Polypyrrole-functionalized porous silicon for gas sensing applications

Electrodeposition of polypyrrole film on porous silicon surface was used to improve its photoluminescence properties for sensing of chemical species in gas phase. Photoluminescence quenching sensor response was measured for water and a homological set of linear alcohols in gas phase. We observed modified photoluminescence quenching response from polypyrrole-modified porous silicon as compared with as-prepared porous silicon. For as-prepared porous silicon samples, the dependence of photoluminescence quenching on analyte concentration revealed Stern–Volmer behavior. Concentration dependence of photoluminescence quenching response of polypyrrole-modified samples for water and methanol exhibited Stern–Volmer behavior as well, for C2–C6 linear alcohols a period of photoluminescence enhancement on the concentration dependence onset followed by photoluminescence quenching at higher concentrations was observed. The interval of photoluminescence enhancement response from polypyrrole-modified samples was continuously decreasing with the length of alcohol chain. Dramatic reduction of sensor photoluminescence response to lower alcohols was attributed to strong interaction with polypyrrole surface layer and suppressed analyte penetration into porous matrix. Operational stability of polypyrrole-modified porous silicon was improved as compared to as-prepared porous silicon.