Photocatalytic Oxidation of Hydrosulfide Ions by Molecular Oxygen Over Cadmium Sulfide Nanoparticles

Photocatalytic activity of CdS nanoparticles in hydrosulfide-ions air oxidation was revealed and thoroughly investigated. HS⁻ photooxidation in the presence of CdS nanoparticles results predominantly in the formation of SO₃ ²⁻ and SO₄ ²⁻ ions. Photocatalytic activity of ultrasmall CdS crystallites in HS^– photooxidation is much more prononced as compared to bulk CdS crystals due to high surface area of nanoparticles, their negligible light scattering, improved separation of photogenerated charge carriers etc. It was shown that hydrosulfide ions can be oxidized in two ways. The first is HS⁻ oxidation by the CdS valence band holes. This process rate depends on the rate of comparatively slow reaction between molecular oxygen and CdS conduction band electrons. The second reaction route is the chain-radical HS⁻ oxidation induced by photoexcited CdS nanoparticles and propagating in the bulk of a solution. In conditions favourable to chain-radical oxidation of HS⁻(i.e. at low light intensities and CdS concentration and high oxygen and Na₂S concentrations) quantum yields of the photoreaction reach 2.5.     

Heterogeneous Photocatalytic Selective Reductive Transformations of Organic Compounds: a Review

Theoretical and Experimental Chemistry - We have reviewed the state-of-the-art in heterogeneous photocatalytic systems derived from various semiconductors, their composites, and other materials for...     

Photocatalytic production of hydrogen in systems based on Cd<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Zn<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>S/Ni<Superscript>0</Superscript> nanostructures

A relation was established between the composition of Cd _x Zn_1–x S nanoparticles and their ability to accumulate excess negative charge during irradiation. The rate of expenditure of the accumulated charge depends on the composition of the nanoparticles and is determined by their electric capacitance. A correlation was found between the photocatalytic activity of the Cd _x Zn_1–x S nanoparticles in the release of hydrogen from solutions of Na₂SO₃, their composition, and their capacity for photoinduced accumulation of excess charge. It was shown that Ni⁰ nanoparticles photodeposited on the surface of Cd _x Zn_1–x S are effective cocatalysts for the release of hydrogen. It was found that Zn^II additions in photocatalytic systems based on Cd _x Zn_1–x S/Ni⁰ nanostructures have a promoting action on the release of hydrogen from water–ethanol mixtures. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 45, No. 1, pp. 8–16, January-February, 2009.     

Effect of the method of production of TiO<Subscript>2</Subscript>/CdS nanohetero film structures on the effectiveness of photoinduced charge separation

The properties of TiO₂/CdS nanohetero structures produced by the chemical and photocatalytic deposition of CdS nanoparticles on the surface of nanocrystalline films of TiO₂ under the conditions of laser pulse photolysis were studied. It was shown that in the case of photocatalytically formed TiO₂/CdS nanocomposites the spatial separation of the photogenerated charges between the components of the hetero structure, leading to the formation of intermediates of the photochemical transformations (Ti^III centers in the TiO₂ nanoparticles and S^– radical-anions in the CdS nanoparticles), is an order of magnitude more effective.     

Characterization of semiconductor core-shell nanoparticles by resonant Raman scattering and photoluminescence spectroscopy

Colloidal CdSe nanoparticles (NPs), passivated with CdS and ZnS, were characterized by resonant Raman scattering and photoluminescence (PL). The effect of the passivating shell, its volume and formation procedure on optical and vibrational spectra is discussed. Analyzing the Raman peaks due to optical phonons inside the core and those related to the core-shell interface allows some understanding of the relation between the core-shell structure and its PL properties to be achieved. In particular, a compositional intermixing at the core/shell interface of the NPs was deduced from the Raman spectra, which can noticeably affect their PL intensity.     

Photocatalytic Selective Oxidation of Organic Compounds in Graphitic Carbon Nitride Systems: A Review

Theoretical and Experimental Chemistry - Recent work is reviewed concerning photocatalytic systems derived from graphitic carbon nitride (GCN) for the selective oxidation of various organic...     

Photochemical reduction of graphene oxide in colloidal solution

Stable aqueous colloidal solutions of graphene oxide stabilized with sodium polyphosphate were obtained. During irradiation of the colloids the oxygen-containing groups of the graphene oxide are eliminated, and the aromatic graphite-like regions in its composition are expanded. This is accompanied by decrease in the energy of the electronic transitions E_bg in such sp2-hybridized fragments. Photoreduction of the colloidal particles of graphene oxide leads to changes in their hydrodynamic size, resulting from 𝜋𝜋 interactions between the aromatic fragments in the particles. It was shown that the E_bg value can be varied purposefully in the range of 0.5-1.9 eV by varying the experimental conditions.