IJCRR - 13(2), January, 2021
Pages: 76-79
Date of Publication: 16-Jan-2021
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Microwave-Assisted Solvothermal Synthesis of Tungsten Oxide (WO3) Nanoparticles for Microbial Inhibition
Author: Harini S, Aswini A, S.C. Kale, Jayashri Narawane, Jayant Pawar, Snehal Masurkar, Shilpa Ruikar
Category: Healthcare
Abstract:Introduction: Tungsten oxide is an n-type semiconductor which possesses the bandgap of 2.6 \? 2.8 eV at room temperature. Additionally, tungsten oxide has the absorption capacity of 480 nm in the visible region resulted from its photocatalytic property. Objective: To synthesize and evaluate tungsten oxide nanoparticles for microbial inhibition. Methods: Microwave-assisted synthesis of tungsten oxide nanoparticles was carried out by solvothermal route for the development of antibacterial agent. 1 M Sodium Tungstate Dihydrate was dissolved in 100 mL distilled water which was then mixed with 20 mL of 0.1 M NaOH and the Conc. HCL was added into the reaction mixture. The precipitation of yellow colour was collected and rinsed with purified water three times. During 8 hours at 60oC and 4 hours, the precipitate having undergone drying and calcination to get tungsten oxide powder. Results: The yellow colour precipitate was obtained after the reaction, which was characterized by UV- Vis Spectroscopy and Scanning Electron Microscopy (SEM). The λmax was found to be at 364 nm and bandgap calculated as 3.41 eV. Conclusion: Antibacterial efficacy was determined by anti-well diffusion assay against E. coli and Pseudomonas Aeruginosa. The bacterial cultures were found to be sensitive for WO3 NPs at a concentration of 1000 µg/mL. The E. coli was more sensitive for WO3 NPs compared to Pseudomonas Aeruginosa.
Keywords: Microwave-assisted method, Solvothermal synthesis, Tungsten oxide, E. coli, Pseudomonas Aeruginosa, Microbial inhibition
Full Text:
INTRODUCTION
Metal oxide nanoparticles which have unique physical and chemical properties due to change in morphology under the range of 1-100nm. Metal oxide nanoparticles are important in many areas in physics, chemistry, and material science.1 There are various semiconductor oxides among these tungsten oxides is an important transition metal oxide semiconductor.2 Tungsten oxide is an n-type semiconductor which possesses the bandgap of 2.6 – 2.8 eV at room temperature.3,4 In addition to that tungsten oxide is having the absorption capacity of 480 nm in the visible region resulted from its photocatalytic property.5 Based on high photocatalytic property tungsten oxide has strong antibacterial activities.2 The properties of tungsten oxide (WO3) are electrochromic, photochromic, gas chromic, Photocatalytic, Ferroelectric properties, optical properties and chromic.6,7 Tungsten oxide (WO3) has obtained multiple industrial applications especially in the field of metallurgy, material science, electronic displays and optical modulators8,9 smart windows 2, dye-sensitized solar cell.7
There are several methods to synthesize tungsten oxide nanoparticles. Among these methods, microwave irradiation method is most preferable due to less time and uniformity.10 The synthesized nanoparticle was studied on bacterial cultures such as Escherichia. coli and Pseudomonas aeruginosa. Thus experimental work was studied on the UV-Visible Spectroscopy, Scanning Electron Microscopy
MATERIALS AND METHODS
Materials
Sodium tungstate (WO3) with the purity of 98% was purchased from LobaChemiePvt.Ltd, Mumbai. Sodium hydroxide pellets (NaOH) with the purity of 98% was purchased from Sisco Research Laboratories Pvt Ltd, Mumbai. Hydrochloric acid (HCl) with the purity of 35% was purchased from Loba Chemie Pvt Ltd Mumbai.
Synthesis of WO3 NPs
0.1 M sodium tungstate was dissolved in 0.1 M sodium hydroxide. The concentrated Hydrochloric acid added dropwise into the reaction mixture with continuous stirring until it reaches pH 1 (Fig. 1). The yellow colour precipitate was obtained and washed for three times using distilled water. The precipitate underwent drying and calcination for 8 hours at 60ºC and 4 hours at 300 ºC respectively, to get tungsten oxide powder.7,8
Characterization of Tungsten Oxide Nanoparticles
Tungsten oxide was characterized by UV-Visible spectroscopy and Scanning Electron Microscopy (SEM) to analyze absorption spectra of nanomaterial, the structural and morphological properties.4,5
Determination of Antibacterial Activity of tungsten oxide nanoparticles
Tungsten oxide was tested for its antibacterial efficacy against bacterial culture. coli and Pseudomonas aeruginosa by Anti Well Diffusion Assay (AWDA). The bacterial inoculum was prepared to a final concentration of approximately 1 X105 CFU/mL for the selected bacterial cultures. The synthesized WO3NPs of concentration 10, 100 and 1000 µg/mL were dispersed in 0.5 % DMSO by ultra-sonication to make the colloidal solution of nanomaterials. On the surface of agar plates, wells of 5 mm in diameter and of 18 µL in capacity were formed by using sterile gel borer. The 15 µL of WO3 NPs suspension was placed in each well and was incubated at 37 °C ± 2 °C for 24 hours and zone of inhibition were recorded to understand antibacterial efficacy of WO3 NPs. 9,10
result and discussion
Synthesis of tungsten oxide nanoparticles
The yellow-coloured precipitate of Tungsten oxide nanoparticles was obtained. The resultant powder was dried and used for further characterization.
UV-Visible spectroscopy
The synthesized tungsten oxide nanoparticles were characterized in UV-Visible Spectroscopy which was shown in fig.2. In the current work, the λmax was found at 364 nm. The same experiment was done by Wei Hao Lai et al.,6,7 by chemical deposition method the change in nanoparticles UV-Visible absorbance λmax at 300 to 900 nm. The optical band gap was calculated by the equation (1), and the calculated bandgap is 3.41 eV.
E = h*c/λ……(1)
Scanning Electron Microscope
Tungsten oxide nanoparticles obtained was characterized by SEM to understand its size and morphology. Fig. 3(a) showed a bunch of nanostructures at low magnification and at high magnification, the flakes ofWO3 NPs was observed and overall size was found in the range of 200-1000nm. 4,5
Antibacterial efficacy of tungsten oxide
Tungsten oxide nanoparticles were tested against the bacteria E. coli and Pseudomonas Aeruginosa. Both bacterial cultures were found sensitive for tungsten oxide nanoparticles and got inhibited effectively at 1000 µg/mL concentration of WO3 NPs. At different concentration, tungsten oxide nanoparticles tested against bacteria are shown in Table 1 and Figure 4.
Conclusion
Tungsten oxide nanoparticles were synthesized successfully which have the maximum absorbance λmax at 364 nm. Nanoparticles of tungsten oxide have been synthesised and characterised by U.V. Vis. spectroscopy and distinguished by SEM. It was observed that the expansion of biofilm formation of Pseudomonas sp. and E. coli was greatly reduced by tungsten oxide nanoparticles. The solvothermal tungsten oxide nanoparticles have demonstrated substantial antibacterial action against Pseudomonas sp. and E. Coli. Thus, it shows positive activity on E. coli and Pseudomonas Aeruginosa bacteria. Moreover, from the evaluative analysis, it was deduced that the WO3 NPS has significant antibacterial potential that can be used in medicine and food industries. The MIC needed to minimize the biofilm formation as observed in microbial studies was 8 wt% of tungsten oxide NPs. Future experiments will explore how tungsten oxide nanoparticle sizes impact on antibacterial activities.
ETHICAL ISSUE: Ethical clearance was taken from institutional ethical committee, KIMSDU, Karad.
FUNDING SOURCES: Krishna Institute of Medical Sciences Deemed To Be University, Karad.
CONFLICT OF INTEREST: Nil.
ACKNOWLEDGEMENT: We acknowledge the contribution and support as being provided by the Department of Electronics and Communication Engineering, Nanotechnology Division, Periyar Maniammai Institute of Science and Technology, Thanjavur, India, Department of Allied Sciences, Krishna Institute of Medical Sciences Deemed to be University, Karad, Maharashtra, India, Directorate of Research, Krishna Institute of Medical Sciences Deemed to be University, Karad, Maharashtra, India.
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