Anticorrosive properties of N-acetylmethylpyridinium bromides

The inhibiting action of N-acetylmethylpyridinium bromides on the corrosion of low-carbon steel in a 3 M sulfuric acid solution at 20, 40, 60, and 80°C was studied. The mechanism of their protective action was examined using electrochemical methods. Compounds exhibiting high anticorrosive properties at elevated temperatures were found.     

Förster Energy Transfer in Arrays of Epitaxial CdSe/ZnSe Quantum Dots Involving Bright and Dark Excitons

Using time-resolved photoluminescence (PL) spectroscopy, we establish the presence of the Förster energy transfer mechanism between two arrays of epitaxial CdSe/ZnSe quantum dots (QDs) of different sizes. The mechanism operates through dipole–dipole interaction between ground excitonic states of the smaller QDs and excited states of the larger QDs. The dependence of energy transfer efficiency on the width of barrier separating the QD insets is shown to be in line with the Förster mechanism. The temperature dependence of the PL decay times and PL intensity suggests the involvement of dark excitons in the energy transfer process.     

Excitons and Biexcitons in Spheroidal Quantum Dots A<Subscript>2</Subscript>B<Subscript>6</Subscript>

In the limit of strong quantum confinement the lower energy states of excitons and biexcitons in spheroidal quantum dots of semiconductors with a fourfold degenerate vertex of the valence band, which are active in the dipole approximation at one- and two-photon excitation, have been considered. The comparative analysis of the order of energy levels of the hole in the potentials of the infinitely deep quantum well and a three-dimensional harmonic oscillator taking into account the axial anisotropy of the quantum dot (QD) shape is carried out. It is shown that the anisotropy of the QD shape can lead to the opposite sign of splitting with respect to angular momentum projection ±3/2, ±1/2 for spatially odd (1P_3/2) and even (1S_3/2) levels of the hole. At the same time, in the case of the potential of an infinitely deep quantum well, an inversion of the order of 1S_3/2 and 1P_3/2 levels can be observed at values of the ratio of the effective masses of the light and heavy holes β = m_lh/m_hh ≈ 0.14. The type of the trial wave functions of the hole for the state 1P_3/2 in the potential of an isotropic three-dimensional harmonic oscillator depending on β is proposed. The dependence of the binding energy of excitons in the considered potentials on β is presented and the possibility of formation of various biexcitonic states is considered.     

Localization of Carriers in Quantum Dots with Uniaxial Anisotropy of Shape and Composition

Physics of the Solid State - The electronic and hole states in quantum dots (QD) of cubic II–VI semiconductors with a spheroidal shape and uniaxial anisotropy have been studied theoretically....     

Intermolecular rearrangement of cobalt phenylsiloxanes

Intermolecular rearrangement of cobalt phenylsiloxanes was studied. The rearrangement leads to the formation of compounds with metal oxide moieties in the organosiloxane structure and is accompanied by a change in the spectral characteristics of cobalt(II), determined by the second coordination sphere of the metal. The rate-determining step is the decomposition of an intermediate complex formed upon the coordination of the metal siloxane moieties.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1912–1914, September, 2004.     

Mie resonances, infrared emission, and the band gap of InN

Mie resonances due to scattering or absorption of light in InN-containing clusters of metallic In may have been erroneously interpreted as the infrared band gap absorption in tens of papers. Here we show by direct thermally detected optical absorption measurements that the true band gap of InN is markedly wider than the currently accepted 0.7 eV. Microcathodoluminescence studies complemented by the imaging of metallic In have shown that bright infrared emission at 0.7-0.8 eV arises in a close vicinity of In inclusions and is likely associated with surface states at the metal/InN interfaces.