Fig. 6From: Enhanced Photoelectrochemical Activity of ZnO-Coated TiO2 Nanotubes and Its Dependence on ZnO Coating ThicknessPL spectra of bare TiO2 NTs (1), 10-cycle ZnO/TiO2 NTs (2), and 25-cycle (3) ZnO/TiO2 NTs measured at 300 K (a) and 20 K (b). The inset in a compares the PL spectra of 25-cycle ZnO/TiO2 NTs measured at 300 and 20 K, and the inset in b shows magnified spectra 1 and 2 recorded at 20 KBack to article page