The Effect of Transition Metal Doping on the Photooxidation Process of Titania-Clay Composites

Montmorillonite-TiO2 composites containing various transition metal ions (silver, copper, or nickel) were prepared, and their photocatalytic efficiencies were tested in the degradation of ethanol vapor at 70% relative humidity. Two light sources, UV-rich ( = 254 nm) and visible ( = 435 nm), were used. The kinetics of degradation was monitored by gas chromatography. It was established that, in the case of each catalyst, ethanol degradation was more efficient in UV-C ( = 254 nm) than in visible light, furthermore, these samples containing silver or copper ions were in each case about twice more efficient than P25 TiO2 (Degussa AG.) used as a reference. In photooxidation by visible light, TiO2/clay samples doped with silver or copper were also more efficient than the reference sample, P25 TiO2. We show that doping metal ions can also be delivered to the surface of the support by ion exchange and significantly alters the optical characteristics of the TiO2/clay composite

LED-light activated antibacterial surfaces using silver-modified TiOembedded in polymer matrix

Silver functionalized TiOpoly(etyl-acrylate co methyl-methacrylate) nanohybrid films were proved to inactivate nosocomial bacteria. The films were prepared on glass plates by spray coating technique and their thickness were 1.48±0.1 μm. During photocatalysis, the films were illuminated with visible LED-light source (λ = 405 nm). The optical and photooxidation properties of prepared nanocomposite films were characterized by diffuse reflectance measurements and the photocatalytic properties were tested in ethanol photooxidation monitored by gas-chromatography experiments. The photocatalytic activity of the nanohybrid films were tested under visible light illumination against bacteria causing nosocomial infections, such as methicillin resistant Staphylococcus aureus, Enterococcus faecium, Pseudomonas aeruginosa and Acinetobacter baumannii. The investigation of the antibacterial activity of the silver functionalized TiOwas carried out by measuring the survival ratio of the original amount of the bacteria on the nutrient agar plate. To verify the photooxidation effect of the reactive films, parallel experiments were carried out without any light source. All of the investigated bacteria were inactivated on the surface of the nanohybrid films within 120 minutes of LED-light illumination. © 2014 Science & Technology Network, Inc

New insights into the relationship between structure and photocatalytic properties of TiO2 catalysts

This work systematically investigated the relationship between structure, morphology, photoelectrochemical (PEC) and photocatalytic (PC) properties of TiO2 catalysts. A series of TiO2 catalysts with various phase compositions (anatase-, brookite- and finally rutile-rich samples) and morphologies (1D morphology, rhomboid nanoparticles (NPs) and flower-like assemblies of nanorods) were prepared by an acidic hydrothermal treatment of hydrogen titanate nanofibres (H-TNFs). The structures of the samples, such as crystal phase composition and their spatial distribution, were extensively characterised, and the samples were tested for photocatalytic degradation of ethanol. A strong correlation is found between PEC and PC properties. PEC measurements revealed that the brookite-rich samples generated high but unstable photocurrents. The anatase and rutile-rich samples showed good stability, but for the rutile-rich samples low photocurrents were detected due to the poor conductivity of this polymorph. In contrast, the sample containing 93.2% anatase and 6.8% brookite with elongated morphology not only showed the ability to generate high photocurrents but also maintained a stable photoresponse upon an extended period of time, because of its well-balanced bi-crystalline structure and elongated morphology. Therefore, the abilities to generate high photocurrents and to maintain a stable photoresponse are equally important and probably a prerequisite for a good photocatalyst