Fresh porous silicon (PS) samples show photoluminescence (PL) in visible. After a short dip in water, the PL peak shifts towards blue. However, a short dipping of PS in toluene and pentane does not change PL. The intensity of PL decreases upon exposing, PS briefly to acetone. The peak position however, remains unchanged. X-Ray diffraction (XRD) and atomic force microscopy (AFM) show the presence of nanocrystals in PS. After dipping in water, XRD and AFM show structural changes. However, dipping in pentane, toluene and acetone has no effect on the XRD and AFM. Using AFM data, John-Singh model of quantum confinement explain the PL results of PS treated with water, toluene and pentane. However, the changes in PL after acetone treatment cannot be explained within this model. (C) 2003 Elsevier B.V. All rights reserved.