Science in China Series B: Chemistry

The coupling of adsorption desulfurization and biodesulfurization is a new approach to produce clean fuels. Sulfur compounds are firstly adsorbed on adsorbents, and then the adsorbents are regenerated by microbial conversion. п-Complexation adsorbent, Cu(l)-Γ, was obtained by ion exchanging Γ-type zeolite with Cu2+ and then by auto-reduction in helium at 450°C for 3 h. Dibenzothiophene (DBT) was used as a model compound. The effects of cell concentration, volume of oil phase, the ratio of aqueous phase to adsorbent on DBT desorption by a bacterium were studied. The amounts of DBT desorbed and 2-HBP produced can be apparently increased with addition of n-octane. BDS activity can be improved by increasing cell concentration and the ratio of water-to-adsorbent. 89% of DBT desorbed from the adsorbents can be converted to 2-HBP within 6 h and almost 100% within 24 h, when the volume ratio of oil-to-water was 1/5 mL/mL, the cell concentration was 60 g·L-1, and the ratio of adsorbent-to-oil was 0.03 g- mL-1. The amount of 2-HBP produced was strongly dependent on the volume ratio of oil-to-water, cell concentration and amount of adsorbent. Adsorption capacity of the regenerated adsorbent is 95% that of the fresh one after being desorbed with Pseudomonas delafieldii R-8, washed with n-octane, dried at 100°C for 24 h and auto-reduced in He.

Rational design and construction of chiral-achiral hybrid structures are of great importance to realize the multifunctional complex chiral structures toward emerging technological applications. However, significant challenges remain due to the lack of fine control over the heterostructure. Here, we have developed a general bottom-up synthetic strategy for the site-selective growth of Cu nanodomains on intrinsically chiral Au nanocrystals. Chiral AuCu heterostructures with three distinct architectures were achieved by controlling the overgrowth of Cu nanodomains in a site-specific manner. The geometry-dependent plasmonic chirality of the heterostructures was demonstrated experimentally by circular dichroism spectroscopy and theoretically through finite-difference time-domain simulations. The site-specific geometric control of chiral AuCu heterostructures was also extended to employ anisotropic chiral Au nanoplates and nanorods as the building blocks. By virtue of the galvanic replacement reactions between metal ions and Cu atoms, chiral heterostructures with increasing architectural complexity and compositional diversity can be further achieved. The current work not only opens up a promising strategy to synthesize complex chiral hybrid nanostructures but also provides an important knowledge framework that guides the rational design of multifunctional chiral hybrid nanostructures toward chiroptical applications.

This study demonstrates an on-line method for continuous measurements of cerebral hypoxanthine in the freely moving rats with integration of selective electrochemical biosensing with in vivo microdialysis sampling. The selective electrochemical biosensing is achieved by using xanthine oxidase (XOD) as the specific sensing element and Prussian blue (PB) as the electrocatalyst for the reduction of H2O2 generated from the oxidase-catalyzed reaction. The method is virtually interference-free from the coexisting electroactive species in the brain and exhibits a good stability and reproducibility. Upon integrated with in vivo microdialysis, the on-line method is well suitable for continuous measurements of cerebral hypoxanthine of freely moving rats, which is illustrated by the measurements of the microdialysates after the hypoxanthine standard was externally infused into the rat brain. This study essentially offers a facile on-line electrochemical approach to continuous measurements of cerebral hypoxanthine and could find some interesting applications in physiological and pathological investigations associated with hypoxanthine.

Silver ions confined in the silver stearate Langmuir-Blodgett (L-B) films of 8–14 layers were electrochemically reduced into Ag clusters, which made the observation of well-ordered scanning tunneling microscope (STM) images of the films with molecular resolution. A hexagonal packing of the hydrophobic chains was obtained. which was superimposed on the two-dimensional Ag clusters of 2–3 nm in diameter. Furthermore, a (2×1) structure of the hexagonal packing was observed. It was attributed to a self-assembled structure of the hydrophilic surface of the L-B films through hydrogen bonding. The strong surface enhanced Raman scattering (SERS) effect of Ag clusters made it possible to record Raman spectra of twoiayer stearic acid L-B films in the region of C—C stretching vibration frequencies. The appearance of the bands at 1 128.0 and 1 100. 7 cm−1, which correspond to the antisymmetric C—C stretching model of the acyl chains in theall-trans conformation and the C—C stretching model of the acyl chains in thegauche conformations, respectively, means that the methylene chains are mainly inall-trans conformation, but some of them become disordered.

Based on the correspondence of the molecular orbital theory and valence bond theory to the description of chemical bonds, theab initio valence bond (VB) calculations of the low-lying states of diatomic molecules are realized. The calculation results for the low-lying states of B2 show that the VB calculation has clear-cut physical significance, and its simulation of the behavior of the potential energy surface about the equilibrium position is superior to that of the molecular orbital theory. The valence bond calculation involving only a few bonded tableaus can correctly reflect the effect of electronic correlation.

Yttria-stabilized zirconia (YSZ) micro tubular electrolyte membranes for solid oxide fuel cells (SOFCs) were prepared via the combined wet phase inversion and sintering technique. The as-derived YSZ micro tubes consist of a thin dense skin layer and a thick porous layer that can serve as the electrode of fuel cells. The dense and the porous electrolyte layers have the thickness of 3–5 μm and 70–90 μm, respectively, while the inner surface porosity of the porous layer is higher than 28.1%. The two layers are perfectly integrated together to preclude the crack or flake of electrolyte film from the electrode. The presented method possesses distinct advantages such as technological simplicity, low cost and high reliability, and thus provides a new route for the preparation of micro tubular SOFCs.

CO oxidation was investigated on various powder oxide supported Pd catalysts by temperature-programmed reaction. The pre-reduced catalysts show significantly higher activities than the pre-oxidized ones. Model studies were performed to better understand the oxidation state, reactivities and stabilities of partially oxidized Pd surfaces under CO oxidation reaction conditions using an in situ infrared reflection absorption spectrometer (IRAS). Three O/Pd(100) model surfaces, chemisorbed oxygen covered surface, surface oxide and bulk-like surface oxide, were prepared and characterized by low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES). The present work demonstrates that the oxidized palladium surface is less active for CO oxidation than the metallic surface, and is unstable under the reaction conditions with sufficient CO.