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Cerium Oxide Nanoparticles: Synthesis, Characterization and Study of Antimicrobial Activity Article in Journal of Nanomaterials & Molecular Nanotechnology · January 2017 DOI: 10.4172/2324-8777.1000219

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Khandavalli Ashwini

D. Y. Patil University, Navi Mumbai

D.y patil university , Navi mumbai

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Reshma and Ashwini, J Nanomater Mol Nanotechnol 2017, 6:3 DOI: 10.4172/2324-8777.1000223

Journal of Nanomaterials & Molecular Nanotechnology

Research Article

Cerium Oxide Nanoparticles: Synthesis, Characterization and Study of Antimicrobial Activity Pol Reshma* and Khandavalli Ashwini

Abstract Cerium an element in lanthanide series exhibit both oxidation state Ce3+ and Ce4+ and as ability to drastically adjust or to switch over its oxidation state easily. Cerium oxide nanoparticles with 20 - 100 nm in diameter were synthesized via hydroxide mediated approach using surfactants. Different surfactants such as sodium dodecyl sulphate (SDS) and cetyl trimethyl ammonium bromide (CTAB) possess the ability to control the shape and size of cerium oxide nanoparticles synthesized by using cerium nitrate hexahydrate as the starting material via hydroxide mediated approach. Cerium oxide nanoparticles were coated using polyvinyl pyrrolidine (PVP) as the polymer. The structural and morphological studies of cerium oxide nanoparticles were characterized by scanning electron microscopy. The antibacterial activities of nanoceria were studied with respect to Gram positive bacteria and Gram negative bacteria by disc diffusion method. Keywords Cerium oxide; Nanoceria; Antibacterial; CTAB; SDS, PVP

Introduction Cerium oxide is a rare earth oxide. Ceria exhibits both oxidation states +3 (Ce2O3) and +4 (CeO2) and has the capacity to switch over these oxidation states very easily. These two oxidation states of the cerium element project its ability to act as a catalyst for both oxidation and reduction reactions [1]. Nanoceria is exceptionally versatile due to its dual valence state and thus exhibits electronic and catalytic properties due to which it has increasing applications in several fields. It is extensively used in gas sensors [2] and electrochemical biosensors [3]. The activity of nanoparticles and its application is dependent on their shape and size. A variety of lower temperature synthetic methods for the production of nanoceria are: co-precipitation [4,5] hydrothermal [6-8], solvothermal [9,10], solgel [11,12] micro emulsion and reversed micelle methods [8,13-15]. The hydrothermal method was advantageous over other methods as high purity products can be synthesized with narrow particle size distribution, chemical homogeneity and low environmental pollution [16]. Surfactants are amphiphiles that reduce the surface tension. They prevent agglomeration of particles and thereby control the size of nanoparticles. Cationic, anionic and non-ionic surfactants can be used in synthesis of nanoparticles. The choice of surfactants modifies the morphology, size and shape of the nanoceria [17]. Cerium oxide *Corresponding author: Dr. Reshma Pol, DY Patil University, School of Biotechnology & Bioinformatics, Plot No. 50, Sector 15, CBD Belapur, NaviMumbai-400614, India, Tel: 022-39486049; E-mail: [email protected] Received: April 21, 2017 Accepted: May 08, 2017 Published: May 14, 2017

International Publisher of Science, Technology and Medicine

a SciTechnol journal nanoparticles were reported to be synthesized using all the three types of surfactants viz; CTAB (cationic) [18], SDS (aninonic) [19] and PEG (non-ionic) [20]. Metal nanoparticles with bactericidal activity may find applications in various fields. i.e;medical instruments, devices and food processing [21]. It has been demonstrated that highly reactive metal oxide nanoparticles exhibit excellent biocidal action against Gram positive and Gram negative bacteria [22]. The main objective of this research is the synthesis of cerium oxide nanoparticles by hydroxide mediated method using surfactants like SDS and CTAB and capping agents like PVP. The antibacterial effect of cerium oxide nanoparticles on Gram positive and Gram negative organisms were studied.

Material and Methods All the chemicals were obtained from S.D. Fine chemicals Ltd., Mumbai, Maharashtra were used for the synthesis of nanoparticles and determination of antibacterial activity of nanoceria.

Synthesis of cerium oxide nanoparticles and characterization The cerium oxide nanoparticles were synthesized by using hydroxide mediated method. The reagents required for the synthesis namely; Cerium nitrate hexahydrate solution (0.1M) and sodium hydroxide solution (0.3M) were dissolved in deionized water. NaOH solution was added to the precursor solution dropwise for 10 minutes at room temperature under constant stirring. A pinkish white solution was obtained that was centrifuged at 9000 rpm for 15 min [16]. The pellet was collected by discarding the supernatant. The obtained pellet was washed thrice with deionized water. It was then dried at 80 in hot air oven for 30min and then annealed at 270ºC for 24 h. The same procedure was followed for the synthesis of CeO2 nanoparticles, using different surfactants such as 0.05 M SDS, 0.05 M CTAB and 0.05 M PVP. The surfactant was added along with cerium nitrate hexahydrate solution. The structural characterization and the grain size of cerium oxide nanoparticles were studied by Field Emission Gun - Scanning Electron Microscope (FEG-SEM). The microscopy studies were carried at the SAIF laboratory, IIT Mumbai.

Antibacterial activity of cerium oxide nanoparticles Test organism: Gram positive organisms namely Corynebacterium diphtheriae, Sarcina lutea and Gram negative organisms namely Escherichia coli, Proteus vulgaris were used as the test organisms for antimicrobial activity. The purity of the bacterial cultures was checked by colony characterization and gram staining. Anti-microbial screening: Antimicrobial activity of the test cultures was screened by disc diffusion method. For this method, the bacterial cultures (100 µl of 105 CFU/ml) were surface spread uniformly onto the entire surface of a Nutrient agar plate. Sterile whatmann filter paper disks of 6 mm diameter were punched and soaked in nanoceria solution (20 µl of 25%, 50% and 100% concentration separately). The nanoparticles laden filter paper was dried in an oven for 1 h and then placed on the surface of each nutrient agar plate. 10 µg/ ml Streptomycin was used as the standard reference. The plates were incubated at 37ºC for 24 h. The zone of inhibition was measured [26].

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Citation: Reshma P, Ashwini K (2017) Cerium Oxide Nanoparticles: Synthesis, Characterization and Study of Antimicrobial Activity. J Nanomater Mol Nanotechnol 6:3.

doi: 10.4172/2324-8777.1000223

Results The cerium oxide nanoparticles were synthesized using different surfactants. The surface and morphological characterization of cerium oxide nanoparticles was carried out using scanning electron microscopy. SEM images of cerium oxide powder prepared by the hydroxide method with surfactants namely SDS, CTAB and PVP are shown in Figures 1-4. From the SEM images, the size of the particles was found to be in the range of 40-100 nm.

Figure 4: SEM image obtained for cerium oxide nanoparticles after treatment with PVP with 60,000X magnification.

Figure 1 exhibits spherical shaped morphology and the grain size were found to be between 37.5 nm and 43.8 nm. Figure 2 exhibits cubical shape with particle size of 65.4 nm and 47.3 nm. Figure 3 indicates spherical clumps with particle size of 36.8 nm and 46.1 nm whereas Figure 4 shows a smaller spherical shape with particle size of 31.3 nm and 38.2 nm. Figure 4 shows a fine circular morphology with a small grain size. The grain size was in the range of 30-40 nm. Figure 1: SEM image obtained for cerium oxide nanoparticles without any treatment with surfactant at 60,000 X magnification.

The antimicrobial screening indicated that 100% concentration of nanoceria to be effective against the test organisms (Figure 5). The zone of inhibition (ZID) was seen for the gram negative organisms Proteus vulgaris (ZID of 5 mm) and Escherichia coli (ZID of 3 mm) whereas, the gram positive organisms Corynebacterium diptheriae and Sarcina lutea showed no inhibition with nanoceria.

Discussion

Figure 2: SEM image obtained for cerium oxide nanoparticles after treatment with SDS with 60,000X magnification.

Figure 3: SEM image obtained for cerium oxide nanoparticles after treatment with CTAB with 60,000X magnification.

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The SEM results indicated that the nanoceria particles have very fine particles on treatment with poly vinyl pyrolidone (PVP). Nanoceria obtained from hydroxide mediated method without using any surfactant was found to be in the range of 18-30.4 nm [23]. Chenguo Hu et al. report the formation of ultrafine nanoceria particles of 1-3 nm at 165ºC for a very short duration and strong agglomeration and nanoceria grain size of 3-6 nm of polygonal shape at 190ºC for 48 h [24]. Using SDS as the surfactant, spherical elongated particles were obtained with a grain size of ~10-15 nm [16]. On using different volumes of 10% PVP Ketzial and his coworkers obtained flake shaped crystals with a grain size of nanoceria in the range of 30 - 35 nm [20]. Proteus vulgaris and Escherichia coli showed inhibition with nanoceria unlike the gram positive organisms Corynebacterium diptheriae and Sarcina lutea. The gram positive and gram negative bacterial cells differ markedly in their cell walls. Gram positive cells are much thicker due to the presence of peptidoglycan layer thus protecting the cells from penetration of heavy metals into the cytoplasm [25,26]. The heavy metals react with the proteins combining with the thiol group which leads to inactivation of the proteins thus playing a vital role in hampering the bacterial growth and thereby leading to cell death [27-29]. Similar findings were reported by Feng and coworkers that silver ions interact with the thiol groups in protein inducing bacterial inactivation. 100% concentration of nanoceria particles inhibits the growth of bacterial cells. The concentration of the heavy metal influences the antibacterial action [30]. As the concentration of nanoparticles increases it leads towards the internalization of more amounts of nanoparticles thereby leading to the toxicity of the bacterial cells. Similar findings were reported by

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doi: 10.4172/2324-8777.1000223

a

b

c

d

Figure 5: Disc diffusion agar plates containing cerium oxide nanoparticle impregnated discs for (a) Proteus vulgaris (b) Escherichia coli (c) Corynebacterium diptheriae (d) Sarcina lutea.

Sasidharan et al, after using zinc oxide nanoparticles [31]. Erdural et al., found that nanostructured titania particles synthesized using hydrothermal processing had higher antimicrobial activity against Escherichia coli [32].

Conclusion Hydrothermal mediated approach for the synthesis of cerium oxide nanoparticles has been achieved. The method was found to be convenient, and efficient for obtaining nanoceria. The morphological and the structural properties revealed that the particle size of the nanoparticles was affected after using surfactants. The agglomeration of particles for the cerium oxide nanoparticles were inferred from SEM measurements. Metal nanoparticles induce nanotoxicity which depends on the gram nature of the bacterial cells. The nanoceria particles exhibited inhibition with respect to the gram negative bacteria as they are more prone to cytotoxicity. Acknowledgements We are thankful to the (SAIF) Sophisticated Analytical Instrument Facility Laboratory at IIT Mumbai for FEG-SEM analysis.

11. Niederberger M (2007) Nonaqueous Sol-Gel routes to metal oxide nanoparticles. Acc Chem Res 40: 793-800. 12. Laberty-Robert C, Long JW, Lucas EM, Pettigrew KA, Stroud RM, et al. (2006) Sol-gel-derived ceria nano-architectures: synthesis, characterization, and electrical properties. Chem Mater 18: 50-58. 13. He YJ, Yang BL, Cheng GX (2003) Controlled synthesis of CeO2 nanoparticles from the coupling route of homogenous precipitation with microemulsion. J Mater Lett 13-14: 1880-1884. 14. Patil S, Kuiry SC, Seal S, Vanfleet R (2002) Synthesis of Nanocrystalline Ceria particles for high temperature oxidation resistant coating. J Nanoparticle Research 4: 433-438. 15. Patil S, Seal S, Yu G, Schulte A, Norwood J (2006) Role of trivalent La and Nd dopants in lattice distortion and oxygen vacancy generation in cerium oxide nanoparticles. Appl Phys Lett 88: 243110. 16. Gnanam S, Rajendran V (2013) Influence of various surfactants on size, morphology, and optical properties of CeO2 nanostructures via facile hydrothermal route. J Nanoparticles. 17. Riccardi CS, Lima RC, dos Santos ML, Bueno PR, Varela JA, et al. (2009) Preparation of CeO2 by a simple microwave hydrothermal method. Solid state Ionics 180: 288-291.

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School of Biotechnology and Bioinformatics, DY Patil University, Plot No. 50, Sector 15, CBD Belapur, Navi-Mumbai 400614, India

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