Highly sensitive room temperature sensors based on the UV-LED activation of zinc oxide nanoparticles

This study describes novel work on the use of UV-light emitting diodes (LEDs) to enhance the room temperature gas sensitivity of thick film zinc oxide sensors. Sensors based on nanoparticulates of zinc oxide activated with a UV-LED of peak wavelength 400 nm and incident light intensity 2.2 mW/cm(2) were capable of detecting acetone and acetaldehyde at extremely low concentrations (1 vppb). The same sensors operated under identical conditions were also capable of detecting a range of other volatiles in the low ppm range, including hydrocarbons such as hexane, butane, propane and methane. The sensors were also sensitive to low ppm levels of volatiles when operated under high humidity conditions (100% relative humidity). We found that the optimal sensitivity of the sensor was dependent on the applied light intensity. The optimal light intensity giving maximum response was found to be analyte dependent, indicating that it is possible to tune the selectivity of the sensors by changing the applied light intensity. A GC-MS study found that the UV irradiated zinc oxide sensor was capable of catalysing the breakdown of a range of volatiles at room temperature. The general type of catalytic decomposition is in agreement with mechanistic studies carried out on heated metal oxide sensors. (c) 2008 Elsevier B.V. All rights reserved.