We describe a portable gas sensor based on cataluminescence. Miniaturization of the gas sensor was achieved by using a miniature photomultiplier tube, a miniature gas pump and a simple light seal. The signal to noise ratio (SNR) was considered as the evaluation criteria for the design and testing of the sensor. The main source of noise was from thermal background. Optimal working temperature and flow rate were determined experimentally from the viewpoint of improvement in SNR. A series of parameters related to analytical performance was estimated. The limitation of detection of the sensor was 7 ppm (SNR = 3) for ethanol and 10 ppm (SNR = 3) for hydrogen sulphide. Zirconia and barium carbonate were respectively selected as nano-sized catalysts for ethanol and hydrogen sulphide.
Detection of hydrogen sulphide (H(2)S) was conducted based on cataluminescence (CTL) sensors, using alkaline-earth metal carbonates as catalysts. Optimal working conditions, analytical characteristics and the response properties of the sensor were investigated. CTL intensity examination showed that sensors fabricated with CaCO(3), SrCO(3) or BaCO(3) could be used to detect H(2)S gas sensitively. The optimal sensing temperature was about 320 °C. Under the sensing conditions with temperature at ca. 320 °C and gas flow rate in the range 180-200 mL/min, the linear range of CTL intensity vs H(2)S concentration was 25-500 ppm, with a detection limit of 2 ppm. The response and recovery times of the sensor were within 5 and 25 min, respectively. Also, the sensor had the property of high selectivity to H(2)S with very weak or no obvious response to 14 other gases, such as NO(2), NH(3), hydrocarbons and alcohol.
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