KCS

Nanocrystalline porous silicon films have been used to detect the vapors of nitroaromatic compounds such as nitrobenzene, dinitrotoluene, trinitrotoluene, and picric acid in gas phase. Quenching efficiencies of photoluminescence of porous silicon have been measured upon the exposure of analyte-saturated air. The intensity of PL from freshly etched porous silicon is reduced upon exposure to the vapor of NB, DNT, TNT or PA. After 5 min, the percentage of quenching for DNT-saturated air (vapor pressure = 200 ppb at 25ﾟC) is 3.3%, and 11% and 9.2% in the case of TNT-saturated air (vapor pressure = 4 ppb at 25ﾟC) and PA-saturated air, respectively. It is interesting to report that 9% of quenching photoluminescence for nitrobenzene was observed just for 10 seconds, since its vapor pressure is much higher than that of others. In the control experiment, the intensity of photoluminescence of a porous silicon sample was found to be stable for one hour under a flow of pure air. Surface of porous silicon chips are derivatized with silole by hydrosilylation to enhance the sensitivity for TNT vapor. Further details will be discussed.