Green Synthesis of Well Dispersed Nanoparticles Micro and Nanosystems, 2012, Vol. 4, No. 3 193Fig. (1A). Aqueous extract of A. vasica (B) Chloroauric acid solution (C) Ruby red colour indicating the formation of gold nanoparticles.Fig. (2). UV-vis spectrum of the gold nanoparticles recorded immediately after synthesis (after 5 min).whole content using whatman No.1 filter paper. The filtrate 983/G detector double beam spectrophotometer. XRDis then stored in refrigerator for further use. The reaction is pattern of the A. vasica reduced AuNPs was carried out usingcarried out using different concentrations of plant extract and a Rich Seifert P3000 instrument operated at a voltage of 40finally optimized to a ratio of 1:10 (Extract: Chloroauric acid kV with Cu K radiations. SEM-EDAX was studied to checksolution). Further 3 mL of extract is added to 30 mL aqueous the surface morphology and elemental analysis of the AuNPssolution of chloroauric acid (10-3 M) and kept in an orbital using XL30 FESEM, Philips. TEM studies were carried outshaker at room temperature. Formation of AuNPs takes place by drop coating AuNPs onto carbon-coated TEM grids usingwithin 4 min, evident from the development of a stable ruby Philips Technai-10.red color (Fig. 1) in the solution indicates the reduction ofAu3+ to Au0 with no color change further. The experiment was RESULTS AND DISCUSSION:repeated thrice to check the formation of AuNPs. The The formation of AuNPs is noted down by the colorsynthesized AuNPs are stable at a pH range of 3.6-9.1 showed change after the addition of aqueous extract to chloroauricno precipitation and color change for a period of 45 days. acid solution as illustrated in (Fig. 1). The formation and stability of metal nanoparticles in aqueous solution is studiedCHARACTERIZATION OF GOLD NANOPARTICLES using UV-vis spectrophotometer. The surface plasmon The UV-vis spectra were recorded using Thermo resonance (SPR) arising due to the oscillation of freeScientific Spectrascan UV 2700 with samples in quartz conduction electrons induced by the absorption ofcuvette. FT-IR of Perkin Elmer spectrophotometer was used electromagnetic field  as a absorption band with ato identify the possible groups responsible for the reduction maximum at 532 nm has been observed in the spectrumof chloroauric acid at a resolution of 4 cm-1 in the range of (Fig. 2). To identify the possible functional groups4000-450 cm-1 and the FT-IR spectrum was recorded by responsible for the reduction of chloroauric acid the FT-employing KBr pellet technique using Perkin Elmer model- IR spectrum is taken and the interaction of biomolecules have
194 Micro and Nanosystems, 2012, Vol. 4, No. 3 Karthick et al.Fig. (3). FT-IR spectra of dried powder of (A) A. vasica extract (B) gold nanoparticles.been studied (Fig 3). The spectrum show a clear difference in or –COOH group might have stabilized the AuNPs.the functional group shifts. The peak seen at 3358 cm-1 The stretching of C=O can be observed in the spectrumcorresponds to the –OH or –COOH group which has shifted indicating the red shift from 1625 to 1675 cm-1. Theto higher wavelength 3687 cm-1 thus, implying that the –OH peak 1406 cm-1 corresponds to the –COO- also shows a shift
Green Synthesis of Well Dispersed Nanoparticles Micro and Nanosystems, 2012, Vol. 4, No. 3 195Fig. (4). Diffraction pattern of gold nanoparticles synthesized using A. vasica.Fig. (5A). SEM image shows the presence of bioorganic compounds involved in the reduction (B) EDAX showing strong signals for goldnanoparticles.
196 Micro and Nanosystems, 2012, Vol. 4, No. 3 Karthick et al.Fig. (6A&B). TEM image taken at various magnifications showing gold nanospheres.which confirms the contribution of carboxylate groups in the constant with value from 0.9 to 1, is the wavelength of thereduction. In the spectrum aromatic resonances have not X-ray source, is the full width at half maximum (FWHM)been identified indicating the absence of aromatic groups in and is the Diffraction angle. From this equation, thethe stabilizing compounds. Thus by using FT-IR, it is particle size calculated was found to be 39 nm which isconcluded that –OH or –COOH, -C=O, -COO- groups has similar to the size observed in TEM image of the AuNPs.involved in the stabilization of AuNPs. The crystalline nature The surface morphology and the scale in which the size ofof AuNPs was examined using XRD where three diffraction the nanoparticle synthesized can be studied using the SEM.peaks were observed in the 2 range of 10º to 70º which can The presence of bioactive components responsible for thebe indexed as (111), (200) & (220) reflections of fcc (face reduction of the chloroauric acid to AuNPs was revealedcentered cubic) matches with Joint Committee on Powder using SEM imaging (Fig. 5A). The image confirms theDiffraction Standards (JCPDS No: 04-0784) revealing that presence bioorganic compounds which has stabilized thesynthesized AuNPs are composed of pure crystalline gold as AuNPs. The EDAX profile has showed strong signal forthere is no other peak found (Fig. 4). The XRD patterns gold atoms (Fig. 5B) and weak signals for chlorine, oxygen,obtained were similar to the results reported earlier on sodium and magnesium which implies that these signalsAuNPs . The particle size of the AuNPs formed were might be from the biomolecules present in the aqueouscalculated using Debye-Scherrer equation extract. The morphology of the synthesized nanoparticles were determined by TEM image and shown in (Fig. 6A&B).D = K / cos For the analysis the image is taken in a random place on the Where D is the average crystalline domain size grid and the morphology is observed carefully. The particlesperpendicular to the reflecting planes, K the Scherrer as seen in TEM image are triangular and spherical in shape
Green Synthesis of Well Dispersed Nanoparticles Micro and Nanosystems, 2012, Vol. 4, No. 3 197Fig. (7). Possible mechanism for the reduction of chloroauric acid by bioactive compounds.with an average size of 38 nm with many similar sized REFERENCESparticles except a few. The uniformity in size is a welcoming  Grzelczak, M.; Juste, J.P.; Mulvaney, P.; Marza, L.M.L. Shaperesult in the green synthesis as in most of the cases the control in gold nanoparticle synthesis, Chem. Soc. Rev., 2008, 37,particle size varies with greater range which is a concern 1783-1791.when applied in a targeted drug for therapeutic applications.  Niemeyer, C.M. Nanoparticles, proteins, and nucleic acids:The particle shape usually observed in most of the green Biotechnology meets materials, Science, Angew. Chem. Int. Ed., 2001, 40, 4128-4158.synthesis is triangles and spheres and sometimes hexagon  Sharma, N.C.; Sahi, S.V.; Nath, S.; Parsons, J.G.; Torresdey,. The synthesis of gold nanoprisms has been J.L.G.; Pal, T. Synthesis of plant-mediated gold nanoparticles anddemonstrated  using a plant Cymbopogon flexuosus and catalytic role of biomatrix-embedded nanomaterials, Environ. Sci.a very clear image of prism structures have been observed in Technol., 2007, 41, 5137-5142.TEM. The possible mechanism for the stabilization of  Shankar, S.S.; Ahmad, A.; Pasricha, R.; Sastry, M. Bioreduction of chloroaurate ions by geranium leaves and its endophytic fungusAuNPs is illustrated in (Fig. 7). However, finding the exact yields gold nanoparticles of different shapes, J. Mater. Chem.,chemistry involved in reduction and elucidating the capping 2003, 13, 1822-1826.agent need further substantiation.  Singaravelu, G.; Arockimary, J.S.; Kumar, V.G.; Govindaraju, K. A novel extracellular synthesis of monodisperse gold nanoparticlesCONCLUSION using marine alga, Sargassum wightii Greville, Colloids Surf., B 2007, 57, 97-101. In the present work, a simple and more rapid method to  Govindaraju, K.; Basha, S.K.; Kumar, V.G.; Singaravelu, G. Silver,procure gold nanospheres of monodisperse nature been gold and bimetallic nanoparticles production using single-cell protein (Spirulina platensis) Geitler, J. Mat. Sci., 2008, 43, 5115-displayed and its characterization has been discussed. In 5122.future, such rapid and eco-friendly method may help  Bhumkar, D.R.; Joshi, H.M.; Sastry, M.; Pokharkar, V.B. Chitosanresearchers to synthesize AuNPs using green synthesis than reduced gold nanoparticles as novel carriers for transmucosalchemical methods. The formation of AuNPs in the reaction delivery of insulin, Pharm. Res., 2007, 24, 1415-1426.  Chandirasekar S.; Dharanivasan, G.; Kasthuri, J.; Kathiravan, K.;indicates the presence of bioactive compounds in the plants Rajendiran, N. Facile synthesis of bile salt encapsulated goldwhich are present on the surface of the AuNPs. Such nanoparticles and its use in colorimetric detection of DNA, J. Phys.compound rich AuNPs can be further used in therapeutic Chem. C, 2011, 115, 15266-15273.  Sobhan, M.A.; Sreenivasan, V.K.A.; Withford M.J.; Goldys, E.M.applications and it may have antiallergeic activity if tested on Non-specific internalization of laser ablated pure golda suitable animal model. nanoparticles in pancreatic tumor cell, Colloids Surf., B, 2012, 92, 190-195.CONFLICT OF INTEREST  Srivastava, S.; Verma, R.K.; Subhash, M.M.G.; Singh, C.; Kumar, S. HPLC determination of vasicine and vasicinone in Adhatoda The author(s) confirm that this article content has no vasica with photo diode array detection, J. Liq. Chrom. & Rel.conflicts of interest. Technol., 2001, 24, 153-159.  Paliwa, J.K.; Dwivedi, A.K.; Singh, S.; Gutpa, R.C.ACKNOWLEDGEMENT Pharmacokinetics and in-situ absorption studies of a new antiallergic compound 73/602 in rats, Int. J. Pharm., 2000, 197, We thank DST-Nanomission, Government of India for its 213- 220.financial support for the project (SR/NM/NS-06/2009) and  Philip, D.; Unni C. Extracellular biosynthesis of gold and silverthe management of Sathyabama University, Chennai for its nanoparticles using Krishna tulsi (Ocimum sanctum) leaf, Physicastanch support in research activities. E, 2011, 43, 1318-1322.
198 Micro and Nanosystems, 2012, Vol. 4, No. 3 Karthick et al. Kumar, K.P.; Paul, W.; Sharma, C.P. Green synthesis of gold  Mulvaney, P. Surface plasmon spectroscopy of nanosized metal nanoparticles with Zingiber officinale extract: Characterization and particles, Langmuir 1996, 12, 788-800. blood compatibility, Proc. Biochem., 2011, 46, 2007-2013.  Long, N.N.; Vu, L.V.; Kiem, C.D.; Doanh, S.C.; Nguyet, C.T.; Kumar V.G.; Gokavarapu, S.D.; Rajeswari, A.; Dhas, T.S.; Hang, P.T.; Thien, N.D.; Quynh, L.M. Synthesis and optical Karthick, V.; Kapadia, Z.; Shrestha, T.; Barathy, I.A.; Roy, A.; properties of colloidal gold nanoparticles, J. Phy.: Conf. Ser., 2009, Sinha, S.; Facile green synthesis of gold nanoparticles using leaf 187, 012026. extract of antidiabetic potent Cassia auriculata, Colloids Surf. B,  Shankar, S.S.; Rai, A.; Ankamwar, B.; Singh, A.; Ahmad, A.; 2011, 87, 159-163. Sastry, M. Biological synthesis of triangular gold nanoprisms, Nat. Mater., 2004, 3, 482-488.Received: April 02, 2012 Revised: May 18, 2012 Accepted: May 18, 2012