Influence of chemical equilibrium in introduced oxygen vacancies on resistive switching in epitaxial Pt-CeO<Subscript>2</Subscript> system

We investigate the introduction of oxygen vacancies by the interaction of Pt with CeO₂(111) (ceria) thin epitaxial film grown on Cu(111) and the influence of the vacancies on resistive switching behavior. For this purpose, we used X-ray photoelectron spectroscopy and conductive atomic force microscopy. We found out that after Pt deposition, the ceria film was partially reduced. By our estimation, the reduction occurs not only at the Pt/CeO₂ interface, but also on the surface of the ceria film which is not covered by Pt, after Pt deposition and annealing. A different distribution of oxygen vacancies in the film proves to have an influence on the resistance switching process of the film. Finally, the proper balance between the reduced and the unreduced species in order to obtain relatively stable repeatable resistance switch with clear resistance window is discussed.     

Two-photon absorption cross section determination for fluorene derivatives: analysis of the methodology and elucidation of the origin of the absorption processes

A comprehensive analysis of the well-known open aperture Z-scan method, using a modified equation for the change in transmittance, is presented and accounts for discrepancies in two-photon absorption (2PA) cross sections between picosecond and femtosecond excitation. This new approach takes into account excited-state absorption and stimulated emission of the molecules studied. The two-photon absorption cross-section spectra of a series of six fluorene-based derivatives, determined using picosecond pulses, over a broad spectral range (500-900 nm), and this approach using a modified fitting procedure in the open aperture Z-scan is reported. We demonstrate that the fluorene derivatives exhibit two-photon absorption cross-section values between 700 and 5000 GM, when excited into the two-photon allowed electronic state. Excitation anisotropy spectra, measured to investigate the nature of the observed linear and nonlinear absorption bands, are presented and provide insight into the 2PA process.     

Synthesis and microstructure investigation of heterogeneous metal-plasma polymer Ag/HMDSO nanoparticles

Metal-polymer nanocomposites have gained increasing attention due to the wide potential applications field. Synthesis of nanoparticles from the gas phase is an intensively studied alternative to the chemical preparation methods. We present a one-step procedure that combines magnetron-based gas aggregation cluster source of silver nanoparticles and simultaneous plasma-enhanced chemical vapour deposition of hexamethyldisiloxane (HMDSO). The key parameter of the process, significantly influencing the morphology and microstructure of studied nanoparticles, was found to be the amount of HMDSO added to the deposition chamber as witnessed by small angle X-ray scattering and X-ray diffraction methods combined with transmission electron microscopy and UV–Vis spectrophotometry. The presence of HMDSO in the chamber leads to changes in the size distribution and also in the architecture of prepared nanoparticles. The increasing amount of HMDSO induces the formation of individual core-shell nanoparticles, chains of core-shell nanoparticles, and for the highest concentration of HMDSO, the synthesis of multi-core-shell nanoparticles. The size of crystallites in the silver cores of nanoparticles decreases with addition of HMDSO, which prevents further aggregation.     

Low-temperature radical polymerization of acrylamide in ethanol and glycerol under the action of molecular chlorine

It is shown by means of calorimetry, IR and EPR spectroscopy, elemental analysis, chromatography, and viscosimetry that radicals formed during the low-temperature action of molecular chlorine on acrylamide or its solutions in ethanol or glycerol initiate the polymerization reaction of acrylamide. It is established that during the low-temperature chlorination of pure acrylamide, polymerization takes place in the temperature range of 180–210 K with a polymer yield of ∼10%. The low-temperature chlorination of 20% solutions of acrylamide in ethanol or glycerol was performed to increase the product yield. It is shown that the low-temperature chlorination of acrylamide solution in glycerol increases the polymer yield by a factor of approximately two, and the content of chlorine in it falls by a factor of around ten. The low-temperature chlorination of acrylamide solution in ethanol did not lead to an increase in the polymer yield. A small reduction was noted in the chlorine content of the polymer.     

Thermodynamic and NMR studies of mixed-ligand complex formation of cadmium ethylenediaminetetraacetate with diamines in an aqueous solution

The mixed-ligand complex formation in the systems Cd2 + Edta4–(CH₂) _n (NH₂)₂, n = 2 (En), 6 (L) has been NMR and calorimetrically studied in aqueous solution at 298.15 K and the ionic strength of I = 0.5 (KNO₃). The thermodynamic parameters of formation of the CdEdtaL²⁻, CdEdtaHL⁻, (CdEdta)₂L⁴⁻, and (CdEdta)₂En⁴⁻ complexes have been determined. The most probable coordination mode for the complexone and the diamine ligand in the mixed-ligand complexes was discussed.     

3-Hydroxybenzo[g]quinolones: dyes with red-shifted absorption and highly resolved dual emission

New derivatives of 3-hydroxyquinolone (3HQ) with a fused benzene ring (3-hydroxybenzo[g]quinolones) have been synthesized. They display a remarkable red shift of their absorption spectrum in comparison with other 3HQ analogs allowing their excitation by common He/Cd and Ar-ion lasers. As a result of their irreversible excited-state intramolecular proton transfer (ESIPT) reaction, they display a dual fluorescence in a series of solvents of varying polarities, starting from toluene to methanol. The dual emission of these dyes correlates well with solvent H-bond basicity, which is connected with the effect of this solvent property on the kinetics of the ESIPT reaction. In addition to their red-shifted absorption and fluorescence, these new derivatives show a larger separation of their two emission bands and a more appropriate range of their intensity ratio than the previously synthesized 3HQs. These properties allow an improved ratiometric evaluation of the local H-bond basicity of unknown environments, which will favor future applications of the new dyes in polymer and biological sciences.     

Asymptotics of activity series at the divergence point

In this article, a simple autonomous transiently chaotic flow with cubic nonlinearities is proposed. This system represents some unusual features such as having a surface of equilibria. We shall describe some dynamical properties and behaviours of this system in terms of eigenvalue structures, bifurcation diagrams, time series, and phase portraits. Various behaviours of this system such as periodic and transiently chaotic dynamics can be shown by setting special parameters in proper values. Our system belongs to a newly introduced category of transiently chaotic systems: systems with hidden attractors. Transiently chaotic behaviour of our proposed system has been implemented and tested by the OrCAD-PSpise software. We have found a proper qualitative similarity between circuit and simulation results.     

A Curie–Weiss theory of the continuum Widom–Rowlinson model

A version of the continuum Widom–Rowlinson model is introduced and studied. It is a two-component gas of point particles placed in ${\mathbf{R}}^d$ in which like particles do not interact and unlike particles contained in a given vessel of volume V repel each other with intensity $a/V$. This model is thermodynamically equivalent to a one-component gas with multi-particle interaction. For both models, a rigorous theory of a phase transition is presented and the ways of its construction in the framework of the grand canonical formalism are outlined.     

Electron Transfer between Different Lanthanide Centers in BaF2 Crystals—Part II: Transfer Mechanisms

Physics of the Solid State - Processes of photo-induced electron transfer from a bivalent acceptor lanthanide (Eu, Sm, and Yb) onto a trivalent donor lanthanide (Nd, Sm, Dy, Tm, and Yb) and the...