Thermal-, photo- and electron-induced reactivity of hydrogen species on rutile TiO2(110) surface: Role of oxygen vacancy

The formation and reactivity of various types of hydrogen species on rutile TiO₂(110), including surface hydroxyl group, surface hydride species and bulk hydrogen species sensitively depend on the oxygen vacancy concentration and structure.     

Enhanced mechanical properties of carbon fiber composites by grafting different structural poly(amido amine) onto fiber surface

The mechanical properties of carbon fiber composites depend on the interfacial strength between fiber and epoxy matrix. Different poly (amido amine) (PAMAM) dendrimers were grafted onto carbon fiber to improve the interfacial strength of the resulting composites. Functional groups on the carbon fiber surface were examined by X-ray photoelectron spectroscopy. The surface morphology of the resulting materials was characterized by scanning electron microscopy and atomic force microscope. The characterization results revealed that PAMAM dendrimers were chemically grafted onto the surface of carbon fiber. More importantly, the mechanical properties of the resulting composites were enhanced owing to the presence of sufficient functional groups on the carbon fiber surface. In addition, after PAMAM containing chair conformations were grafted, the interlaminar shear strength had the highest increase of 53.13%, higher than that of the fiber grafted with PAMAM containing terminated linear amine. This work provides an alternative approach to enhance the mechanical properties of fiber composites by controlling the interface between fiber and epoxy matrix.     

Relationship between the volume phase transition and the surface area of poly (N-isopropylacrylamide) and poly (N-isopropylacrylamide-co-sodium methacrylate) hydrogels

The volume phase transition of poly(N-isopropylacrylamide) (PNIPAAm) and poly(N-isopropylacrylamide-co-sodium methacrylate) (P(NIPAAm-co-SMA)) hydrogels was investigated with consideration of the pore characteristics. The volume phase transition temperature of the hydrogel increased by incorporating sodium methacrylate (SMA). Based on the BET equation, the surface area was evaluated by a gas adsorption method. The surface area of PNIPAAm and P(NIPAAm-co-SMA) hydrogels decreased with increasing temperature, resulting from the fact that the depth and the size of pores decreased significantly in the course of the volume phase transition. Hence, it is suggested that the change of surface area has a close relationship with the volume phase transition of PNIPAAm and P(NIPAAm-co-SMA) hydrogels.     

Chemical images of marine bio-active compounds by surface enhanced Raman spectroscopy and transposed orthogonal partial least squares (T-OPLS)

Surface enhanced Raman spectroscopy combined with transposed Orthogonal Partial Least Squares (T-OPLS) was shown to produce chemical images of the natural antibacterial surface-active compound 1,1,3,3-tetrabromo-2-heptanone (TBH) on Bonnemaisonia hamifera. The use of gold colloids functionalised with the internal standard 4-mercapto-benzonitrile (MBN) made it possible to create images of the relative concentration of TBH over the surfaces. A gradient of TBH could be mapped over and in the close vicinity of the B. hamifera algal vesicles at the attomol/pixel level.     

TiCl4(THF)2 impregnation on a flat SiOx/Si(1 0 0) and on polycrystalline Au foil: determination of surface species using XPS

TiCl₄(THF)₂ was impregnated by spin-coating on a Si(1 0 0) wafer covered with a thin SiO_x layer and on a polycrystalline Au foil. The nature of the surface species was determined at room temperature and after annealing, by X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM). A mixed Si:O:Ti interfacial layer was formed on the silicon substrate while in the case of Au, TiOCl_x and TiO_x were the main surface species at room temperature. Annealing at 723 K leads to the total desorption of the Cl atoms, and in both cases a significant amount of Ti atoms was reduced to the Ti³⁺ state. AFM measurements revealed a homogenous distribution of nano-sized TiO_x clusters with semi-ellipsoid shape and increased contact area with the underlying silica.     

Zn(Ac)2/超高比表面积活性炭催化剂上乙炔法合成醋酸乙烯宏观动力学

在接近工业生产条件下研究了Zn(Ac)2/超高比表面积活性炭 (AＢＥＴ=2713m2/g) 催化剂上，乙炔法合成醋酸乙烯 (VAc) 反应宏观动力学，并与Zn(Ac)2/日本普通椰壳炭 (AＢＥＴ=1 384 m2/g) 催化剂进行了比较。实验结果求得两种不同比表面积载体催化剂的宏 观动力学方程分别为：υ1=28.22pＣ２Ｈ２1.00p VAc -0.62和υ2=25.03pＣ２Ｈ２1.01 p VAc -0.52，即合成 VAc的反应对乙炔是1级反应，对VAc是负的反应级数，载体的比表面积越高催化剂的 催化反应活性越高。求得在160 ℃～175 ℃两种催化剂反应的平均表观活化能分别为： 52.49 (kJ·mol-1)和53.87(kJ·mol-1)，均小于文献报道的反应真实活化能87.80(kJ·mol-1)。     

A downsized flow set up based on multicommutation for the sequential photometric determination of iron(II)/iron(III) and nitrite/nitrate in surface water

In this work, a downsized flow set up designed based on multicommutation concept for photometric determination of iron(II)/iron(III) and nitrite/nitrate is surface water is described. The flow system network comprised a set of three-way solenoid valves, reaction coil and a double-channel flow cell, which were nested in order to obtain a compact and small-size instrument. To accomplish the downsizing requirement light source (LED) and radiation detection (phototransistor) were coupled to the flow cell. In order to demonstrated the effectiveness of the system, the photometer methods based on Griess reaction and 1-10-phenantroline for nitrite and iron(II) determination, respectively, were selected. Under computer control the set up provided facilities to handle four reagent solutions employing a single pumping channel, thus permitting also the determination of nitrate and iron(III) after its reduction to nitrite and to iron(II), respectively. The overall system performance was demonstrated working several days running standard solution, no significant variation of base line, linear response range and slop (less than 1%) were observed. The usefulness of the downsized system was ascertained by analyzing a set of surface water. Aiming to access the accuracy sample were also analyzed employing reference procedures and no significant difference at 95% confidence level were observed for the four analytes. Other profitable features such as analytical throughput of 40 determination per hour; relative standard deviation of 1%; linear response range between 50 and 300 μg l⁻¹ for nitrite and nitrate, 0.5-6.0 mg l⁻¹ iron(II) and iron(III); low reagent consumption 75 μg for nitrate/nitrite and 0.6 mg for iron(II)/iron(III) per determination; and 2.4 ml waste generation per determination were also achieved.