Possibility of obtaining TiO2 material by plasma dynamic method into an air atmosphere

This paper shows the possibility to synthesize directly the titanium dioxide in a supersonic jet of an electric discharge erosive plasma. Using the X-ray diffractometry it is shown that the obtained product contains two main crystalline phases: anatase and rutile with tetragonal syngony. The size of the coherent scattering region is less 100 nm

Band-gap and sub-band-gap photoelectrochemical processes at nanocrystalline CdS grown on ZnO by successive ionic layer adsorption and reaction method

Cadmium sulfide nanoparticle (NP) deposition by the successive ionic layer adsorption and reaction (SILAR) method on the surface of mesoporous ZnO micro-platelets with a large specific surface area (110 ± 10 m2g− 1) results in the formation of ZnO/CdS heterostructures exhibiting a high incident photon-to-current conversion efficiency (Y) not only within the region of CdS fundamental absorption (Ymax = 90%; 0.1 M Na2S + 0.1 M Na2SO3), but also in the sub-band-gap (SBG) range (Ymax = 25%). The onset potentials of SBG photoelectrochemical processes are more positive than the band-gap (BG) onset potential by up to 100 mV. A maximum incident photon-to-current conversion efficiency value for SBG processes is observed at larger amount of deposited CdS in comparison with the case of BG ones. The Urbach energy (EU) of CdS NPs determined from the photocurrent spectra reaches a maximal value on an early deposition stage (EU = 93 mV at SILAR cycle number N = 5), then lowers somewhat (EU = 73 mV at N = 10) and remains steady in the range of N from 20 to 300 (EU = 67 ± 1 mV). High efficiency of the photoelectrochemical SBG processes are interpreted in terms of light scattering in the ZnO/CdS heterostructures

Effect of [OH-] linkages on luminescent properties of ZnO nanoparticles

Optical properties of ZnO nanoparticles prepared from a simple chemical method using sodium zincate bath show strong white light emission. X-ray absorption fine structure studies reveal a completely different local environment around Zn in these ZnO nanoparticles. The observed luminescence properties and local structural changes have been explained on the basis of a linkage between Zn and OH- ions in the surface layers of ZnO nanoparticles.Comment: J. Phys. Chem. C. (2011) (in print

Photoluminescence and structural properties of CdSe quantum dot-gelatin composite films

a b s t r a c t Optical and structural properties of composite films of CdSe quantum dots (QDs) embedded in gelatin matrix have been investigated by photoluminescence (PL), optical absorption and X-ray diffraction (XRD) methods. The optical absorption of the composite in the visible spectral range is found to be determined mainly by light absorption in the QDs. The decrease of the film transparency and the shift of the absorption edge to lower energies observed upon thermal annealing of the films at 140-160 1C are ascribed to the formation of chromophore groups in gelatin matrix. XRD patterns of the composite revealed helix to coil transition in gelatin matrix under thermal annealing of the composite at 100-160 1C. It is found that PL spectra of the composite are dominated by exciton and defect-related emission of the QDs and also contain weak emission of gelatin matrix. It is found that thermal annealing of the composite at 100-160 1C changes PL intensity and produces the shift of the PL bands to lower energies. As the annealed composite was kept in air for several months, the shift of exciton-related PL band position restored partially and the PL intensity increased. It is proposed that the increase of the PL intensity upon the thermal annealing of composite at 140 1C can be used for enhancement of the QDrelated PL. Changes that occurred in the PL spectra of composite are ascribed to structural and chemical transformations in gelatin matrix and at the QD/gelatin interface

Band-gap and sub-band-gap photoelectrochemical processes at nanocrystalline CdS grown on ZnO by successive ionic layer adsorption and reaction method

Cadmium sulfide nanoparticle (NP) deposition by the successive ionic layer adsorption and reaction (SILAR) method on the surface of mesoporous ZnO micro-platelets with a large specific surface area (110 ± 10 m2g− 1) results in the formation of ZnO/CdS heterostructures exhibiting a high incident photon-to-current conversion efficiency (Y) not only within the region of CdS fundamental absorption (Ymax = 90%; 0.1 M Na2S + 0.1 M Na2SO3), but also in the sub-band-gap (SBG) range (Ymax = 25%). The onset potentials of SBG photoelectrochemical processes are more positive than the band-gap (BG) onset potential by up to 100 mV. A maximum incident photon-to-current conversion efficiency value for SBG processes is observed at larger amount of deposited CdS in comparison with the case of BG ones. The Urbach energy (EU) of CdS NPs determined from the photocurrent spectra reaches a maximal value on an early deposition stage (EU = 93 mV at SILAR cycle number N = 5), then lowers somewhat (EU = 73 mV at N = 10) and remains steady in the range of N from 20 to 300 (EU = 67 ± 1 mV). High efficiency of the photoelectrochemical SBG processes are interpreted in terms of light scattering in the ZnO/CdS heterostructures

Optically detected magnetic resonance study of relaxation/emission processes in the nanoparticle-polymer composite

Two nanocomposites containing CdS nanoparticles in polymeric matrices were studied using the photoluminescence (PL) and optically detected magnetic resonance (ODMR) methods. Due to equal sizes of NPs in the composites (~5 nm) but different matrices – the oxygen-containing polymer PVA (polyvinyl alcohol) and oxygen-free polymer PEI (polyethyleneimine) – differences of nanocomposites properties are predominantly caused by different interfacial conditions. ODMR spectra have revealed five types of centers related to the PL emission – four centers involved in radiative recombination and one center related to non-radiative recombination processes. The oxygen-related interfacial center in CdS/PVA (LK1-center) and sulfur vacancy center in CdS/PEI (Vs-center) were identified