Preparation of colloidal CdSe and CdS/CdSe nanoparticles from sodium selenosulfate in aqueous polymers solutions

Cadmium selenide nanoparticles formation at the interaction between CdCl2 and Na2SeSO3 in aqueous solutions of sodium polyphosphate and gelatin has been studied. Structural and optical properties of CdSe nanoparticles have been characterized. It has been shown that the temperature and the ratio of reagents concentrations are the basic parameters, controlling the size of CdSe nanoparticles. Photocatalytic activity of CdS nanoparticles in Na2SeSO3 reduction has been found and investigated; structural and optical properties of binary CdS/CdSe nanoparticles have been characterized. This photoreaction, when carried out in the presence of CdCl2, results in the formation of composite CdS/CdSe nanoparticles. It has been shown that slow interaction of adsorbed selenosulfate with surface-trapped CdS conduction band electrons is the limiting stage of the photocatalytic reaction.     

(∈, ∈∨q)-fuzzy subnear-rings and (∈, ∈∨q)-fuzzy ideals of near-rings

In this paper, we introduce the notions of (∈, ∈∨q)-fuzzy subnear-ring, (∈, ∈∨q)-fuzzy ideal and (∈, ∈∨q)-fuzzy quasi-ideal of near-rings and find more generalized concepts than those introduced by others. The characterization of such (∈, ∈ ∨q)-fuzzy ideals are also obtained.     

Photopolymerization of Butyl Methacrylate Initiated by Hydrated Ferric Oxide Nanoparticles

Colloidal hydrated ferric oxide nanoparticles in 2-propanol solution are efficient initiators of the polymerization of butyl methacrylate by the action of UV and visible light. The kinetics of this reaction was established and elucidated. A mechanism of the photoinitiated polymerization involving photoexcited semiconductor particles was proposed in accord with the experimental and literature data.     

Photochemical reduction of sulfur in the presence of ZnO nanoparticles in ethanol

The photochemical reduction of sulfur by the action of ZnO nanoparticles of various shapes and sizes under the conditions of stationary and pulsed photoexcitation was studied. The mechanism of this process was proved; the main route to the formation of the reaction product zinc sulfide is reduction of the sulfur by photochemically produced metallic zinc. It was demonstrated that ordered agglomerates of ZnS nanoparticles in the form of nanotubes and nanorods are formed in the systems based on ZnO nanorods.     

Photocatalytic production of hydrogen from water–alcohol media with the participation of mesoporous TiO<Subscript>2</Subscript>

Samples of mesoporous TiO₂ containing 80-85% of anatase and 15-20% of rutile with average particle and pore sizes of ∼10 nm and specific surface areas of 70 m²/g were obtained. The nanohetero structures TiO₂/Cu formed during photocatalytic reduction of Cu^II exhibit photocatalytic activity in the release of hydrogen from water–ethanol mixtures. The quantum yield with respect to atomic hydrogen amounts to 1.5.     

The effect of bio-conjugation on aging of the photoluminescence in CdSeTe–ZnS core–shell quantum dots

The aging of the photoluminescence (PL) in bio-conjugated and non-conjugated CdSeTe–ZnS core–shell quantum dots (QDs) is studied by the micro-PL, micro-Raman and X-ray diffraction (XRD) in the samples of buffered QD solution dried on a crystalline Si wafer and stored in the atmospheric ambience for about 2 years. The aging of the PL consists in a “blue” spectral shift of the PL band, an increase in PL band half-width and the decrease in the PL intensity. These changes are more pronounced in the conjugated QD samples. The XRD analysis of the aged samples revealed that the QD core diameter is reduced by ∼1.5 nm in the conjugated QDs as compared to the non-conjugated ones. The possible mechanism of PL spectrum aging is the oxidation that decreases the QD core dimension. It is concluded that the bio-conjugation promotes QD oxidation and the mechanism of the effect is proposed.     

Structural and optical characterization of colloidal Se nanoparticles prepared via the acidic decomposition of sodium selenosulfate

Colloidal selenium nanoparticles (NPs) were synthesized via acidic decomposition of sodium selenosulfate. The effects of synthesis and post-synthesis treatment conditions on the size, structure and size distribution of the Se nanoparticles are discussed. It is shown that the decomposition of sodium selenosulfate with non-oxidative acids (e.g., HCl) in aqueous solutions of polymers (sodium polyphosphate, gelatin, polyvinyl alcohol, polyethyleneglycole) and surfactants (sodium dodecylsulfonate, cetylpyridinium chloride) results in the formation of amorphous 25–200 nm Se nanoparticles converting upon ageing at 90 °C into trigonal 150–250 nm Se nanocrystals. Optical properties (absorption and Raman spectra) of freshly prepared and aged Se nanoparticles both in colloidal solutions and in polymeric (polyvinyl alcohol) films are analyzed.     

Photochemical synthesis of ZnO/Ag nanocomposites

Composite ZnO/Ag nanoparticles have been formed via the photocatalytic reduction of silver nitrate over the ZnO nanocrystals, their optical, electrophysical and photochemical properties have been investigated. Mie theory has been applied to analyze the structure of the absorption spectra of ZnO/Ag nanocomposite. The irradiation effects upon the optical properties of ZnO/Ag nanostructure have been investigated. It has been found that the irradiation of ZnO/Ag nanoparticles results in electrons accumulation by both the semiconductor and the metallic components of the nanocomposite. It has been found that silver nitrate can be photochemically deposited onto the surface of ZnO nanoparticles under the illumination with the visible light in the presence of the sensitizer – methylene blue. Kinetics of the sensitized Ag(I) photoredution has been studied. It has been concluded that the key stage of this process is the electron injection from singlet-excited methylene blue molecule into ZnO nanoparticle.     

Preparation and spectral properties of high-efficiency luminescent polyethylenimine-stabilized CdS quantum dots

Feasibility was demonstrated for obtaining ultrasmall colloidal CdS nanoparticles (with diameter about 2 nm) stabilized in aqueous solution by polyethylenimine with a narrow size distribution (~10%) and luminescing at 400-600 nm (quantum yield about 10%). Complexation between Cd^II and polyethylenimine is a necessary condition for formation of such nanoparticles.