In this work, photoluminescent porous silicon (PS) stain etched and passivated by means of oxidation in HNO3/H2SO4 or HNO3/H2O2 solutions has been studied. These passivation methods have preserved the PS photoluminescence and also have increased the photocarriers' lifetime, which are required for efficient down-conversion properties. The samples have been characterized by Fourier transform infrared spectroscopy, spectrofluorometry and microwave photoconduction decay. The results show that the photocarriers lifetime and the photoluminescence values are sensitively dependent on the evolution of the Si-H, Si-O and O-H bonds. (c) 2005 Elsevier B.V All rights reserved.