Abstract
Here we report on the use of pulsed UV light for activating the gas sensing response of metal oxides. Under pulsed UV light, the resistance of metal oxides presents a ripple due to light-induced transient adsorption and desorption phenomena. This methodology has been applied to tungsten oxide nanoneedle gas sensors operated either at room temperature or under mild heating (50 °C or 100 °C). It has been found that by analyzing the rate of resistance change caused by pulsed UV light, a fast determination of gas concentration is achieved (ten-fold improvement in response time). The technique is useful for detecting both oxidizing (NO2) and reducing (NH3) gases, even in the presence of different levels of ambient humidity. Room temperature operated sensors under pulsed UV light show good response towards ammonia and nitrogen dioxide at low power consumption levels. Increasing their operating temperature to 50 °C or 100 °C has the effect of further increasing sensitivity.
Highlights
Metal oxide gas sensors have been attracting important research efforts because of their low cost and good sensitivity
The information extracted from the transient response is not used to improve selectivity, but to estimate gas concentration in a faster way, despite sensors being operated at low temperatures or even at room temperature
We have explored further the approach of using pulsed UV to promote the response of WO3 nanoneedle gas sensors, either operated at room temperature or under mild heating (≤100 ◦ C), in the presence of ammonia or nitrogen dioxide
Summary
Metal oxide gas sensors have been attracting important research efforts because of their low cost and good sensitivity. Extracting information from the transient response of metal oxide gas sensors has achieved good results in the improvement of selectivity. Low-temperature operated metal oxide sensors suffer from slow response and recovery dynamics, which is not desirable in the continuous monitoring of ambient gases. We explore a new way to create a transient in sensor response by pulsing a source of UV light to enable gas detection. In this case, the information extracted from the transient response is not used to improve selectivity, but to estimate gas concentration in a faster way, despite sensors being operated at low temperatures (compared to the standard operating temperatures of non-illuminated sensors) or even at room temperature. The prospects of this procedure for reducing the influence of ambient moisture in sensor response are investigated
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