Designed nanostructured pt film for electrocatalytic activities by underpotential deposition combined chemical replacement techniques

Multiple-deposited Pt overlayer modified Pt nanoparticle (MD-Pt overlayer/PtNPs) films were deliberately constructed on glassy carbon electrodes through alternately multiple underpotential deposition (UPD) of Ag followed redox replacement reaction by Pt (II) cations. The linear and regular growth of the films characterized by cyclic voltammetry was observed. Atomic force spectroscopy (AFM) provides the surface morphology of the nanostructured Pt films. Rotating disk electrode (RDE) voltammetry and rotating ring-disk electrode (RRDE) voltammetry demonstrate that the MD-Pt overlayer/PtNPs films can catalyze an almost four-electron reduction of O(2) to H(2)O in air-saturated 0.1 M H(2)SO(4). Thus-prepared Pt films behave as novel nanostructured electrocatalysts for dioxygen reduction and hydrogen evolution reaction (HER) with enhanced electrocatalytic activities, in terms of both reduction peak potential and peak current, when compared to that of the bulk polycrystalline Pt electrode. Additionally, it is noted that after multiple replacement cycles, the electrocatalytic activities improved remarkably, although the increased amount of Pt is very low in comparison to that of pre-modified PtNPs due to the intrinsic feature of the UPD-redox replacement technique. In other words, the electrocatalytic activities could be improved markedly without using very much Pt by the technique of tailoring the catalytic surface. These features may provide an interesting way to produce Pt catalysts with a reliable catalytic performance as well as a reduction in cost.     

Synthesis and Crystal Structure of （Et4N）2[Pd2（mp）2（mpH）2]

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Crystal Structure and Molecular Absolute Configuration of （＋）－Isocedranol （C_（15）H_（26）O）

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MODIFICATION OF TRANSITION METAL CATIONS TO POLYMER-STABILIZED PLATINUM COLLOIDAL CLUSTERS IN ENANTIOSELECTIVE HYDROGENATION OF METHYL PYRUVATE

Modification of transition metal cations to polymer-stabilized Pt colloidal clusters modified with cinchonidine was studied in enantioselective hydrogenation of methyl pyruvate. Compared to the enantiomeric excess (e.e.) value (71.4%) obtained without the presence of metal cations, obvious e.e. enhancement (up to 82.5%) was resulted from the addition of Zn^2 but with a certain decrease in activity. The reaction parameters in the presence of Zn^2 were also studied. It was found that the Pt colloidal catalysts in the presence of metal cations performed very differently from that in the absence of metal cations.     

Fabrication of ultrathin films with large third-order nonlinear optical properties.

An ultrathin composite film containing anionic Ag-His complexes (His: L-Histidine) and oppositely charged BH-PPV was fabricated by means of the electrostatic layer-by-layer self-assembly technique. UV/Vis spectra showed a continuous deposition process of Ag-His complexes and BH-PPV. The film structure was characterized by using small-angle X-ray diffraction, AFM, and SEM. The nonlinear optical properties of the ultrathin film were studied by using the Z-scan technique with a laser duration of 8 ns at a wavelength of 532 nm. The film sample exhibited a strong nonlinear saturated absorption, with an alpha2 value of -3.9 x 10(-5) mW(-1) and a self-defocusing effect with an n2 value of -4.78 x 10 (-12) m2W(-1).     

Synthesis of isoxazoline-fused chlorins and bacteriochlorins by 1,3-dipolar cycloaddition reaction of porphyrin with nitrile oxide

The 1,3-dipolar cycloaddition reaction of meso-tetraaryl porphyrin with 2,6-dichlorobenzonitrile oxide yielded novel isoxazoline-fused chlorins and two stereoisometric bacteriochlorins. The crystal structure of bacteriochlorin was characterized by X-ray diffraction.     

Analysis of acyclovir by high performance capillary electrophoresis with on-column amperometric detection

The separation of acyclovir (ACV) by high performance capillary electrophoresis (HPCE) with on-column amperometric detection using alpha-amino-5-mercapto-3,4-dithiazole (AMD) as internal standard is described. The calibration line was linear in the range of 0.5-20 mg/L of ACV. The detection limit was 0.15 mg/L of ACV. Its recovery ranged from 98 to 101% with relative standard deviations (RSDs) from 1.9 to 3.2% (n = 5). This method was successfully used for determining ACV in some pharmaceuticals and human urine. Comparable results with HPCE with ultraviolet (UV) detection and amperometric detection were obtained.     

A semi-rigid bis(imidazolyl) ligand for the construction of nanoscopic supramolecules. From the molecular rectangle to the 1D coordination polymer

Reaction of the semi-rigid ligand 2,4-bis(1-imidazolylmethyl)-mesitylene (m-bimms) with CdCl₂ afforded a boat-like molecular rectangle [Cd(m-bimms)Cl₂]₂ · 1/2H₂O (1), with the orientation of the two imidazolyl arms of the ligand in syn-conformation and bridging chloride ions bisecting the macrocycle. Weak Cl· · ·H—C interations further extended the dimers into 1D infinite chains with nanoscopic channels. An analogous reaction with Cd(NO₃)₂ gave a 1D coordination polymer [Cd(m-bimms)₂(NO₃)₂]_n · 2nH₂O (2) composed of nanoscopic metallamacrocycles, where the two imidazolyl arms adopt an anti-conformation. Different anions result in different ligand conformations and thus determine the varied molecular architectures.