Enhanced Stability and Dispersion of Aqueous TiO2 Nanoparticles via Acrylic Acid Surface Modification

Amorphous titanium dioxide (TiO2) nanoparticles were synthesized via a sol–gel reaction using titanium tetrachloride (TiCl4) as the precursor. Acrylic acid (AA) was introduced to modify the particle surface, preventing aggregation and enabling functionalization. Fourier transform infrared analysis revealed that a reaction time of 48 h was necessary to complete the surface modification through chelation and condensation. To optimize processing conditions, reactions were performed at 25 and 50°C with varied TiO2 : AA molar ratios. Results showed that at 50°C, excessive AA (1 : 14) led to over-polymerization, while insufficient AA (1 : 6) failed to stabilize the particles. In contrast, the intermediate concentration (1 : 10) produced well-dispersed spherical nanoparticles (10–15 nm), as confirmed by dynamic light scattering (DLS) and transmission electron microscope (TEM). This study demonstrates that tuning AA concentration and reaction temperature enables kinetic control over surface modification, effectively stabilizing amorphous TiO2 in aqueous media. It offers a simple and scalable approach for preparing size-controlled, surface-functionalized amorphous TiO2 nanoparticles with potential optical and functional applications.