Interactions of ozone with organic surface films in the presence of simulated sunlight: impact on wettability of aerosols.
Heterogeneous reactions between organic films, taken as proxies for atmospheric aerosols, with ozone in presence of simulated sunlight and the photosensitizer 4-carboxybenzophenone (4-CB) were observed to alter surface properties as monitored by contact angle during the reaction. Attenuated total reflectance Fourier transform infrared spectroscopy (FTIR-ATR) was used in addition for product identification. Two types of model surfaces were systematically studied: 4-CB/4-phenoxyphenol and 4-CB/catechol. Solid organic films made of 4-CB/catechol were observed to become hydrophilic by simultaneous exposure to ozone and simulated sunlight, whereas organic films made of 4-CB/4-phenoxyphenol become hydrophobic under the same conditions. These changes in contact angle indicate that photo-induced aging processes involving ozone (such as oligomerisation) not necessarily favour increased hygroscopicity of organic aerosols in the atmosphere. The ratio between hydrophobic and hydrophilic functional groups should reflect the chemical property of organic films with respect to wettability phenomena. Contact angles and surface tensions of the exposed organic film made of 4-CB/4-phenoxyphenol were found to correspond to the hydrophobic/hydrophilic ratios obtained from the FTIR-ATR spectra.
Nieto-Gligorovski
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L
Universités d'Aix-Marseille I, II, III - CNRS, UMR 6264: Laboratoire Chimie Provence, Equipe Instrumentation et Réactivité Atmosphérique, Marseille Cedex 03, France.
Net
S
S
Gligorovski
S
S
Zetzsch
C
C
Jammoul
A
A
D'Anna
B
B
George
C
C
D000336:Aerosols / Q000737:chemistry* / Q000528:radiation effects; D001577:Benzophenones / Q000737:chemistry* / Q000528:radiation effects*; D002396:Catechols / Q000737:chemistry / Q000528:radiation effects; D008567:Membranes, Artificial; D010126:Ozone / Q000737:chemistry* / Q000528:radiation effects*; D010647:Phenyl Ethers / Q000737:chemistry / Q000528:radiation effects; D017319:Photosensitizing Agents / Q000737:chemistry* / Q000528:radiation effects*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D013472:Sunlight; D013499:Surface Properties; D013997:Time Factors; D017155:Wettability
C530484:4-carboxybenzophenone; D000336:Aerosols; D001577:Benzophenones; D002396:Catechols; D008567:Membranes, Artificial; D010647:Phenyl Ethers; D017319:Photosensitizing Agents; D010126:Ozone; C530483:4-phenoxyphenol; C034221:catechol