STRUCTURAL AND OPTOELECTRONIC CHARACTERISATIONS OF ZINC OXIDE STRUCTURES FOR ANTIBACTERIAL ACTIVITIES ON SKIN BACTERIA

STRUCTURAL AND OPTOELECTRONIC CHARACTERISATIONS OF ZINC OXIDE STRUCTURES FOR ANTIBACTERIAL ACTIVITIES ON SKIN BACTERIA

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dc.contributor.author	LING, CHUO ANN
dc.date.accessioned	2015-07-30T00:22:36Z
dc.date.available	2015-07-30T00:22:36Z
dc.date.issued	2014-09
dc.description.abstract	The main objective for this research work is to investigate the structural and optoelectronic properties of zinc oxide (ZnO) structures with their correlation on antibacterial activities against Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa (P. aeruginosa) and Streptococcus pyogenes (S. pyogenes). Two ZnO powder samples, one with rod-like (ZnO-Pharma) and the other with plate-like (ZnO-White) structures, were characterised for their morphological, structural, optical and electrical properties. The rods structures were 30-120 nm in diameter and the plates structures were 40-200 nm thick. Electron spectroscopy imaging showed the different distribution of oxygen and zinc atom on the ZnO structures, that is higher O:Zn ratio on rods structures whiles lower O:Zn ratio on plates structures. Using annealing temperature of 700°C, oxygen annealing induced high oxygen adsorption on ZnO structures surface while nitrogen annealing caused oxygen desorption on ZnO structures surface. The photoluminescence results revealed higher green emission from ZnO surface under nitrogen annealing but the oxygen annealing exhibited adverse effect on green emission. Due to the adsorption and desorption of oxygen, nitrogen annealing improved the surface conductance by about 60% while oxygen annealing decreased the surface conductance by about 80%. UVA illumination was found to enhance the surface conductance significantly, up to 6 times compared to non-exposure ZnO. On the other hand, antibacterial responses of ZnO structures were studied towards S. aureus, P. aeruginosa and S. pyogenes. ZnO-Pharma and ZnO-White samples exhibited excellent inhibition towards S. pyogenes with the percentage inhibition above 95%. This phenomenon was probably due to the absence of catalase, making the bacteria vulnerable to the toxic reactive oxygen species (ROS) released by ZnO. ZnO-Pharma induced higher inhibition toward S. aureus and P. aeruginosa than that of ZnO-White because of the smaller particle size of rod structures compared to plate structures. The antibacterial results showed that oxygen-treated ZnO exhibited slightly higher growth inhibition on S. aureus and P. aeruginosa compared with unannealed ZnO. UVA illumination on ZnO causes the greatest inhibition toward the bacteria where the inhibition of S. aureus increased by 9% (ZnO-Pharma) and 15% (ZnO-White) while inhibition of P. aeruginosa increased by 48% (ZnO-Pharma) and 32% (ZnO-White). Antibacterial enhancement by oxygen annealing and UVA illumination was probably due to the activated release of reactive oxygen species in ZnO suspension. The toxicology level of ZnOPharma and ZnO-White samples was determined to be less than 0.3 mM from the cytotoxicity test on L929 mouse fibroblast cell lines. ZnO-Pharma and ZnO-White calamine lotions were successfully prepared, which showed remarkable antibacterial response toward three skin bacteria.	en_US
dc.identifier.uri	http://hdl.handle.net/123456789/871
dc.subject	OXIDE	en_US
dc.subject	ANTIBACTERIAL	en_US
dc.title	STRUCTURAL AND OPTOELECTRONIC CHARACTERISATIONS OF ZINC OXIDE STRUCTURES FOR ANTIBACTERIAL ACTIVITIES ON SKIN BACTERIA	en_US
dc.type	Thesis	en_US

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