Preparation and Photochromic Properties of Doped TiO2/PMMA Composite Films

In this study, we propose an improved sol-gel method to synthesize TiO2 nanoparticles with photocatalytic reduction properties through ion doping, and fabricate TiO2/PMMA composite films with rapid ultraviolet-visible light response. This method allows for the low-cost preparation of photochromic films with high light response speed. Most photochromic systems based on semiconductor TiO2 rely solely on ultraviolet light to drive the redox dye’s color change; however, no reports have been made on visible light-driven color-changing systems. By doping TiO2 with various ions, we introduce abundant oxygen vacancies into the semiconductor, enhancing its photocatalytic reduction activity. This extends the light-responsive range of the photochromic films to the visible light spectrum in turn. Experimental results show that the film color undergoes significant changes under 365 nm light irradiation. Moreover, different ion doping further modify the light-responsive range of the films. Characterization analysis indicates a significant increase in the number of Ti3+ ions in the films, revealing that the photochromic effect is due to the interaction between photogenerated electrons and adjacent Ti atoms, resulting in the formation of Ti3+.