Comparative Photocatalytic Ability of Nanocrystal-Carbon Nanotube and -TiO2 Nanocrystal Hybrid Nanostructures

We synthesized various nanocrystal (e.g., CdS, CdSe, and Cu2S)-carbon nanotube (NC-CNT) and NC-TiO2 hybrid nanostructures using the solvothermal method and compared their photocatalytic ability toward the visible-light-driven degradation of methylene blue (MB) dye. The free US NCs exhibited higher degradation efficiency than the CdSe and Cu2S NCs. The photocatalytic abilities of the NCs were found to determine the relative degradation efficiency of their CNT and TiO2 hybrid nanostructures. These results suggest that the oxidative N-demethylation degradation involves the transfer of holes from the NCs to MB. The hybridization of the NCs with the TiO2 NCs and CNTs enhances the oxidative degradation rate to the same extent, suggesting that the interfacial electron transfer process from the NCs to the attached CNTs (or TiO2), which retards the recombination of the electrons and holes, is comparable for both hybrid nanostructures.