Fabrication and photochromic study of titanate nanotubes loaded with silver nanoparticles

Pure anatase-TiO₂ and/or titanate nanotubes, photochromic Ag loaded titanium dioxide nanotubes (TNTs) and AgCl loaded titanate nanotubes were synthesized by hydrothermal method. The pH value during the neutralization process plays a crucial role in controlling the morphology and composition of the nanotubes. All these nanotubes were confirmed by XRD, TEM, EDS and XPS analysis. Most of them have open ends with inner/outer diameters of 7/10 nm and several hundred nanometers in length. For photochromic behavior in the case of AgCl-titanate nanotubes, the red color can be clearly observed after irradiation by red light, while the yellow, green, blue ones displayed pale black after the corresponding irradiation. On the other hand, Ag loaded TNT sample exhibited multicolor photochromism corresponding to that of incident light. The photoreduction of silver halide to Ag particle in the case of loaded AgCl particles and a particle-plasmon-assisted electron transfer from Ag nanoparticles to TiO₂ in the case of loaded Ag particles are considered to be responsible for this different behavior.