Phyto-mediated synthesis of Gold Nanoparticles using the aqueous extract of Eichhornia crassipes (Mart.) SOLMS

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1 Research Article ISSN: Available online through Phyto-mediated synthesis of Gold Nanoparticles using the aqueous extract of Eichhornia crassipes (Mart.) SOLMS M. Jannathul Firdhouse 1 and P. Lalitha* 2 1 Research Scholar, Department of Chemistry, Avinashilingam Institute for Home Science and Higher Education for Women University, Coimbatore , Tamil nadu, India. *2 Assistant Professor (SS), Department of Chemistry, Avinashilingam Institute for Home Science and Higher Education for Women University, Coimbatore , Tamil nadu, India. Received on: ; Revised on: ; Accepted on: ABSTRACT An environmental benign, non-toxic and safe method of synthesis of gold nanoparticles was employed using the aqueous extract of Eichhornia crassipes under various experimental conditions. The formation of gold nanoparticles was investigated by UV-visible spectrophotometer. The size and shape of the synthesized gold nanoparticles was confirmed by X-ray diffraction analysis, Scherrer s formula and Scanning Electron Microscopy. Comparative study of experimental methods revealed that the homogenization method results in rapid synthesis of gold nanoparticles. The size of the gold nanoparticles varies depending upon the method of synthesis. KEY WORDS: Eichhornia crassipes, Gold nanoparticles, XRD, SEM. INTRODUCTION The application of nanoscale materials and structures, which by definition should fall in the range between 1 to 100 nanometers (nm) is an emerging area of nanoscience and nanotechnology [1]. Currently, the main thrust of research in nanotechnology focuses on applications in the field of electronics, energy, medicine and life sciences [2]. Nanoparticles often exhibit novel properties, different from those of bulk materials, which strongly depend on size, shape and surface configuration [3]. Nanoparticles increase chemical activity due to crystallographic surface structure with their large surface to volume ratio [4]. Gold nanoparticles possess catalytic activity and hence are used for reaction such as the water gas shift reaction and selective oxidation of CO. Gold nanoparticles also used in the field of sensors. In biology, gold nanoparticles are used for the development of biosensors, DNA labels and in medicine. However, spherical gold nanoparticles have been used to generate functional electrical coatings [5]. *Corresponding author. P. Lalitha 1 Research Scholar, Department of Chemistry, Avinashilingam Institute for Home Science and Higher Education for Women University, Coimbatore , Tamil nadu, India. Gold nanospheres have a characteristic red colour, but anisotropic gold nanorods have a dramatically changed colour. More recent treatments have shown that the colour is due to the collective oscillation of the electrons in the conduction band, known as the surface plasmon oscillation. The oscillation frequency is usually in the visible region for gold giving rise to the strong surface plasmon resonance absorption which has an absorption coefficient orders of magnitude larger than strongly absorbing dyes. Gold nanoparticles generate enhanced electromagnetic fields that affect the local environment. The field is determined by the geometry of the nanoparticle and can enhance fluorescence of the gold itself, the Raman signal of a molecule on the surface, and the scattering of light [6]. There are several methods of synthesis of nanogold particles most common being chemical and biological methods. The biological method of synthesis of nanoparticles have proved to be better than the chemical methods due to slower kinetics, which offers a better control over crystal growth and reduced capital involved in production. Elimination of hazardous chemicals favours green synthesis as an eco-friendly one. Research in this area is mainly motivated by the possibility of designing nanostructured materials that possess novel electronic, optical, magnetic, photochemical and catalytic properties [7]. An earlier study was found that Bacillus subtlis 168 was able to reduce Au 3+ ions to gold nanoparticle with a range of 5-25 nm inside the cell walls. Sastry and co-workers (2003) reported some biological syntheses of gold and silver nanoparticles using microorganisms intracellularly or extracellularly [8]. Different plants involved in both the intra- and extracellular preparation of silver and gold nanoparticles (GNPs) are reported, for example, oat (Avena sativa), lemongrass extract (Cymbopogon flexuosus), leguminous shrub (Sesbania drummondii), (Brassica juncea), neem

2 leaf broth (Azadirachta indica), pine (Pinus desiflora), persimmon (Diopyros kaki), ginkgo (Ginko biloba), magnolia (Magnolia kobus), and platanus (Platanus orientalis) [9]. The water hyacinth, Eichhornia crassipes (Mart.) Solms, is a tropical species belonging to the pickerelweed family (Ponte-deriaceae). It is a free floating aquatic plant well known for its production abilities and removal of pollutants from water. It can quickly grow to very high densities. The presence of proteins, carbohydrates, alkaloids, quinones and anthocyanins in aqueous extract was also reported [10]. Recently, rapid synthesis of silver nanoparticles using aqueous extract of Eichhornia crassipes (Water Hyacinth) and its antimicrobial activity were studied [11]. In this paper, we explore the phyto-mediated synthesis of gold nanoparticles from the aqueous extract of Eichhornia crassipes under different experimental methods. The synthesized gold nanoparticles were characterized by UV-visible spectrophotometer, XRD and SEM analysis. MATERIALS AND METHODS A.Plant collection Fresh plant of Eichhornia crassipes was collected from local water body in Coimbatore. B.Preparation of the extract The aqueous extract (~1 g) of Eichhornia crassipes was weighed and boiled for 5 mins with 100 ml of Millipore water in a 500 ml Erlenmeyer flask. The prepared extract was filtered thrice using Whatman filter paper to obtain clear solution. The colour of the extract was dark brown and refrigerated for further experiments. C.Synthesis of gold nanoparticles The aqueous extract of Eichhornia crassipes was treated with gold chloride solution under various experimental conditions is given below. i.room temperature The aqueous extract of Eichhornia crassipes (5ml) was treated with five different concentrations (1ml, 2ml, 3ml, 4ml and 5ml) of 3mM gold chloride solution and kept under room temperature. ii.higher temperature The different concentrations of gold chloride solutions with constant volume of aqueous extract of Eichhornia crassipes were heated in a water bath maintaining a temperature of about C. iii.sonication The same concentrations of gold chloride solutions with constant volume of aqueous extract of Eichhornia crassipes were sonicated using an ultrasonic bath (PCI Ultrasonics (1H)). iv.homogenization Varied concentrations (1ml, 2ml, 3ml, 4ml and 5ml) of gold chloride solutions was treated with 5ml of aqueous extract of Eichhornia crassipes using homogenizer (Ultrasonic Homogenizer Model 300 V/T). D.Separation of gold nanoparticles The formation of purple colour was monitored by UV-visible spectrophotometer. The separation of the synthesized nanoparticles was done using centrifugation (Spectrofuge 7M). Redispersion of the pellets into Millipore water and repeated centrifugation was carried out. The supernatant solutions were refrigerated for further experiments. E.Characterization of gold nanoparticles a) UV visible spectra analysis The bioreduction of aurate ions in aqueous solution was monitored by UV visible spectra of the supernatant solution as a function of time at room temperature using Double beam spectrophotometer 2202 (Systronics). b)xrd analysis X-ray diffraction (XRD) analysis of drop-coated films of gold nanoparticles in a glass substrate was prepared for the determination of the formation of Au nanoparticle by an Lab X XRD-6000 (Shimadzu) operated at a voltage of 40 kv and a current of 30 ma with Cu Ka radiation. c)determination of crystalline size of AgNPs XRD patterns were analyzed to determine peak intensity, position and width. Fullwidth at half maximum (FWHM) data was used with the Scherrer s formula to determine mean particle size. Scherrer s equation is given by D= 0.94l/ßcosq where d is the mean diameter of the nanoparticles, λ is wavelength of X-ray radiation source, β is the angular FWHM of the XRD peak at the diffraction angle θ in radians [12,13]. d)sem observation of gold nanoparticles SEM samples of the aqueous suspension of gold nanoparticles were fabricated by dropping the suspension onto glass substrate and allowing water to completely evaporate. SEM observations were carried out on a TESCAN Electron microscope (Vega TC software). RESULTS AND DISCUSSION The bioreduction of chloroaurate ions using the aqueous extract of Eichhornia crassipes with gold chloride solution was monitored by the change in colour from brown to purple as shown in fig. 1. The varied concentrations of gold chloride solutions with a constant volume of 5ml of aqueous extract of Eichhornia crassipes were studied under different conditions (i.e) Room temperature, Higher temperature, Sonication and Ultrasonic Homogenization. The formation of gold nanoparticles was investigated by UV-visible spectrophotometer. The surface Plasmon resonance band appears at 540nm and peak intensity increases as concentration of the gold chloride increases as shown in fig.2.

3 Figure.4 (a), (b), (c) and (d) shows the XRD patterns of the synthesized gold nanoparticles from the aqueous extract of Eichhornia crassipes under room temperature, higher temperature, sonication and homogenization methods. The diffraction peaks at 2θ = 38.15, 44.33, and were identical with those reported for standard gold metal [14]. Similar type of diffraction peaks was observed for the other three methods with little variation in 2θ. The intense peaks at 38.15, 38.19, and corresponding to the (111) Bragg s reflection based on the fcc structure of gold nanoparticles for the four different experimental conditions. Figure. 1 Aqueous extract of Eichhornia crassipes (a) various concentrations of gold chloride solutions with 5ml of aqueous extract of Eichhornia crassipes The (200), (220) and (311) Bragg reflections are weak and considerably broadened relative to the intense (111) reflection [15]. These observation indicate that the gold nanoparticles formed by the reduction of Au 3+ ions by aqueous extract of Eichhornia crassipes were dominated by the (111) facets. The particle size of the synthesized nanoparticles were determined using the Scherrer s equation as explained previously and given in table. 1. The average particle size is nm, 14.82, and corresponding to the room temperature, higher temperature, sonication and homogenization methods respectively. Figure. 2 UV-visible spectra of synthesized gold nanoparticles from the aqueous extract of Eichhornia crassipes The comparative study of different experimental methods revealed that the synthesis of gold nanoparticles with reduction in time was achieved in homogenization followed by sonication than other methods as shown in fig.3. Figure. 4 (a) XRD patterns of synthesized gold nanoparticles using the aqueous extract of Eichhornia crassipes Room temperature Figure.3 Comparative study of experimental methods at different concentrations and its variation with time Figure. 4 (b) XRD patterns of synthesized gold nanoparticles using the aqueous extract of Eichhornia crassipes Higher temperature

4 Fig.5 (a), (b), (c) and (d) represents SEM micrographs of drop coated on the glass substrate of the synthesized gold nanoparticles from the aqueous extract of Eichhornia crassipes under room temperature, higher temperature, sonication and homogenization methods. The SEM images showed that the particles are well separated, mainly in spherical shape possessing different sizes in various experimental conditions as shown in fig.5. The presence of capping agent on the gold nanoparticles is clearly seen in fig.5 (c) and (d) corresponds to the sonication and homogenization methods. (d) ROOM (b) SONICATION Figure. 4 (c) XRD patterns of synthesized gold nanoparticles using the aqueous extract of Eichhornia crassipes Sonication (c) HIGHER (a) HOMOGENIZATION Figure. 4 (d) XRD patterns of synthesized gold nanoparticles using the aqueous extract of Eichhornia crassipes Ultrasonic Homogenization Table. 1. Determination of crystalline size of AuNP s by using Debye-Scherrer s equation - Experimental conditions S.No 2θ FWHM b = π*fwhm/180 D = kl / b. Cosθ (degrees) (degrees) (radians) (nm) Room temperature Higher temperature Sonication Ultrasonic Homogenization Figure.5 (a), (b), (c) and (d) SEM micrographs gold nanoparticles from the aqueous extract of Eichhornia crassipes under various experimental conditions CONCLUSION The reduction of chloroaurate ions by aqueous extract of Eichhornia crassipes under various experimental process revealed that stable gold nanoparticles are formed. The rate of reaction for the formation of gold nanoparticles was rapid in the case of homogenization methods compared to other processes. The particle size was smaller in normal room temperature conditions and not in homogenization due to the capping nature of phytoconstituents present in this extract. The size and shape of the synthesized gold nanoparticles was less than 100nm possessing spherical shape which was confirmed by XRD and Scherrer s equation. The SEM micrographs showed that the particle size ranged from nm. Thus the present study of synthesis of gold nanoparticles enhance the greener method of synthesis and find potent use in the field of pharmaceutical industry due to its availability and cost of production.

5 ACKNOWLEDGEMENT The authors sincerely thank the Avinashilingam Institute for Home Science and Higher Education for Women University, Coimbatore, Tamilnadu, for providing research facilities, Department of Physics, Avinashilingam University for Women, for recording XRD and Periyar Maniammai University for recording SEM. REFERENCES 1. Kaler A, Patel N, and Banerjee UC, Green synthesis of silver nanoparticles - Review article, Current Research and Information on Pharmaceutical Sciences, 11(4), 2010, Moaveni P, Karimi K and Valojerdi MZ, The Nanoparticles in plants: Review paper, Journal of Nanostructure in Chemistry, 2(1), 2010, Hadjipanayis GC, Siegel RW, Nanophase materials, synthesis, properties, applications, Kluwer, Dordrecht, Arya V, Komal R, Kaur M, and Goyal A, Silver nanoparticles as a potent antimicrobial agent: A Review, Pharmacology online, 3, 2011, Kumar V, and Yadav SK, Plant mediated synthesis of silver and gold nanoparticles and their applications, J.Chem.Techol.biotechnol., 84, 2009, Long NN, Vu LV, Kiem CD, Doanh SC, Nguyet CT, Hang PT, Thien ND, Quynh LM, Synthesis and Optical properties of colloidal gold nanoparticles, Journal of Physics, Conference series, 187, 2009, Vijayaraghavan K, and Nalini SPK, Biotemplates on the green synthesis of silver nanoparticles, Biotechnology Journal, 5, 2010, He S, Zhang Y, Guo Z, and Gu N, Biological synthesis of gold nanowires using extract of Rhodopseudomonas Capsulata, Biotechnol. Prog., 24, 2008, Krpetic Z, Scari G, Caneva E, Speranza G, and Porta F, Gold nanoparticles prepared using Cape Aloe active components, Langmuir, 25(13), 2009, Jayanthi P, Lalitha P, and Shubashini KS, Phytochemical investigation of the extracts of Eichhornia crassipes and its solvent fractionates, Journal of Pharmacy Research, 4(5), 2011, Kiruba Daniel SCG, Nehru K and Sivakumar M, Rapid Biosynthesis of Silver Nanoparticles using Eichornia crassipes and its Antibacterial Activity, Current Nanoscience, 8(1), 2012, Cullity BD, Elements of X-ray Diffraction, Edison-Wesley Publishing Company Inc, 2nd ed. USA, Jeffrey JW, Methods in crystallography, Academic press, New York, Shankar SS, Ahmad A, Pasricha R, Sastry M, Bioreduction of chloroaurate ions by Geranium leaves and its endophytic fungus yields gold nanoparticles of different shapes, J.Mater.Chem., 13, 2003, Ankamwar B, Biosynthesis of Gold nanoparticles (Green Gold) using leaf extract of Terminalia Catappa, E-Journal of Chemistry, 7(4), 2010, Source of support: Nil, Conflict of interest: None Declared