CdS possesses higher conduction band and valence band than TiO2[9, 14, 15]. The band configuration induces the transfer of photogenerated electrons from CdS to TiO2 and photogenerated click here holes from TiO2 to CdS, which
makes charge separation effective. Under simulated solar irradiation, the CdS particles and TiO2 NWs could both be excited; photogenerated electrons and holes are transported to the TiO2 NWs surfaces and CdS particles’ surface, respectively; while under visible light irradiation, only the CdS particles could be excited. Photogenerated electrons are transported to the inner TiO2 NW surfaces, and holes are kept on the CdS particles’ surface, which reduces the photocatalytic activity when compared with simulated solar irradiation. At first, with the increase of deposition cycle number, more CdS particles are deposited on the TiO2 NW surfaces, more photogenerated electrons are generated by the visible light irradiation, and accordingly, the photodegradation efficiency is increased. TGF-beta tumor When the deposition cycle numbers are 6 and 10, the TiO2 NW surfaces are thoroughly covered with CdS nanoparticles. For sample CdS(10)-TiO2 NWs, the inner CdS nanoparticles on the TiO2 NW surfaces cannot receive visible light irradiation, whose photocatalytic efficiency has been saturated and almost the same with that of sample CdS(6)-TiO2 NWs. Based on the above mechanism, it is understood
that a remarkable absorption enhancement with the increase of deposition cycle number could not be translated to major photocatalytic efficiency increase. In addition, due to its photocorrosion, CdS QDs have been
often exploited to sensitize a certain semiconductor with regulated band configuration and help separate the photogenerated electrons and holes . In order to evaluate the photodegradation of MO by plain CdS QDs, a control experiment was made. CdS QDs were prepared onto a clean glass substrate with the same size via Staurosporine nmr the S-CBD approach. The cycles were repeated six times, and the photodegradation efficiency is only 11.4% after a 120-min visible irradiation, which further supports the synergistic effect mechanism between CdS QDs and TiO2 NWs. The recyclability and ease of collection for the photocatalysts are very important in practical application. Figure 4c shows the cycling experiment for the as-prepared photocatalysts for MO using sample CdS(4)-TiO2 NWs. The degradation efficiency after 120 min reduces from 98.83% to 96.32% after ten cycles. Evidently, the photocatalytic activity for MO degradation does not see more change much after each cycle, revealing the excellent cycling stability of the as-prepared CdS(4)-TiO2 NWs. The undercurve inset in Figure 4c shows the photographs and photocatalytic degradation efficiency of a typical sample CdS(4)-TiO2 NWs for recycled MO reduction, which shows ease of collection for the photocatalysts. Conclusions In summary, TiO2 NWs on Ti foils were prepared using simple hydrothermal treatment followed by annealing.