Spectral,Optical, and Photocatalytic Characteristics of Quantum-Sized Particles of CdTe

Methods were developed for the synthesis of quantum-sized particles of CdTe, stabilized in aqueous solutions of thioglycolic acid, using H₂Te or NaHTe produced in situ by electrochemical reduction of tellurium. The spectral and optical characteristics of the synthesized CdTe nanoparticles were studied. It was found that they have photocatalytic activity in the reduction of methylviologen with sodium sulfite.     

Search for inelastic scattering of thermal neutrons by planar magnetic excitations

The experimental technique of searching for high-frequency (～10¹³ Hz) surface magnetic excitations by neutron reflectometry is considered. The first experimental results are reported.     

A Nonlinear Electric Model of the Transient Photoelectric Current in an Organic Photodiode

One of the possible causes of the degradation of organic photodiodes is explained in terms of a nonlinear resistance–capacitance model. Electronic switches for switching photodiode parameters when light is turned on and off are used as nonlinear elements in the equivalent circuit. The model treats the photodiode as a spatially localized photovoltage generator loaded on a passive four-terminal device connected with the electrodes through passive interface layers. The presence of passive layers that have areas with oppositely directed built-in pulling electric fields is the main cause of the degradation of photodiode characteristics. The proposed equivalent circuit well reproduces the experimental transient and steady-state processes in organic photodiodes and can be useful both for measuring the electrical parameters of photodiodes and for studying the processes leading to their degradation.     

Chemical-electric energy conversion effect in zirconia nanopowder systems

Issues concerned with the energy conversion of exothermal heterophase processes are discussed using the physico-chemical interaction between ZrO₂–Y₂O₃ (3 mol %) nanopowder system and atmospheric moisture as an example. The electrical properties of an experimental sample are investigated upon moisture saturation in the case of a molecular-flow density gradient. A probable mechanism for the effect based on the theory of contact phenomena in semiconductors is proposed. The idea of developing chemical-electric converters fabricated from nanoscale materials with dielectric conduction is suggested.     

Estimation of the influence of scattered magnetic fields on the polarization of a beam of thermal neutrons during their propagation through an electromagnet-zero-field-chamber system using the Monte Carlo method

In spectrometers with polarized neutrons, the nonuniformity of the guiding field and also the scattered magnetic fields of separate components, which determine the behavior of the polarization vector, lead to partial polarization loss and decreasing accuracy of the obtained experimental data. A module created using the VITESS program package allows the behavior of neutron-beam polarization in fields measured separately or calculated using specialized software and imported into the VITESS to be simulated. This makes it possible to significantly improve the agreement between the simulation results and experimental data. This paper is dedicated to studying the behavior of the neutron polarization vector when neutrons propagate through a system of magnetic fields produced by an electromagnet and a zero-field chamber. Based on the performed calculations, the problem of optimization of the arrangement of the separate components of a spin-echo spectrometer is solved in this paper.     

Stable vector bundles over cuspidal cubics

We give a complete classification of stable vector bundles over a cuspidal cubic and calculate their cohomologies. The technique of matrix problems is used, similar to [2, 3].     

Structure and physicochemical properties of thin film photosemiconductor cells based on porphine derivatives

Photosemiconductor thin films based on two organic porphine derivatives have been investigated. These compounds have different pendent groups; the film morphology, along with the specific fabrication technique, is determined to a great extent by these groups. The films have been fabricated by vacuum sputtering and using the Langmuir?Schaefer method. According to the atomic force microscopy (AFM) data, the Langmuir?Schaefer films are more homogeneous than the sputtered ones. It is shown that the sputtered films based on substituted porphine have a looser stacking than the initial analog. A spectroscopy study revealed a bathochromic shift of the Soret band in the Langmuir?Schaefer films–sputtered films series. This shift is explained by the increase in the concentration and size of molecular aggregates in sputtered films. It is shown that a polycrystalline C₆₀ fullerene film deposited onto an amorphous substituted porphine layer improves the photoelectric characteristics of the latter. Both the time stability of the photodiode structure and its ampere?watt sensitivity increase (by a factor of 10 in the transition regime). The steady-state current does not change. The effect of polarity reversal of the photovoltaic signal is observed in a planar С₆₀?substituted metalloporphine heterostructure, which is similar to the pyroelectric effect. The polarity reversal can be explained by the contribution of the trap charge and discharge current at the interface between the amorphous photosemiconductor and crystalline photosemiconductor to the resulting photoelectric current.     

A neutron reflectometer on thermal neutrons with variable wavelength

A neutron reflectometer for investigating layered structures was developed as an additional model of the MOND diffractometer on the horizontal experimental channel no. 4 of the IR-8 reactor. The reflectometer was manufactured using standard tuning devices of linear and rotation translations. The experiments were carried out on model samples of layered structures of nanosized thickness. The technical characteristics of the reflectometer were determined and compared with those of the available reflectometric installations on stationary neutron sources.