Photoelectron Spectra and Molecular Properties: Real-Time Gas Analysis in Flow Systems

For the analysis and optimization of numerous gas phase reactions in flow-systems, photoelectron spectroscopy has proven most valuable. This real-time measuring probe allows one to determine—with millimol quantities and within a few hours—the temperatures for different decomposition channels. Simultaneously, main products are characterized and, if need be, their yield can be improved. By careful performance of the experiment, short-lived and/or reactive molecules such as P₂, thioformaldehyde or silabenzene can be detected. PE-spectroscopic gas analysis is of particular advantage in the search for heterogeneous catalysts; they can be tested within a day using gas mixtures of varying composition over the temperature range from 300 K to 1300 K. In addition, PE-spectrometers are well-suited for on-line connection to computers; portable instruments for laboratory use are under development.     

Preparation of DSA@MNPs and application as heterogeneous and recyclable nanocatalyst for oxidation of sulfides and oxidative coupling of thiols

Research on Chemical Intermediates - Dopamine sulfamic acid-functionalized magnetic Fe3O4 nanoparticles (DSA@MNPs) were prepared by a very simple and inexpensive procedure using commercial...     

Phase relations and binary clathrate hydrate formation in the system H2-THF-H2O

Experimentally determined equilibrium phase relations are reported for the system H2-THF-H2O as a function of aqueous tetrahydrofuran (THF) concentration from 260 to 290 K at pressures up to 45 MPa. Data are consistent with the formation of cubic structure-II (CS-II) binary H2-THF clathrate hydrates with a stoichiometric THF-to-water ratio of 1:17, which can incorporate modest volumes of molecular hydrogen at elevated pressures. Direct compositional analyses of the clathrate phase, at both low (0.20 mol %) and stoichiometric (5.56 mol %) initial THF aqueous concentrations, are consistent with observed phase behavior, suggesting full occupancy of large hexakaidecahedral (51264) clathrate cavities by THF, coupled with largely complete (80-90%) filling of small dodecahedral (512) cages by single H2 molecules at pressures of >30 MPa, giving a clathrate formula of (H2) < or =2.THF.17H2O. Results should help to resolve the current controversy over binary H2-THF hydrate hydrogen contents; data confirm recent reports that suggest a maximum of approximately 1 mass % H2, this contradicting values of up to 4 mass % previously claimed for comparable conditions.     

ChemInform Abstract: Aromatic‐Like Behavior of Germanium Nanocrystals.

Aromatic Ge₁₈H₁₂ and Ge₁₉H₁₂ nanocrystals composed of three parallel, planar hexagons with one additional Ge atom close to the cluster center in the latter are predicted by DFT calculations.     

Three-dimensional simulation of long-wavelength free-electron lasers with helical wiggler and ion-channel guiding

A three-dimensional simulation of a steady-state amplifier model of a long-wavelength free-electron laser (FEL) with realizable helical wiggler and ion-channel guiding is presented. The set of coupled nonlinear differential equations for electron orbits and fields of TE 11 mode in a cylindrical waveguide are solved numerically by the Runge-Kutta algorithm with averages calculated by the Gaussian quadrature technique. Self-fields and space-charge effects are neglected, and the electron beam is assumed to be cold and slippage is ignored. The parameters correspond to the Compton regime. Evolution of the radiation power and growth rate along the wiggler is studied. Ion-channel density is chosen to obtain optimum efficiency. Simulations are preformed for the FEL operating in the neighborhood of 35 GHz and 16.5 GHz for the electron beam energies of 250 keV and 400 keV, respectively. The result of the saturated efficiency was found to be in good agreement with the simple estimation based on the phase-trapping model.     

Hollow fiber-based liquid-liquid-liquid microextraction followed by flow injection analysis using column-less HPLC for the determination of phenazopyridine in plasma and urine

Hollow fiber-based liquid-liquid-liquid microextraction (HF-LLLME) followed by flow injection analysis and diode array detection (FIA-DAD) was applied as a simple and sensitive quantitative method for the determination of phenazopyridine in urine and plasma samples. Flow injection system included a conventional HPLC system (without a chromatographic column) and a diode array detector. The extraction of phenazopyridine was carried out using diphenyl ether as the organic phase for filling the pores of the hollow fiber wall, and 0.1 M H(2)SO(4) solution as acceptor phase in the lumen of the fiber. The factors affecting the HF-LLLME and flow injection analysis including type of organic solvent, pH of donor phase, extraction temperature, extraction time, stirring rate, and pH of mobile phase were investigated and the optimal extraction conditions were established. With the consumption of 5 mL of sample solution, the enrichment factor was about 230. The limit of detection was 0.5 μg/L with inter- and intra-day precision being (RSD%) 6.9 and 4.9, respectively. Excellent linearity was found between 5 and 200 μg/L.