Crystal structure of a second modification of the mercury oxychloride Hg3O2Cl2

The crystal structure of a monoclinic mercury oxychloride of composition Hg₃ O₂ Cl₂ has been described. A crystallographically different mercury oxychloride of the same composition was reported. The crystal structure of this second modification, called the -form, has been established through a single-crystal x-ray diffraction study. The -form is also monoclinic, with space groupP2₁/c andZ = 8. The unit-cell at 25 ° C hasa = 10.826(5),b = 9.310(4),c = 11.5 15(5) Å and = 71.04(8) °. The density is calculated to be 8.53 g cm^–3, that observed by displacement being 8.53(2) g cm^–3. Diffraction data were obtained using the -2 scanning mode on a Picker four-circle automatic diffractometer with CuK radiation. This apparently unsuitable radiation was chosen in order to test rigorously an absorption correction procedure. The structure was refined toR ₁ = 4.0% through conventional least-squares reduction basedF. The structure of -Hg₃ O₂ Cl₂ is found to be markedly different from that of the earlier-determined -Hg₃O₂Cl₂; distorted Hg₄O tetrahedra are linked into a three-dimensional array, terminated at four locations within the cell by covalent Hg-Cl bonds.     

Planar micro sensors for in vivo myocardial pH measurements

Potentiometric responses of microelectronically fabricated planar pH sensors based on both TDDA or ETH 5294 proton neutral carriers, in aminated PVC matrix, were evaluated with respect to main analytical parameters (linear ranges, slopes, reproducibility of potential measurements, potential drift and membrane resistance). In order to increase the electrode life time, increased amounts of membrane material were applied on the Ag/AgCl-poly-HEMA active spots of the polyimide substrate. The electrodes were implanted into an in situ porcine beating heart preparation at a midmyocardial depth in order to monitor H(+) concentration changes during the course of coronary artery occlusion.     

Aliphatic polyurethane as a matrix for pH sensors: effects of native sites and added proton carrier on electrical and potentiometric properties

The potentiometric and impedance characteristics of polymeric membranes, based on aliphatic polyurethane (Tecoflex) as a matrix, are described and interpreted by theory and experiments for H(+) and alkali metal ion-sensitive sensors. Both dummy plasticized membranes and proton carrier-loaded membranes can show pH response. The pH response of dummy membranes is due to protonated natural negative sites in the polyurethane matrix. The electrodes with added proton carrier show improved rejection of Li(+), Na(+), and K(+) responses and give useful analytical responses. Optimal performance requires control of negative site concentration by addition of lipophilic salt (e.g. tetraphenylborate derivatives). Impedance analyses show surface-rate semicircles and, depending on the bathing electrolyte solution, appearance of a diffusional Warburg impedance. In addition to these time-dependence surface region effects, changes in the bulk membrane resistance with soaking time can be well correlated with equilibrium water content of plasticized membranes.     

Investigation of aggregation in solvent extraction of lanthanides by acidic extractants (organo-phosphorus and naphthenic acid)

Three acidic extractants (Ⅰ) di(2-ethylhexyl) phosphoric acid (HDEHP),(Ⅱ) 2-ethylhexyl phos-phonic acid mono-2-ethylhexyl ester (KEHPEHE) and (Ⅲ) naphthenic acid were employed in preparing the samples for the characterization of the coordination structure of lanthanlde-extractant complexes and the physicochemical nature of aggregates formed in the organic diluent of the solvent extraction systems.Photo correlation spectroscopy (PCS) re-suits on the aggregates formed by the partially saponified HDEHP in n -heptane showed that the hydrodynamic radius of the aggregates was comparable to the molecular dimensions of HDEHP.The addition of 2-octanol into the diluent,by which the mixed solvent was formed,increased the dimensions of the corresponding aggregates.Aggregates formed from the ianthamde ions and HDEHP in the organic phase of the extraction systems were found very unstable.In the case of naphthenic acid,PCS data showed the formation of w/o microemulsion from the saponified naphthenic acid in the mix     

Quantum dot fluorescence quenching pathways with Cr(III) complexes. photosensitized NO production from trans-Cr(cyclam)(ONO)2+

Described is the photoluminescence (PL) of water-soluble CdSe/ZnS core/shell quantum dots (QDs) as perturbed by salts of the chromium(III) complexes trans-Cr(cyclam)Cl2+ (1), trans-Cr(cyclam)(ONO)2+ (2), and trans-Cr(cyclam)(CN)2+ (3) (cyclam = 1,4,8,11-tetraazacyclo-tetradecane). The purpose is to probe the characteristics of such QDs as antennae for photosensitized release of bioactive agents (in the present case, the bioregulatory molecule NO) from transition metal centers. Addition of 1 or 2 to a QD solution results in concentration-dependent quenching of the band edge emission, but 3 has a minimal effect. Added KCl strongly attenuates the quenching by 1, and this suggests that the Cr(III) cations and the QDs form electrostatic assemblies via ion pairing on the negatively charged QD surfaces. Quenching by 2, a known photochemical NO precursor, was accompanied by photosensitized NO release. All three, however, do quench the broad red emission ( approximately 650-850 nm) attributed to radiative decay of surface trapped carriers. The effect of various concentrations of 1 on time-resolved PL and absorbance were explored using ultrafast spectroscopic methods. These observations are interpreted in terms of the F?rster resonance energy-transfer mechanism for quenching of the band edge PL by multiple units of 1 or 2 at the QD surface, whereas quenching of the low-energy trap emission occurs via a charge-transfer pathway.     

Activation of Aromatic C−F Bonds by a N-Heterocyclic Olefin (NHO)

A N-heterocyclic olefin (NHO), a terminal alkene selectively activates aromatic C−F bonds without the need of any additional catalyst. As a result, a straightforward methodology was developed for the formation of different fluoroaryl-substituted alkenes in which the central carbon–carbon double bond is in a twisted geometry.     

Electrochemical investigation of magnetite-carbon nanocomposite in situ grown on nickel foam as a high-performance binderless pseudocapacitor

Journal of Solid State Electrochemistry - Magnetite-carbon nanocomposite was grown in situ on nickel foam by a novel auto-combustion method, and it was investigated for application as a...