Porphyrin鈥揘anoclay Photosensitizers for Visible Light Induced Oxidation of Phenol in Aqueous Media
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- 作者：Dominik Drozd ; Krzysztof Szczubia艂ka ; Micha艂 Skiba ; Mariusz Kepczynski ; Maria Nowakowska
- 刊名：Journal of Physical Chemistry C
- 出版年：2014
- 出版时间：May 1, 2014
- 年：2014
- 卷：118
- 期：17
- 页码：9196-9202
- 全文大小：424K
- 年卷期：v.118,no.17(May 1, 2014)
- ISSN：1932-7455
文摘
A new type of hybrid photosensitizer (Po鈥揅30B) was obtained by efficient adsorption of a 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (Po) by Cloisite 30B (C30B)鈥攁 monotallow bis(hydroxyethyl)ammonium-modified montmorillonite clay鈥攆rom acidic solution in methanol. Structural and spectroscopic properties of Po-nanoclay photosensitizer were determined using X-ray diffraction, laser scanning fluorescence confocal microscopy, and electronic absorption/emission spectroscopies. Po is present not only at the surface of the nanoclay but also in the interior of the Po-C30B hybrid material. The obtained material was found to be an efficient photosensitizer for the oxidation of phenol in aqueous solution under irradiation with the visible light (位 > 470 nm). The mechanism and the quantum yield of that process were shown to be strongly pH-dependent. They were controlled by the acid鈥揵ase equilibria of porphyrin associated with imine N-protonation as well as by the ionization of the phenol molecule. The quantitative information regarding these dependencies was obtained. The values of K3 and K4 acid鈥揵ase equilibrium constants were determined (pK3 = 5.88 and pK4 = 2.46) from the absorption spectra recorded during acid鈥揵ase titration and using an evolutionary factor analysis with the mathematical model including dicationic (H2Po2+), monocationic (HPo+), and neutral (Po) porphyrin forms. They were used to evaluate the importance of these forms in singlet oxygen generation by Po鈥揅30B under defined pH conditions. Moreover, the hybrid photosensitizer can be used repeatedly, which makes it possible to use it in industrial applications.