Phenol transformation and dimerisation, photosensitised by the triplet state of 1-nitronaphthalene: A possible pathway to humic-like substances (HULIS) in atmospheric waters

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• 作者：Elisa De Laurentiis^a ; Babita Sur^a ; ^b ; Marco Pazzi^a ; Valter Maurino^a ; Claudio Minero^a ; Gilles Mailhot^c ; ^d ; Marcello Brigante^c ; ^d ; ^{marcello.brigante@univ-bpclermont.fr} ; Davide Vione^a ; ^e ; ^{davide.vione@unito.it}
• 关键词：Photoinduced transformation ; Singlet oxygen ; Phenoxy radical ; Kinetic modelling
• 刊名：Atmospheric Environment
• 出版年：2013
• 出版时间：May, 2013
• 年：2013
• 卷：70
• 期：Complete
• 页码：318-327
• 全文大小：1368 K

文摘

The nitroderivatives of polycyclic aromatic hydrocarbons are potentially important photosensitisers in the atmospheric condensed phase. Here we show that the triplet state of 1-nitronaphthalene (³1NN*) is able to directly react with phenol, causing its transformation upon irradiation of 1NN in aqueous solution. Additional but less important processes of phenol degradation are reactions with OH and ¹O₂, both photogenerated by irradiated 1NN. Dihydroxybiphenyls and phenoxyphenols were detected as main phenol transformation intermediates, likely formed by dimerisation of phenoxy radicals that would be produced upon phenol oxidation by ³1NN*. Very interestingly, irradiation with 1NN shifted the fluorescence peaks of phenol (Ex/Em?=?220-230/280-320?nm and 250-275/280-320?nm, with Ex/Em?=?excitation and emission wavelengths) to a region that overlaps with ¡°M-like¡± fulvic substances (Ex/Em?=?250-300/330-400?nm). Moreover, at longer irradiation times a further peak appeared (Ex/Em?=?300-450/400-450?nm), which is in the region of HULIS fluorescence. Irradiated material was also able to photoproduce ¹O₂, thus showing photosensitisation properties. Therefore, compounds with fluorescence properties that closely resemble those of HULIS (they would be identified as HULIS by fluorescence if present in environmental samples) can be formed upon triplet-sensitised transformation of phenol by 1NN.