroughly under tap water and then with distilled water. Fruit pulp was removed and seeds were separated. The pulp was dried in hot air oven at 60 o C for 48 h. Dried fruit pulp was ground in coarse powder and stored in air-tight container for further use. 2 gm of fruit pulp mixed with 100 ml deionized water and heated at 70 o C for 15 min. This mixture was cooled and filtered using Whatman No 1 filter paper. The obtained extract was used further for the synthesis of silver nanoparticles. Silver nanoparticle synthesis Silver nanoparticles were synthesized using five different concentration Aegle marmelos fruit pulp extract (2ml-10ml). Aqueous solutions of silver nitrate (Merk, India) were prepared so that it will give 0.1 mm final concentration after mixing with different concentrations of plant extract. The reaction mixtures were monitored for colour change from light yellow to brown which indicates the formation of silver nanoparticles. Uv-visible spectrum study The UV-visible analysis was done by using Shimadzu UV-2450 spectrophotometer at room temperature. UVvisible spectra of reaction mixtures were recorded at 15 min time interval during the process of maturation of silver nanoparticle. UV-spectra of synthesized silver nanoparticles were recorded for ten weeks at every one week time interval to observe changes in optical properties of silver nanoparticle in relation to plant extract concentration and time. RESULTS AND DISCUSSION Surface plasma resonance observed in the visible absorption spectrum is the dominant feature of metal nanoparticles. However, the exact position of resonance depends upon particle size, shape, embedding medium, chemical surroundings, interparticle interaction, and free electron density. 11 SPR is the resonant interaction between plasma and incident light. Plasma is conduction band electron near the surface of nanoparticles, the strong absorption of light occurs when the frequency of the incident light matches the resonant frequency of the plasma. This property efficiently used for monitoring the electron injection and aggregation in nanoparticles. 12 In silver nanoparticles, conduction band and valence band lie very close to each other in which electrons moves freely, this gives SPR absorption band. 13 This band is due to collective oscillation of silver nanoparticles electrons in resonance with the light wave, which is the origin of observed colour. 14 UV-visible spectroscopy is one of the popular characterization techniques to determine particle formation and its optical properties. The UV-visible spectra during the process of biological silver nanoparticles synthesis are given in figure 1. These spectra were recorded at every 15 min time interval which shows the absorption peaks at 431 nm. The peak intensity increased with time till maturation of silver nanoparticles (260 min) while there is no change in bandwidth. Also, the peak positions remain same throughout the maturation. According to quantum theory plasma resonance broadens with the decrease in particle size, this study shows no broadening of peaks which confirms there was an increase in silver nanoparticle concentration in the reaction mixture with same size as time passes. There is no any absorption peak at longer wavelength (beyond 600 nm) confirms that the reaction was saturated. This may be due to the fact that the reaction gets saturated and reduction of Ag + to Ag 0 was complete. The saturated reaction results from the saturation of electron injection into the silver nanoparticles by plant extract. 14,15 B-687

3 Figure 1 UV-visible spectra of biological silver nanoparticles during maturation at every 15 min time interval To study the effect biological reducing agent concentration on the rate of synthesis, stability, size and SPR silver nanoparticles were synthesized using five concentrations of A. marmelos fruit pulp extract (2-10 ml) and the UV spectra were recorded at fixed time. It shows that intensity of absorbance increased with increase in fruit pulp extract concentration used for synthesis. There was very slight change in peak position; higher concentration shows blue shift from 432 nm to 427 nm due to change in particle size. This confirms the higher plant concentration lower the size of biological nanoparticle. During synthesis intensity of colour was increased with increasing plant extract concentration which indicates the rate of silver nanoparticle synthesis increases with A. marmelos fruit pulp extract concentration. Figure 2 UV-visible spectra of silver nanoparticles synthesized using five different concentration of fruit pulp extract Silver nanoparticles were synthesized using five different concentrations of fruit pulp extract and Uvvisible spectra of five biological silver nanoparticles were recorded for 10 weeks at 1 week time interval. The spectra are given in figure 3, it shows that absorption silver nanoparticle band in visible light region within typical silver nanoparticle range at 432 nm for 2 ml, 430 nm for 4ml, 428 nm for 6 ml, 427 nm for 8 ml and 427 nm for 10 ml. As the extract concentration increases peak shows blue shift indicates there is reduction in the particle size. 11 The plasmon peak and the full-width of half-maxima (fwhm) depends on the extent of colloid aggregation. 16 The stability of the biological silver nanoparticles was monitored by measuring the absorption of the colloid at different periods of time. There was no obvious change in peak position for silver B-688

4 nanoparticles synthesized from 2 and 4 ml concentration. But the increase in absorbance (figure 3) indicates that amount of silver nanoparticles increases with time. The stable position of absorbance peak indicates that new particles are not aggregated. 17 A shift of the peak position to longer wavelengths cannot be recognized for the silver nanoparticles because they are still too small. The peak position is at λ 430 nm which corresponds to the peak position of small silver spheres calculated with the Mie theory. Since the silver nanoparticles possessed a negative charge due to the adsorbed plant extract molecules such as phenols, a repulsive force worked along particles and prevented aggregation. This increased absorbance is due to change in colour of silver nanoparticles. 18 The nanoparticle synthesized by 6, 8 and 10 ml plant extract shown slight red shift. Nanoparticle optical properties are also sensitive to the proximity of other plasmonic materials. When two or more plasmonic nanoparticles are closer each other their surface plasmons couple as the conduction electrons on each particle surface collectively oscillate. This effect is similar to molecular orbital theory in that plasmon coupling results in the oscillating electrons assuming the lowest energy state, causing the plasmon resonance wavelength of the coupled particles to red-shift to longer wavelengths (lower energies). 19,20 This coupling effect is responsible for the visible colour change in plasmonic nanoparticle solution from reddish brown to blackish brown. Figure 3 UV-visible spectra of silver nanopartilcles recorded at every one week time interval for ten weeks a) 2ml b) 4ml c) 6ml d) 8ml e) 10ml Figure 4 UV-absorbance of biological silver nanoparticles synthesized using five concentrations of fruit pulp extract at different time intervals. B-689

5 The figure 4 1 shows that absorbance of silver nanoparticles synthesized from different plant extract concentration was increased with time. A large oscillator strength is expected for longitudinal plasmon modes, consistent with the absorbance increase observed over time. 21 The absorbance of silver nanoparticle synthesized with 2, 4, and 6 ml extract increased with time. However silver nanoparticles of 8 and 10 ml extract shown increased absorbance till 6 weeks and low absorbance rate observed after 7 weeks with band shift. This indicates there is an increase in particle size with no further increase in absorbance with time. Silver nanoparticles dimer formation was followed with time by visible spectroscopy. The shift in plasmon absorption band for 8 and 10 ml ( nm) were ascribed to an increase in particle aspect ratio upon dimer formation with time. 22 CONCLUSION Silver nanoparticles have been synthesized by the biological method and analyzed using UV-visible spectra. It observed that as the concentration of plant extract and time increases the spectral absorption increases. Higher plant extract concentration gives smaller particle size, while lower plant extract concentration gives more stable particles without changing absorbance peak position. The extract (reducing agent) concentration modulates the rate of synthesis, morphology and surface plasmon resonance of silver nanoparticles. By changing plant extract concentration and silver nitrate ratio can be possible to synthesize silver nanoparticle with desired optical properties for various applications. ACKNOWLEDGEMENT Authors Thanks to Department of Science and Technology, Government of India for financial support vide reference No. SR/WOS-A/LS-1196/2015 under Women Scientist Scheme to carry out this work. CONFLICT OF INTEREST Conflict of interest declare none. REFERENCES 1. Baia L, Simon S. UV-VIS and TEM assessment of morphological features of silver nanoparticles from phosphate glass matrices. Modern Research Education Topics im Microscopy 2007; Krishnaraj S, Balamurugan V, Chandramohan S. UV VIsible spectroscopic analysis of green synthesized silver nano particles Eur j pharm med res 2017 Jan 4(2): Noginov MA, Zhu G, Bahoura M, Adegoke J, Small C. The effect of gain and absorption on surface plasmons in metal nanoparticles. Appl Phys 2007 Feb;86: Wiley JB, Im SH, Li Z,McLellan J, Siekkinen A, Xia Y. Maneuvering the Surface Plasmon Resonance of Silver Nanoparticles through Shape- Controlled Synthesis. J Phy Chem 2006 Apr 21; 110: Das R, Nath SS, Chakdar D, Gope G. Preparation of Silver Nanoparticles and Their Characterization. J Mat 2009 Jun 17; Biswas PK, Dey S. Effects and applications of silver nanoparticles in different fields. Int J Rec Sci Res 2015Aug 28;6: Ghosh SK, Pal T. Interparticle Coupling Effect on the Surface Plasmon Resonance of Gold Nanoparticles : From Theory to Applications. Chem Rev 2007 Nov 3; 107: Desai R, Mankad V, Gupta SK, Jha PK. Size Distribution of Silver Nanoparticles : UV-Visible Spectroscopic Assessment. Nanosci Nanotechnol Lett 2012;4(1): Peddi SP, Sadeh BA. Structural Studies of Silver Nanoparticles Obtained Through Single-Step Green Synthesis. Mat Sci Eng 2015; 92: Thombre, R., Parekh, F. & Patil, N. Green synthesis of silver nanoparticles using seed. Int J Pharm Bio Sci 2014 Jan; 5(1): Kumarasamyraja D, Jeganathan NS. Green synthesis of silver nanoparticles using aqueous extract of Acalypha indica and its antimicrobial activity.int J Pharm Bio Sci 2013 Jul; 4(3): Mulvaney P. Surface Plasmon Spectroscopy of Nanosized Metal Particles. Langumir 1996 Jul 7;(12): Amamoto SY, Ujiwara KF, Atarai HW. Surface- Enhanced Raman Scattering from Oleate-Stabilized Silver Colloids at a Liquid / Liquid Interface. Ana Sci 2004 Sep;20(9): Šileikaitė AS, Evas IPČ, Puišo J, Juraitis A, Ė AG. Analysis of Silver Nanoparticles Produced by Chemical Reduction of Silver Salt Solution. Mat Sci 2006;12(4): Quinten M, Optical Properties of Nanoparticle Systems. Boschstr. 12, Weinheim, Germany. Wiley-VCH Verlag & Co. KGaA; NanoComposix Plasmonics. [citated 2017 May 2] Available from Liveri, Lockwood, editor. Controlled Synthesis of Nanoparticles in Microheterogeneous Systems Vincenzo. United States of America, Springer; Kreibig U, Quinten M, Schoenauer D. Optical Properties of Many-Particle Systems. Physica Scripta 1986; 13: Dimers N, Brousseau L, Marinakos S, Marinakos M, Feldheim DL, Assembly of Phenylacetylene- Bridged Gold. Adv Mat 1999 Jun 10; 11(6): Geoprincy G, Srri BNV, Poonguzhali U, Gandhi NN, Renganathan S. A review on green synthesis of silver nanoparticles. Asian J Phrmaceutical Clin Res. 2013;6(3): Majeed A, Ullah W, Anwar AW, Shuaib A, Ilyas U, Khalid P, et al. Cost-effective biosynthesis of silver nanoparticles using different organs of plants and their antimicrobial applications: A review. Mater Technol Mar 9: Dimers N, Brousseau L, Marinakos S, Marinakos M, Feldheim DL, Assembly of Phenylacetylene- Bridged Gold. Adv Mat 2014 Jun 11(6): B-690

6