Development of PPy films doped with thiol-SAM-Cu particles for NH ₃ gas sensing

We have developed a high-sensitivity polypyrrole (PPy) film with a porous structure using a simple and easy method of doping thiol self-assembled monolayer (SAM)-Cu particles into a PPy film. The thiol-Cu-SAM particles were doped by the adsorption of thioxylenol or decanethiol into the porous PPy film surface, resulting in an improvement in sensitivity of the film to NH ₃. Owing to the addition of thiol-Cu-SAM particles formed using various 4-tert-butylcalix-6-arene thiol derivatives, the sensitivity correspondingly decreased. In particular, for the case of poly(propylene oxide)-calix-6-arenethiol, a marked decrease in sensitivity was observed. Using this composite nanomaterial, we found that the detection limit for NH ₃ increased to concentration levels of several ppm. We present a novel preparation method for these sensor films aimed at controlling their porosity and sensitivity.