Hydrothermal synthesis and structural characterization of a one-dimensional coordination polymer [Zn(Pydc)(Dppz)] n (H2Pydc = 2,6-pyridinedicarboxylic acid, Dppz = dipyrido[3,2-a:2′,3′-c]phenazine)

A new metal-organic coordination polymer [Zn(Pydc)(Dppz)] _n (I) (H₂Pydc = 2,6-pyridinedicarboxylic acid, Dppz = dipyrido[3,2-a:2′,3′-c]phenazine) was hydrothermally synthesized and characterized by elemental analysis, IR and X-ray single-crystal diffraction. The X-ray diffraction analysis reveals that I crystallizes in the monoclinic system, space group P2₁/c. The Pydc^2? ligands adopt O,N,O′-tridentate chelating and monodentate bridging coordination mode to link two adjacent Zn2+ ions to form a one-dimensional (1D) zigzag chain. The adjacent chains are further linked through hydrogen bonds and π-π stacking interactions, forming a three-dimensional (3D) supramolecular framework. The unit cell parameters for I: a = 7.332(3) Å, b = 36.023(9) Å, c = 7.8838(13) Å, β = 105.65(3)^○, V = 2005.1(10) ų, Z = 4.     

Solvothermal synthesis and structural characterization of a new one-dimensional metal-organic framework [Co(Atibdc)(Dpa)] n (H2Tibdc = 5-amino-2,4,6-triiodoisophthalic acid, Dpa = 2,2′-dipyridylamine)

The title cobalt(II) coordination polymer, [Co(Atibdc)(Dpa)] _n (I) (H₂Atibdc = 5-amino-2,4,6-triiodoisophthalic acid, Dpa = 2,2′-dipyridylanine), has been synthesized under solvothermal conditions and characterized by elemental analysis, IR, and X-ray crystallography structural analysis. Complex I exhibits a one-dimensional chain structure in which 5-amino-2,4,6-triiodoisophthalate as a bridging ligand interconnects adjacent two Co(II) centers to form a helical chain structure. The asymmetric unit includes one Co(II) center, one atibdc ligand, and one Dpa ligand. Each Co(II) center is five-coordinated and surrounded by two nitrogen atoms and three oxygen atoms from one Dpa ligand and two individual Atibdc ligands, leading to distorted trigonal bipyramid geometry. Adjacent chains are further linked through hydrogen bonds, C-H-π and π-π stacking interactions to form a three-dimensional supramolecular framework.     

Calorimetric study and thermal analysis of Al–Sn system

The results of calorimetric study and thermal analysis of binary Al–Sn system are presented in this paper. The Oelsen calorimetry was used in thermodynamic analysis. Following thermodynamic properties were determined at 727 °C: activities, activity coefficients, partial/integral molar Gibbs excess, and mixing energies. The energetics of mixing in liquid Al–Sn alloys has been analyzed through the study of concentration fluctuation in the long-wavelength limit. Thermal analysis of selected alloys in Al–Sn system was done using differential thermal analysis. Defined characteristic phase transition temperatures were used for comparison with calculated phase diagram of investigated system. Good agreement with available literature data was obtained. Structural analysis of selected alloys was done using optic microscopy.     

Facile electrochemical synthesis of a conducting copolymer from 5-aminoindole and EDOT and its use as Pt catalyst support for formic acid electrooxidation

5-Aminoindole and 3,4-ethylenedioxythiophene (EDOT) were copolymerized electrochemically on a carbon cloth (CC) electrode in an aqueous sulfuric acid solution. The as-prepared copolymer was characterized by cyclic voltammogram, SEM, and UV-vis and FT-IR spectra through which the electrochemical properties, structure, and composition of the as-obtained copolymer were determined. The electrochemical activity and stability of the as-formed copolymer are significantly improved in comparison with poly(5-aminoindole) due to the incorporation of EDOT units into the conjugated chain. The copolymer film-modified CC electrode was used as substrate for Pt particle deposition (denoted as Pt/copolymer/CC), and then, its catalytic activity towards formic acid electrooxidation was studied. Experimental results indicate that the catalytic activity of Pt/copolymer/CC towards formic acid electrooxidation is enhanced in comparison with that of Pt/homopolymer/CC, which can be attributed to the homogeneous distribution of Pt nanoparticles on the copolymer/CC substrate and the improved electrochemical activity of the copolymer film.     

Electrodeposited nanogold decorated graphene modified carbon ionic liquid electrode for the electrochemical myoglobin biosensor

In this paper, a carbon ionic liquid electrode (CILE) was fabricated using ionic liquid 1-hexylpyridinium hexafluorophosphate as modifier, which was further in situ electrodeposited with graphene (GR) and gold nanoparticles step by step to get an Au/GR nanocomposite modified CILE. Myoglobin (Mb) was further immobilized on the Au/GR/CILE surface with Nafion film to get the modified electrode denoted as Nafion/Mb/Au/GR/CILE. Cyclic voltammetric experiments indicated that a pair of well-defined quasi-reversible redox peaks appeared in pH 3.0 phosphate buffer solution with the formal potential (E ^0′) located at ?0.197 V (vs. saturated calomel electrode), which was the typical characteristics of Mb heme Fe(III)/Fe(II) redox couples. Thus, the direct electron transfer rate between Mb and the modified electrode was promoted due to the high conductivity and increased surface area of Au/GR nanocomposite present on electrode surface. Based on the cyclic voltammetric data, the electrochemical parameters of Mb on the modified electrode were calculated. The Mb-modified electrode showed excellent electrocatalytic activities towards the reduction of trichloroacetic acid and H₂O₂ with wider linear range and lower detection limit. Using GR and Au nanoparticles modified CILE, a new third-generation electrochemical Mb biosensor was constructed with good stability and reproducibility.     

Improved electrochemical performance of nano-crystalline Li2FeSiO4/C cathode material prepared by the optimization of sintering temperature

Li₂FeSiO₄/C cathode materials have been prepared using the conventional solid-state method by varying the sintering temperature (650 °C, 700 °C and 750 °C), and the structure and electrochemical performance of Li₂FeSiO₄/C materials are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), galvanostatic charge–discharge tests, respectively. The results show that Li₂FeSiO₄ nano-crystals with a diameter of about 6–8 nm are inbedded in the amorphous carbon, and the Li₂FeSiO₄/C material obtained at 700 °C exhibits an initial discharge capacity of 195 mA?h g^?1 at 1/16 C in the potential range of 1.5–4.8 V. The excellent electrochemical performance of Li₂FeSiO₄/C attributes to the improvement of conductivity and reduction of impurity by the optimization of the sintering temperature.     

Environmentally Benign and Efficient Ag2S‐ZnO Nanowires as Photoanodes for Solar Cells: Comparison with CdS‐ZnO Nanowires

In this work, we develop a low‐temperature, facile solution reaction route for the fabrication of quantum‐dot‐sensitized solar cells (QDSSCs) containing Ag₂S‐ZnO nanowires (NWs), simultaneously ensuring low manufacturing costs and environmental safety. For comparison, a CdS‐ZnO NW photoanode was also prepared using the layer‐by‐layer growth method. Ultraviolet photoelectron spectroscopy analysis revealed type‐II band alignments for the band structures of both photoanodes which facilitate electron transfer/collection. Compared to CdS‐ZnO QDSSCs, Ag₂S‐ZnO QDSSCs exhibit a considerably higher short‐circuit current density (J_sc) and a strongly enhanced light‐harvesting efficiency, but lower open‐circuit voltages (V_oc), resulting in almost the same power‐conversion efficiency of 1.2 %. Through this work, we demonstrate Ag₂S as an efficient quantum‐dot‐sensitizing material that has the potential to replace Cd‐based sensitizers for eco‐friendly applications.     

Effect of Molecular Crowding on the Temperature–Pressure Stability Diagram of Ribonuclease A

FT‐IR spectroscopic and thermodynamic measurements were designed to explore the effect of a macromolecular crowder, dextran, on the temperature and pressure‐dependent phase diagram of the protein Ribonuclease A (RNase A), and we compare the experimental data with approximate theoretical predictions based on configuration entropy. Exploring the crowding effect on the pressure‐induced unfolding of proteins provides insight in protein stability and folding under cell‐like dense conditions, since pressure is a fundamental thermodynamic variable linked to molecular volume. Moreover, these studies are of relevance for understanding protein stability in deep‐sea organisms, which have to cope with pressures in the kbar range. We found that not only temperature‐induced equilibrium unfolding of RNase A, but also unfolding induced by pressure is markedly prohibited in the crowded dextran solutions, suggesting that crowded environments such as those found intracellularly, will also oppress high‐pressure protein unfolding. The FT‐IR spectroscopic measurements revealed a marked increase in unfolding pressure of 2 kbar in the presence of 30 wt % dextran. Whereas the structural changes upon thermal unfolding of the protein are not significantly influenced in the presence of the crowding agent, through stabilization by dextran the pressure‐unfolded state of the protein retains more ordered secondary structure elements, which seems to be a manifestation of the entropic destabilization of the unfolded state by crowding.     

CuNPs@Cu（Ⅱ）-AMTD金属有机凝胶复合材料的合成及其催化性能

在Cu（Ⅱ）-AMTD金属有机凝胶基质中原位生长铜纳米粒子,得到了CuNPs@Cu（Ⅱ）-AMTD纳米复合材料,并分别进行了IR,SPR,SEM,TEM,EDX,XPS等测试分析其形貌组成。所得材料对4-硝基酚还原为4-氨基酚以及其他硝基苯的还原反应显示了优良的催化性能。同时也讨论了催化反应的机理。