The nanometer titanium dioxide particles were modified with the coupling agent vinyltriethoxysilane, dispersed in the medium of methanol applying the ultrasonic technique and encapsulated by in situ dispersion copolymerization with styrene (ST) and then with acrylamide or vinylpyrrolidone (VP). Titanium dioxide inorganic core and polymer shell composite nanoparticles were successfully prepared by two-step in situ dispersion copolymerization. The spectra and micromorphology of two composite nanoparticles were characterized by Fourier transform IR spectroscopy, ultraviolet-visible spectroscopy measurement and transmission electron microscopy. The results show that with the photoactivation formed, which derived from coordination bond between core of TiO₂ nanoparticles and shell of amphiphilic copolymers that contain a lot of amide structure, the maximum absorption of both kind of composite nanoparticles are red shifted and the absorption spectra extent of two composite nanoparticles are broadened in the UV-Vis spectra figures, especially TiO₂/(PST-co-PVP). This means their photosensitization and photoactivation are enhanced especially in visible light region. It is advantageous for photocatalytic properties of some wide bandgap semiconductor materials such as titanium dioxide nanoparticles, and indicates that the applied domain of this kind of material is enlarged.

Key words: two-step in situ dispersion copolymerization, inorganic core-polymer shell, composite nanoparticle, TiO₂ nanoparticle, UV photosensitization