Photocatalytic oxidation of sulfide ion catalyzed by phthalocyanine modified titania

Photodegradation of organic pollutants in water by immobilized porphyrins and phthalocyanines

New methods for water treatment are required as a result from an increasing awareness in the reduction of the pollution impact in the environment. In the perspective of the photo-oxidation of organic pollutants present in water, the principal incentive for the preparation of heterogeneous photocatalysts is their easy recovery from the reaction mixture, which allows their reuse in successive runs, minimizing the loss of their original photocatalytic properties. Different types of supports can be used in the immobilization of photoactive species, such as porphyrins (Pors) and phthalocyanines (Pcs). This mini-review will consider the different methodologies for the immobilization of Pors and Pcs and their photocatalytic performance in the photodegradation of organic pollutants in water, addressing also their recycling ability in successive water treatments.

Metallophthalocyanines and metalloporphyrins as electrocatalysts: a case of hydrogen peroxide and glucose detection

This review summarizes the applications of metallophthalocyanine (MPc) and metallo-porphyrin (MP) complexes as electrocatalysts immobilized onto various electrodes for the detection of hydrogen peroxide and glucose. The uses of MPc and MP complexes as electron mediators for the detection of glucose at glucose oxidase modified surfaces are discussed.

Spectrophotometric studies of visible light induced photocatalytic degradation of methyl orange using phthalocyanine-modified Fe-doped TiO2 nanocrystals

In this paper, preparation and visible light induced photocatalytic activity of phthalocyanine-modified Fe-doped TiO(2) nanocrystals (Pc/Fe-TiO(2)) with different Fe doping content (0, 0.05, 0.5 and 3.0 mol% Fe) as photocatalysts for the degradation of methyl orange have been reported. The study carried out using XRD, FT-IR, EDX, BET, DRS, UV-Vis, SEM and TEM techniques. Results revealed that modified TiO(2) nanocrystals possessed only the anatase phase with crystal sizes of about 10-23 nm and high surface areas of 2.8-37.3 m(2)/g. It can be seen phthalocyanine and Fe(3+) ion exist in photocatalysts based on analysis of FT-IR and EDX. The doping amount of Fe remarkably affects the activity of modified TiO(2) nanocrystals as catalysts. The 0.5 mol% Fe doping exhibited enhanced photocatalytic activity in this work. It was found that phthalocyanine and Fe induced a shift in the energy band gap to lower energies, which changes from 3.26 to 2.26 eV for pure TiO(2) and Pc/3% Fe-TiO(2) nanocrystals, respectively. Results of the degradation of methyl orange revealed that modified TiO(2) nanocrystals showed much more photocatalytic activity than pure TiO(2) under visible light which makes the applicability of TiO(2) photocatalysts even more versatile.

Photocatalytic degradation of methylene blue on magnetically separable FePc/Fe3O4 nanocomposite under visible irradiation

A novel magnetically separable photocatalyst iron phthalocyanine/Fe3O4 (FePc/Fe3O4) nanocomposite was easily prepared by an organic–inorganic complexation technique, and characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and Fourier transform-infrared (FTIR). This functional nanocomposite has been found to exhibit high catalytic activity in the presence of added hydrogen peroxide, for oxidative degradation of methylene blue (MB) under visible light irradiation. Under these conditions, MB (10 mg/l) underwent about 78 % oxidation in 2 h, and the catalyst still retained high activity after five catalytic cycles. Intervening recovery was easily achieved by changing the external magnetic field.

Photosensitized oxidation of sulfides: discriminating between the singlet-oxygen mechanism and electron transfer involving superoxide anion or molecular oxygen

The oxidation of diethyl and diphenyl sulfide photosensitized by dicyanoanthracene (DCA), N-methylquinolinium tetrafluoroborate (NMQ(+)), and triphenylpyrylium tetrafluoroborate (TPP(+)) has been explored by steady-state and laser flash photolysis studies in acetonitrile, methanol, and 1,2-dichloroethane. In the Et(2)S/DCA system sulfide-enhanced intersystem crossing leads to generation of (1)O(2), which eventually gives the sulfoxide via a persulfoxide; this mechanism plays no role with Ph(2)S, though enhanced formation of (3)DCA has been demonstrated. In all other cases an electron-transfer (ET) mechanism is involved. Electron-transfer sulfoxidation occurs with efficiency essentially independent of the sulfide structure, is subject to quenching by benzoquinone, and does not lead to Ph(2)SO cooxidation. Formation of the radical cations R(2)S(*+) has been assessed by flash photolysis (medium-dependent yield, dichloroethane>>CH(3)CN>CH(3)OH) and confirmed by quenching with 1,4-dimethoxybenzene. Electron-transfer oxidations occur both when the superoxide anion is generated by the reduced sensitizer (DCA(*-), NMQ(*)) and when this is not the case (TPP(*)). Although it is possible that different mechanisms operate with different ET sensitizers, a plausible unitary mechanism can be proposed. This considers that reaction between R(2)S(*+) and O(2)(*-) mainly involves back electron transfer, whereas sulfoxidation results primarily from the reaction of the sulfide radical cation with molecular oxygen. Calculations indeed show that the initially formed fleeting complex RS(2)(+)...O-O(*) adds to a sulfide molecule and gives strongly stabilized R(2)S-O(*)-(+)O-SR(2) via an accessible transition state. This intermediate gives the sulfoxide, probably via a radical cation chain path. This mechanism explains the larger scope of ET sulfoxidation with respect to the singlet-oxygen process.