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Ultraviolet photocatalytic degradation of cholesterol on TiO2: secondary ion mass spectrometry

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PROCHAZKA Michal STUPAVSKÁ Monika HALASZOVA Sona JERIGOVA Monika VELIC Dusan

Rok publikování 2017
Druh Článek v odborném periodiku
Časopis / Zdroj Surface and Interface Analysis
Fakulta / Pracoviště MU

Přírodovědecká fakulta

Citace
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Doi http://dx.doi.org/10.1002/sia.6129
Klíčová slova photocatalysis; titanium oxide; cholesterol; cholesterol oxidation products; secondary ion mass spectrometry
Popis Cholesterol (C27H46O 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 (TiO2) 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 0.0207min(-1) within 2h. 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 30min, respectively. The roles of electrons and holes, primarily generated in TiO2 by UV, and also of superoxide anion radical and hydroxyl radical, as the secondary reactive species, are discussed to illustrate the bottom/top mechanisms.

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