Kinetics of TiO2 photochromic response in different hole scavenging solvents.

There has recently been a renewed interest in the photochromic properties and uses of TiO2 as a potential candidate for smart windows. However, the surrounding medium of TiO2 nanoparticles (NPs) is of equal importance, as it facilitates hole scavenging and, in turn, photochromism. Here, we investigated the impact of scavenging power on the photochromic properties of TiO2. TiO2 NP colloids in these solvents exhibit a photochromic response in a broad wavelength range from the visible to near-infrared region. We have shown that solvents such as ethanol have the best hole scavenging properties among the alcohols tested. The response can be further modified by the addition of a supplementary hole scavenger, such as hydroxylamine. The photochromism of TiO2 is fully reversible and could be used for applications in smart windows.