“…Rutile TiO 2 , a model photocatalytic material, has aroused extensive attention due to its low cost, high stability, and excellent reactivity. − The band gap of its bulk case is about 3.04 eV in the ultraviolet range. , It has been found that the light absorption and reactivity of rutile is strongly related to the excess electrons, which has been proved to be Holstein polarons. − Various kinds of factors greatly influence the formation of polaron including lattice defects (such as O v − or T int , ), atomic coordination, external doping, , crystal boundary effects, and processes of optical excitation. , Numerous scholarly works focus on investigating the polarons. − From the experimental side, Macdonald et al used electron paramagnetic resonance (EPR) to study photoexcited electrons in nanocrystalline rutile, and they found that an EPR signal appears after UV–visible light irradiation. The signal can even remain after turning off the irradiation, suggesting the stability of polarons.…”