Photoinduced Release of Volatile Organic Compounds from Fatty Alcohols at the Air-Water Interface: The Role of Singlet Oxygen Photosensitized by a Carbonyl Group.

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.