Gao Yunlong, Lockart Molly, Kispert Lowell D, Bowman Michael K
College of Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
Department of Chemistry, BOX 870336, University of Alabama, Tuscaloosa, Alabama 35487, USA.
Dalton Trans. 2019 Aug 7;48(29):10881-10891. doi: 10.1039/c9dt01455a. Epub 2019 May 20.
The efficiency of photocatalytic charge separation is much higher for 7-hydroxycoumarin (7-CN) and 6,7-dihydroxycoumarin (6,7-CN) adsorbed on the surface modified TiO where the surface hydroxyl group was replaced by a fluorine atom (F-TiO) than on TiO. EPR measurements find 5- and 12-fold increases in free radical yields for 7-CN and 6,7-CN, respectively. DFT calculations for the coumarins on TiO and F-TiO were performed to investigate these phenomena. The calculations show that when the coumarins act as the H-bond donors, the driving force for photo-induced electron transfer from the dyes to TiO is higher, and the dye's excited state mixes strongly with the TiO conduction band states. This is attributed to the shorter distance between the coumarins and the surface of TiO when the coumarins act as the H-bond donors. These calculations explain why the efficiency of charge separation of the coumarins is much higher on F-TiO than on TiO.
对于吸附在表面羟基被氟原子取代的表面改性二氧化钛（F-TiO）上的7-羟基香豆素（7-CN）和6,7-二羟基香豆素（6,7-CN），其光催化电荷分离效率比在二氧化钛（TiO）上高得多。电子顺磁共振（EPR）测量发现，7-CN和6,7-CN的自由基产率分别提高了5倍和12倍。对TiO和F-TiO上的香豆素进行了密度泛函理论（DFT）计算，以研究这些现象。计算结果表明，当香豆素作为氢键供体时，光致电子从染料转移到TiO的驱动力更高，并且染料的激发态与TiO导带态强烈混合。这归因于当香豆素作为氢键供体时，香豆素与TiO表面之间的距离较短。这些计算解释了为什么香豆素在F-TiO上的电荷分离效率比在TiO上高得多。
