Surface modification of TiO2 nanoparticles with silane coupling agents

Due to their excellent photo-catalytic activities making TiO2 nanoparticles applicable as self-cleaning and anti-bacterial agents, as well as for UV protection and environmental purification, a great potential for multi-functionalization of fabrics by TiO2 nanoparticles is considered. In order to improve the durability of nanoparticles at a fabric surface, the surface of commercial TiO2 nanoparticles was modified by 3-aminopropyltrimethoxysilane (APTMS) and 3-Isocyanatopropyltrimethoxysilane (IPTMS) by an aqueous process in this study. The grafting efficiency of agents to TiO2 nanoparticles at different reaction conditions was estimated by thermal gravimetric analysis. FTIR spectra confirmed that organic functional groups were successfully grafted onto the TiO2 nanoparticles surface both for APTMS-grafted TiO2 nanoparticles (A-TiO2) and IPTMS-grafted TiO2 nanoparticles (I-TiO2) through TiOSi chemical bonds. After the surface modification of TiO2 nanoparticles, isoelectric point (IEP) of nanoparticles was shifted approximately from pH 6.4 to pH 9.4 and the zeta potential plateaus increased significantly which was explained by the protonation of NH2 groups in the acidic region. The significant reduction of particle hydrodynamic diameters and polydispersity index (PDI) indicated the particle dispersion stability was positively affected by an increase in particle zeta potential. With increasing the organosilane ratio from 0 wt.% to 200 wt.%, a slight decline of the rate constant of A-TiO2 photocatalytic activity and a rapid decrease for I-TiO2 were revealed, which was significantly dependent on the grafting efficiency.