Microstructure characterization and NO2-sensing properties of porous silicon with intermediate pore size

► The porous silicon (PS) with intermediate pore size (50-200 nm) was successfully prepared using electrochemical etching method without additional oxidizing agents and illumination. ► The pore morphology of PS was changed noticeably by varying the etching time. ► Optimized PS structure has a high porosity of 75% and direct excellent gas diffusion channels, exhibiting good and desirable gas-sensing properties toward sub-ppm NO2 at room temperature. ► NO2-sensing mechanism of PS was also discussed. ► The PS kept its gas-sensing characteristic during four weeks.