Photoinduced Release of Volatile Organic Compounds from Fatty Alcohols at the Air–Water Interface: The Role of Singlet Oxygen Photosensitized by a Carbonyl Group
Jingyi Lin, Qin Dai, He Zhao, Hongbin Cao, Tianyu Wang, Guangwei Wang, Chuncheng Chen
Abstract
Photoinduced interfacial release of volatile organic compounds (VOCs) from surfactants receives emerging concerns. Here, we investigate the photoreaction of 1-nonanol (NOL) as a model surfactant at the air–water interface, especially for the important role of 1O2 in the formation of VOCs. The production of VOCs is real-time quantitated. The results indicate that the oxygen content apparently affects the total yields of VOCs during the photoreaction of interfacial NOL. The photoactivity of NOL is about 8 times higher under air than that under nitrogen, which is mainly attributed to the generation of 1O2. Additionally, the production of VOCs increased by about 4 times with the existence of the air–water interface. Quenching experiments of 1O2 also illustrate the contribution of 1O2 to VOC formation, which could reach more than 95% during photoirradiation of NOL. Furthermore, density functional theory calculations show that 1O2 generated via energy transfer of photosensitizers can abstract two hydrogen atoms from a fatty alcohol molecule. The energy barrier of this reaction is 72.3 kJ/mol, and its reaction rate coefficient is about 2.742 s–1 M–1. 1O2 significantly promotes photoinduced oxidation of fatty alcohols and VOC formation through hydrogen abstraction, which provides a new insight into the interfacial photoreaction.