Fabrication and characterization of ZnO-coated TiO2 nanotube arrays

In this study, we prepared highly ordered TiO₂ nanotube arrays on Ti through an anodizing process. Then, utilizing its proven antibacterial properties, we coated our TiO₂ nanotubes (TiO₂-NTs) with ZnO using the sol–gel method. We characterized the morphology, structure, and composition of the ZnO-coated TiO₂ nanotubes (ZnO-TNTs) using field-emission scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopy, respectively. We investigated surface topography and roughness of the coatings by atomic force microscopy operated in the tapping mode. Our results revealed impurity-free, anatase-phase TiO₂ nanotubes that are uniformly coated with a ZnO layer. Finally, we tested the antibacterial activity of ZnO-TNTs against Staphylococcus aureus, and found ZnO-TNTs significantly improved the antibacterial properties of Ti implants. We conclude that ZnO-TNTs provide Ti with antibacterial activity, which highlights its potential in orthopedic and dental implants.     

掺杂二氧化锡的二氧化钛的光学性质及其光催化特性

二氧化钛多相催化是一种极具前途的环境污染深度净化技术。 本文以钛酸四丁酯和四氯化锡为原料,无水乙醇为溶剂,采用溶胶-凝胶法制备了掺杂二氧化锡的二氧化钛薄膜和复合氧化物粉体。通过测量薄膜的吸收光谱推算光学能隙,结果发现掺杂样品的光学能隙比纯二氧化钛样品有所变小。随着热处理温度的提高,掺杂和纯二氧化钛样品的光学能隙都略微降低。X-射线衍射分析表明,复合氧化物粉体的热处理温度对样品的晶体结构和光催化性能有重要影响。以掺杂二氧化锡5 % 摩尔比的样品与纯二氧化钛对照,500 ℃以下热处理样品以锐钛矿结构为主,600 ℃热处理样品为锐钛矿与金红石相共存,并显示了较好的光催化性能。透射电子显微镜观察显示,同样600 ℃热处理,掺杂样品要比纯二氧化钛具有更小的颗粒尺寸。在700 ℃热处理的样品中,掺杂样品只存在金红石相而纯二氧化钛样品中仍存有锐钛矿相。用阿伦尼乌斯经验关系式推测的晶粒生长的活化能,纯二氧化钛47.486 kJ.mol, 掺杂5 % 摩尔比的复合氧化物样品33.103 kJ.mol。以亚甲基蓝为降解物质,考察了掺杂量和热处理温度对样品的光催化性能。     

Direct Electrochemistry of Cytochrome c on a Silica Sol‐Gel Film Modified Electrode

Dilute silica sol‐gel was simply dropped on the surface of a basal plane graphite electrode (BPGE) to form a silica sol‐gel film modified electrode. Direct electrochemical response of cytochrome c (Cyt c) on the modified electrode was observed by cyclic voltammetry (CV). The results suggested that Cyt c could be tightly adsorbed on the surface of the silica sol‐gel film modified electrode. A couple of well‐defined and nearly reversible redox peaks can be observed in a phosphate buffer solution (pH 7.0), which anodic and cathodic peak potentials were at ?0.243 and ?0.306 V (vs. Ag/AgCl), respectively. Cyt c adsorbed on the surface of silica sol‐gel film shows a remarkable electrocatalytic activity for the reduction of oxygen. Based on these, a third‐generation biosensor could be constructed to detect the concentration of oxygen in aqueous solution.     

Polyoxometalates entrapped in sol–gel matrices for reducing electron exchange column applications

Electron exchange columns were developed by utilizing the redox properties of polyoxometalates (POMs) entrapped in silica matrices via the sol–gel route. The properties of the columns strongly depend on the composition of the precursors used to prepare the matrices. The columns exhibit good reversibility and are the first ‘reducing’ electron exchange columns ever prepared. They are also the first columns where both the matrix and the entrapped redox agent are inorganic compounds. This increases their stability. However, the redox properties of the entrapped POMs in the matrices are affected by the composition of the matrices.     

The Peculiarities of Silica Aerogel Production Using Azeotropic Mixtures

At the first time it was carried out the theoretical researches regarding pathways to get into a supercritical region at the ambient pressure with the main aim to avoid expensive and hazardous supercritical drying process and to make a silica aerogel production in whole more economical and commercial. These investigations based on fundamental knowledge about the critical phenomena in multicomponent systems. The representation of phase states in such systems by graphical images was used for the estimation of LV (x_L = x_V) azeotrope influence on SLV and L?V equilibria. In the course of empiric selection of azeotropic mixtures the negative azeotropes advantage over positive ones was determined and grounded in theory. We report on the synthesis of hydrophobic silica aerogel by ambient pressure drying (APD) procedure, which involves two-step sol–gel process with tetraethyl orthosilicate (TEOS) as a silica precursor and isopropanol as the solvent and an elaborated flow chart using both types of azeotropes as the pore fluids. Guided by receiving our theoretical investigation, we obtained transparent crack-free silica aerogel samples with specific surface in the range of 711–913 m²/g, average pore diameter of ～95–137 nm, and density of ca. 0.39–0.081 g/cm³.     

烧绿石结构Y2-xMgxRu2O7-δ(x=0.05、0.1、0.15)的制备及其OER催化活性

采用溶胶-凝胶法制备系列的镁掺杂Y2-xMgxRu2O7-δ(YMRO?x,x=0.05、0.1、0.15)催化剂,通过X射线光电子能谱对其进行价态分析发现,采用小离子半径的Mg^2+取代烧绿石结构中处于A位的部分Y^3+,进一步增加了烧绿石结构中氧缺陷数量,也引发了部分Ru^4+转变为Ru^5+,释放电子到表面,促进了氧析出反应(OER)。其中YMRO?0.1催化剂的含氧缺陷浓度最高,其催化活性最高。在达到10 mA·cm^-2电流密度时,相比于RuO2(358 mV)、Y2Ru2O7-δ(294 mV),YMRO?0.1仅需施加265 mV过电位并且其Tafel斜率相对于RuO2(88 mV·dec^-1)和Y2Ru2O7-δ(64 mV·dec^-1)仅为45 mV·dec^-1。此外,由于氧空位增多,即活性位点增多,降低了自由基从金属位点脱附的吉布斯自由能,促进了OER催化性能。第一性原理表明,替位原子MgY与氧空位形成复合体,可以降低氧空位形成能,同时随着Mg^2+引入,带隙变小,电荷迁移能也随之变小,进而可以得到更高的催化活性。     

完全液相法Cu-Zn-Si-Al催化剂一步合成二甲醚

采用完全液相法,以廉价的硅溶胶作为硅原料,制备了一系列的Cu-Zn-Si-Al双功能浆状催化剂,考察不同硅铝比对浆态床CO加氢合成二甲醚的影响。 两周的活性评价表明,硅的引入显著提高了催化剂的活性和稳定性。 当n(Si)/n(Al)=2时,CO转化率最高,为58.1%,且二甲醚的选择性为80.2%。 通过FTIR、XRD、TPR、TPD、BET、XPS和TEM等技术手段对催化剂进行了表征,结果表明,硅组分的添加可以促进活性组分Cu物种的分散,并能够改善完全液相法热处理而导致的积碳现象。 且Si组分的引入与催化剂中的Al相互作用,显著提高了催化剂的甲醇脱水性能,从而使催化剂具有较高的二甲醚选择性。     

Homogeneous organic/inorganic hybrid scaffolds with high osteoinductive activity for bone tissue engineering

Composite scaffolds of polymers/β-tricalcium phosphate (TCP) have been widely used for bone regeneration due to the combination of osteoinductivity of TCP and mechanical properties of the polymers. However, the difference in surface properties of the two material causes composite has poor uniformity and weak two-phase interaction, resulting in poor TCP release and weak new bone-forming ability. In this research, a TCP sol was developed to replace traditional TCP nanoparticles for the preparation of homogeneous polycaprolactone (PCL)/TCP sol nanofibrous scaffolds. It was found that compared with TCP nanoparticles, TCP sol homogeneously distributed in PCL nanofibers, and greatly improved the hydrophilicity, biodegradability, and mechanical properties of the scaffolds. It is also confirmed that loading TCP sol promoted the formation of bone-like apatite on the surface of the scaffolds. Biological experiments showed that all scaffolds supported rat bone marrow mesenchymal stem cells (rBMSCs) proliferation, especially scaffolds loaded with TCP sol. The increase in alkaline phosphatase activity and collagen production, enhanced calcium deposition, and up-regulation of osteocalcin expression demonstrated that the loading TCP sol expanded an advantage of scaffolds in promoting rBMSCs osteogenic differentiation, suggesting it dramatically improved the osteoinductive activity of PCL/TCP hybrid system and had a great potential application in bone regeneration.     

The effective diffusivity in polycrystalline material in the presence of interphase boundaries

The problem of calculating the long-time-limit effective diffusivity in stable two-phase polycrystalline material is addressed for the first time. We make use of a phenomenological model where the high-diffusivity interphase boundaries are treated as connected ‘coatings’ of the individual grains. The derivation of expressions for the effective diffusivity with segregation is along the lines of the analysis by Maxwell in . Monte Carlo computer simulation using lattice-based random walks on a very fine-grained mesh is employed to test the validity of the expressions. It is shown that, for the specific cases analysed, the derived expressions for the effective diffusivity are in very good agreement with results from the simulations. Since the pattern of behaviour is not entirely clear at present, it is difficult to guide the choice for the best expression in a given case. The equivalent of the Hart equation for this problem is also derived. This equation is shown to be invariably in poor agreement with simulation results.