Tailoring the electrochemical charge storage properties of carbonaceous support by redox properties of heteropoly acids: where does the synergy come from?

Journal of Solid State Electrochemistry - The synergistic effects between two Keggin-type heteropoly acids (HPAs) and carbon surface were examined and elucidated. An improved high rate capability...     

Cocoa Shell as a Step Forward to Functional Chocolates—Bioactive Components in Chocolates with Different Composition

Chocolate is considered as both caloric and functional food. Its nutritional properties may be improved by addition of fiber; however, this may reduce polyphenols content. The aim of this research was to determine the influence of cocoa shell addition (as a source of fiber) and its combination with different ingredients (cocoa butter equivalents (CBE), emulsifiers, dairy ingredients) on polyphenols of dark and milk chocolates. Total polyphenol (TPC) and total flavonoid (TFC) contents were determined spectrophotometrically, identification and quantification of individual compounds by high pressure liquid chromatography and antioxidant capacity by ferric reducing antioxidant power (FRAP) assay. Results showed that even though addition of cocoa shell to chocolate results in reduced contents of TPC, TFC, and individual compounds, it is not significant compared to ones reported by other authors for commercial chocolates. Other ingredients influence determined values for all investigated parameters; however, additional research is needed to reveal exact mechanisms and implications.     

3D electrogenerated chemiluminescence: from surface-confined reactions to bulk emission

Among luminescence techniques, electrogenerated chemiluminescence (ECL) provides a unique level of manipulation of the luminescent process by controlling the electrochemical trigger. Despite its attractiveness, ECL is by essence a 2D process where light emission is strictly confined to the electrode surface. To overcome this intrinsic limitation, we added a new spatial dimension to the ECL process by generating 3D ECL at the level of millions of micro-emitters dispersed in solution. Each single object is addressed remotely by bipolar electrochemistry and they generate collectively the luminescence in the bulk. Therefore, the entire volume of the solution produces light. To illustrate the generality of this concept, we extended it to a suspension of multi-walled carbon nanotubes where each one acts as an individual ECL nano-emitter. This approach enables a change of paradigm by switching from a surface-limited process to 3D electrogenerated light emission.     

Structure of CO2 adsorbed on the KCl(100) surface

The structure and dynamics of the adsorbate CO(2)/KCl(100) from a diluted phase to a saturated monolayer have been investigated with He atom scattering (HAS), low-energy electron diffraction (LEED), and polarization dependent infrared spectroscopy (PIRS). Two adsorbate phases with different CO(2) coverage have been found. The low-coverage phase is disordered at temperatures near 80 K and becomes at least partially ordered at lower temperatures, characterized by a (2√2×√2)R45° diffraction pattern. The saturated 2D phase has a high long-range order and exhibits (6√2×√2)R45° symmetry. Its isosteric heat of adsorption is 26 ± 4 kJ mol(-1). According to PIRS, the molecules are oriented nearly parallel to the surface, the average tilt angle in the saturated monolayer phase is 10° with respect to the surface plane. For both phases, structure models are proposed by means of potential calculations. For the saturated monolayer phase, a striped herringbone structure with 12 inequivalent molecules is deduced. The simulation of infrared spectra based on the proposed structures and the vibrational exciton approach gives reasonable agreement between experimental and simulated infrared spectra.     

Mass spectrometric determination of appearance energies for ions formed from CoF(4) and CoF(3) molecules

Knudsen cell mass spectrometry was applied to the evaluation of the ionization efficiency curves for the ions originating from CoF(4) molecules. Cobalt tetrafluoride was obtained in the gas phase over the CoF(3)(s)-TbF(4)(s) system in the temperature range from 640 to 690 K. From the ionization efficiency curves the appearance energies of the ions formed from the CoF(4) molecules were determined by means of Vogt's deconvolution method. Clausius-Clapeyron plots for the ions from CoF(4) molecules were measured. Evaporation of pure CoF(3)(s) was carried out, and the appearance energies of the ions formed from CoF(3) molecules were determined. The ionization energies for CoF(4) and CoF(3) molecules were found to be (14.3 +/- 0.2) and (13.3 +/- 0.1) eV, respectively.     

Stark Broadening of F III Lines in Laboratory and Stellar Plasma

Using a semiclassical approach, we have considered electron-, proton-, and ionized helium-impact line widths and shifts for the F III 2p^{3 4}S^o-3s ⁴P resonant line. Moreover, for 10 F III multiplets where the full semiclassical perturbation approach is not applicable in an adequate way due to the lack of reliable atomic data, electron-impact line widths have been calculated within the modified semiempirical approach. Results are obtained as a function of temperature for perturber density of 10¹⁷ cm⁻³. The theoretical data obtained have been used to consider the influence of Stark broadening for A-type star atmosphere conditions. __________ Published in Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 3, pp. 412–415, May–June, 2005.     

Planar microcoil-based microfluidic NMR probes

Microfabricated small-volume NMR probes consisting of electroplated planar microcoils integrated on a glass substrate with etched microfluidic channels are fabricated and tested. 1H NMR spectra are acquired at 300 MHz with three different probes having observed sample volumes of respectively 30, 120, and 470 nL. The achieved sensitivity enables acquisition of an 1H spectrum of 160 microg sucrose in D2O, corresponding to a proof-of-concept for on-chip NMR spectroscopy. Increase of mass-sensitivity with coil diameter reduction is demonstrated experimentally for planar microcoils. Models that enable quantitative prediction of the signal-to-noise ratio and of the influence of microfluidic channel geometry on spectral resolution are presented and successfully compared to the experimental data. The main factor presently limiting sensitivity for high-resolution applications is identified as being probe-induced static magnetic field distortions. Finally, based on the presented model and measured data, future performance of planar microcoil-based microfluidic NMR probes is extrapolated and discussed.     

Sublimation properties of CoF(3): mass spectrometric and quantum chemical studies

The sublimation of cobalt trifluoride was studied using the Knudsen effusion method combined with mass spectrometry. The pressure of F was directly measured for decomposition of CoF(3)(s) into CoF(2)(s). The average kinetic energy of CoF(2)(+), CoF(+) and Co(+) fragment ions was determined and the relative ionisation cross section curves measured from 6 eV to 100 eV. Thermodynamic functions of gaseous CoF(3) and Co(2)F(6), were evaluated from geometrical and vibrational parameters provided from theoretical calculations. Heats of formation of CoF(3)(s), CoF(3)(g), Co(2)F(6)(g) were established as (-784 +/- 6) kJ/mol, (-565 +/- 11) kJ/mol and (-1289 +/- 22) kJ/mol, respectively.     

Parameter determination of a thermal desorption model

A new method for the analysis of thermal desorption spectra is presented, based on the experimental peak maximum functions for temperatureT _m(β) and pressureP _m(β) and a rigorous mathematical treatment. The resonant heating rate β_r is determined, satisfyingT _m(β_r)=T _r, whereT _r is the resonant temperature defined byA exp(−E _d/(RT _r))=1. Desorption energyE _d and frequency factorA can be determined simultaneously with relatively high robustness towards statistical experimental errors as demonstrated by computer-simulated thermal desorption spectra.     

Strong bulk-edge coupling in the compressible half-filled quantum Hall state

We study bulk and edge correlations in the compressible half-filled state, using a modified version of the plasma analogy. The corresponding plasma has anomalously weak screening properties, and as a consequence we find that the correlations along the edge do not decay algebraically as in the Laughlin (incompressible) case, while the bulk correlations decay in the same way. The results suggest that due to the strong coupling between charged modes on the edge and the neutral fermions in the bulk, reflected by the weak screening in the plasma analogue, the (attractive) correlation hole is not well defined on the edge. Hence, the system there can be modeled as a free Fermi gas of electrons. We finally comment on a possible scenario, in which the Laughlin-like dynamical edge correlations may nevertheless be realized.