Amplified detection of chemicals using photoluminescence and interferometry from a porous silicon chip: detection of nitrobenzene and 24-dinitrotoluene in air

摘要

Abstract: The detection of nitroaromatic molecules by porous silicon films has been explored using direct and indirect detection methods. In the direct method, detection is achieved by monitoring the photoluminescence of a nanocrystalline porous Si films upon exposure to the analyte of interest. Photoluminescence is quenched upon adsorption of the nitroaromatic, presumably via an electron transfer mechanism. For nitrobenzene a detection limit of 350 ppm (after an exposure time of $LS 2 minutes) was observed. For 2,4-dinitrotoluene, a much lower detection limit of 250 ppb (after an exposure time of $LS 6 minutes) was obtained. Both the detection limit and the response time of the material can be lowered by the use of a catalyst (PtO$-2$/ at 250$DGR@C) in the carrier gas line upstream of the porous silicon detector. The enhanced sensitivity comes from catalytic oxidation of the nitroaromatic to NO$-2$/, which irreversibly oxidizes the surface of the porous Si, providing an integrating function. The demonstrated limit for NO$-2$/ detection is 70 ppb. A complementary detection technique involving measurement of spectral shifts of a porous Si film Fabry-Perot interferometer upon oxidation will also be presented.!15