Each flower consists of bundles of 15 nanometre-wide nanorods, created when a zinc solution was treated with ultrasound.
Conventional breathalyzers are made using zinc oxide; adsorption of ethanol vapour changes the resistance of a film of zinc oxide powder, causing it to change colour. The zinc oxide first has to be heated to temperatures of up to 300°C to become sensitive to ethanol.
Chen and colleagues produced an ethanol sensor by connecting two groups of nanoflowers on a circuit. By exposing one of the nanoflower patches to ethanol vapour, and then comparing its electrical resistance to that of the other, which was sealed, the presence of alcohol could be detected.
The sensor is ultra-sensitive, detecting alcohol levels as low as 50 parts-per-million. This sensitivity could be increased by doping the structures with gold or platinum nanoparticles. And, because the nanoflower structures are so small, the zinc oxide needs to be heated to just 140°C to become sensitive to ethanol.
“The observation of ultra-high sensitivity for ethanol at such an unusually low temperature is striking,” says Edman Tzang, a professor of chemistry at the University of Reading. “I can envisage a wide range of [other] potential applications, including monitoring combustion gases from factories or vehicles, food and odour analysis.”
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