GREEN SYNTHESIS OF ZINC OXIDE NANOPARTICLES- REVIEW PAPER

Abstract

Plants have been used in the synthesis of metallic nanoparticles because they are more ecofriendly. These plant extracts also allow a controlled synthesis. Organic chemical solvents are toxic and require extreme conditions during nanoparticle synthesis. Plant extracts function as stabilizing, capping or hydrolytic agents. The ZnO nanoparticles are of significant interest as they provide many practical applications worldwide. The most important application of ZnO nanoparticles would be as antibacterial agents. The increases surface area and smaller size of these particles make them an ideal antibacterial agent. In this review, the overview of green synthesis of ZnO nanoparticles along with their antimicrobial activity. The mechanism of this activity was also reviewed. The green synthesis of ZnO nanoparticles from Azadirachta indica, Aloe vera, Murraya koenigii and Anisochilus carnosus were also highlighted.

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GREEN SYNTHESIS OF ZINC OXIDE NANOPARTICLES- REVIEW
PAPER
G. Parthasarathy1*, Dr. M. Saroja2, Dr. M. Venkatachalam3, Dr. S. Shankar4,
V.K. Evanjelene5
1Department of Electronics, Erode arts and Science College (Autonomous), Erode-638 009.
2Associate Professor of Electronics.
3Head & Associate professor of Electronics.
4Department of Electronics.
5R and D Manager, Alpha Omega Hi Tech Bio Research centre, Salem.
ABSTRACT
Plants have been used in the synthesis of metallic nanoparticles
because they are more ecofriendly. These plant extracts also allow a
controlled synthesis. Organic chemical solvents are toxic and require
extreme conditions during nanoparticle synthesis. Plant extracts
function as stabilizing, capping or hydrolytic agents. The ZnO
nanoparticles are of significant interest as they provide many practical
applications worldwide. The most important application of ZnO
nanoparticles would be as antibacterial agents. The increases surface
area and smaller size of these particles make them an ideal
antibacterial agent. In this review, the overview of green synthesis of
ZnO nanoparticles along with their antimicrobial activity. The
mechanism of this activity was also reviewed. The green synthesis of
ZnO nanoparticles from Azadirachta indica, Aloe vera, Murraya koenigii and Anisochilus
carnosus were also highlighted.
KEYWORDS: Green synthesis, nanoparticles, zinc oxide nanoparticles, antimicrobial
activity.
GREEN SYNTHESIS OF NANOPARTICLES
Lot of attention has been diverted to the green synthesis of metal nanoparticles using
biological material as the reducing and stabilizing agents and due to the usage of ecofriendly,
WORLD JOURNAL OF PHARMACY AND PHARMACEUTICAL SCIENCES
SJIF Impact Factor 6.041
Volume 5, Issue 4, 922-931 Review Article ISSN 2278 – 4357
*Correspondence for
Author
G. Parthasarathy
Department of
Electronics, Erode arts
and Science College
(Autonomous), Erode-638
009.
Article Received on
15 Feb 2016,
Revised on 06 March 2016,
Accepted on 26 March 2016
DOI: 10.20959/wjpps20164-6533

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non-toxic and safe reagents during the biosynthesis process, green synthesis has been
considered in the field of toxic chemical and physical methods (Moritz et al., 2013; Rajiv et
al., 2013; Caruthers et al., 2007; Nath and Banerjee, 2013; Salam et al., 2012). In the
biological method, plant extracts are used for controlled and precise synthesis of several
metallic nanoparticles (Rajiv et al., 2013). High surface and a large fraction of surface atoms
are responsible for the nanoparticles’ atom-like behavior (Dijiken et al., 2000; Singhal et al.,
2012). Despite the fact that conventional methods use less time for synthesizing
nanoparticles, they contribute to environmental toxicity because they require toxic chemicals
as capping agents. Green nanotechnology is an eco-friendly alternative and is cost effective
(Chandran et al., 2000; Shankar et al., 2004; Huang et al., 2007) and utilizes proteins as
natural capping agents. Synthesis of metal nanoparticles by plants utilize various secondary
metabolites, enzymes, proteins and or other reducing agents.
ZnO NANOPARTICLES
Zinc oxide (ZnO) are a class of inorganic metal oxides available and exhibit a wide range of
nanostructures. Photocatalytic and photo oxidizing ability against chemical and biological
species are used to characterize these metal oxides (Szabo, 2003). U.S. Food and Drug
Administration have recognized ZnO as safe (Premanathan et al., 2011). Lower cost, UV
blocking properties, high catalytic activity, large surface area, white appearance and their
remarkable applications in the field of medicine and agriculture are the advantages of ZnO
particles (Kairyte et al., 2013; Kumar et al., 2013; Kajbafvala et al., 2012). Recently, ZnO
have been used extensively in environmental remediation and antibacterial activity
(Kuriakose et al., 2013).
ZnO nanoparticles exhibit strong strong antibacterial activity against high temperature and
pressure resistant spores (Nicole et al., 2008; Neal, 2008). It is postulated that the generation
of hydrogen peroxide or due to the electrostatic binding of the particles on the microbial
surface contribute to the antimicrobial activity of ZnO nanoparticles (Zhang et al., 2007).
Antibacterial activity of ZnO nanoparticles is of remarkable applications in designing
microbial resistant articles (Sharma et al., 2010) for preserving food and wood products
(Singhal et al., 2012), cosmetics, novel nanomedicines (Dijiken et al., 2000) wound dressing
(Shalumon et al., 2011) and disinfecting agents (Dijiken et al., 2000). Photocatalytic activity
of ZnO nanoparticles offers a promising method for waste water treatment (Reddy et al.,
2012). Toxic water pollutants released from textile and dying industries by utilizing natural

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source of energy, sunlight are degraded by ZnO and exhibit photochemical reactivity. This
could be because of the presence of many active sites and fabrication of hydroxyl radicals on
ZnO surface (Baruah et al., 2009; Kajbafvala et al., 2012).
Zinc oxide has vast applications in optical, piezo electric, magnetic, and gas sensing. They
exhibits high catalytic efficiency, strong adsorption ability and used in sunscreens
manufacture (Seshadri et al., 2004), ceramics and rubber processing, waste water treatment,
and fungicide (Theodore, 2006; Wang et al., 2008). ZnO nanoparticles can absorb both UV-A
and UV-B radiation and therefore offers better protection and improved opaqueness
(Theodore, 2006).
ANTIMICROBIAL ACTIVITY OF ZnO NANOPARTICLES
Understanding the mechanism of antibacterial effect of ZnO nanoparticles is necessary to
make better use of these nanoparticles in food products and to develop nontoxic,
antimicrobial derivatives but the mechanism is not very clear till date. Some studies have
showed that morphology and oxidative stress are responsible for the antibacterial activity of
zinc nanoparticles activity (Sourabh et al., 2014; Krishna et al., 2011). However, a few
studies have suggested that the antibacterial activity might be because of the disruption of cell
membrane activity (Brayner et al., 2006).
Another mechanism might be because of the induction of intercellular reactive oxygen
species, including hydrogen peroxide (H2O2), which is harmful to bacterial cells (Jones et al.,
2008, Sawai, 2003). ZnO have also been reported to be activated by UV and visible light in
order to generate highly reactive oxygen species such as OH−, H2O2, and O22−. These radicals
and superoxides cannot penetrate into the cell membrane and are likely to remain on the cell
surface, but H2O2 penetrate into bacterial cells (Padmavathy and Vijayaraghavan, 2008).
Yamamoto et al., 2000 stated that the presence of reactive oxygen species (ROS) generated
by ZnO nanoparticles was responsible for their bactericidal activity. Zhang et al., 2010
further stated that chemical interactions between hydrogen peroxide and membrane proteins,
or between other chemical species produced in the presence of ZnO nanoparticles and the
outer lipid bilayer of bacteria could be responsible for the antibacterial behaviour of ZnO
nanoparticles. The hydrogen peroxide which is produced enters the cell membrane of bacteria
and kills them. The study also showed that bacterial growth is inhibited by nano-sized ZnO
particles. Further, Padmavathy and Vijayaraghavan, 2008 also proposed that the bactericidal

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activity of ZnO nanoparticles was because of hydrogen peroxide generated by ZnO
nanoparticles and the nanoparticles remain in contact with the dead bacteria thereby
preventing further bacterial action and continue to generate and discharge hydrogen peroxide
to the medium.
Phototoxic effect is induced in the aqueous solution of ZnO nanoparticles under UV radiation
and produce Reactive Oxygen Species such as hydrogen peroxide (H2O2) and superoxide ions
(O2-) (Zhang et al., 2011). The active species penetrate into the cells and inhibit or kill
microorganisms. This is used in bionanotechnology and in bionanomedicine for many
antibacterial applications. Therefore, as ZnO absorbs UV light, enhancement of ZnO
bioactivity is thought to be as a result of the produced free radicals (Seil et al., 2009).
ZnO NANOPARTICLES SYNTHESIS
ZnO nanoparticles have been reported to be synthesized from many plant extracts. In
Azadirachta indica, stabilizing agents for the nanoparticle synthesis are flavanones,
terpenoids and reducing sugars, the constituents of the Neem leaf broth (Nath and Banerjee,
2013). It is suggested that the aldehyde groups are responsible for reduction of zinc oxide to
zinc oxide nanoparticles and also stabilize the nanoparticles (Nath and Banerjee, 2013).
Noorjahan et al., 2015 proposed a method to synthesize zinc oxide nanoparticles from the leaf
extract of Azadirachta indica and its characterization by FTIR and SEM analysis. It was seen
that from FTIR analysis, alcohols, terpenoids ketones, aldehydes and carboxylic acid were
surrounded by synthesized nanoparticles. SEM analysis showed stable Zinc oxide nanoflakes
and spindle shaped nanoparticles. The size of the ZnO nanoparticles synthesized were found
to be 50 μm.
Elumalai and Velmurugan, 2015 reported the MIC, MBC and MFC values of prepared ZnO
NPs against bacteria and fungi. Significant inhibition by the ZnO NPs was seen against S.
aureus, B. subtilis, P.aeruginosa, P. mirabilis and E. coli and fungi strains such as C. albicans
and C. tropicalis with distinct differences in the susceptibility to ZnO NPs in a dose-
dependent manner. Among them, S. aureus was found to be more susceptible to ZnO NPs.
The mean zones of inhibition ranged from 9.8 ± 0.76 to 23 ± 0.50 (mm). The highest mean
zones of inhibition ranged from 14.4 ± 0.76 to 23 ± 0.50 (mm) against S. aureus. The MIC
values ranged between to 6.25 to 50 (µg/mL) and MBC and MFC from 12. 5 to 50 (µg/mL).
Antimicrobial activities of ZnO NPs increased with increase of concentrations (50, 100 and

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200 µg/ml) and was considered to be due to the increase of H2O2 concentration on the surface
of ZnO.
Aloe vera has been stated to have immune-modulatory, anti-inflammatory, UV protective,
antiprotozoal, and wound- and burn-healing promoting properties. Single crystalline
triangular gold nanoparticle (~50-350 nm in size) and spherical silver nanoparticles (~15 nm
in size) in high yield have been successfully synthesized. This synthesis is by the reaction of
aqueous metal source ions (chloroaurate ions for Au and silver ions for Ag) with the extract
of the Aloe vera plant. Aloe vera extract was used to synthesize Spherical zinc oxide
nanoparticles and their optical properties were studied (Sangeethaa et al., 2011).
Lakshmi et al., 2012 have reported the antibacterial study of zinc oxide nanoparticles
synthesized from Aloe vera hot extract (ZnO-AH), cold extract (ZnO-AC) and chemical
method (ZnO-C) on six clinically isolated strains namely, Bacillus subtilis, Escherichia coli,
Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella typhi and Staphylococcus
aureus. Significant activity was seen in the zinc oxide particles synthesized by chemical
method and particles obtained using Aloe vera cold extract. ZnO-AH showed lesser activity.
There was a significant difference in the antibacterial activities of ZnO-AH and ZnOAC
though both synthesized in a similar manner. This variation was because of the size as the
size of ZnO-AH is much more than that of ZnO-AC. The smaller the size of nanoparticles
better is their activity (Yamamoto 2001a, Makhluf et al., 2005).
Mariam et al., 2014 reported a novel synthesis for In2O3 and ZnO Nanoparticles with particle
sizes in the range of 10 to 30 nm using indium nitrate and zinc nitrate solutions. They utilized
A. vera extract as a solvent instead of organic solvents. The antibacterial and antifungal
activities of the particles were studied using S. aureus, S. pyogenes, P. aeruginosa, E. coli,
and S. typhi and the fungal strains were A. niger, A. flavus, A. fumigatous, Rhizopus indicus
and Mucor indicus. Highest inhibitory activity against the tested bacteria were displayed by
the extracts with ZnO + In2O3+ A. vera. A. niger growth was also inhibited by the extract. It
was concluded that ZnO nanoparticles mixed with A. vera were effective in inhibiting
bacterial growth.
Murraya koenigii has been reported to have hypoglycemic (Khan et al., 1995) and anti-fungal
effects (Das et al., 1965) and also against colon carcinogenesis (Khan et al., 1996). The plant
has active agents like polyphenols and flavonoids which have strong roles in the synthesis

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and stabilization of metal NPs (Roy et al., 2012; Roy et al., 2010). Alam et al., 2014) reported
that the contents of polyphenol and flavonoids present in the leaf of M. koenigii are 81.9mg
Gallic acid equivalent g_1 and 39.98 mg of quercetin g_1, respectively. These compounds act
as reducing agents and as the stabilizing agents by adhering on the surface of the NPs formed,
and thereby prevent their aggregation and control the particle size.
Elumalai et al., 2015 reported that to study the antimicrobial activity of the leaf extract of
Murraya koenigii the bioassay was carried out using five bacterial strains such as S. aureus,
B. subtilis, P. aeruginosa E. coli, P.mirabilis and two fungal strains such as C. albicans and C.
tropicalis as per the disc diffusion and dilution technique. It was concluded that the zone of
inhibition increased with increase in zinc oxide nanoparticle concentration and decrease in
particle size. The ZnO-NPs were found to be effective for both S. aureus and E. coli and
P.aeruginosa.
Anbuvannan et al., 2015 reported the ZnO nanoparticle synthesis and antibacterial activity of
Anisochilus carnosus. Antibacterial activity was studied against the Gram-negative and the
Gram-positive bacteria S. paratyphi, V.cholerae, S. aureus, and E. coli. Inhibition zones of
6mm, 10 mm, 7 mm and 9 mm were observed from the synthesized ZnO nanoparticles
against S. paratyphi, V.cholerae, S. aureus, and E. coli, respectively. In the present study,
green synthesized ZnO NPs exhibited a greater significant zone of inhibition compared to
leaf extract and solvent.
CONCLUSION
The green synthesis of metal nanoparticles is an interesting subject of nanoscience. Also, of
latest concern is the biosynthesis of metal nanoparticles using plants for the large-scale
biosynthesis. Nanoparticles produced by plants are more stable and more varied in shape and
size in comparison with those produced by other organisms. In this review, the synthesis of
ZnO nanoparticles were reported. The ZnO nanoparticles have varied applications in all
fields. Of special mention is the antimicrobial activity of ZnO nanoparticles. The enhanced
bioactivity of ZnO nanoparticles is attributed to the higher surface area to volume ratio. The
antimicrobial activity of ZnO nanoparticles were reported with respect to Azadirachta indica,
Aloe vera, Murraya koenigii and Anisochilus carnosus. Therefore, based on the reported
antibacterial and antifungal activity, it can be concluded that the ZnO nanoparticles constitute
an effective antimicrobial agent against pathogenic microorganisms.

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REFERENCES
1. Ameta, R. Ameta, M. Ahuja, Sci. Rev. Chem. Commun, 2013; 3: 172–180.
2. B. Srinivasa. Reddy, V. Krishna. Veni, K. Ravindhranath, K, J. Chem. Pharm. Res., 2012;
4682–4694.
3. B.A. Khan, A. Abraham, S. Leelamma, Investig. New Drugs, 1996; 14: 365–369.
4. B.A. Khan, A. Abraham, S. Leelamma, Indian J. Bio Chem. Biophys, 1995; 32: 106–108.
5. Brayner, R., et al., 2006. Toxicological impact studies based on Escherichia coli bacteria
in ultrafine ZnO nanoparticles colloidal medium. Nano Lett, 2006; 6: 866-870.
6. C. M. Noorjahan, S. K. Jasmine Shahina, T. Deepika, Summera Rafiq. Green Synthesis
and Characterization of Zinc Oxide Nanoparticles from Neem (Azadirachta indicia).
International Journal of Scientific Engineering and Technology Research, August-2015;
04(30): 5751-5753.
7. D. Jain, H.K. Daima, S. Kachhwaha, S.L. Kothari, Synthesis of plant-mediated silver
nanoparticles using papaya fruit extract and evaluation of their antimicrobial activities,
Digest Journal of Nanomaterials and Biostructures, 2009; 4: 557–563.
8. D. Nath, P. Banerjee, Environ. Toxicol. Pharmacol, 2013; 36: 997–1014.
9. D. Sharma, J. Rajput, B.S. Kaith, M. Kaur, S, Thin Solid Films, 2010; 519: 1224–1229.
10. Dijiken A.V., E.A. Meulenkamp, D. Vanmaekelbergh, A. Meijerink, J. Lumin, 2000; 90:
123–128.
11. G. Sangeetha, S. Rajeshwari, R. Venckatesh, Mater. Res. Bull, 2011; 46: 2560–2566.
12. G. Singhal, B.Riju, R.S. Ashish, P.S. Rajendra, Adv. Sci. Eng. Med., 2012; 4: 62–66.
13. H. Zhang, B. Chen, H. Jiang, C. Wang, H. Wang, X. Wang, A strategy for ZnO nanorod
mediated multi-mode cancer treatment. Biomaterials, 2011; 32(7): 1906–1914.
14. H.A. Salam, P. Rajiv, M. Kamaraj, P. Jagadeeswaran, S. Gunalan, R. Sivaraj, Int. Res. J.
Biol. Sci., 2012; 1: 85–90.
15. J. Huang, Q. Li, D. Sun, Y. Lu, Y. Su, X. Yang, et al., Nanotechnology, 2007; 18;
105104.
16. J. Nicole, R. Binata, R.T. Koodali, M.C. Adhar, FEMS Microbiol. Lett., 2008; 279:
71–76.
17. J.T. Seil, E.N. Taylor, T.J. Webster, Reduced activity of Staphylococcus epidermidis in
the presence of sonicated piezoelectric zinc oxide nanoparticles, in 2009 IEEE 35th
Annual Northeast Bioengineering Conference, Boston, MA, USA, 3–5 April 2009 (IEEE,
2009; 1–2.

www.wjpps.com Vol 5, Issue 4, 2016.
929
Parthasarathy et al. World Journal of Pharmacy and Pharmaceutical Sciences
18. Jones, N., B. Ray, K. T. Ranjit, and A. C. Manna, Antibacterial activity of ZnO
nanoparticle suspensions on a broad spectrum of microorganisms. FEMS Microbiol. Lett,
2008; 279: 71-76.
19. K. Elumalai, S. Velmurugan, Green synthesis, characterization and antimicrobial
activities of Zinc Oxide nanoparticles from the leaf extract of Azadirachta indica (L.),
Applied Surface Science, 2015.
20. K. Kairyte, A. Kadys, Z. Luksiene, J. Photochem. Photobiol. B, 2013; 128: 78–84.
21. K. T Shalumon, K. H Anulekha, S.V. Nair, K.P. Chennazhi, R. Jayakumar, Int. J. Biol.
Macromol, 2011; 3: 247–254.
22. K.C. Das, D.P. Chakraborty, P.K. Bose, J. Spreng, Experientia, 1965; 21: 340–345.
23. Kajbafvala A, H. Ghorbani, A. Paravar, J.P. Samberg, E. Kajbafvala, S. K. Sadrnezhaad,
Superlattice Microstruct., 2012; 51: 512–522.
24. Kajbafvala, J.P. Samberg, H. Ghorbani, E. Kajbafvala, S. K. Sadrnezhaad, Mater. Lett,
2012; 67: 342–345.
25. Krishna RR, Ranjit TK, Adhar CM. Size-Dependent Bacterial Growth Inhibition and
Mechanism of Antibacterial Activity of Zinc Oxide Nanoparticles. Langmuir, 2011; 27:
4020-4028.
26. L. Theodore, Nanotechnology: Basic Calculations for Engineers and Scientists, Wiley,
Hoboken, 2006.
27. L. Zhang, Y. Jiang, Y. Ding, M. Povey, D. York, J. Nanopart. Res., 2007; 9: 479–489.
28. M. Moritz, M.G. Moritz, Chem. Eng. J., 2013; 228: 596–613.
29. M. Premanathan, K. Karthikeyan, K. Jeyasubramanian, G. Manivannan, Nanomed:
Nanotech. Biol. Med., 2011; 7: 184–192.
30. M.N. Alam, S. Das, S. Batuta, N. Roy, A. Chatterjee, D. Mandal, N.A. Begum, ACS
Sustain. Chem. Eng., 2014; 2: 652–664.
31. Makhluf S, Dror R, and Nitzan Y; Microwave-assisted synthesis of nanocrystalline ZnO
(MgO) and its use as bacteriocide, 2005; 15: 1708-1715.
32. N. Khandelwal, A. Singh, D. Jain, M.K. Upadhyay, H.N. Verma, Green synthesis of
silver nano particles using Argimone mexicana leaf extract and evaluation of their
antimicrobial activities, Digest Journal of Nanomaterials and Biostructures, 2010; 5:
483–489.
33. N. Roy, M.N. Alam, S. Mondal, I. Sk, R.A. Laskar, S. Das, D. Mandal, N.A. Begum,
Process Biochem, 2012; 47(9): 1371–1380.

www.wjpps.com Vol 5, Issue 4, 2016.
930
Parthasarathy et al. World Journal of Pharmacy and Pharmaceutical Sciences
34. N. Roy, S. Mondal, R.A. Laskar, S. Basu, D. Mandal, N.A. Begum, Biog. Colloids Surf.
B, 2010; 76(1): 317–325.
35. Neal A.L., Ecotoxicology, 2008; 17: 362–371.
36. P. Rajiv, S. Rajeshwari, R. Venckatesh, Spectrochim. Acta A, 2013; 112: 384–387.
37. Padmavathy, N. and R. Vijayaraghavan, 2008. Enhanced bioactivity of ZnO
nanoparticles—an antimicrobial study. Sci. Technol. Adv. Mater, 2008; 9: 1-7.
38. R. Seshadri, in: C.N.R. Rao, A. M ¨ uller, A.K. Cheetham (Eds.), The Chemistry of
Nanomaterials, Vol.1, Wiley-VCH Verlag GmbH, Weinheim, 2004: 94–112.
39. S. Baruah, S.S. Sinha, B. Ghosh, S.K. Pal, A.K. Raychaudhuri, J. Dutta, J. Appl. Phys,
2009; 105: 074308.
40. S. Kuriakose, N. Bhardwaj, J. Singh, B. Satpati, S. Mohapatra, J. Beilstein,
Nanotechnology, 2013; 4: 763–770.
41. S.D. Caruthers, S.A. Wickline, G.M. Lanza, Curr. Opin. Biotechnol., 2007; 18: 26–30.
42. S.P. Chandran, M. Chaudhary, R. Pasricha, A. Ahmad, M. Sastry, Biotechnol. Prog,
2000; 22: 577–583.
43. S.S. Kumar, P. Venkateswarlu, V.R. Rao, G.N. Rao, Int. Nano Lett., 2013; 3: 1–6.
44. S.S. Shankar, A. Rai, A. Ahmad, M. Sastry, J. Colloid Interface Sci., 2004; 275: 496–502.
45. Sangeethaa G, Rajeshwaria S, Venckateshb R Green synthesis of zinc oxide nanoparticles
by aloe barbadensis miller leaf extract: Structure and optical properties, Materials
Research Bulletin, 2011; 46: 2560–2566.
46. Sawai, J, 2003. Quantitative evaluation of antibacterial activities of metallic oxide
powders (ZnO, MgO and CaO) by conductimetric assay. J. Microbiol. Methods, 2003;
54: 177-182.
47. Sourabh D, Rizwan W, Farheen K, Yogendra KM, Javed M, Abdulaziz AA. Reactive
Oxygen Species Mediated Bacterial Biofilm Inhibition via Zinc Oxide Nanoparticles and
Their Statistical Determination. PLoS One, 2014; 9: 111289.
48. T. Szabo, J. Nemeth, I. Dekany, Colloids Surf. A, 2003; 230: 23–25.
49. T.C. Prathna, L. Mathew, N. Chandrasekaran, A.M. Raichur, A. Mukherjee, Biomimetic
synthesis of nanoparticles: science, technology & applicability, Biomimetics Learning
from Nature, 2010; 1.
50. X. Wang, J. Lu, M. Xu, B. Xing, Sorption of pyrene by regular and nanoscaled metal
oxide particles: influence of adsorbed organic matter, Environmental Science and
Technology, 2008; 42: 7267–7272.

www.wjpps.com Vol 5, Issue 4, 2016.
931
Parthasarathy et al. World Journal of Pharmacy and Pharmaceutical Sciences
51. Yamamoto O, Influence of particle size on the antibacterial activity of zinc oxide. Int. J.
Inorgan. Mater, 2001; 3: 643–646.
52. Yamamoto, O. - Sawai, J. And Sasamoto, T. 2000. Change in Antibacterial
Characteristics with Doping Amount of ZnO in MgO–ZnO Solid Solution.
In International Journal of Inorganic Materials, 2000; 2: 451-454.