Selective detection of the inorganics NOx, SO2, and H2S in the presence of volatile BTEX contaminants toluene,benzene, and xylene

We demonstrate the highly selective detection of the inorganics NO_x (NO, NO₂), SO₂, and H₂S in the presence of toluene, benzene, and xylene using nanostructure metal-oxide-decorated interfaces. This selectivity can be obtained for sensors whose sensitivities are varied for a diversity of nanostructured metal oxides which are applied to a porous silicon (PS) interface. We focus on NO_x and SO₂ and include additional new evaluations for the response to H₂S. In all cases, the response to these inorganic analytes strongly dominates that for toluene, benzene, and xylene. The responses are also consistent with the recently developing inverse hard/soft acid/base concept. The nanostructure metal-oxide-decorated PS conductometric sensors are found to have selectivity ratios well in excess of 10⁴:1 for toluene and benzene and well in excess of 10³:1 for xylene. The dominance of the response of these small inorganic sulfur and nitrogen compounds has important implications for the monitoring of significant contaminants associated with the venting and flaring of natural gas pits, as they can be present in oil and gas formations.