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2015-04-25 - Colloque/Présentation - communication orale - Anglais - 1 page(s)

Debliquy Marc , "Light Assisted Gas Sensing at Room Temperature with Metal Oxides" in Analytix 2015, Nanjin, Chine, 2015

  • Codes CREF : Capteurs et périphériques (DI2563), Matériaux optiques (DI1256)
  • Unités de recherche UMONS : Science des Matériaux (F502)
  • Instituts UMONS : Institut de Recherche en Science et Ingénierie des Matériaux (Matériaux)
  • Centres UMONS : Ingénierie des matériaux (CRIM)

Abstract(s) :

(Anglais) Semiconductor metal oxide gas sensors are well known for the detection of various toxic or combustible gases at low concentrations such as O3, NOx, CO, COV’s, Cl2, H2S, etc. These sensors consist in a sensitive layer made of a semiconductor that changes its electrical conductivity when in contact with a target gas due to a reversible doping at the surface of the sensitive layer. These sensors show a very good sensitivity, long lifetime and can easily be miniaturized. Moreover, the signal is simple, a variable resistance, and the insertion in electronics is easy. Metal oxide sensors are generally operated at elevated temperatures (100~400°C) in order to accelerate chemical reactions between metal oxide surface and target gas molecules. Due to the thermo-activated chemical reactions involved in detection mechanisms of these gas sensors, the working temperature is a critical parameter as it influences the sensor response, response time, selectivity, power consumption and even sensor structure. Working at a high temperature implies expensive sensor architectures, difficulties in maintaining stable sensor response and high-power consumption. In recent years, partly inspired by research in the field of hybrid photovoltaic cells, there have been reports of gas sensors based on ultra-violet (UV) or visible light activated metal oxide semiconductors. Usually, the surface of these oxides is modified by impregnation with a dye allowing electron transfer between the target gas and the semiconductor. Illuminating these sensors with light is a feasible alternative to activate chemical reactions at metal oxide surface without the necessity of heating. It was suggested that UV light affects gas sensor performance through the following ways: (1) lead to dissociation of target gas and chemical surface adsorbed species; (2) facilitate carrier generation and thus increase density of free electron-hole pairs. These physical-chemical phenomena allow gas sensing at room temperature and implantation of these light activated metal oxide gas sensors in different applications, such as portable devices or low power consumption applications. A brief review will be made of the different sensors using this kind of technology.