Preparation of titanium dioxide porous thin films via photopolymerization of the colloidal TiO2 dispersion

Titanium dioxide (TiO2) thin films with porous structures have been successfully achieved by photopolymerization stimulating the particle dispersion combined TiO2 colloid with photoinitiator and monomer. The photopolymerization monomer Pentaerythritol Triacrylate (PETA) and photoinitiator 2-Hydroxy-2-methyl-propiophenone (HMPP) are added to the TiO2 colloidal solution to form the new colloidal TiO2 dispersion. After coating the dispersion on the substrate, the coating is cured with UV light. With the evaporation of solvent and the formation of microgels induced by polymerization, a phase separation occurs in the system. A porous TiO2 film with various pore sizes from mesoporous to macroporous could be produced after heat treatment. The morphology and size of pores could be tuned by changing the process of phase separation, which is controlled by the composition of colloidal TiO2 dispersion. The content of photoinitiator and the temperature of heat treatment were decided by UV-vis absorption spectra and thermal analysis (DTA-TGA), respectively; Real-Time Fourier-transform infrared (RT-FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffractometer (XRD) and high-resolution transmission electron microscopy (HR-TEM) were used to characterize the TiO2 films. The as-prepared TiO2 porous films exhibited higher photocatalytic activity for degradation methylene blue in comparison with conventional TiO2 dense film due to its porous structure.