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

Abstract

Phototransformation of 4-phenoxyphenol sensitised by 4-carboxybenzophenone in aqueous solution and at the aerosol interface: Evidence of new photochemical pathways in the bulk aqueous phase and on the surface of aerosol deliquescent particles. Atmos. Environ. 2013, 81, 569-578. DOI: 10.1016/j.atmosenv.2013 You may download, copy and otherwise use the AAM for non-commercial purposes provided that your license is limited by the following restrictions:(1) You may use this AAM for non-commercial purposes only under the terms of the CC-BY-NC-ND license.(2) The integrity of the work and identification of the author, copyright owner, and publisher must be preserved in any copy. AbstractIn 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 (4PP). The process takes place via the CBP triplet state ( 3 CBP*), which has an oxidising nature. 4PP is fluorescent, unlike the photosensitizer CBP, with two emission bands at ∼320 and ∼380 nm. However, addition of CBP to a 4PP solution considerably decreases the intensity of 4PP fluorescence bands and causes a very intense new band to appear at ∼420 nm. This behaviour suggests a possible interaction between CBP and 4PP 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 photosensitizer-substrate interactions may have a role in HULIS fluorescence properties. The interaction between CBP and 4PP 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 4PP, induced by 3 CBP* 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.

Heterogeneous reactions of mineral dust aerosol: implications for tropospheric oxidation capacity

“…Heterogeneous reactivity of 4-phenoxyphenol towards ozone was significantly enhanced in the presence of aromatic ketones (4-carboxybenzophenone) under light irradiation compared to the dark ozone reaction (Net et al, 2010d). This photosensitized reaction proceeds through the electron transfer reaction to ozone with formation of an ozonide anion (O − 3 ) which can further react to produce OH radicals (De Laurentiis et al, 2013), and the formation of OH radicals was confirmed during such photochemical processing on the silica particles. The same group (Net et al, 2009) proposed a comprehensive reaction mechanism based on identified products arising from the OH-addition to 4-phenoxyphenol.…”

Heterogeneous reactions of ozone with commonly used pesticides adsorbed on silica particles

“…The adsorption of the pesticide can influence K ðO3Þ and the nature of the adsorption sites. In addition, the relative humidity is an important parameter that has not been much studied (De Laurentiis et al, 2013) but that may influence the partitioning of ozone between the gas phase and the particle surface.…”

Photochemical processes induced by the irradiation of 4-hydroxybenzophenone in different solvents

“…The triplet states of benzophenones often behave as effective photosensitisers for the transformation of phenolic compounds. 46,47 The reactivity between 3 4BPOH* and phenol was assessed by studying the effect of phenol concentration on the value of k 520 nm in acetonitrile. The value of k 520 nm increases linearly with increasing phenol (see Fig.…”