Synthesis and Glass Immobilization of Carbon and Nitrogen Doped TiO2-SiO2 and Its Effect on E. coli ATCC 25922 Bacteria

Abstract

Aim: To evaluate the antimicrobial properties of carbon and nitrogen doped titanium dioxide (C-TiO2 and N-TiO2) immobilized on glass support by examining the inactivation of E. coli ATCC 25922 bacteria in water. Study Design: Sol gel synthesis was used to prepare a series of visible light responsive photo-catalysts of titanium dioxide. The photo-catalysts were characterized via Fourier transform infrared spectroscopy (FT-IR), Scanning X-ray Photoelectron Spectroscopy (SXPS), X-ray Diffraction (XRD), Diffuse reflectance spectroscopy (DRS) and Energy Dispersive X-Ray Spectroscopy (EDS or EDX). Modified titanium dioxide photo-catalysts (TiO2-SiO2, C-TiO2-SiO2, and N-TiO2-SiO2) immobilized on glass supports were evaluated for their antimicrobial properties on the inactivation of E. coli ATCC 25922 in water. Place and Duration of Study: Department of Chemistry (Water Research Group) and Department of Biochemistry and Microbiology, University of Fort Hare Alice Campus, between July 2013 and November 2013. Methodology: A 0.5 McFarland standard solution containing approximately 1.5×108 organisms was prepared by adding Escherichia coli ATCC 25922 to a saline solution (0.85% NaCl). A battery of experiments was carried out to evaluate the antimicrobial properties of glass-immobilized and powder photo-catalysts. Every 30 minutes, swabs were taken from each reactor vessel and placed on the freshly prepared nutrient agar plates. Plates were incubated at 37°C for 24 hours. Results: The number of active E. coli cells after treatment with TiO2 was determined by colony counting after 24 hours of incubation. When E. coli ATCC 25922 was treated with powder TiO2 (i), there was a small decrease in the number of colonies within the first 30 minutes, but after exposure for 60 minutes about 98% of the bacterial colonies had been destroyed. Conclusion: Immobilized titanium dioxide photo-catalyst was shown to be less effective in the deactivation of E. coli bacteria. The three nano-composite photo-catalysts; TiO2-SiO2, C-TiO2-SiO2, and N-TiO2-SiO2 showed little cytotoxicity (the degree to which an agent possesses a specific destructive action on certain cells) towards the growth of E. coli ATCC 25922 while powder titanium dioxide proved to be very effective towards the inactivation of E. coli ATCC 25922 bacteria.