کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6340538 | 1620390 | 2013 | 10 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Phototransformation of 4-phenoxyphenol sensitised by 4-carboxybenzophenone: Evidence of new photochemical pathways in the bulk aqueous phase and on the surface of aerosol deliquescent particles Phototransformation of 4-phenoxyphenol sensitised by 4-carboxybenzophenone: Evidence of new photochemical pathways in the bulk aqueous phase and on the surface of aerosol deliquescent particles](/preview/png/6340538.png)
- Carboxybenzophenone (CBP) photosensitises phenoxyphenol (4Â PP) degradation.
- The reaction involves oxidation of 4Â PP to a phenoxy radical by CBP triplet state.
- Interaction in solution between CBP and 4Â PP modifies the 4Â PP fluorescence spectrum.
- The modified fluoresce overlaps with that of Hulic-like substances.
- The reaction is faster in a gas-solid system in the absence of water vapour.
In addition to direct photolysis, degradation of organic compounds by solar light can also occur by indirect photolysis or photo-sensitised processes. These reactions are important because they are involved in, among others, direct and indirect climate changes, adverse health effects from inhaled particles, effects on cloud chemistry and ozone production. In this work, the importance of atmospheric photo-sensitisation is evaluated in bulk aqueous solution and on the surface of aerosol deliquescent particles. Irradiation experiments in aqueous solution indicate that 4-carboxybenzophenone (CBP) is able to photosensitise the degradation of 4-phenoxyphenol (4Â PP). The process takes place via the CBP triplet state (3CBP*), which has an oxidising nature. 4Â PP is fluorescent, unlike the photosensitiser CBP, with two emission bands at â¼320 and â¼380Â nm. However, addition of CBP to a 4Â PP solution considerably decreases the intensity of 4Â PP fluorescence bands and causes a very intense new band to appear at â¼420Â nm. This behaviour suggests a possible interaction between CBP and 4Â PP in solution, which could favour further light-induced processes. Moreover, the new band overlaps with the fluorescence spectrum of atmospheric HULIS (HUmic-LIke Substances), suggesting that supramolecular photosensitiser-substrate interactions may have a role in HULIS fluorescence properties. The interaction between CBP and 4Â PP coated on silica particles (gas-solid system) was also investigated under simulated sunlight, and in the presence of variable relative humidity. The water molecules inhibit the degradation of 4Â PP, induced by 3CBP* on the surface of aerosol particles, indicating that the process could be even faster on particles than in solution. We demonstrate that phenol substances adsorbed on aerosol surfaces and in bulk solution are substantially altered upon photosensitised processes.
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Journal: Atmospheric Environment - Volume 81, December 2013, Pages 569-578