Raevskaya A. Photocatalytic and catalytic oxidation of sulfur-containing ions by oxygen with the participation of CdS and CuS nanoparticles

CdS nanoparticles with quantum confinement effects have been synthesized, their spectral characteristics and photochemical behaviour under stationary and pulse irradiation have been examined. From the absorption spectra of CdS colloids the basic characteristics of CdS nanoparticles (namely the mean size of the particles, their band gap, valence and conduction bands potentials, oscillator strength of the first exitonic transition etc.) have been derived. It has been shown that bleaching bands arise in the non-stationary differential optical spectra of CdS colloids under the pulse irradiation as a result of free electrons accumulation within the semiconductor nanoparticles. Kinetics regularities of non-stationary signals decay have been elucidated, mechanisms of fast photoprocesses have been proposed. It was found that CdS nanoparticles are the efficient photocatalysts of hydrosulfide and sulfite ions air oxidation. Kinetic peculiarities of these reactions have been examined in details. It was established that these reactions occur via a chain-radical mechanism. Kinetic equations of the photoreactions under examination have been derived. In case of hydrosulfide ions, it was established that the oxidation can occur not only through a chain-radical route but also via the interaction between photo-generated CdS valence band holes with adsorbed HS- on the surface of semiconductor. CuS nanoparticles with quantum confinement effects have been synthesized, their spectral features in the visible and near infrared regions have been studied, correlation dependence between the band gap of CuS nanoparticles and their mean diameter has been defined. It was found that CuS nanoparticles act as efficient catalysts of hydrosulfide ions oxidation by methylviologen and molecular oxygen. It was shown that hydrosulfide catalytic oxidation occur via a chain-radical mechanism.