There has recently been a renewed interest in the photochromic properties and uses of TiO2 as a potential candidate for smart windows. TiO2 nanoparticle (NP) suspensions are capable of changing their transmittance across both the visible and near-infra red spectral range via irradiation with UV light1. Furthermore, this change in transmittance is fully reversible with exposure to air as seen in figure 1. However, the surrounding medium for TiO2 NPs, is of equal importance, as it facilitates hole scavenging and, in turn, the photochromism. This is but one of the ways in which TiO2 photochromism can be tuned.