Microwave Absorbing by Conducting Hybrid Nanocomposites Based on Magnetite Nanoparticles

Microwave absorbing properties of hybrid nanocomposites of Fe3O4 nanoparticles with carbon nanotubes and polyaniline (PANI) doped with dodecylbenzenesulfonic acid have been studied. It has been found that the the addition of nanostructured components increases the absorbtion of the nanocomposites. Moreover, CNTs affect the absorbtion in high frequency range, and Fe3O4 nanoparticles – in low frequency range. Introduction of conductive PANI into the matrix enhances the influence of nanomaterials on the absorbance of the films. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3491

Injection Spectroscopy of Deep Traps in Nanostructured Films of Cadmium Sulfide

Nanocrystallin CdS films with controlled stoichiometry deposited by CSVS were investigated by meth-od of the current-voltage characteristics in ITO/CdS /In structures. It was shown that in the case of cadmi-um excess (S Cd) charge flow mechanism is deter-mined by monomolecular recombination. In the band gap of CdS with excess of cadmium there was detect-ed localized states with energy Et = 0.514 ± 0.026 eV, while in the material with Excess sulfur there are two localized states with energy Et1 = 0.514 ± 0.026 eV and Et2 = 0.700 ± 0.026 eV. Full concentration of lo-calized states is more than 2·1021 m-3 – 5·1022 m-3. Dependence of injection in parameters and nature of in-jection in the structures based on nanostructured CdS films on their stoichiometry was determined When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3524

Injection Spectroscopy of Deep Traps in Nanostructured Films of Cadmium Sulfide

Nanocrystallin CdS films with controlled stoichiometry deposited by CSVS were investigated by meth- od of the current-voltage characteristics in ITO/CdS /In structures. It was shown that in the case of cadmi- um excess (S <Cd) charge flow mechanism both in the dark and under illumination is determined by bimo- lecular recombination in the material. In the case of excess sulfur (S>Cd) charge flow mechanism is deter- mined by monomolecular recombination. In the band gap of CdS with excess of cadmium there was detected localized states with energy Et = 0.514 ± 0.026 eV, while in the material with Excess sulfur there are two localized states with energy Et1 = 0.514 ± 0.026 eV and Et2 = 0.700 ± 0.026 eV. Full concentration of localized states is more than 2·1021 m-3 – 5·1022 m-3. Dependence of injection in parameters and nature of injection in the structures based on nanostructured CdS films on their stoichiometry was determined. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3390

Electrochemical stability and transformations of fluorinated poly(2,6-dimethyl-1,4-phenylene oxide)

Fluorination of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) leads to narrowing of its window of electrochemical stability in a cathodic range of potentials. It is found this is connected with appearance of both perfluorinated and incompletely fluorinated units in the polymer. The former units are liable to electrochemical reduction (at potentials <−2.0 V) followed by elimination of fluorine anions and the latter react with basic products (generated at potentials <−1.8 V) of electrochemical reduction of the background solution. In the both cases this results in appearance of conjugated multiple bonds in the fluorinated macromolecules. Quantities of these units in fluorinated PPO were determined with a help of direct and indirect electrochemical reductive degradation techniques

Reactions and stability of fluorinated poly(vinyl trimethylsilane) in electrochemical systems

Fluorinated poly(vinyl trimethylsilane) (FPVTMS) unlike virgin PVTMS is able to participate in electrochemical reactions and undergoes direct and indirect electrochemical reductive degradation. Specifically, its perfluorinated units are reduced irreversibly at a glass carbon electrode in a 0.05-M (C4H9)4ClO4 solution in dimethylformamide with subsequent splitting of C–F bonds and formation of conjugated double bonds in macromolecules at the polymer surface. On the other hand, the incompletely fluorinated units at the FPVTMS surface interact with the previously electrochemically reduced background solution to be dehydrofluorinated. This is accompanied by the formation of conjugated double bonds and dissolution of the dehydrofluorinated layer also. The data obtained allowed distinguishing the incompletely fluorinated units from the perfluorinated ones in the fluorinated layer of FPVTMS. Moreover, the quantity of the incompletely fluorinated units in FPVTMS can be determined. It was found that the strengthening of fluorination conditions led to an enhancement of the electrochemically induced FPVTMS transformations

Study of the dissociation of imidazoline derivatives by means of a field mass spectrometer

[No abstract available

Study of the dissociation of imidazoline derivatives by means of a field mass spectrometer

[No abstract available

Macroscopic versus microscopic photovoltaic response of heterojunctions based on mechanochemically prepared nanopowders of kesterite and n-type semiconductors

Mechanochemically prepared nanopowder of selenium-free kesterite Cu2ZnSnS4 (CZTS) in combination with n-type semiconductors, i.e., CdS, ZnO and TiO2, was tested in planar and bulk-heterojunction solar cells. The samples have been studied by macroscopic current-voltage (I-V) measurements and Kelvin-probe atomic-force microscopy (KPFM). KPFM images taken under light illumination showed the distribution of the potential across the surface, with negative potential on the n-type semiconductor domains and positive potential on the CZTS domains, which indicated charge separation at the interface of the counterparts. The best result was found for the CdS-CZTS composition, which showed a potential difference between the domains up to 250 mV. These results were compared with the planar heterojunctions of CdS/CZTS and TiO2/CZTS, where CZTS nanopowder was pressed/deposited directly onto the surface of films of the corresponding n-type semiconductors. Again, I-V characteristics showed that cells based on CdS/CZTS heterojunctions have the best performance, with a photovoltage up to 200 mV and photocurrent densities up to 0.1 mA/cm2. However, the carrier generation was found to occur mainly in the CdS semiconductor, while CZTS showed no photo-response and served as the hole-transporting layer only. It is concluded that sensitization of the kesterite powder obtained by mechanochemical method is necessary to improve the performance of the corresponding solar cells

Linear electro-optical behaviour of hybrid nanocomposites based on silicon carbide nanocrystals and polymer matrices

International audienceAn electro-optical activity has been recently reported for hybrid nanocomposite thin films where inorganic silicon carbide nanocrystals (ncSiC) are incorporated into polymer matrices. The role of the interface SiC polymer is suggested as the origin of the observed second order nonlinear optical susceptibility in the hybrid materials based on poly-(methylmethacrylate) (PMMA) or poly-(N-vinylcarbazole) matrices. In this work, we report an analysis of the electro-optical response of this hybrid system as a function of the ncSiC content and surface state in order to precise the interface effect in the observed phenomenon. Two specific ncSiC samples with similar morphology and different surface states are incorporated in the PMMA matrix. The effective Pockels parameters of the corresponding hybrid nanocomposites have been estimated up to 7.59±0.74pm/V (1wt.% of ncSiC in the matrix). The interfacial region ncSiC polymer is found to play the main role in the observed effect. Particularly, the electronic defects on the ncSiC nanocrystal surface modify the interfacial electrical interactions between the two components. The results are interpreted and discussed on the basis of the strong influence of these active centers in the interfacial region at the nanoscale, which are found to monitor the local hyperpolarizabilities and the macroscopic nonlinear optical susceptibilities. This approach allows us to complete the description and understanding of the electro-optical response in the hybrid SiC/polymer systems