Atomic correlation energy from the electron density at the nucleus

Ground-state atomic correlation energies, and their kinetic energy and potential energy components, are shown to be well-represented by empirical formulas of the form CNrho(0)Z(-gamma), where C and gamma are constants that are largely invariant within various sets of atoms and positive ions, Z is the atomic number, N is the number of electrons, and rho(0) is the electron density at the nucleus. Results are given for neutral atoms, singly charged positive ions, and many isoelectronic series-315 atomic species in all.     

Observations on photochemical fluorescence enhancement of the terbium(III)-sparfloxacin system.

Fluorescence of terbium(III) was sensitized when excited in the presence of sparfloxacin (SPFX) in the aqueous solution because a Tb(III)-SPFX complex was formed. The sensitized fluorescence was further enhanced when this system was exposed to 365 nm ultraviolet light. By the spectral properties and contrast experiments, it is proved that irradiation makes this system undergo photochemical reactions and a new terbium complex which is more favorable to the intramolecular energy transfer is formed. The mechanism of photochemical fluorescence enhancement of the Tb(III)-SPFX system is discussed and a new sensitive and selective photochemical fluorimetry for the determination of SPFX is established. Under the optimum conditions, the linear range is 1.0-50 x 10(-7) M for SPFX, the detection limit is 3.0 x 10(-9) M and the R.S.D. for 5.0 x 10(-7) M SPFX is 1.3% (n = 9). Without any pretreatment the recovery of SPFX in human urine was determined with satisfaction.     

On the nature of radicals formed in methanol catalytic oxidation

The quantum-chemical calculations of the hydroxymethyl radical •CH₂OH were performed for the first time and a theoretical EPR spectrum of this radical was constructed. The formation of the hydroxymethyl radical in the reaction of methanol oxidation is thermodynamically favorable. The shape and parameters of the constructed spectrum differed from those for radicals experimentally detected in the catalytic oxidation of methanol using the matrix isolation method. However, they are consistent with the spectrum ascribed to the EPR spectrum of •CH₂OH observed in the direct photolysis of methanol. This result allows one to refine the identification of the nature of radicals formed in the catalytic reaction of methanol oxidation.     

Synthesis of bimetallic nanocompositions Au<Subscript>x</Subscript>Pd<Subscript>1-x</Subscript>/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> for catalytic CO oxidation

Colloidal suspensions of Au_xPd_1-x nanoalloys were prepared via hydrazine co-reduction of [AuCl₄]^? and [PdCl₄]^2? complex anions in aqueous solution. High molecular weight polymeric compounds polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), and cryptoionic surfactants (AF-6 and AF-12 neonols, Triton X-100) were used as surface capping agents. Nanoparticles prepared under different experimental conditions were immobilized on γ-Al₂O₃ supports. The removal of the capping agents from the surface of the active particles was achieved through calcination of samples in oxidative atmosphere (air, 500 °C). This pretreatment of the catalysts significantly enhances their performance. Powder XRD, TEM, and EDX were employed to characterize the structure, size, and composition of the Au_xPd_1-x/γ-Al₂O₃ catalysts. The immobilized particles consist of uniformly mixed alloys having multi-domain face-centered cubic structure with typical crystallite size of 3–6 nm. The activity of the prepared samples was examined with temperature-programmed CO oxidation reaction (TP-CO+O₂). Triton X-100 surfactant is superior in a number of parameters. Among all Au_xPd_1-x/γ-Al₂O₃ catalysts tested, the one stabilized with Triton X-100 (0.4%Au-0.2%Pd@Triton X-100) was found to have the highest activity for conversion of CO into CO₂.     

Spherical α-Ni(OH)2 nanoarchitecture grown on graphene as advanced electrochemical pseudocapacitor materials

This work reports a new graphene-based composite for supercapacitor material, and the maximum specific capacitance of 1760.72 F g(-1) at a scan rate of 5 mV s(-1), with excellent cycling stability.     

Investigation of thermal properties of double complex salts [M(NH3)5Br][AuBr4]2·nH2O, M?=?Rh, Ir

Novel double complex salts [M(NH₃)₅Br][AuBr₄]₂·nH₂O, M?=?Rh, Ir, have been synthesized and examined. The processes of thermal decomposition of the compounds in inert and reductive atmospheres have been studied and intermediate products identified. Simultaneous thermal analysis with parallel mass-spectrometric analysis of evolved gases (STA-EGA) has been employed for identification of main gaseous products of thermolysis in inert atmosphere. It has been revealed that the final products of decomposition in inert or reductive atmospheres are fine powders of gold and the corresponding platinum metal with sizes of crystallites 4?C40?nm. The possibility of preparation of the metastable solid solution Au_0.05Ir_0.95 on thermolysis of [Ir(NH₃)₅Br][AuBr₄]₂·H₂O in inert atmosphere has been demonstrated.     

The structure of zirconium-silicate fiberglasses and Pt-containing fiberglass catalysts as revealed by solid-state NMR spectroscopy

¹H, ²³Na and ²⁹Si solid-state NMR spectroscopy was used to investigate the formation of fiberglass zirconium-silicate supports and catalysts (glass → fiberglass → leached fiberglass → catalyst). The main emphasis was made on OH-H₂O domains in fiberglass and their role in catalyst preparation. The size of OH-H₂O domains and their accessibility to H-D exchange were determined. Platinum was shown to be anchored on the bridging hydroxyl groups. The quantum-chemical calculations demonstrated the activity of Pt⁰ clusters forming in fiberglass to depend on their nuclearity.