Nanoparticles (NPs) are an essential material for science and technology, for instance in materials, medicals, and cosmetics. Controlling the dispersion of NPs is necessary to manage the properties of the final products. For this reason the surface modification of NPs is done by many techniques. In this work Nano-TiO2 were modified using methanol as solvent and diacids based on natural amino acids as modifier at room temperature and using ultrasonic irradiation. Diacids were grafted onto the surface of TiO2 NPs to improve the dispersion of the particles. The obtained modified TiO2 were characterized by Fourier transform IR spectroscopy (FT-IR), X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) techniques. These analyses proved this modification process at room temperature was possible. TEM and FE-SEM showed that fairly good dispersed TiO2 NPs were obtained after surface modification. Since TiO2 and diacids which were used in this work are biologically active, the modified powder would be environmentally friendly. 2013 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.