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Ultraviolet photocatalytic degradation of cholesterol on TiO 2 : secondary ion mass spectrometry
Author(s) -
Prochazka Michal,
Stupavska Monika,
Halaszova Sona,
Jerigova Monika,
Velic Dusan
Publication year - 2017
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.6129
Subject(s) - chemistry , photocatalysis , hydroxyl radical , photochemistry , irradiation , ion , ultraviolet , degradation (telecommunications) , mass spectrometry , kinetics , radical , molecule , oxide , analytical chemistry (journal) , catalysis , organic chemistry , chromatography , materials science , telecommunications , physics , optoelectronics , quantum mechanics , computer science , nuclear physics
Cholesterol (C 27 H 46 O stated as M) is used as a model of bio‐organic contamination, because this compound is in almost every living organism, and its photocatalytic degradation on titanium oxide (TiO 2 ) surface with UV exposure is investigated. Secondary ion mass spectrometry as a surface‐sensitive technique is suited to study this degradation process with focus on intermediates. A fragment of M–OH represents the intact molecule of cholesterol and provides its relative concentration on the surface. The intensity of M–OH decreases after 24‐h UV irradiation, and the level of degradation is 89% with the pseudo‐first kinetic constant of 0.0207 min −1 within 2 h. A fragment of MO–H represents an intermediate as one of the cholesterol oxidation products. The irradiation from a bottom in comparison with a top reveals the differences in the mechanism of the intermediate formation through the intensity and the kinetics with values of factor of 1/3 and 30 min, respectively. The roles of electrons and holes, primarily generated in TiO 2 by UV, and also of superoxide anion radical and hydroxyl radical, as the secondary reactive species, are discussed to illustrate the bottom/top mechanisms. Copyright © 2016 John Wiley & Sons, Ltd.