Structural, Optical, Antibacterial and Antifungal Properties of Zirconia Nanoparticles by Biobased Protocol

Accepted Manuscript Structural, Optical, Antibacterial and Antifungal Properties of Zirconia Nanoparticles by Biobased Protocol S. Gowri, R. Rajiv Gandhi, M. Sundrarajan PII:

S1005-0302(14)00029-2

DOI:

10.1016/j.jmst.2014.03.002

Reference:

JMST 295

To appear in:

Journal of Materials Science & Technology

Received Date: 28 March 2013 Revised Date:

3 May 2013

Please cite this article as: S. Gowri, R. Rajiv Gandhi, M. Sundrarajan, Structural, Optical, Antibacterial and Antifungal Properties of Zirconia Nanoparticles by Biobased Protocol, Journal of Materials Science & Technology (2014), doi: 10.1016/j.jmst.2014.03.002. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Structural, Optical, Antibacterial and Antifungal Properties of Zirconia Nanoparticles by Biobased Protocol S. Gowri, R. Rajiv Gandhi, M. Sundrarajan*

[Manuscript received March 28, 2013, in revised form May 3, 2013]

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Advanced Green Chemistry Lab, Department of Industrial Chemistry, School of Chemical Sciences, Alagappa University, Karaikudi -3, Tamil Nadu, India

*Corresponding author. Tel/Fax: +91 94444 96151; Fax: +91 4565 225202; E-mail address: [email protected] (M. Sundrarajan).

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Biological entities and inorganic materials have been in constant touch with each other ever since inception of life on earth. This method has lots of merits such as not requiring complex procedures, template supporting etc. In this work, Aloe vera plant mediated synthesis of tetragonal zirconia nanoparticles has been performed and thermogravimetric and differential thermal analysis (TG/DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), ultraviolet–visible (UV-VIS) technique and Fourier transform infrared spectroscopy (FTIR) have been provided for characterizing the nanoparticles. Formation of homogeneously distributed spherical zirconia nanoparticles of 50–100 nm in size is predicted. The antimicrobial and antifungal properties are also investigated for synthesis of zirconia nanoparticles and the treated cotton by agar diffusion method against S. aureus and E. coli bacterial pathogens and fungal strains C. albicans and A. niger, respectively.

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1. Introduction

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KEY WORDS: Zirconia nanoparticles; Biosynthesis; Aloe vera; Cotton; Antibacterial property

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Fabrication of nanomaterials of various shape, size and controlled dispersity have been the subject of supreme interest due to their prospective properties such as high surface area and high fraction of surface atoms[1–3]. With the development of new chemical or physical methods, the concerns for environmental contamination are also heightened and resulted in generation of large amount of hazardous byproducts. Thus there is a need for the development of green, cost effective and environmentally benign methods and materials for the synthesis of nanoparticles that do not use toxic chemicals in their synthesis protocols[4]. Though numerous chemical methods are available for the nanoparticle synthesis such as sol-process, sol-gel, chemical precipitation, pyrolysis, chemical vapor deposition[5–7] but copious reactants and starting materials, external agents and chemical reduction of metal salt involved in these process are toxic and potentially hazardous[8]. To defeat these problems, a viable alternative and advanced approach have been raised over chemical methods, of which the biological synthesis has more environmental concerns such as eco-friendliness and compatibility for various applications in biomedical and pharmaceutical field. Many biotechnological syntheses using microorganisms, 1

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plant extracts or enzymes and templates like DNA, membranes, viruses and diatoms, have been raised[9–11]. Among different greener protocols, like the usage of greener solvent ionic liquids[12], the plant mediated synthesis is the desired method for eco-friendly production of nanoparticles, because it results in tightly controlled and highly reproducible synthesis, biocompatible particles and the avoidance of toxic surfactants or organic solvents[13]. Moreover the potential of plants as biological materials for the synthesis of nanoparticles is yet to be fully explored. In continuation of the green protocol efforts, a medicinal plant, Aloe vera is used to synthesize zirconia (ZrO2) nanoparticles. Aloe vera belongs to a member of lily family, known as Aloe barbadensis. Aloe vera contains wide range of active ingredients such as amino acids, minerals, vitamins, enzymes, proteins, sugars, anthroquinones, lignins, saponins, fatty acids and biological stimulators[14–17]. It has been reported to have many therapeutic properties in human areas, which are immunostimulation, wound healing, promotion of radiation damage repair, antidiabetic, antiinflammatory, antifungal, antimicrobial, antiprotozoal and antioxidant effects[18–20]. ZrO2 nanoparticles have received a special interest for their attractive scientific and technological aspects in different fields due to mechanical and electrical properties, high dielectric constant, and wide band gap. These mechanical and electronic properties were discovered and studied mainly in microcrystalline zirconia, but recently they have also been studied in nanocrystalline zirconia. Its attractive properties have extended for many applications in various fields like gas sensors, solid fuel cells, high durability coating, catalytic agents, etc[21– 23] . Zirconia nanoparticles synthesized by means of different physico-chemical methods such as sol-gel synthesis[24], aqueous precipitation method[25], thermal decomposition and hydrothermal methods[26] requires extreme temperatures, while as the biological synthesis dodges some of the detrimental features and proceeds the synthesis beneficially at low cost in mild condition by means of an environmental benign approach without exploding toxic waste to environment. Hence the biosynthesis of zirconia has been executed with the leaf extract of wide spread plant Aloe vera. In recent years, inorganic antimicrobial agents are increased widely for control of microorganisms in various areas especially in textile field[27–29]. The key advantages of inorganic antmicrobial agents are improved safety and stability compared with organic antimicrobial agents[30]. ZrO2 nanoparticles are also able to possess remarkable antimicrobial property[30]. Our previous studies have reported the biosynthesis of TiO2, SnO2 and MgO using plant extracts as first attempt and their activity on cotton against bacterial pathogens[31–33]. Hence herein we report for the first time, biosynthesis of ZrO2 nanoparticles by utilizing Aloe vera leaf extract as a hydrolysing agent instead of synthetic chemicals and also imparting their antibacterial asset on cotton fabric. Antibacterial studies were carried out for both ZrO2 nanoparticles and treated cotton against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) bacterial pathogens and antifungal activity was demonstrated against Candida albicans (C. albicans) and Aspergillus niger (A. niger) for only ZrO2 nanoparticles. This kind of biobased synthesis of zirconia nanoparticles and their application on cotton with non toxic chemicals is an ecofriendly cost effective approach.

2. Experimental 2.1. Materials 2

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Zirconium oxychloride octahydrate [ZrOCl2·8H2O (95%)] was purchased from Merck, India Pvt. Ltd. Woven cotton fabric was purchased from Ayyappa Textiles, Karaikudi. Aloe vera leaves were harvested from agricultural land of Karaikudi, Tamil Nadu, India. Deionised water (with resistivity being 18.2 MU cm) was used throughout the reaction process.

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2.2. Preparation of aloe vera gel extract

2.3. Synthesis of ZrO2 nanoparticles

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Freshly collected leaves of Aloe vera plant were first washed thoroughly with pure water before extraction. Inner gel of the leaf was extracted by peeling the outer skin manually using a cleaned knife. About 50 g portions of the collected inner gel were finely cut into small portions and extracted by boiling with 100 mL double distilled water. The resulting extract was cooled to room temperature and filtered using a pure cotton cloth followed by filtration with Whatmann No. 1 filter paper. The filtrate was collected in a closed container and stored in a refrigerator at 4 °C for further use. This filtrate was used as the solvent and hydrolyzing agent instead of external chemical agents for the synthesis of ZrO2 nanoparticles.

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Synthesis of ZrO2 nanoparticles was performed by biological approach using Aloe vera gel extract. About 0.4 mol/L ZrOCl2·8H2O was prepared using 50 mL of aqueous extract of Aloe vera gel. The reaction mixture was subjected to vigorous stirring at room temperature for about 4 h. The precipitation of the product was predicted by the turbid white colloidal particles at the bottom of the flask, which can be believed that due to the progress of the starting material to form zirconium hydroxide. The precipitated sample was allowed to stand for one day before centrifugation. The particles were separated by centrifugation (KUBOTA-6800 Centrifuge machine) at 10000 r/min for 15 min for removing the unwanted organic waste and after they were filtered, washed with deionized water and dried in an oven to get the as-prepared sample, i.e. zirconium hydroxide. The dried sample was subjected to calcination in muffle furnace at 500 °C to form the ZrO2 nanoparticles by dehydration of the as-prepared sample. 2.4. Characterization techniques

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Thermogravimetric and differential thermal analysis (TG-DTA) were performed using an SDT Q600 V8.3 101 TG-DTA instrument in air atmosphere between room temperature and 1000 °C. The weight of the sample used was 6.05 mg and the rate of elevating temperature was 10 °C/min. X-ray diffraction (XRD) analysis was carried out on a PANanlytical X-Pert PRO Diffractometer operated at 40 kV with a current of 30 mA using Cu-Kα for the determination of crystallinity and crystallite size of the nanoparticles. Surface morphology of the ZrO2 nanoparticles and the treated fabric were examined by scanning electron microscopy (SEM) on a JEOL JSM 6390 scanning electron microscope instrument operated at an accelerating voltage at 15 kV. For energy dispersive X-ray (EDX) analysis, the particles were dried on a carbon coated copper grid and performed on SEM instrument with thermo EDX attachment. Height and width distribution of the ZrO2 nanoparticles were studied by atomic force microscopy in an SPM Solver P47H PRO instrument. The Fourier transform infrared spectroscopy (FTIR) analysis of 3

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the tin oxide nanoparticles was performed by using a Perkin Elmer make Model Spectrum RX1 (Range 4000 cm–1–400 cm–1). Absorption of ZrO2 nanoparticles by ultraviolet–visible (UV-VIS) technique were studied using a Perkin Elmer LAMBDA 35 UV-VIS spectrophotometer. 2.5. Treatment of ZrO2 nanoparticles on cotton

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Fine medium weight of 100% woven cotton fabric was used for the treatment of biosynthetic ZrO2 nanoparticles by direct application system. The cotton fabric specimen of dimensions 12 cm × 12 cm is immersed in the solution containing 6% of citric acid, as crosslinking agent and 3% of ZrO2 nanoparticles for about 3 h. Treatment of cotton fabric was carried out by pad dry cure method and padded on the Laboratory padder. The fabric was passed between the rollers at a padding pressure of 20.68 kPa (3 psi) for the uniform distribution of nanoparticles and 100% wet pickup on the fabric. Finally the padded fabric was subjected to air drying and curing at 80 °C and 150 ºC for 5 and 3 min, respectively.

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2.6. Evaluation of antimicrobial activity of ZrO2 nanoparticles and treated cotton

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Agar diffusion method, a relatively quick and easily executed semiquantitative test is employed to determine the antibacterial potential of both ZrO2 nanoparticles treated cotton and ZrO2 nanoparticles against bacterial pathogens. S. aureus (gram positive) and E. coli (gram negative) bacterial pathogens were used for testing. The agar used is Muller-Hinton agar that is rigorously tested for composition and pH. Nutrient agar media was inoculated with the test organism for the growth of bacteria. A small amount of the samples was placed on it for intimate contact followed by incubation at 37 °C for 24 h or until visible growth was established. The antibacterial activity was demonstrated by the diameter of the zone of inhibition developed in and around the sample. Further antifungal activity of the ZrO2 nanoparticles and ZrO2 nanoparticles treated cotton was also determined against non-filamentous fungus, A. niger and filamentous fungus, C. albicans by agar diffusion method using potato dextrose agar as a medium. Zone of inhibition is the area in which the bacterial growth is stopped due to bacteriostatic effect of the compound and it measures the inhibitory effect of compound towards a particular microorganism.

3. Results and Discussion

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3.1. Thermal analysis

The thermal decomposition characteristics were studied to obtain the calcination temperature of as-prepared zirconia at a constant heating rate of 10 °C/min in air. The TG curve (Fig. 1) exhibits a weight loss with two distinct steps that can be attributed to the dehydration of the as-prepared zirconia. A sharp reduction in sample weight of about 25% was detected from room temperature to 150 °C as the physically adsorbed water leaves from the surface of the sample. Weight loss related to the formulation of organic part with simultaneous crystallization of as-prepared sample i.e Zr(OH)4 occurred upto 450 °C. This weight loss of 25% is mainly due to the decomposition of organic components, adsorbed water on the inorganic material for the crystallization of zirconia from amorphous as-prepared zirconia. At higher temperatures, there 4

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are no appreciable weight changes especially exceeding 500 °C, indicating that the completion of different types of surface hydroxyl group condensation. The DTA curve presented in Fig. 2 reveals a distinct endothermic peak and exothermic peak. An endothermic peak appeared below 150 °C could be related to the liberation of surface adsorbed water. The heat flow change shows that some exothermic reactions occurred at 350 °C, which could also explain the oxidation of organic components of natural material adsorbed in the as-prepared zirconia. This exothermic peak also can be attributed to the crystallization of zirconia particles from the initially amorphous as-prepared zirconia. 3.2. XRD analysis

3.3. SEM analysis

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The phase and the crystallographic structure of the as-prepared and calcined zirconia samples were characterized by XRD patterns displayed in Fig. 3. The XRD peaks are consistent with the JCPDS data card 79-1769 of tetragonal zirconia. The amorphous scattering peaks in the XRD pattern of the as-prepared sample (Fig. 3(a)) indicate that the crystals included in it are not perfect due to the inadequacy of the heat treatment and aging time during the preparation process. The broadening of the peaks can be well assigned to their amorphous nature and truncated particles. The XRD pattern of the calcined zirconia (Fig. 3(b)) exhibit sharper and narrower diffraction peaks pointing out that calcination process has been known to change the phase from amorphous to crystalline state. There are no other crystal peaks related to organic impurities, zirconium metal and metal salts indicating the high purity of biosynthesized zirconia from Aloe vera extract. Moreover, purity of the calcined ZrO2 sample indicates that the asprepared zirconia has been completely free from the organic matters of Aloe vera extract. The broad contours express that the particles are in smaller size. The detected peaks corresponded with those of tetragonal zirconia were found at the lattice planes of (101), (110) (112) (200) (211) (202) and (220) in the 2θ value: 30.22°, 35.2°, 50.3°, 50.7°, 60.2°, 63° and 74.5°, respectively. The crystallite size of the most intense plane (101) were 27.4 nm, determined by employing Debye-Scherrer’s equation, d = 0.89λ/(βcosθ), where d is the particle size, λ the wavelength (0.1542 nm for Cu-Kα radiation), β the full width at half maximum and θ the Bragg angle of the (101) plane. Nanosized value of ZrO2 suggests that the Aloe vera extract can be employed as the hydrolytic agent for the preparation of ZrO2 nanoparticles.

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SEM analysis is employed to visualize the size and shape of the calcined ZrO2 nanoparticles. SEM micrographs of calcined ZrO2 nanoparticles under different magnifications are displayed in Fig. 4. It is observed that most of the particles are spherical in shape with smooth and fused surface. The particles are homogeneously distributed without much of agglomeration and ensured the average size of about 50 nm. The boundary of the single particles can be well regarded by intense observation of the SEM images though it has agglomerates. The reason for the unvarying size distribution of the particles may be attributed to the calcination process that allows growth by aggregation of particles through their grain boundaries. Moreover the organic matters of Aloe vera material such as proteins, polysaccharides and phenolic compounds at midst the particles and on the surface of the as-prepared zirconia control the aggregation of particles to some extent of calcination process by covering a layer thereby hinders 5

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the longer growth of nanoparticles. Further analysis of the ZrO2 nanoparticles by EDX spectrum in Fig. 5 confirmed the signal characteristic of zirconium and oxygen. All the presented peaks are assigned to Zr and O without any unidentified signals, proving the purity and formation of ZrO2 by calcination.

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3.4. AFM analysis AFM analysis is utilized here to receive the exact size distribution of the calcined ZrO2 nanoparticles. AFM Topographic and 3D image (Fig. 6(a) and (b)) of calcined ZrO2 nanoparticles was scanned in an area of 10 µm × 10 µm. Spherical shaped morphology with smooth and fused surfaces and weak accumulation of particles were clearly resolved from AFM images. Most of the particles distributed are homogeneous and holds the size less than 50 nm. Fig. 6(c) and (d) displays the height and width distribution line profile spectrum of biosynthesized ZrO2 nanoparticles. The maximum height and width distribution of the spherical ZrO2 nanoparticles are 21 and 27 nm, respectively. These results almost agree with the XRD and SEM results thereby adding evidence for its structural information.

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3.5. FTIR analysis

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FTIR measurements were carried out to identify the possible biomolecules of Aloe vera responsible for the hydrolysis of zirconium ions. Fig. 7 shows the FTIR spectra of as-prepared (a) and calcined ZrO2 (b) nanoparticles in the 400–4000 cm–1 regions. Fig. 7(a) depicts a broad prominent band around 3200–3400 cm–1 which is related to the –OH stretching vibrations of adsorbed water molecules on as-prepared sample. Smaller peaks present in the range of 2900– 3700 cm–1 were resulted from the amide linkages between the amino acid residues in Aloe vera gel material. The peaks at 1620 cm–1 represent carbonyl groups (C=O) and 1000–1200 cm−1 indicate C–O single bonds from polyphenolic compounds of natural material. A stretching vibration at 1392 cm–1 could be attributed to the groups of carbonyl and O–H deformation frequency possibly from the carboxylic acid and phenolic groups in aloe vera extract. It is well known that the peaks at 705 and 634 cm–1 are distinctive for Zr–O–Zr vibrations. Existence of Zr–OH vibrations can be evidenced by the appearance of peak at 530 cm–1. After calcination of as-prepared zirconia at 500 °C (Fig. 7(b)), intensity of the entire peaks characteristic of biological molecules of Aloe vera extract decreased obviously or completely disappeared due to the weakening of bonds. It is apparent that the intensity of absorption in the region of 500–700 cm–1 characteristic of tetragonal Zr–O–Zr vibrations is greatly enhanced by calcination at 500 °C. This observation achieved conformity with XRD data. Moreover the peak characteristic of Zr– OH vibration disappeared due to their condensation of hydroxyl groups to form ZrO2. IR spectroscopic study confirmed that the carbonyl group from amino acid residues and proteins of Aloe vera gel material has the stronger ability to bind metal by covering the metal nanoparticles to prevent agglomeration for some magnitude of calcination. This suggests that the biological molecules could possibly act as hydrolyzing agent for the metal oxide nanoparticles. 3.6. UV-VIS analysis UV absorbance spectra of calcined ZrO2 nanoparticles are displayed in Fig. 8. The pronounced absorption peak appeared at 213 nm is blue shifted from the bulk ZrO2 material and 6

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characteristic for the tetragonal ZrO2 nanoparticles. The sharp and prominent absorption band may arise due to the transitions from valence band to conduction band and agrees with the reported literature for ZrO2 nanoparticles. The direct band gap of calcined ZrO2 nanoparticles is determined from the band gap equation of (αhν)2 = K(Eg – hν) where α is the absorption coefficient, K is the Boltzmann constant and Eg is the separation between valence and conduction bands. Fig. 9 presents the Tauc’s plot of (αhν)2 as a function of hν, and the value of band gap can be estimated by extrapolating the straight portion to the energy axes. The estimated band gap is 5.42 eV that coincides well with the reported band gap value of ZrO2 nanoparticles. This higher value of band gap usually occurs with the fine nanosized particles. Variation of band gap from the bulk can be related to the surface morphology and defects present in the nanocrystals. The increasing trends of the band gap energy upon the decreasing particle size are well presented for the quantum confinement effect. 3.7. SEM analysis of treated cotton

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The difference in morphology on the fibre surface area of cotton before and after the treatment of ZrO2 nanoparticles can be analyzed by SEM in Fig. 10. The surface property of untreated cotton is noticeable grooves and fibrils in the SEM micrographs (Fig. 10(a)) without deposition of any other material. SEM images of ZrO2 nanoparticles treated cotton (Fig. 10(b)) shows homogeneous distribution in significant proportion. The size of the ZrO2 nanoparticles coated on the cotton fibre is in the nanoscale range as determined from other analysis. But the real size of the cotton fibre is about 50 µm which is noted from the scale bar provided in the SEM images. It is evident from the images that the nanoparticles do not appear to form aggregates and are well distributed inside the fabric due to the stabilization of prepared ZrO2 nanoparticles within the cellulose network. The treatment of ZrO2 nanoparticles are further confirmed by their EDX spectra. Appearance of zirconium, oxygen and carbon peaks of treated cotton is shown in Fig. 11(b), in which no such peaks in the EDX spectrum of untreated cotton (Fig. 11(a). The presence of Zr and O atoms confirms the treatment of ZrO2 nanoparticles on cotton, and carbon atoms may be from the cellulosic cotton.

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3.8. Antibacterial assessment of ZrO2 nanoparticles and treated cotton

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ZrO2 nanoparticles and ZrO2 nanoparticles treated cotton are tested for its antibacterial activity against the bacterial pathogens, S.aureus among gram positive and E.coli, among gram negative by Agar diffusion method. Zone of inhibition values determined for the treated cotton and ZrO2 nanoparticles is shown in Table 1. Both treated fabric and ZrO2 nanoparticles pronounced significant growth inhibitory effect against both bacteria due to their large surface area by their nanosize (Fig. 12). However ZrO2 nanoparticles treated fabrics possess superior antibacterial activity against E. coli bacteria than with S. aureus bacteria which are clearly visualized in the antibacterial photographs. This difference in antibacterial performance may be due to the following assumptions: active oxygen species generated from the ZrO2 nanoparticles actively inhibits the growth of S.aureus cells by accumulation or deposition on the surface of S.aureus cells. It has been suggested that ZrO2 nanoparticles are able to slow down E.coli growth due to disorganization of E. coli membranes, which increases membrane permeability leading to accumulation of nanoparticles in the bacterial membrane and cytoplasmic regions of the cells. 7

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From the above probable discussions we clearly came to know about the enhanced antibacterial activity of ZrO2 nanoparticles. 3.9. Antifungal assessment of ZrO2 nanoparticles

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Antifungal images of ZrO2 nanoparticles treated cotton and ZrO2 nanoparticles in Fig. 13 clearly predict its antifungal activity by actively inhibiting the growth of both C. albicans and A. niger strains. Due to its high surface area, ZrO2 nanoparticles almost show similar and significant inhibition effect against both fungal strains (Table 1). As per our literature survey, only very few studies were carried out on the antifungal activity of ZrO2 nanoparticles. ZrO2 nanoparticles may actively inhibit the growth of fungal strains by interfering cell function and causing deformation in fungal hyphae. 3.10. Cost effective analysis

4. Conclusion

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Cost effective analysis was carried out for the biological synthesis of ZrO2 nanoparticles by means of chemical method of synthesis (Table 2). Apart from source of metal salt like zirconium oxychloride and zirconium oxynitrate, external agents like solvents such as ethanol, isopropanol etc, precipitating agents like alkali and acidic solutions, and surfactants like polyvinylpyrrolidone (PVP) for stabilization are required for the formation of metal oxide nanoparticles by chemical methods. In the case of biosynthesis, source of metal salt and the biological extract solution is adequate to form the stabilized and size controlled nanoparticles. Hence biosynthetic protocol to fabricate metal oxide nanoparticles will be economically feasible and environmentally benign.

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It is demonstrated at the first time that tetragonal spherical ZrO2 nanoparticles can be synthesized by biological material of Aloe vera extract. This generous biosynthesis fulfills the green chemistry perspectives such as selection of solvent medium, environmentally benign agents and nontoxic substances for the fabrication of stable ZrO2 nanoparticles. Crystallization and thermal behavior evaluated by TG/DTA exhibit the crystallization temperature of 450 °C. Particle growth of ZrO2 nanoparticles limited to about 50 nm is resulted by XRD, SEM and AFM techniques. FTIR analysis confirms the interaction of biological molecules of Aloe vera and formation of ZrO2 nanoparticles. Blue shifted UV absorbance from the bulk ZrO2 is achieved by the quantum confinement effect in nanostructure of ZrO2. Antifungal and antibacterial potential of ZrO2 nanoparticles and ZrO2 nanoparticles treated cotton exhibit pronounced skill against the test organisms. In spite of variety of antimicrobial agents, the application of nanoparticles in textile finishing has wide spread applications, since nanoparticles have high ratio of surface area to volume, and hence they show enhanced property at their minimum concentration. The fabrication of nanoparticles as nanocapsules could improve the durability of the imparted property on the fabricated textile[34]. Therefore, the biosynthesized non-toxic zirconia nanoparticle of average size 50 nm, can play a significant role in textile field as an effective antimicrobial agent and an alternative to some traditional antimicrobial agents with detrimental effect[35,36]. This kind of treated fabric can be used successfully to minimize the 8

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infections with pathogenic bacteria. Hence this work demonstrates that biological method may serve as a useful synthetic tool for producing biocompatible ZrO2 nanoparticles.

Acknowledgements

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The authors express sincere thanks to University Grants Commission (UGC), New Delhi for their financial support by awarding UGC-BSR Fellowship and Department of Physics, Alagappa University, Karaikudi, Tamil Nadu, India for providing XRD analysis.

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Table and figure captions

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Fig. 1 TGA curve of the as-prepared zirconia in an air atmosphere. Fig. 2 DTA curve of as-prepared zirconia in an air atmosphere. Fig. 3 XRD patterns of as-prepared (a) and calcined (b) ZrO2 nanoparticles. Fig. 4 SEM micrographs of calcined ZrO2 nanoparticles under different magnifications. Fig. 5 EDX spectrum of calcined ZrO2 nanoparticles. Fig. 6 (a) AFM topographic image, (b) 3D image, (c) height distribution and (d) width distribution line profile of calcined ZrO2 nanoparticles. Fig. 7 FTIR spectra of as-prepared (a) and calcined (b) ZrO2 nanoparticles. Fig. 8 UV-Vis absorbance spectrum of calcined ZrO2 nanoparticles. Fig. 9 Plot of (αhν)2 versus photon energy (hν) for calcined ZrO2 nanoparticles. Fig. 10 SEM micrographs of untreated (a) and ZrO2 nanoparticles (b) treated cotton. Fig. 11 EDX spectra of untreated (a) and ZrO2 nanoparticles treated (b) cotton. Fig. 12 Antibacterial activity of ZrO2 nanoparticles treated cotton (a), ZrO2 nanoparticles (b) against E.coli (1) and S.aureus (2), respectively. Fig. 13 Antifungal activity of ZrO2 nanoparticles treated cotton (a), ZrO2 nanoparticles (b) against C. albicans (1) and A. niger (2), repectively.

AC C

Table 1 Zone of inhibition (mm) values against test organisms Table 2 Cost effective analysis of biological method with chemical method

10

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Table 1 Zone of inhibition (mm) values against test organisms Samples

S.aureus

E.coli

C.albicans

A.niger

13

14

13

12

23

32

22

18

SC

ZrO2 nanoparticles treated cotton

Fungal strains

RI PT

ZrO2 nanoparticles

Bacterial pathogens

Reagents

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Table 2 Cost effective analysis of biological method with chemical method Chemical method

required Reagents

Quantity

Cost (INR)

ZrOCl2·8H2O

Solvent

Ethanol

50 mL

80

Precipitating

NaOH

8g

8

27

PVP

2g

Reagents

Quantity

Cost (INR)

ZrOCl2·8H2O

6.44 g

27

Extract of

50 g

10

Aloe vera gel 12

AC C

Surfactant

EP

agent

6.44 g

TE D

Metal source

Biological method

Total cost

127

11

Total cost

37

SC

RI PT

ACCEPTED MANUSCRIPT

M AN U

Fig. 1

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Fig. 3

EP

TE D

Fig. 2

12

RI PT

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EP

Fig. 5

TE D

M AN U

SC

Fig. 4

Fig. 6

13

RI PT

ACCEPTED MANUSCRIPT

M AN U

SC

Fig.7

Fig. 9

AC C

EP

TE D

Fig. 8

14

AC C

EP

Fig. 10

TE D

M AN U

SC

RI PT

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Fig. 11

15

EP AC C

Fig. 12

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

16

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Fig. 13

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

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