Self-disinfecting surfaces.For years, researchers have been exploring the many wonders of titanium dioxide. Long used to whiten paints, puddings, and paper used for U.S. currency, this powerful catalyst is being developed to decompose de·com·pose v. de·com·posed, de·com·pos·ing, de·com·pos·es v.tr. 1. To separate into components or basic elements. 2. To cause to rot. v.intr. 1. crude oil (SN: 5/22/93, p. 332), strip away organic debris from treated windows (SN: 9/2/95, p. 157), and defog de·fog tr.v. de·fogged, de·fog·ging, de·fogs To remove condensed water vapor from: defog a windshield. de·fog mirrors (SN: 8/2/97, p. 70). Japanese chemists now believe they have identified what may prove to be an even more important role for this agent -- to kill germs and disarm their poisons. Akira Fujishima of the University of Tokyo “Todai” redirects here. For the restaurant called Todai, see Todai (restaurant). The University of Tokyo (東京大学 and his colleagues coated a plate of glass with a 0.4-micrometer film of titanium dioxide, then placed water harboring Escherichia coli Escherichia coli (ĕsh'ərĭk`ēə kō`lī), common bacterium that normally inhabits the intestinal tracts of humans and animals, but can cause infection in other parts of the body, especially the urinary tract. bacteria on the top of the glass. When they illuminated the underside with a 15-watt black light, its ultraviolet (UV) radiation triggered a catalytic reaction between the coating and the bacteria. Though UV radiation killed E. coli E. coli: see Escherichia coli. E. coli in full Escherichia coli Species of bacterium that inhabits the stomach and intestines. E. coli can be transmitted by water, milk, food, or flies and other insects. placed on an untreated glass, it did nothing to endotoxin Endotoxin A biologically active substance produced by bacteria and consisting of lipopolysaccharide, a complex macromolecule containing a polysaccharide covalently linked to a unique lipid structure, termed lipid A. , a poison spewed by the dying bacteria that can prove dangerous at concentrations of just a few nanograms per liter of blood. Germs on the coated glass disappeared more quickly when irradiated, and their poison vanished too, Fujishima's team reports in the March 1 Environmental Science & Technology. This shows that the light-activated coating "can kill bacteria and simultaneously degrade the toxic compounds ... from the bacteria," they say. Ordinarily, the scientists note, eliminating endotoxins requires caustic chemicals or heating to 250[degrees] C for at least 30 minutes. The low-cost, light-driven process holds out the promise of disinfecting and detoxifying at room temperature these surfaces carrying all but the heaviest bacterial contamination -- probably "in less than 1 hour," Fujishima told Science News. At present, he says, 20 Japanese hospital operating rooms are testing ceramic tiles coated with titanium dioxide. The tiles "work well in terms of self-disinfection and also disinfection disinfection, n the process of destroying pathogenic organisms or rendering them inert. disinfection, full oral cavity, n a procedure used to reduce active periodontal disease, usually completed within a certain short time frame. of the air in a room," Fujishima says, and "are also now becoming extremely popular for use in public rest rooms, where they can help to control both bacteria and noxious odors." |
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