Science & Technology Almanac

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As reported in the May 22, 2001, Proceedings of the National Academy of Sciences, a team of chemists and microbiologists has developed a novel coating designed to kill bacteria on contact. Unlike most antibacterial treatments, which become impotent as the active agent leaches out and so must be reapplied continuously, the new coating uses a permanent built-in biochemical mechanism for destroying microbes. Therefore, it may have the future application of rendering commonly used surfaces such as pay phones, countertops, and door-knobs permanently antiseptic.

Joerg C.Tiller of the Massachusetts Institute of Technology and his colleagues developed their coating using polymers known to kill bacteria in water. Their coating works by bonding one end of the polymer to a glass slide, leaving the other end free to penetrate the bacterial cell membrane, thus killing the microbe. In an effort to mimic conditions caused by an airborne release of bacteria such as a cough or sneeze, they suspended common infectious microbes in distilled water and sprayed the mixture onto glass slides coated with a series of polymers. After letting the slides air-dry, the percentage of killed bacteria was determined. The researchers found that the most effective polymer, hexyl-PVP (polyvinylpyrrolidone), killed up to 99 percent of bacteria on the slides. Unfortunately, this coating proved ineffective when applied to common materials such as ceramics, plastics, metals, and woods. However, this study provides a useful starting point in the development of permanent antiseptic surface coatings.

A team of researchers from Washington State University, Pacific Northwest National Laboratory in Washington State, and Utah State University has produced theoretical and experimental evidence of all-metal aromatic molecules that may eventually lead to the creation of novel materials. This work was published in the February 12, 2001, issue of Science.

Aromaticity is a chemical concept used to account for the extraordinary stability of some ring-shaped organic molecules. Aromatic compounds are so named because many of them, such as benzene and its derivatives, have a distinct aroma. However, not all aromatics have an odor, and the new all-metal aromatics are aroma free. According to rules established by quantum mechanics, aromatic compounds can be distinguished by the presence of two pi electrons that produce their unique structural stability.

The interuniversity group produced evidence of aromaticity in aluminum-based molecules. The team created the never-before observed all-metal aromatic molecules by zapping an aluminum-copper alloy with a laser. Team member Alexander Boldyrev of Utah State University preformed calculations predicting the distinguishing characteristic of two pi electrons, and his model was confirmed experimentally by photoelectron spectroscopy. The laser-treated alloys produced gaseous molecules of pyramidal shape, with aluminum atoms forming the base and a copper atom at the apex.

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