In this paper, a kind of novel p-type intermediate size porous silicon (Intermediate-PS) with large specific surface area and highly ordered pore channel was successfully prepared by a galvanostatic electrochemical etching method. The microstructure and surface bonding configuration of the PS characterized by using field emission scanning electron microscope (FESEM) and Fourier transform infrared spectroscopy (FTIR), respectively. The freshly prepared PS could achieve stable surface passivation after one week storage in air due to the effect of natural oxidation. Moreover, the NO2 gas-sensing performances of the PS sensor were systematically investigated at different temperatures ranging from room temperature (25 degrees C) to 100 degrees C over NO2 concentrations in the range of 0.125-2 ppm. The gas sensor based on the Intermediate-PS showed a typical p-type semiconductor behavior together with perfect reproducibility and very rapid response-recovery speed at room temperature. The good sensing properties of the Intermediate-PS sensor can be attributed to its favorable microstructure features. In addition, the conceivable sensing mechanism has also been discussed in detail. (C) 2013 Elsevier Ltd. All rights reserved.