All-organic device with integrated chemical filter dedicated to the selective measurement of NO2 in air

An original organic semiconductor gas sensor devoted to the selective monitoring of nitrogen dioxide in air has been successfully developed. This device combines the great sensitivity and the partial selectivity toward oxidizing gases of a molecular organic semiconductor, copper phthalocyanine, with the O3 filtering selectivity of an organic material, indigo. Experimental measurements highlight filtering yield of indigo close to 100% toward O3 and lower than 10% for NO2. Nanometric indigo layers were realized for the first time by thermal evaporation and characterized by FT-IR spectroscopy. Such all-organic device exhibits a high NO2 sensitivity for low concentrations, a resolution better than 20 ppb, a threshold of detection to few ppb and a high level of selectivity. The influence of filtering layer thickness and the optimization for real-time measurements are also discussed. Beyond sensor development, such nanostructured indigo layers are relevant as protective element of electronic components against adverse ozone effects.