Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 135 (2015) 373–378

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Antibacterial and catalytic activities of green synthesized silver nanoparticles M.R. Bindhu, M. Umadevi ⇑ Department of Physics, Mother Teresa Women’s University, Kodaikanal 624101, Tamil Nadu, India

h i g h l i g h t s

g r a p h i c a l a b s t r a c t

 Ag NPs were synthesized using

beetroot extract as reducing agent.  Spherical Ag nanoparticles were

prepared.  Shows good antimicrobial and

catalytic activity.

a r t i c l e

i n f o

Article history: Received 29 March 2014 Received in revised form 1 July 2014 Accepted 18 July 2014 Available online 27 July 2014 Keywords: Green synthesis Silver nanoparticles Surface plasmon resonance Antibacterial activity Catalytic activity

a b s t r a c t The aqueous beetroot extract was used as reducing agent for silver nanoparticles synthesis. The synthesized nanoparticles were characterized using UV–visible spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The surface plasmon resonance peak of synthesized nanoparticles was observed at 438 nm. As the concentration of beetroot extract increases, absorption spectra shows blue shift with decreasing particle size. The prepared silver nanoparticles were well dispersed, spherical in shape with the average particle size of 15 nm. The prepared silver nanoparticles are effective in inhibiting the growth of both gram positive and gram negative bacteria. The prepared silver nanoparticles reveal faster catalytic activity. This natural method for synthesis of silver nanoparticles offers a valuable contribution in the area of green synthesis and nanotechnology avoiding the presence of hazardous and toxic solvents and waste. Ó 2014 Elsevier B.V. All rights reserved.

Introduction Metal nanoparticles have been extensively studied for many years because of both their attractive optical and electronic properties related to the quantum size effect and their promising applications in areas such as optics, optoelectronics, catalysis, nanostructure fabrication and chemical/biochemical sensings [1]. Metal catalysts play a key role in a wide range of chemical ⇑ Corresponding author. Tel.: +91 04542241685. E-mail address: [email protected] (M. Umadevi). http://dx.doi.org/10.1016/j.saa.2014.07.045 1386-1425/Ó 2014 Elsevier B.V. All rights reserved.

industries, since they enable the environmentally friendly conversion of various chemical substances. The recent escalation of energy, environmental and resource issues has led to the ever increasing importance of catalytic processes. Thus, extensive efforts have been devoted to the development of high-performance catalytic materials that can promote desired reactions more effectively and selectively. In particular, nano-sized metal particles attract increasing attention as highly active heterogeneous catalysts, due to their unique electronic properties and extremely large specific surface areas. The use of silver ion or metallic silver as well as silver nanoparticles can be exploited in medicine for burn


M.R. Bindhu, M. Umadevi / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 135 (2015) 373–378

treatment, dental materials, coating stainless steel materials, textile fabrics, water treatment, sunscreen lotions, etc. and posses low toxicity to human cells, high thermal stability and low volatility. Among various metal nanoparticles, AgNPs have several effective applications as antibacterial, sensors and detectors besides their biomedical applications due to their attractive physiochemical properties [2,3]. Increasing the awareness towards green chemistry and other biological processes has led to a desire to develop an eco-friendly approach for the synthesis of nanoparticles which has several advantages such as simplicity, cost effectiveness, compatibility for antibacterial, antioxidant, and antitumor activity of natural products. In very recent years, many interesting methods are being applied currently to the green preparation of nanosized silver nanoparticles such as green synthesis of nanoparticles where plant extract is used for the synthesis of nanoparticles without any chemical ingredients [4,5]. Sharma et al. [4] presented an extended overview of silver nanoparticles preparation by green synthesis approaches including mixed-valence polyoxometallates, polysaccharides, Tollens, irradiation and biological. Recently the studies started under green chemistry for the search of benign methods for the development of nanoparticles and searching antibacterial, antioxidant, and antitumor activity of natural products. Biosynthetic processes have received much attention as a viable alternative for the development of metal nanoparticles where plant extract is used for the synthesis of nanoparticles without any chemical ingredients. Extracts of Daucus carota, Solanum lycopersicums, Hibiscus cannabinus leaf, Moringa oleifera flower, Murraya koenigii leaf, mushroom, coconut oil, Macrotyloma uniflorum, neem leaf, geranium leaf and Ananas comosus have been found suitable for the green synthesis of silver nanoparticles [6–16]. In this work, silver nanoparticles were synthesized using beetroot extract as reducing agent. Beetroot is a commonly available vegetable and an excellent source of folate and a good source of manganese and betaines. It also contains potassium, magnesium and iron as well as carbohydrates, protein, powerful antioxidants, soluble fibre, vitamins A, B6 and C, and folic acid. They are a wonderful tonic for the liver, works as a purifier for the blood, and can prevent various forms of cancer. Betaines helps to reduce the concentration of homocysteine, a homolog of the naturally occurring amino acid cysteine. Betanins are used industrially as red food colorants. Main objective of this present study is to synthesize silver nanoparticles using beetroot extract as reducing agent and to reveal its catalytic and antimicrobial activity.

Preparation of silver nanoparticles For the green synthesis of silver nanoparticles, 1 ml of beetroot extract was mixed to 50 ml aqueous solution of AgNO3 (3 mM) and stirred continuously for 5 min at room temperature and it was turned to brown in colour after 7 h which gives silver colloid (B1). Similarly by adding 5 and 10 ml of extract four more set of samples henceforth called B5 and B10 respectively were prepared. UV–visible spectra were taken when the solutions were in solution form. After one month the solutions were dried at 100 °C for 1 h. The dried powders were taken for the different characterization such as X-ray diffraction (XRD), Transmission Electron Microscope (TEM). Characterization of synthesized nanoparticles The X-Ray Diffraction (XRD) analysis was conducted by PANalytical X’pert – PRO diffractometer using monochromatic Cu Ka radiation (k = 1.5406 Å) running at 40 kv and 30 mA. The FTIR spectra of the samples were recorded over a spectral range of 400–4000 cm1. The optical properties of the silver nanoparticles were studied using UV–visible absorption (UV-1700 Spectrometer of SHIMADZU) spectrometer with samples in quartz cuvette. Morphology and size of the prepared silver nanoparticles was done using a JEOL JEM 2100 High Resolution Transmission Electron Microscope operating at 200 kV. The catalytic reduction of

Experimental methods Materials Beetroots were purchased from local market, Kodaikanal, Tamilnadu, India. Silver nitrate (AgNO3) is obtained from Sigma Aldrich Chemicals. The water used throughout this experiment was distilled water. All glasswares have been properly washed with distilled water and dried in oven before use.

Preparation of beetroot extract 5 g Of beetroot pieces were boiled with distilled water for 2 min. The extract was then separated by centrifugation at 1000 rpm for 5 min to remove insoluble fractions and macromolecules and finally a red extract was collected for further experiments.

Fig. 1. Optical absorption spectra of silver nanoparticles (i) at different reaction time, and (ii) at different concentration of beetroot extract.


M.R. Bindhu, M. Umadevi / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 135 (2015) 373–378

Fig. 2. X-ray diffraction pattern of (a) beetroot extract, and (b) B1 and (c) B10 (* due to beetroot extract).

prepared silver nanoparticles was studied by the reduction of 4-nitrophenol to 4-aminophenol by NaBH4 is performed as a probe reaction. The antimicrobial assay was done on various pathogenic bacteria like Escherichia coli (ATCC 25922) and Pseudomonas aeroginosa (ATCC 27853) (gram negative), Streptococcus aureus (ATCC 12384) and Staphylococcus aureus (ATCC 25923) (gram positive). Muller Hinton Agar (MHA) medium used to grow bacteria was prepared from 2 gm of beef extract, 3.5 gm of casein acid, and 300 mg of starch, 3 g of agar and 200 ml of water. A bacterial culture (which has been adjusted to 0.5 McFarland standard), was used to lawn Muller Hinton agar plates evenly using a sterile swab. The dried powder of silver nanoparticles (B10) solution was taken at the concentration of 50 lg/ml for the antibacterial tests. The dried powder of BR extract (50 lg/ml) was used as control. These dishes were incubated at 37 °C for 24–48 h. Then inhibitory action of nanoparticles on the growth of the bacteria was determined by the measurement of diameter of inhibition zone. Results and discussion UV–visible spectral studies The time variation study was carried out by measuring its optical spectra of B10 recorded at different time. Since time is an important parameter in synthesis of nanoparticles. Fig. 1(a) shows the SPR peak of BR extract and AgNPs as a function of time. The optical spectrum of aqueous BR extract exhibits three bands at 263, 480 and 534 nm. The absorption at 263 nm indicated the presence of aromatic amino acids of tryptophan and tyrosine

and, to a small extent, disulfide bonds of two cysteine residues [17]. Amino acids were joined together by peptide bonds to form the structure of proteins. The absorption peak at 534 and 480 nm indicated the presence of betalain alkaloid pigments [18]. When BR extract added to the aqueous silver nitrate solution, the intensity of absorption peak at 263, 534 and 480 nm gradually reduced and of 438 nm increased up to 7 h after that there was no obvious change in the SPR peak position. Here, almost all Ag+ ions have reduced within 7 h to (Ag0) metallic species simultaneously, followed by growth of the crystal nuclei. After 7 h, the availability of a larger number of nuclei induces a decrease in the particle size, because smaller metal nuclei grow and consume metal ions at the same time. Generally the characteristic part of surface plasmon band of silver nanoparticles falls within the wavelength range of 350–500 nm. The appearance of surface plasmon peak around 440 nm confirms the formation of silver nanoparticles. There was no obvious change in the peak position even after three months and this indicates the stability of the silver nanoparticles. Here, the formation of silver nanoparticles got completed at 7 h, which was expected due to the lower reduction potential (Ag+/Ag0 = 0.80 V versus SCE). This synthesis method of silver nanoparticles was slower compared to that of our previous reports [6–9,16]. The optical absorption spectrum of prepared silver nanoparticles (B1, B5 and B10) obtained at different concentration of extract is shown in Fig. 1(b). The fwhm value decreased and a blue shift was observed (from 446 nm to 438 nm) as the concentration of the BR extract increased in the reaction medium. As the concentration of the BR extract increases more number of biomolecules are available to reduce silver ion and forms large number of very small nanoparticles, which gives rise to sharp and intense SPR [19,20]. As the particles decrease in size, the absorption peak usually shifts toward the blue wavelengths, higher frequency and energies [21]. This represents the size of the prepared nanoparticles decrease with increasing concentration of the BR extract. The shape of the observed surface plasmon band is symmetric with a single peak evidences the formation of monodispersed spherical silver nanoparticles. Structural studies Fig. 2(a) shows XRD pattern of dried beetroot extract. It shows five diffraction peaks at 28.35°, 40.46°, 50.05°, 66.52° and 73.73°. These observed diffraction peaks represent the presence of folic acid (JCPDS No. 53-1579 and 42-1963), antioxidant betacyanin (JCPDS No. 50-2216), amino acid cysteine (JCPDS No. 23-1662, 52-1922) and Vitamin C (JCPDS No. 22-1536, 22-1560). Fig. 2(b) and (c) shows the XRD pattern of B1 and B10. Four diffraction peaks observed at 38.1°, 44.3°, 64.4° and 77.4° in the 2h range can be indexed to the (1 1 1), (2 0 0), (2 2 0), and (3 1 1) reflections of face centered cubic structure of metallic silver nanopowders with space group of Fm-3m (JCPDS file No. 04-0783). In addition to the Bragg peaks representative of fcc silver nanocrystals, additional as yet unassigned peak observed at 28.43°, 40.68°, 50.07°. This suggesting the presence of folic acid (JCPDS No. 53-1579 and 42-1963), betacyanin (JCPDS No. 50-2216) and cysteine (JCPDS No. 23-1662, 52-1922) in the BR extract. These peaks were much weaker than those of silver, which indicates that the

Table 1 Particle size, lattice constant, volume, SSA, SA:V and Strain of the prepared silver nanoparticles (B1 and B10). Prepared AgNPs

Particle size ‘D’ (nm)

Lattice constant ‘a’ (Å)

Volume ‘V’ (Å3)

SSA (m2/g)


Strain ‘e’

B1 B10

46.65 21.63

4.0917 4.0859

68.5 68.21

12.61 26.41

0.128 0.277

0.00219 0.00296


M.R. Bindhu, M. Umadevi / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 135 (2015) 373–378

Fig. 3. TEM micrograph of the B10 (a) the scale bar corresponds to 100 nm, (b) the scale bar corresponds to 50 nm, (c) SAED pattern, and (d) EDX graph of B10.

silver is the main material in the composite compared with those of the bulk counterpart. This observation conforms the crystallization of bio-organic phase occurs on the surface of the Ag nanoparticles. Based on our XRD results, broadening in peaks at B10 occur due to the smaller particle size, which reflect the effects of the experimental conditions on the nucleation and growth of the crystal nuclei [22]. This was also confirmed by the estimation of particle size using Debye–Scherrer formula by using the width of the (1 1 1) Bragg’s reflection and tabulated in Table. 1. It was found to be decreasing particle size with increasing extract concentration. The lattice parameter and cell volume of B1 and B10 was evaluated and tabulated in Table. 1. The calculated lattice parameters are in very good agreement with the standard value 4.086 Å (JCPDS 04-0783). The values of surface area to volume ratio (SA:V), Specific Surface Area (SSA) and strain can be calculated and tabulated in Table 1. The SA:V ratio and SSA was high for the silver nanoparticles synthesized using higher concentration of BR extract (B10). This reveals that the Ag+ of silver nitrate had been reduced rapidly to Ag0 because of having additional reaction surfaces with high SSA in B10. TEM and EDS analysis Fig. 3(a) and (b) shows that the TEM image of silver nanoparticles (B10) synthesized at higher concentration of beetroot extract. Silver nanoparticles have sizes ranging from 10 to 15 nm with an average diameter of 15 nm. As the concentration of the BR extract was increased, the strong interaction between more number of biomolecules in the BR extract and surface of nanoparticles was sufficient to the formation of spherical nanoparticles preventing them from sintering and also providing size reduction of the spherical nanoparticles. The high specific surface area and surface area to volume ratio of the B10 also tends towards smaller particles as explained in XRD pattern of B10. The selected-area electron diffraction (SAED) pattern of B10 was shown in Fig. 3(c) show the crystalline (fcc) nature of the nanoparticles. The formation of silver atoms in the prepared nanoparticles was further confirmed by the analysis of the EDX of B10 shown in Fig. 3(d). It reveals higher

Fig. 4. (a) UV–visible absorption spectra of 4-NP solution in presence and absence of NaBH4, and (b) catalytic degradation curves of 4-NP over B10.

M.R. Bindhu, M. Umadevi / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 135 (2015) 373–378

counts at 3 keV due to silver nanoparticles. It was also due to surface plasmon resonance of metallic silver nanocrystals as shown in optical absorption spectra. Catalytic activity The catalytic activities of the obtained silver nanoparticles (B10) were studied for the aqueous reduction of 4-NP to 4-AP with NaBH4. It was an effective method for the removal of 4-NP due to its carcinogenic, mutagenic, and cyto- and embryonic-toxic. The UV–visible spectra for the catalytic reduction of 4-NP by NaBH4 in the presence of silver nanoparticles obtained from 1 ml of extract was shown in Fig. 4(a). A UV–visible spectrum of aqueous 4-NP shows an absorption peak at 317 nm with yellow colour. To reduce 4-NP, when NaBH4 was added, a yellowish green colour appeared and a red shift was observed from 317 nm to 400 nm due to the formation of 4nitrophenolate ion [23]. In the absence of silver catalyst, the peak at 400 nm and the yellowish green colour were unaltered due to the high kinetic barrier between the mutually repelling negative ions 4-NP and BH 4 which suggests that the reduction did not continue at all [24,25]. Aromatic compounds having –NO2 group are inert to the reduction of NaBH4 [26]. With the addition of 1 ml of prepared silver colloids to the reaction mixture caused a fading of the yellowish green colour to a colorless solution and the peak at 400 nm disappeared with the appearance of new peak at 300 nm indicating the formation of 4-aminophenol [27]. 4-Aminophenol was the intermediate in the industrial synthesis of paracetamol and dyes and it was also used in analgesic and antipyretic drugs, photo developers, rubber antioxidant [23,28]. The time for the reduction of 4-NP over B10 was 12 min in the presence of NaBH4. The small size particles have large surface to volume ratio and more atoms on the surface as potential catalytic sites. This result suggests that the prepared silver nanoparticles B10 show higher catalytic activities due to their high specific surface


area. In this case, the electron transferred from BH 4 ions to the nitro group of 4-NP and it was reduced to 4-AP, when the silver catalytic surface adsorbed both BH 4 and 4-NP. For estimating quantitatively catalytic wwww activities of prepared silver nanoparticles, the pseudo-first order kinetics with respect to the concentration of 4-NP was employed to calculate the rate constant (k) of this catalytic reaction. The ratio of absorbance at of 4-NP at time t to Ao measured at t = 0 must be equal to the concentration ratio Ct/Co of 4-NP. The kinetic equation for the reduction can be written as

dCt =dt ¼ kapp C t or InðC t =C 0 Þ ¼ InðAt =A0 Þ ¼ kapp t where Ct is the concentration of 4-NP at time t and kapp is the apparent rate constant, which can be obtained from the decrease of the peak intensity at 400 nm with time. Fig. 4(b) shows the catalytic degradation curves of 4-NP over B10. A good linear correlation, ln (At/A0) versus time, is obtained and the apparent rate constant of this catalytic reaction was 0.0731/min. Small nanoparticles (B10) having large specific surface area and large number of metal atoms exposed on the surface, gives more possibility of faster reaction relative to larger nanoparticles. Smaller nanoparticles exhibit faster rate of electron transfer than the rate of desorption from the particle surface, which was due to the less potential barrier height at the interface between the nanoparticles and 4-NP. Thus we can infer that the size, shape and uniform dispersion of silver nanoparticles play important role in catalytic activity. No reactivity modifications were observed at the end of the reaction, which showed the stability of the catalyst. Antibacterial activity Elemental silver and silver compounds have been used as antimicrobial agents from ancient times. The mechanism of

Fig. 5. Zone of inhibition of B10 for (a) E. coli, (b) Pseudomonas aeruginosa, (c) Staphylococcus aureus, and (d) Streptococcus aureus, respectively.


M.R. Bindhu, M. Umadevi / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 135 (2015) 373–378

Table 2 Antibacterial activity of silver nanoparticles (B10). Bacteria

Escherichia coli Pseudomonas aeroginosa Staphylococcus aureus Streptococcus aureus

Zone of inhibition diameter (mm) 5 ll

10 ll

Resistant 10 10 8

7 11 19 16

bactericidal effect of silver colloid particles against bacteria is not very well-known. The antibacterial activity is probably derived, through the electrostatic attraction between negative charged cell membrane of microorganism and positive charged nanoparticles. The inhibitory effect of silver on microorganisms tested is effected via two possible mechanisms First, is the electrostatic attraction between the negatively charged cell membrane of the microorganisms and the positively charged Ag, and second, is the formation of ‘pits’ in the cell wall of bacteria related to Ag concentration [29]. Shrivastava and Dash [30] studied antimicrobial activity against E. coli, S. aureus and salmonella typhi. They reported that the effect was dose dependent and was more pronounced against gramnegative organisms than gram-positive ones. Silver nanoparticles has been reported to show antibacterial activity against various pathogens have also been established [31–33]. In the present study, the antibacterial assay of silver nanoparticles (B10) was done on various pathogenic bacteria like Staphylococcus and Streptococcus (gram positive) and E. coli and Pseudomonus aeroginosa (gram negative), which are commonly found in water. Zone of inhibition around silver nanoparticles (B10) for individual bacterial culture was shown in Fig. 5. The results of antibacterial activity of prepared silver nanoparticles evaluated from the disc diffusion method are given in Table 2. As expected, no zone of inhibition was observed for control. Among the tested four bacteria, Staphylococcus has maximum zone of inhibition of 19 mm and E. coli has minimum zone of inhibition of 7 mm. The differences observed in the diameter of zone of inhibition may be due to the difference in the susceptibility of different bacteria to the prepared silver nanoparticles. The differential sensitivity of gram negative and gram positive bacteria towards silver nanoparticles possibly depends upon their cell structure, physiology, metabolism and their interaction with the charged silver nanoparticles. The effective interaction against gram-positive S. aureus was also due to absence of outer membrane in the cell wall. As significant antibacterial activity is found in all the four bacteria, synthesized silver nanoparticles is effective in inhibiting the growth of both gram positive and gram negative bacteria. The present study clearly indicates that the prepared silver nanoparticles (B10) show good antibacterial activity against both gram negative and positive organism. Effective antibacterial agents should be toxic to different pathogenic bacteria with the ability to be coated as antimicrobial coating on variety of surfaces like wound dressings, medical appliances, biomaterials, purifying and purity testing devices, textiles, biomedical and food packaging, consumer products and so on. Silver nanoparticles are excellent antibacterial agents, since their area of contact with bacteria is higher as nanoparticles have larger surface area. All these combined beneficial qualities, make the prepared silver nanoparticles a good antibacterial agent which may be used in water purification as well as in other biomedical applications. Conclusion In this study, silver nanoparticles were synthesized by a natural, low cost biological reducing agent, beetroot extract. Silver

nanoparticles of size 15 nm were synthesized using beetroot extract by varying the concentration of extract. The nanoparticles were characterized by UV–visible, HRTEM and XRD measurements. UV–visible absorbance spectral analysis confirmed the surface plasmon resonance of biosynthesized AgNPs. Crystalline nature of the nanoparticles is evident from bright spots in the SAED pattern and peaks in the XRD pattern. The prepared nanoparticles were spherical in shape and monodispersed. The biosynthetic method developed in this study for producing AgNPs has distinct advantages over chemical synthetic techniques such as a high biosafety, is ecofriendly and nontoxic to the environment. Furthermore, the biosynthesized silver nanoparticles displayed a pronounced antibacterial activity against different clinically important pathogenic microorganisms and also exhibited good catalytic activity. Acknowledgement The authors are thankful to DST-CURIE New Delhi, UGC-DAECSR, Indore for financial assistance and TEM measurements done at UGC-DAE-CSR, Indore. References [1] Z. Qi, H. Zhou, N. Matsuda, I. Honma, K. Shimada, A. Takatsu, K. Kato, J. Phys. Chem. B 108 (2004) 7006–7011. [2] A. Panacek, L. Kvítek, R. Prucek, M. Kolar, R. Vecerova, N. Pizúrova, V.K. Sharma, T. Nevecna, R. Zboril, J. Phys. Chem. B 110 (2006) 16248–16253. [3] A.D.L. Escosura-Muniz, C. Sanchez-Espinel, B. Dıaz-Freitas, A. GonzalezFernandez, M.M. Costa, A. Merkoci, Anal. Chem. 81 (2009) 10268–10274. [4] V. Parashar, R. Parashar, B. Sharma, A.C. Pandey, Dig. J. Nanomater. Biostruct. 4 (2009) 45–50. [5] K.N. Thakkar, S.S. Mhatre, R.Y. Parikh, Nanomed. Nanotechnol. Biomed. 6 (2010) 257–262. [6] M. Umadevi, S. Shalini, M.R. Bindhu, Adv. Nat. Sci. Nanosci. Nanotechnol. 3 (025008) (2012) 1–6. [7] M. Umadevi, M.R. Bindhu, V. Sathe, J. Mater. Sci. Technol. 29 (2013) 317–322. [8] M.R. Bindhu, M. Umadevi, Spectrochim. Acta A 101 (2013) 184–190. [9] M.R. Bindhu, V.G. Sathe, M. Umadevi, Spectrochim. Acta A 115 (2013) 409–415. [10] Daizy Philip, C. Unni, S. Aswathy Aromal, V.K. Vidhua, Spectrochim. Acta A 78 (2011) 899–904. [11] D. Philip, Spectrochim. Acta A 73 (2009) 374–381. [12] M. Meena Kumari, D. Philip, Spectrochim. Acta A 111 (2013) 154–160. [13] S. Aswathy Aromal, V.K. Vidhu, D. Philip, Spectrochim. Acta A 85 (2012) 99– 104. [14] S.S. Shankar, A. Rai, A. Ahmad, M. Sastry, J. Colloid Interface Sci. 275 (2004) 496–502. [15] B. Ankamwar, M. Chaudhary, M. Sastry, Synth. React. Inorg. Met. Org. Nanomet. Chem. 35 (2005) 19–26. [16] M.R. Bindhu, M. Umadevi, Spectrochim. Acta A 121 (2014) 596–604. [17] D. Philip, C. Unni, Physica E 43 (2011) 1318–1322. [18] J.A. Fernandez, Lopez, L. Almeta, J. Chromatography A 913 (2001) 415–420. [19] V. Parashar, R. Parashar, B. Sharma, A.C. Pandey, Dig. J. Nanomater. Biostruct. 4 (2009) 45–50. [20] M.M. Ganesh Babu, P. Gunasekaran, Colloids Surf. B 74 (2009) 191–195. [21] S.L. Smitha, K.M. Nissamudeen, D. Philip, K.G. Gopchandran, Spectrochim. Acta part A 71 (2008) 186. [22] A. Becheri, M. Durr, P.L. Nostro, P. Baglioni, J. Nanopart. Res. 10 (2008) 679– 689. [23] Y. Du, H. Chen, R. Chen, N. Xu, Appl. Catal. A 277 (2004) 259–264. [24] J. Huang, S. Vongehr, S. Tang, H. Lu, X. Meng, J. Phys. Chem. C 114 (2010) 15005–15010. [25] H. Zhang, X. Li, G. Chen, J. Mater. Chem. 19 (2009) 8223–8231. [26] M. Dotzauer, J. Dai, L. Sun, M.L. Bruening, Nano Lett. 6 (2006) 2268–2272. [27] Y. Chen, J. Qiu, X. Wang, J. Xiu, J. Catal. 242 (2006) 227–230. [28] C.V. Rode, M.J. Vaidya, R.V. Chaudhari, Org. Process Res. Dev. 3 (1999) 465– 470. [29] I. Sondi, B. Salopek-sondi, J. Colloid Interface Sci. 275 (2004) 177–182. [30] S. Shrivastava, D. Dash, J. Nanotechnol. 12 (2009) 240–243. [31] M. Yamanaka, K. Hara, J. Kudo, Appl. Environ. Microbiol. 71 (2005) 7589–7593. [32] A.R. Shahverdi, A. Fakhimi, H.R. Shahverdi, S. Minaian, Nanomed.: Nanotechnol. Biol. Med. 3 (2007) 168–171. [33] K. Yoon, J.H. Byeon, J. Park, J. Hwang, Sci. Total Environ. 373 (2007) 572–575.

Antibacterial and catalytic activities of green synthesized silver nanoparticles.

The aqueous beetroot extract was used as reducing agent for silver nanoparticles synthesis. The synthesized nanoparticles were characterized using UV-...
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