The detection of nitrogen dioxide in air with fiber optical sensor based on sol-gel film

Sol-gel sensing film for nitrogen dioxide was prepared with tetraethylorthosilicate (TEOS), which immersed sulfanilamide as diazotizing reagent and N, N-dimethyl-1-naphthyl-amine as coupling reagent. The fiber optical sensor was consist of the sensing film and optical fiber, which could detect NO, in air in the dynastic range from 60 similar to 600 ng/L with an accumulation method. The recipes of Sol-gel film were optimized to prepare the sensing film with high specific surface and good sensitivity to NO, at ng/L level in air. The acidity and concentrations of the sensing reagents as well as the flow rate of the sample gas were optimized. The effect of the coexist gases such as N-2, O-2, CO2, SO2 and NO on the sensor was studied. The detection limit of sensor was 5 ng/L hourly, and the relative standard deviation was 4.4% (n = 6, C-No2 = 200 ng/L, 1 hour), which showed the sensor could be applied to monitoring NO, at low level in air.