Detection of nitric oxide and nitrogen dioxide with photoluminescent porous silicon

The visible photoluminescence of porous Si is quenched by nitric oxide and nitrogen dioxide to detection limits of 1.4 x 10(-3) and 5.3 x 10(-5) Torr, respectively (corresponding to 2 ppm and 70 ppb). At analyte partial pressures in the low milliTorr range, the photoluminescence quenching is partially reversible; recovery from nitrogen oxide exposure occurs on a time scale of minutes. For both NO and NO2, the reversible photoluminescence quenching response fits a Stern-Volmer kinetic model. At higher partial pressures, quenching deviates from Stern-Volmer kinetics and some permanent loss of photoluminescence intensity occurs due to oxidation of the porous Si surface. Photoluminescence from porous Si is not quenched by nitrous oxide or carbon dioxide and only slightly quenched by carbon monoxide and oxygen.