In this work, the preparation of hybrid oxo-TiO2 nanoparticles modified by salicylic acid (SA) is reported. The size-selected TiO2 nanoparticles were synthesized in a sal-gel reactor with rapid micromixing of reagents and binding of SA molecules occurs at the nucleation stage. UV-visible absorption, Raman spectroscopy and Light scattering measurements evidence the formation of a SA oxo-TiO2 charge-transfer complex. In particularly, the C=O vibration mode of SA shifts to lower frequencies upon complexation while the C-O vibration modes of both carboxylate and phenolic groups retain their position. The absence of C-O shift comes from two effects that cancel each other, i.e. the hardening of this mode related to the C=O mode changes and its softening due to the replacement of hydrogen in COH group by Ti atoms. Kinetic studies of the oxo-TiO2 nanoparticles nucleation and growth in presence of SA show that the acidic ligand at the nanoparticle surface acts as an attractor for another oxo-TiO2 nanoparticle leading to polycondensation. This mechanism is responsible for the acceleration of the nanoparticle aggregation kinetics and shortening of the induction time. The hybrid nanoparticles are stable at pH <= 7.7 and release SA molecules at pH >= 8.5. (C) 2014 Elsevier B.V. All rights reserved.