A nanocrystalline tungsten oxide photochromic thin film was prepared by colloid chemistry method. The microstructure, phase transition involved in the solution process, photochromic behavior, and mechanism of the film were investigated by means of transmission electron microscope, x-ray diffraction, ultraviolet-visible absorption spectra, and x-ray photoelectron spectra. It was found that the particle size and crystallinity of the thin film could be easily controlled by adjusting the concentration of oxalic acid in the colloid solution of tungsten oxide hydrate. With the increase of the oxalic acid concentration, the size of nanoparticles in the film decreased sharply, and meanwhile, a blue shift of the absorption peaks caused by the quantum size effect was observed accordingly. With the increase of the pH in the solution, tungsten oxide hydrate was gradually transformed into an oxided 12-tungstate with Keggin structure, which led to the change of photochromic property of the films. The photochromism of the film is believed to be due to the electron transfer between the different valence states of tungsten ions located in adjacent sites.

Raman microscopy was used to investigate microstructural properties of amorphous MoO3 thin films that had been subjected to a photochromic (PC) or electrochromic (EC) process. The Raman spectra changed reversibly when the films went through PC or EC coloration and decoloration cycles. Different molybdenum bronzes were produced with PC and EC treatments, as indicated by the shifts in the Raman bands. The same observation was made in the surface photovoltage spectral experiments. Hence, it was concluded that the microstructure of molybdenum bronze was affected by the coloration means (PC or EC process); the injected cations in an EC process were bonded to the triply coordinated O atoms, whereas the injected H+ ions in a PC process were bonded to both the triply coordinated and doubly coordinated O atoms. The size of the injected cations via EC processes had little effect on the microstructure of the colored films.

Large-scale pure titanate nanotubes were synthesized through the hydrothermal reaction between TiO 2 powders and concentrated NaOH under an unexpected high temperature of 240 °C, while it was generally claimed that it is impossible to form nanotubes at temperatures higher than 180 °C. The titanate nanotube was found to be an inevitable intermediate product, which finally transformed into a nanowire upon increasing the hydrothermal treatment duration. It was proven that the successive appearance of nanosheets, nanotubes, and nanowires are three unavoidable kinetic products of the reaction. Increasing the temperature could only accelerate the nanotube-nanowire transformation process but could not affect the sequence of the reaction events. The transformation kinetics from nanotubes to nanowires under different reaction temperatures was studied. Detailed studies indicate that this transformation process was accompanied by a coarsening process induced by both oriented attachment (OA) and Ostwald ripening (OR) mechanisms simultaneously; thereafter, the OA-OR cooperative mechanism was proposed.