Organic silicone, polydimethylsiloxane (PDMS), was covalently grafted onto the porous silicon (PS) surface to improve its stability to oxidation. Transmission Fourier-transform infrared (FTIR), photolummescence (PL) and interferometric reflectance spectra have been recorded to evaluate the surface modification and the passivation effect. After modification, the porous nanostructure retained, the stability against oxidation was significantly improved and the PL still kept. (C) 2004 Elsevier B.V. All rights reserved.