Enhanced Photogenerated Electron Transfer in a Semiartificial Photosynthesis System Based on Highly Dispersed Titanium Oxide Nanoparticles

In this study, a hybrid semiartificial photosynthesis system based on chloroplast (CLP) and titanium oxide nanoparticles (TiO2 NPs) was constructed. 2,6-Dichlorophenolindophenol (DCPIP) reduction by TiO2/CLP complex and methylene blue (MB) reduction by TiO2 were used to determine enhanced photogenerated electron transfer in this hybrid system. The DCPIP reduction by the TiO2/CLP complex showed the same trend as MB reduction by TiO2 as a function of concentration of TiO2 NPs, indicating interception of photogenerated electrons in TiO2 by CLP that leads to enhanced photosynthesis efficiency. Decreased photoluminescence intensity and shortened excited-state lifetime of the TiO2/CLP complex compared to that of pure TiO2 also support electron transfer from TiO2 to CLP. Longer visible light absorption wavelength and increasing valence band edges reveal the narrower band gap of TiO2/CLP, which finally results in the enhanced electron transfer from TiO2 to CLP. Higher ferricyanide reduction and enhanced ATP formation with the TiO2/CLP complex demonstrate the accelerated electron-transfer rate of the electron-transfer chain. This study reveals the mechanism of how TiO2 interacts with CLP to enhance the photosynthesis via constructing a semiartificial photosynthesis system.