Color-changing metal seen as gas detector

Canadian researchers say metals modified to change color in the presence of particular gases could warn consumers if packaged food has been exposed to air. Chemists at Queen's University in Ontario say the specialized metals could also warn if there's a carbon monoxide leak in the home. The finding could lead to advances in both industrial and commercial air quality sensors, a Queen's release reported Thursday. "We initially found out by accident that modified rhodium reacts in a colorful way to different gases," says chemistry Professor Cathleen Crudden. "That happy accident has become a driving force in our work with rhodium." Rhodium modified using carbon, nitrogen or hydrogen-based compounds changes to yellow in the presence of nitrogen, deep blue in the presence of oxygen, and brown in the presence of carbon monoxide, the researchers say. The color change is the result of the way gases bind to the compound's central metal, they say. Rhodium is used in catalytic converters to reduce the toxicity of car exhaust emissions. Crudden's team says it is currently investigating whether cobalt, a significantly less expensive metal than rhodium, can be made to react in a similar way.