In the present study, surface chemistry of porous silicon was tailored by thermal oxidation and thermal hydrosilylation method. Porous silicon nanoparticles were prepared by applying ultrasound to freestanding porous silicon films. The results showed a mesoporous silicon layer with an average pore diameter of 28.26 nm, porosity of 70.7% and thickness of 4660 nm. Porous silicon surface was modified and compared with native surface by Fourier transform infrared spectroscopy. Ultrasonic fracture of porous silicon films for 8 h resulted in nanoparticles with average particle size of 149 nm. Zeta potential measurements of nanoparticles at varying pH reveal presence of different surface chemistry of particles. (C) 2014 Elsevier Ltd. All rights reserved.