In this communication we report the fabrication of nanoparticles (NPs) and nanostructures through the interaction of ultrashort laser pulses (similar to 40 fs) with bulk aluminum immersed in chloroform and carbon tetrachloride. The size distribution and surface morphology of substrates were investigated using scanning electron microscope images. Depending on the focal position we observed sub-micron structures and nano-ripples on the irradiated surface. Picosecond nonlinear optical studies of the prepared NPs colloidal solutions using open aperture Z-scan technique demonstrated complex behavior of switching from saturable absorption to reverse saturable absorption (RSA) at lower peak intensities to pure RSA at higher peak intensities. (C) 2012 Elsevier B. V. All rights reserved.