Reversible Humidity-Driven Transformation of a Bimetallic {EuCo} Molecular Material: Structural, Sorption, and Photoluminescence Studies

Functional molecule-based solids built of metal complexes can reveal a great impact of external stimuli upon their optical, magnetic, electric, and mechanical properties. We report a novel molecular material, {[EuIII(H2O)3(pyrone)4][CoIII(CN)6]}·nH2O (1, n = 2; 2, n = 1), which was obtained by the self-assembly of Eu3+ and [Co(CN)6]3− ions in the presence of a small 2-pyrrolidinone (pyrone) ligand in an aqueous medium. The as-synthesized material, 1, consists of dinuclear cyanido-bridged {EuCo} molecules accompanied by two H-bonded water molecules. By lowering the relative humidity (RH) below 30% at room temperature, 1 undergoes a single-crystal-to-single-crystal transformation related to the partial removal of crystallization water molecules which results in the new crystalline phase, 2. Both 1 and 2 solvates exhibit pronounced EuIII-centered visible photoluminescence. However, they differ in the energy splitting of the main emission band of a 5D0 → 7F2 origin, and the emission lifetime, which is longer in the partially dehydrated 2. As the 1 ↔ 2 structural transformation can be repeatedly reversed by changing the RH value, the reported material shows a room-temperature switching of detailed luminescent features including the ratio between emission components and the emission lifetime values.

Формирование гетероперехода II типа в полупроводниковой структуре InAsSb/InAsSbP

The results of studying the electroluminescent and current-voltage characteristics of the n-InAs/n-InAsSb/p-InAsSbP heterostructure grown by gas-phase epitaxy from organometallic compounds are presented. Intense electroluminescence was detected in the spectral range 0.23–0.29 eV at the temperature T = 77 K. The position of the maximum of the main emission band (h ~ 0.24 eV) showed a noticeable “blue” shift with increasing applied forward bias. Based on the performed studies, it was concluded that there is a staggered type II heterojunction at the InAs0.84Sb0.16/InAs0.32Sb0.28P0.40 heterointerface, which is confirmed by the results of the calculation of the energy band diagram.

Спектроскопические свойства полимерных пленок, активированных супрамолекулярным наноалмазным комплексом европия с батофенантролином

For the first time, using the supramolecular diamond-containing europium (III) complex with bathophenanthroline, new luminescent films were obtained, converting UV radiation in the wavelength range of 220–410 nm with high efficiency to luminescence of europium ions, with the ability to control the degree of monochromaticity of radiation in the main emission band of Eu3+ ions with maximum of 615 nm. It was found that the shape of the excitation spectra, the half-width of the main emission band of 615 nm (transition 5D0–7F2), the values of quantum yields (within ~ 0.3–0.8) depend on the type of matrix material. The proposed optical materials can be used in the development of various light-emitting devices: screens, indicators, solar concentrators, organic light-emitting diodes, laser media.

Investigation of optical properties and local structure of Gd3+ doped nano-crystalline GeSe2

Pure and Gd-doped nano-crystalline GeSe2 were prepared by the melt-quenching technique. Structure analysis using Rietveld program suggests monoclinic structure for both virgin and doped samples with nano-particle size 41 nm for GeSe2 and 48 nm for Gd-doped sample. A wide optical band gap as estimated from absorbance measurements is 4.1 and 4.8 eV for pure and doped samples in accordance with the confinement effects. Raman spectra show two unresolved components at [Formula: see text]202 cm[Formula: see text] with broad line width. Also, well identified low intensity ([Formula: see text] [Formula: see text] 145 cm[Formula: see text]) and high intensity ([Formula: see text] [Formula: see text] 250 cm[Formula: see text]) bands are detected. For Gd-doped sample, the main band is shifted to lower energies and its full width at half maximum (FWHM) is reduced by [Formula: see text]50% accompanied by an intensity increase of about [Formula: see text]17 fold times. The photoluminescence analysis of the pure sample shows a main emission band at [Formula: see text]604 nm. This band is split into two separated bands with higher intensity. The detected emission bands at wavelength [Formula: see text]650 nm are assigned to transmission from 6G[Formula: see text] to the different 6P[Formula: see text] terms.