Recently, under the circumstances of pandemic of COVID-19 much attention has been paid to titanium dioxide TiO 2 as bactericidal agent; however, conventional TiO 2 requires ultraviolet radiation or visible light to exercise its photocatalytic properties and its induced antimicrobial activity. In order to expand its applications directed at wide civil life, antibacterial TiO 2 being usable under dark conditions has been demanded. The present paper describes the powder characterization of newly developed potassium K and phosphorous P co-doped nanometer-size anatase TiO 2 powders using X-ray diffraction (XRD), scanning and transmission electron microscopies (SEM & TEM), Brunauer-Emmett-Teller method (BET), fourier-transform infrared spectroscopy (FT-IR), X-ray absorption fine structure (XAFS), electron spin resonance (ESR) and chemiluminescence (CL). It was found for the first time that thus prepared anatase TiO 2 could submit much reactive oxygen species (ROS) even in the dark, which has close relation with bactericidal activity in light interception.
Three crystal structures of titanium dioxide are mainly reported: low-temperature form tetragonal anatase (a-TiO2), high-temperature stable tetragonal rutile (r-TiO2) and middle temperature orthorhombic brookite (b-TiO2) [
The authors have been studying metal oxide powders which can reveal strong antimicrobial activity in the shade for long time. Biocompatible zinc oxide ZnO also has been interested due to its microbial toxicity. However, its activity is a little lower than TiO2 NPS. Recently, ZnO powders have been prepared by hydrothermal treatment in zinc nitrate aqueous solution with a concentration of 3 mol·L−1 at 443 K for 2.52 × 104 s, followed by re-oxidation heating at 873 K for 3.6 × 103 s in air. And then it has been cleared that thus obtained ZnO powders can reveal strong antibacterial activity even under dark conditions [
The effects of potassium K doping on physicochemical properties of TiO2, such as their crystallinity, surface areas SA, solubility, photocatalytic activity, and band gap Eg, were studied by several researchers [
Yu et al. [
Up to now, there is no report on the generation of ROS from a-TiO2 NPS under dark conditions. Then, we started to investigate the relationship between the amount of ROS and the contents of K, P, and their combined doping, from the viewpoint of the microstructure and physicochemical properties. Finally, we found that anatase (a-TiO2) powders which could submit a lot of ROS even in the dark; the amounts of ROS were much higher than our previous antibacterial ZnO, in addition, this powder could be prepared with much simpler process. The present paper treats the physicochemical properties in relation with the microbial toxicity of thus prepared anatase (a-TiO2) as a function of impurity contents and its doping method.
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