The electron-injection mechanisms determined for TiO2-carotenoic acid （CA） suspensions. Subpicosecond time-resolved absorption spectra were recorded for retinoic and carotenoic acids, i.e., RA5, CA6, CA7, CA8, CA9 a...The electron-injection mechanisms determined for TiO2-carotenoic acid （CA） suspensions. Subpicosecond time-resolved absorption spectra were recorded for retinoic and carotenoic acids, i.e., RA5, CA6, CA7, CA8, CA9 and CA11 （hereafter, collectively referred to ‘CAs’） having the number of conjugated double bonds, n = 5, 6, 7, 8, 9 and 11, respectively, free in ethanol solution and bound to TiO2 nano-particles. The time-resolved spectra were analyzed by singular-value decomposition followed by global fitting based on an energy diagram consisting of the 3Ag-, 1Bu-, 1Bu+ and 2Ag- states that were extrapolated from those in carotenoids with n = 9 - 13 （K. Furuichi, T. Sashima, Y. Koyama, Chem. Phys. Lett. 356 （2002） 547 - 555）. The scheme and the time constants of internal conversion and electron injection, in the very initial stage after excitation, were determined; here, the time constants of internal conversion that were determined for CAs in solution were transferred to the case of CAs bound to TiO2. It was found that electron injection took place from both the 1Bu+ and 2Ag- states in RA5, CA6, CA7 and CA8, whereas only from the 1Bu+ state in CA9 and CA11. The electron-injection efficiencies were determined by the use of the relevant time constants as follows: RA5 37%, CA6 92%, CA7 98%, CA8 94%, CA9 60% and CA11 29%; the electron-injection efficiency in CA7 was almost unity. In the final stage, both the D 0 and T1 states remained and then decayed.展开更多
文摘The electron-injection mechanisms determined for TiO2-carotenoic acid （CA） suspensions. Subpicosecond time-resolved absorption spectra were recorded for retinoic and carotenoic acids, i.e., RA5, CA6, CA7, CA8, CA9 and CA11 （hereafter, collectively referred to ‘CAs’） having the number of conjugated double bonds, n = 5, 6, 7, 8, 9 and 11, respectively, free in ethanol solution and bound to TiO2 nano-particles. The time-resolved spectra were analyzed by singular-value decomposition followed by global fitting based on an energy diagram consisting of the 3Ag-, 1Bu-, 1Bu+ and 2Ag- states that were extrapolated from those in carotenoids with n = 9 - 13 （K. Furuichi, T. Sashima, Y. Koyama, Chem. Phys. Lett. 356 （2002） 547 - 555）. The scheme and the time constants of internal conversion and electron injection, in the very initial stage after excitation, were determined; here, the time constants of internal conversion that were determined for CAs in solution were transferred to the case of CAs bound to TiO2. It was found that electron injection took place from both the 1Bu+ and 2Ag- states in RA5, CA6, CA7 and CA8, whereas only from the 1Bu+ state in CA9 and CA11. The electron-injection efficiencies were determined by the use of the relevant time constants as follows: RA5 37%, CA6 92%, CA7 98%, CA8 94%, CA9 60% and CA11 29%; the electron-injection efficiency in CA7 was almost unity. In the final stage, both the D 0 and T1 states remained and then decayed.
基金Supported by the National Natural Science Foundation of China(62001297,61921002 and 61988102)Shenzhen Science and technology(JCYJ 2020019105415835 and KQTD 20200820113046084。
