氧化锌分散体光反应产生的自由基中间体

溶液中光诱导的电子转移反应已进行了大量的研究。而半导体粉末在水相或非水溶剂中的光化学研究也与自俱增。这种光化学与成像体系、太阳能转换以及光催化或污物的光降解有关。因此,越来越引起人们的重视。 Harbour和Hair用自旋捕捉技术研究了在ZnO-H_2O的分散体系中光合成过氧化氢,并检测到羟基自由基。他们认为氧化锌可能通过水的氧化将O_2还原成H_2O_2,从而使太阳能转换成化学能。人们自然会想到ZnO在其它溶剂中是否-也能观察到溶剂光氧化

FREE RADICAL INTERMEDIATES FORMED UPON PHOTOREACTION OF ZnO DISPERSION

The combination of ESR spectroscopy and spin trapping technique was used to detect free radical intermediates formed upon irradiation of ZnO powders dispersed in a mixture of water and alcohol (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol) The ESR signals for the 5,5-dimethyl-l-pyrroline-N-oxide (DMPO) adducts were observed. Hydro-xyalkyl adducts were identified Experiments performed with ZnO aqueous dispersions containing various amounts of alcohol suggest that alcohol should be very sensitive toward oxidation by the photogenerated holes. Hydroxyl radical formation seems to be the first step in the pho-tooxidation process of water. Alcohols can be oxidized by the radical, leading to the formation of hydroxyalkyl radicals.