2008 AUG 18 - (VerticalNews.com) -- "A clean indoor air is important for the well-being and health of people. Lately, new photocatalytic paints have been launched on the market, which are claimed to have air-purifying effects," scientists in Finland report.

  "Photocatalysis initiates radical reactions. Radicals are formed when a photocatalyst (e.g. TiO2) is Subjected to radiation. Typical radicals are the hydroxyl radical ((OH)-O-center dot) and the superoxide radical (O-center dot(2)-). Radicals cause chain reactions, which degrade and decompose organic compounds. The end products of these chain reactions are water and carbon dioxide, if the reactions are fully completed (mineralization). If mineralization does not take place, then a great number of side products can be formed, whose properties are not well understood. The side products of photocatalytic reactions can be permanent and stabile. The decomposition of indoor air impurities on the surface of photocatalytic paints is not obvious. The ability of photocatalytic indoor paints to reduce chemical indoor air impurities is the key issue of this study. Six different paints with different binder systems, such as lime, polyorganic siloxane, silica sol-gel and organic binders, were examined. The experiments were divided into three topics: degradation of an organic binder, photocatalytic decomposition of formaldehyde, and a volatile organic compound (VOC) mixture consisting of five different indoor air VOCs. All tests were carried out in an environmental test chamber under dynamic conditions. The test results indicate that many indoor pollutants are generated under normal- and UVA-light. Typical compounds formed include formaldehyde, acetone, acetaldehyde, etc. A clear decrease of formaldehyde or the VOC mixture concentration was not observed. All possibly generated compounds could not be collected or analyzed in this research project, but the measurements show that photocatalytic reactions do not generate only carbon dioxide and water," wrote J. Auvinen and colleagues, Helsinki University ...read more

  2008 MAR 31 - (VerticalNews.com) -- According to recent research from the United States, "We present a combined experimental and modeling study of the dependence of solution-based zinc oxide (ZnO) selective-area growth rates on pattern dimension. Selective growth is achieved by patterning a portion of the substrate with an organic template that inhibits growth."

  "The density of ZnO nanorods and the mass grown per unit area of exposed surface increases as the distance between the exposed growth regions is increased and as the width of the exposed lines is decreased. A 2-D model was developed to calculate selective growth at the exposed surface regions, the loss of reactant material due to a competing reaction in solution, liquid-phase and surface diffusive mass transport to (or on) the growth surface, and the ZnO growth reaction at the surface. To explain the experimental results, we found it necessary to include a reaction by-product in the chemistry model, the desorption of which is the rate limiting step. A relatively simple, three-step reaction mechanism, combined with the species mass transport model, provides a good, semi-quantitative description of the experimental observations in the selective-area growth of ZnO from supersaturated solutions," wrote M.E. Coltrin and colleagues ...read more

  2008 MAR 10 - (VerticalNews.com) -- According to recent research from the United States, "A new approach to combining a p-type semiconductor photocathode with sacrificial electron donors in the anode compartment in a two-compartment cell is described for photocatalytic hydrogen production. This approach is demonstrated for electrodeposited p-Cu2O film supported on a transparent conducting oxide substrate."

  "The oxide semiconductor surface was photochemically modified in situ with an ultra-thin Ni layer prior to use. A variety of organic and organometallic electron donors was screened by cyclic voltammetry, and the optimal candidate was hydroquinone at pH 10. Importantly, no photocurrents were measured at zero bias voltage in the two-compartment cell in the absence of an electron donor, signaling that water photosplitting is not feasible with p-Cu2O. Methyl viologen (MV2+) was effective as an electron relay in the photocathode chamber as shown by in situ spectroscopic monitoring of the MV+ radical cations. Finally, practical perspectives of this new approach and value-added options for combining it with pollutant destruction are described," wrote S. Somasundaram and colleagues, University of Texas ...read more