ChemWeb Newsletter

Not a subscriber? Join now.August 2, 2005


The Alchemist turns his beady eye to the Amazonian environment, the future of self-cleaning cities, smelly feet and bad breath, nanotech hydrogen storage, and finally adding a little color to polymers to make them more stable.

The rivers of the Amazon basin are recycling carbon dioxide far more quickly than environmental scientists realized, according to the latest radiocarbon dating study, using both carbon-13 and -14, reported in Nature. The reports shows that most of the carbon being "exhaled" - or outgassed - as carbon dioxide from Amazonian rivers and wetlands has spent just five years sequestered in the trees, other plants and soils of the region. Emilio Mayorga of the University of Washington and colleagues suggest that their finding is rather surprising because earlier measurements showed carbon in the rivers that has come from surrounding forest to be anywhere from 40 to more than a thousand years old. The new lower limit on this range suggests that the Amazon basin is not the long-term carbon sink scientists had hoped, which could be bad news for global chemistry and the environment.

A new type of cement based on the increasingly useful titanium dioxide could be used to coat sidewalks and destroy pollutants when the sun shines, according to Karin Pettersson of Swedish construction giant Skanska. Skanska, Cementa, and several other companies are participating in a US$1.7 million (€1.4m) Swedish-Finnish project to develop catalytic cement and concrete products coated with titanium dioxide. Photocatalytic cement has already shown its prowess in city testing where nitrogen oxide levels were reduced by up to 60% depending on the weather conditions as the titania photocatalyzes their degradation to nitrates. Other experiments have produced results between 20 and 80%. Optimizing the formulation for particular applications could make the materials viable for use in the construction industry and bring about a titanium dioxide-fueled war on pollution.

Ann Wood and her colleagues at Kings College London have discovered the bacteria that feed on the pungent organosulfur compounds that cause bad breath. The researchers discovered that the odor eaters, methylotrophic bacteria, grow on the tongue, tooth plaques, and gum edges and include among their number Bacillus, Brevibacterium casei, Hyphomicrobium sulfonivorans, Methylobacterium, Micrococcus luteus, and Variovorax paradoxus. Intriguingly, the team had previously found that related methylated sulfides found on the feet can also serve as a food source for the same bacteria, suggesting a new approach to deodorizing smelly feet, and breath.

Two crucial properties of a hydrogen storage material for future fuel cells and other hydrogen-powered devices might be met by titanium-coated carbon nanotubes according to Taner Yildirim and colleagues at the US National Institute of Standards and Technology and Turkey's Bilkent University. An efficient hydrogen storage material must be able to adsorb or otherwise trap hydrogen molecules adequately and must also be willing to relinquish the gas on demand. Earlier research has shown that nanotubes could be 6% efficient, but this is an obstacle to commercial viability, according to Yildirim. Now, he and his colleagues have shown that the presence of titanium atoms allows a nanotube to amass 8% of its weight in hydrogen molecules rather than 6% and so tip the balance towards the development of these materials for hydrogen storage.

Chemists have known for some time that organic and inorganic pigments added to polymers can affect the tensile strength and other physical properties of the polymer. Now, Rex Kanu of Ball State University and colleague Thomas Spotts, and Michael Chesebrough of Tomken Tool and Engineering, Inc. have extended their earlier work to show that their organic and inorganic pigments can affect the color and stability to ultraviolet of injection-molded polypropylene. They suggest that the pigments act as nucleating agents during the polymer crystallization process. Different pigments result in a different degree of nucleation and so the polymer can be tailored to have particular color and physical properties.