Chemically modified discriminating gas sensors

Metal oxide gas sensors are small devices - 2 mm x 2mm that are used to detect trace gases in air. They are widely used in cars (exhausts and air intake vents), in weather balloons, in environmental monitoring (land fill sites) and in ozone detection. They work by showing a change in electrical resistance when exposed to a gas. The problem with these sensors is that they can't distinguish very well, if at all, mixtures of different gasses - for example ammonia and methane both give a change in resistance to the sensor. For these sensors to find wide spread application they need to be able to sense a specific target gas in the presence of a complex gas mixture. To date this has not been acheived. This proposal will generate a new type of sensor that has an additional discriminating sensor layer either on top of the traditional metal oxide or embedded within the metal oxide. This new layer contains a material called a zeolite- essentially a very porous solid that can let certain types of gases permeate through the structure. The zeolite gives enhanced sensitivity and sieves gas molecules on the basis of their size, shape and chemical composition. These zeolite layers will give us enhanced sensitivity and most importantly selectivity. By combining different types of zeolites we are able to make an array of sensors that can function as well as or better than the human nose. Specific problems that can be addressed include:1 Detection of contaiminated water, foodstuffs, chemicals and perfumes.2 A single breath detector that can analyse for a range of diseases and for alcohol/ drug content.3 Environmental monitoring (land fill, waste dump. brown field sites).