Surface-renewable cobalt(II) hexacyanoferrate-modified graphite organosilicate electrode and its electrocatalytic oxidation of thiosulfate

Cobalt(II) hexacyanoferrate (CoHCF) was deposited on graphite powder by an in situ chemical deposition procedure and then dispersed into methyltrimethoxysilane-derived gels to prepare a surface-renewable CoHCF-modified electrode. The electrochemical behavior of the modified electrode in different supporting electrolyte solutions was characterized by cyclic voltammetry. In addition, square-wave voltammetry was employed to investigate the pNa-dependent electrochemical behavior of the electrode. The CoHCF-modified electrode showed a high electrocatalytic activity toward thiosulfate oxidation and could thus be used as an amperometric thiosulfate sensor.

Amperometric determination of thiosulfate at a surface-renewable nickel(II) hexacyanoferrate-modified carbon ceramic electrode

Graphite powder-supported nickel(II) hexacyanoferrate (NiHCF) was prepared by the in situ chemical deposition method and then dispersed into methyltrimethoxysilane-derived gels to form a conductive composite. The composite was used as electrode material to construct a surface-renewable three-dimensional NiHCF-modified carbon ceramic electrode. Electrochemical behavior of the chemically modified electrode was well characterized using cyclic and square-wave voltammetry. The electrode presented a good electrocatalytic activity toward the oxidization of thiosulfate and thus was used as an amperometric sensor for thiosulfate in the photographic waste effluent. In addition, the electrode exhibited a distinct advantage of surface-renewal by simple mechanical polishing, as well as simple preparation, good chemical and mechanical stability. (C) 2001 Elsevier Science B.V. All rights reserved.

硫代硫酸钠及葡萄糖对蓝细菌Synechocystis sP.PCC6803脂及光合器组成的影响

本文通过对蓝细菌Synechocystis sp. PCC 6803在添加葡萄糖、Na2S203的BG-11培养基中的生长特性、脂类及脂肪酸组成、细胞低温荧光、色素组成进行分析测定，总结出如下规律： 当蓝细菌Synechocystis sp. PCC 6803在添加有葡萄糖的BG-11培养基中培养时细胞出现了一种新的糖脂（记为糖脂-x），在添加果糖、麦芽糖、乳糖等其它碳源的培养基中生长的细胞中也检测到糖脂-x糖脂-x的出现经推测是与活性氧相作用的产物，当在含糖的培养基中加入活性氧猝灭剂Na2S203时能有效地抑制糖脂-x的出现。糖脂一x的出现伴随着其它脂、尤其是双半乳糖甘油二酯(DGDG)的含量下降，这可能与细胞营养代谢类型的转变相适应。糖脂-x的出现使细胞适应异养生长条件，这时藻胆体(PBS)，光系统II(PSII)，光系统I(PSD降解，叶绿素消失。 糖脂-x经1H-NMR波谱术检测证实为甘油糖脂，经气质联谱分析其脂肪酸组成中含大量的枝链脂肪酸，12-甲基十四碳酸、12-甲基十五碳酸、12-甲基十六碳酸以及两种稀有的含氮脂肪酸。这些脂肪酸在添加高浓度葡萄糖的培养基中生长的．Synechocystis sp. PCC 6803中的单半乳糖甘油二酯(MGDG)也能检测到。ESI-MS以及P-SI-MS测定结果表明糖脂．x含一分子的脂酰基侧链以及两分子的己糖，半乳糖与葡萄糖。 对．Synechocystis sp. PCC 6803生长在不同浓度的葡萄糖与Na2S203培养基中脂类组成与脂肪酸组成进行比较，发现Na2S203能有效地增加膜脂中硫代异鼠李糖二酰基甘油(SQDG)和磷脂酰甘油(PG)的百分含量，培养基中同时添加葡萄糖时能抵消Na2S203的这一效应。此外，Na2S203能显著增加单半乳糖甘油二酯(MGDG)、双半乳糖甘油二酯(DGDG)中十六碳酸(C16:0)的百分含量，这一效应也能为葡萄糖恢复。Na2S203不能显著地改变SQDG中C16:0的百分含量，加入葡萄糖时能降低C16:0的百分含量。这些结果说明Na2S203可能充当一种还原剂使膜脂处于一种低的不饱和状态，同时加入葡萄糖时能降低Na2S203的还原力。此外，Na2S203还可作为SQDG合成中的硫供体。 用HPLC测定．Synechocystis sp. PCC 6803在添加不同浓度的Na2S203，葡萄糖的BG-11培养基中生长时的叶绿素与类胡萝卜素浓度，结果表明葡萄糖表现出对叶绿素与类胡萝卜素水平的抑制效应，Na2S203在低浓度时表现出对叶绿素与类胡萝卜素水平的促进效应，但在高浓度时表现出抑制效应。因此适当浓度的Na2S203的加入有利于维持蓝细菌在培养基中添加葡萄糖的生长条件下的低水平自由基，能使葡萄糖表现出促进细胞生长的特性。 通过测定Synechocystis sp. PCC 6803生长曲线中葡萄糖、Na2S203的浓度效应，结果表明葡萄糖在低浓度（例如5 mmoI.L-l）时表现出促进细胞的生长，在相对高的浓度表现出抑制细胞生长的效应。在培养基中同时加入Na2S203时可恢复葡萄糖对细胞的生长的促进效应。单独加入Na2S203表现出对细胞生长的抑制效应。这说明葡萄糖、Na2S203对细胞的生长存在着正的协同效应。

A novel urchinlike gold/platinum hybrid nanocatalyst with controlled size

In this paper, we have explored a simple and new strategy to obtain quasimonodisperse Au/Pt hybrid nanoparticles (NPS) with urchinlike morphology and controlled size and Pt shell thickness. Through changing the molar ratios of Au to Pt, the Pt shell thickness of urchinlike Au/Pt hybrid NPs could be easily controlled; through changing the size of Au NPs (the size was easily controlled from similar to 3 to similar to 70 nm via simple heating of HAuCl4-citrate aqueous solution), the size of urchinlike Au/Pt hybrid NPs could be facilely dominated. It should be noted that heating the solution (100 degrees C) was very necessary for obtaining three-dimensional (3D) urchinlike nanostructures while H2PtCl6 was added to gold NPs aqueous solution in the presence of reductant (ascorbic acid). The electrocatalytic oxygen reduction reaction (ORR, a reaction greatly pursued by scientists in view of its important application in fuel cells) and the electron-transfer reaction between hexacyanoferrate(III) ions and thiosulfate ions of urchinlike Au/Pt hybrid NPs were investigated. It is found that the as-prepared urchinlike Au/Pt hybrid NPs exhibited higher catalytic activities than that of similar to Pt NPs with similar size.

A General Route to Construct Diverse Multifunctional Fe3O4/Metal Hybrid Nanostructures

We have developed a simple, efficient, economical, and general approach to construct diverse multifunctional Fe3O4/metal hybrid nanostructures displaying magnetization using 3-aminopropyltrimethoxysilane (APTMS) as a linker. High-density Au nanoparticles (NPs) could be supported on the surface of superparamagnetic Fe3O4 spheres and used as seeds to construct Au shell-coated magnetic spheres displaying near-infrared (NIR) absorption., which may make them promising in biosensor and biomedicine applications. High-density flower-like Au/Pt hybrid NPs could be supported on the surface of Fe3O4 spheres to construct multifunctional hybrid spheres with high catalytic activity towards the electron-transfer reaction between potassium ferricyanide and sodium thiosulfate. High-density Ag or Au/Ag core/shell NPs could also be supported on the surface of Fe3O4 spheres and exhibited pronounced surface-enhanced Raman scattering (SERS), which may possibly be used as an optical probe with magnetic function for application in high-sensitivity bioassays.

"Green synthesis" of monodisperse Pt nanoparticles and their catalytic properties

A green synthetic strategy to prepare monodisperse Pt nanoparticles was reported. Aminodextran acted as the reductive and protective agents, and Pt nanoparticles were characterized by UV/vis spectroscopy (UV-vis), Pt nanoparticles were conveniently obtained at one step. transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). By changing the initial molar ratio of arninodextran to platinum precursor, Pt nanoparticles with different size were obtained. Amino groups of aminodextran could absorb on Pt nanoparticles surfaces and serve as a very good stabilizer. However, dextran without amino groups could not effectively stabilize Pt nanoparticles and aggregation of Pt nanoparticles were obtained. Catalytic activity of these Pt nanoparticles for the electron-transfer reaction between hexacyanoferrate (III) ions and thiosulfate ions was also studied, and they showed good catalytic efficiency.

Carboxyl-cored dendrimer and toluene-assisted fabrication of uniform platinum nanodendrites at a water/oil interface and their potential application as a catalyst

Uniform platinum nanodendrites have been prepared at a water/oil interface by a facile catalyst-free method at room temperature. This is carried out by introducing NaBH4 into the platinum precursor solution in the presence of the second generation of carboxyl-cored dendrimer ([G-2]-CO2H dendrimer) and toluene to act as a protective agent and a linker, respectively. The average fractal dimension of 1.61 of the obtained platinum nanodendrites is calculated by analysing the transmission electron micrographs using the programs Fractal Dimension Version 1.1 and Fractal Dimension Calculator. Control experiments show that the fabrication of platinum nanodendrites can be operated with a wide parameter window, which undoubtedly raises the degree of control of the synthesis process. The potential application of such a nanostructure as a catalyst is investigated, and the results reveal that they show highly efficient catalytic properties for the typical redox reaction between hexacyanoferrate (III) and thiosulfate ions at 301 K.

Surface renewable graphite organosilicate composite electrode containing indium(III) hexacyanoferrate(II/III)

Indium(III) hexacyanoferrate(II/III) (InHCF) supported on graphite powder was prepared using the in situ chemical deposition procedure and subsequently dispersed into methyltrimethoxysilane-derived gels to yield a conductive graphite organosilicate composite. The composite was used as the electrode material to fabricate a three-dimensional InHCF-modified electrode. InHCF acts as a catalyst, graphite powder ensures conductivity by percolation, the silicate provides a rigid porous backbone and the methyl groups endow hydrophobicity and thus limit the wetting section of the modified electrode. The chemically modified electrode can electrocatalyze the oxidation of thiosulfate, and exhibits a good repeatability of surface-renewal by simple mechanical polishing, as well as simple preparation, good chemical and mechanical stability.