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The vibrational spectroscopy of semiconductor nanostructures can provide important information on their structure. In this work, experimental Raman and infrared spectra are compared with vibrational spectra of CdSe/CdS core/shell nanoplatelets calculated from first principles using the density functional theory. The calculations confirm the two-mode behavior of phonon spectra of nanostructures. An analysis of the experimental spectra reveals the absence of modes with a high amplitude of vibrations of surface atoms, which indicates their strong damping. Taking into account the difference in the damping of different modes and their calculated intensities, all bands in the spectra are unambiguously identified. It is found that the frequencies of longitudinal optical modes in heterostructures are close to the frequencies of LO phonons in bulk strained constituents, whereas the frequencies of transverse modes can differ significantly from those of the corresponding TO phonons. It is shown that an anomalous thickness dependence of CdS TO mode is due to a noticeable surface relaxation of the outer Cd layer in the nanostructure.

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In this work, the hybrids based on nanocrystalline SnO2 or In2O3 semiconductor matrixes and heterocyclic Ru(II) complex are studied as materials for gas sensors operating at room temperature under photoactivation with visible light. Nanocrystalline semiconductor oxides are obtained by chemical precipitation with subsequent thermal annealing and characterized by XRD, SEM and single-point BET methods. The heterocyclic Ru(II) complex is synthesized for the first time and investigated by 1H NMR, 13C NMR APT, MALDI-MS analysis, and UV-Vis spectroscopy. The HOMO and LUMO energies of the Ru(II) complex are calculated from cyclic voltammetry data. The hybrid materials are characterized by TGA-MS analysis and EDX mapping. The optical properties of hybrids are studied by UV-Vis spectroscopy in the diffuse reflection mode. The investigation of spectral dependencies of photoconductivity of hybrid samples demonstrates that the role of organic dye consists in shifting the photosensitivity range towards longer wavelengths. Sensor measurements demonstrate that hybrid materials are able to detect NO2 in the concentration range of 0.25–2 ppm without the use of thermal heating under periodic illumination with even low-energy long-wavelength (red) light.

A highly reproducible photoresponse is observed in nanocrystalline SnO 2 thick films sensitized with CdSe quantum dots. The effect of the SnO 2 matrix microstructure on the photoconductivity kinetics and photoresponse amplitude is demonstrated. The photoresponse of the sensitized SnO 2 thick films reaches more than two orders of magnitude under illumination with the wavelength of the excitonic transition of the quantum dots. Long-term photoconductivity kinetics and photoresponse dependence on illumination intensity reveal power-law behavior inherent to the disordered nature of SnO 2 . The photoconductivity of the samples rises with the coarsening of the granular structure of the SnO 2 matrix. At the saturation region, the photoresponse amplitude remains stable under 10 4 pulses of illumination switching, demonstrating a remarkably high stability.

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It is shown that the impedance spectroscopy allows identification of the resistive switching mechanisms in complex composite structures. This statement was demonstrated on an example of organic based sandwich structures with a modified polymer matrix as an active element. The impedance spectroscopy scanning was performed for a series of intermediate states formed within the switching process. Analysis of the experimentally obtained impedance spectra shows that the electron transport is provided by delocalized charge carriers and proceeds via conducting filaments formed in a highly resistive matrix. The filament configuration changes during the switching. With the shift from isolating to conducting states, single isolated filaments are reorganized into a branched network.