The effect of Sn dopant on crystal structure and photocatalytic behavior of nanostructured titania thin films

In this study, preparation of Sn doped (0–30 mol % Sn) TiO₂ dip-coated thin films on glazed porcelain substrates via sol–gel process have been investigated. The effects of Sn content on the structural, optical, and photo-catalytic properties of applied thin films have been studied by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), field emission SEM (FE-SEM), and high resolution transmission electron microscopy (HR-TEM). Surface topography and surface chemical state of thin films were examined by atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). XRD patterns showed an increase in peak intensities of the rutile crystalline phase by increasing the Sn dopant. The prepared Sn-doped TiO₂ photo-catalyst films showed optical absorption edge in the visible light area and exhibited excellent photo-catalytic ability for degradation of methylene blue solution under UV irradiation. The result shows that doping an appropriate amount of Sn can effectively improve the photo-catalytic activity of TiO₂ thin films, and the optimum dopant amount is found to be 15 mol%. The Sn⁴⁺ dopants substituted Ti⁴⁺ in the lattice of TiO₂ and increased surface oxygen vacancies and the surface hydroxyl groups. TEM results showed small increase in planar spacing (was detected by HR-TEM caused by Sn dopants in titania based crystals).     

Raft mediated surface grafting of t‐butyl acrylate onto an ethylene–propylene copolymer initiated by gamma radiation

RAFT mediated grafting of poly(t‐butyl acrylate) onto the surface of a commercial poly(ethylene‐co‐propylene), Elpro, has been carried out using initiation by ⁶⁰Co γ‐radiation at 298 and 273 K. The polymerizations were in bulk monomer and using the RAFT agent 1‐phenylethyl phenyldithioacetate. The rates of homopolymerization and grafting were found to decrease with increasing RAFT agent concentration, indicating that both polymerization processes involve participation of the RAFT agent. There was good agreement between the predicted and experimental molecular weights of the homopolymer that had a narrow polydispersity. The poly(t‐butyl acrylate) grafts were hydrolyzed by trifluoroacetic acid to form poly(acrylic acid) grafts, which could either be further functionalized or used to control the surface polarity of the Elpro. ATR‐FTIR spectroscopy was used to characterize the grafts and Raman spectroscopy was used to assess the depth of the grafts. The water contact angle for the Elpro surface grafted with poly(acrylic acid) was found to be linearly dependent on the amount of the graft present. The living nature of the grafted chains was demonstrated by the addition of a second block of polystyrene. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1074–1083, 2007     

掺杂双(N-2-甲基苯基-水杨醛亚胺)合铜(II)配合物的碳糊电极电催化测量过氧化氢HosseinKhoshro,HamidR.Zare,RasoulVafazadeh简

The electrochemical behavior of a bis(N-2-methylphenyl-salicyldenaminato)copper(Ⅱ) complex spiked in a carbon paste electrode (BMPSCu-CPE) and its electrocatalytic reduction of H₂O₂ were examined using cyclic voltammetry, chronoamperometry, and differential pulse voltammetry. Cyclic voltammetry was used to study the redox properties of BMPSCu-CPE at various potential scan rates. The apparent charge transfer rate constant and the transfer coefficient for the electron transfer between BMPSCu and the carbon paste electrode (CPE) were 1.9±0.1 s^-1 and 0.43, respectively. BMPSCu-CPE had excellent electrocatalytic activity for H₂O₂ reduction in 0.1 mol/L phosphate buffer solution (pH 5.0), and it decreased the overpotential by 300 mV as compared to CPE alone. The diffusion coefficient and kinetic parameters such as the heterogeneous catalytic electron transfer rate constant and electron transfer coefficient for the reduction of H₂O₂ at the BMPSCu-CPE surface were also determined using electrochemical methods. Differential pulse voltammetry showed two linear dynamic ranges of 1.0-10.0 and 10.0-300.0 μmol/L and a detection limit of 0.63 μmol/L H₂O₂. The BMPSCu-CPE has excellent reproducibility and long term stability, and it was successfully applied for the determination of H₂O₂ in two pharmaceutical samples: an antiseptic solution and a hair dying cream.     

在3,4-二羟基肉桂酸介质中以多壁碳纳米管为传感器电催化检测L-半胱氨酸(英文)

A highly sensitive electrochemical sensor was prepared for the determination of L-cysteine using a modified multiwall carbon nanotubes paste electrode in the presence of 3,4-dihydroxycinnamic acid(3,4-DHCA) as a mediator, based on an electrocatalytic process. The results indicate that the electrode is electrocatalytically efficient for the oxidation of L-cysteine in the presence of 3,4-DHCA. The interaction between the mediator and L-cysteine can be used for its sensitive and selective determination. Using chronoamperometry, the catalytic reaction rate constant was calculated to be 2.37 × 102 mol–1 L s–1. The catalytic peak current was linearly dependent on the L-cysteine concentration in the range of 0.4–115 μmol/L. The detection limit obtained by linear sweep voltammetry was 0.25 μmol/L. Finally, the modified electrode was examined as a selective, simple, and precise new electrochemical sensor for the determination of L-cysteine in real samples.     

Study of Slip Flow in Unconventional Shale Rocks Using Lattice Boltzmann Method: Effects of Boundary Conditions and TMAC

Steady, laminar, fully developed flows of a Newtonian fluid driven by a constant pressure gradient in (1) a curvilinear constant cross section triangle bounded by two straight no-slip segments and a circular meniscus and (2) a wedge bounded by two rays and an adjacent film bulging near the corner are studied analytically by the theory of holomorphic functions and numerically by finite elements. The analytical solution of the first problem is obtained by reducing the Poisson equation for the longitudinal flow velocity to the Laplace equation, conformal mapping of the corresponding transformed physical domain onto an auxiliary half-plane and solving there the Signorini mixed boundary value problem (BVP). The numerical solution is obtained by meshing the circular sector and solving a system of linear equations ensuing from the Poisson equation. Comparisons are made with known solutions for flows in a rectangular conduit, circular annulus and Philip’s circular duct with a no-shear sector. Problem (2) is treated by the Saint-Venant semi-inverse method: the free surface (quasi-meniscus) is reconstructed by a one-parametric family, which specifies a holomorphic function of the first derivative of the physical coordinate with respect to an auxiliary variable. The latter maps the flow domain onto a quarter of a unit disc where a mixed BVP for a characteristic function is solved by the Zhukovsky–Chaplygin method. Velocity distributions in a cross section perpendicular to the flow direction are obtained. It is shown that the change of the type of the boundary condition from no slip to perfect slip (along the meniscus) causes a dramatic increase of the total flow rate (conductance). For example, the classical Saint-Venant formulae for a sector, with all three boundaries being no-slip segments, predict up to four times smaller rate as compared to a free surface meniscus. Mathematically equivalent problems of unconfined flows in aquifers recharged by a constant-intensity infiltration are also addressed.     

On {\phi}-contractibility of the Lebesgue–Fourier algebra of a locally compact group

For a locally compact group G, we present some characterizations for f{\phi}-contractibility of the Lebesgue–Fourier algebra LA(G){\mathcal{L}A(G)} endowed with convolution or pointwise product.     

Inner- and outer-sphere complexation of ions at the goethite-solution interface

Formation of inner- and outer-sphere complexes of environmentally important divalent ions on the goethite surface was examined by applying the charge distribution CD model for inner- and outer-sphere complexation. The model assumes spatial charge distribution between the surface (0-plane) and the next electrostatic plane (1-plane) for innersphere complexation and between the 1-plane and the head end of the diffuse double layer (2-plane) for the outersphere complexation. The latter approach has been used because the distance of closest approach to a charged surface may differ for different ions. The surface structural approach implies the use of a Three-Plane model for the compact part (Stern layer) of solid-solution interface, which is divided into two layers. The thickness of each layer depends on the capacitance and the local dielectric constant. The new approach has been applied to describe the adsorption of magnesium, calcium, strontium, and sulfate ions. It is shown that the concept can successfully describe the development of surface charge in the presence of Ca(+2), Mg(+2), Sr(+2), and SO4(-2) as a function of loading, pH, and salt level, and also the shift in the isoelectric point (IEP) of goethite. The CD modeling revealed that, for the conditions studied, magnesium is mainly adsorbed as a bidentate innersphere complex, calcium can be a combination of bidentate innersphere and a monodentate inner- or outer-sphere complexes, and strontium is probably adsorbed as an outersphere complex. Sulfate is present as a mixture of inner- and outer-sphere monodentate complexes. Outersphere complexation is less pH dependent than innersphere complexation. The CD model predicts that the outersphere complexation of divalent cations and anions is relatively favorable at respectively low and high pH. Increase of ion loading favors the formation of innersphere complexes.     

A new surface structural approach to ion adsorption: tracing the location of electrolyte ions

Electrolyte ions differ in size leading to the possibility that the distance of closest approach to a charged surface differs for different ions. So far, ions bound as outersphere complexes have been treated as point charges present at one or two electrostatic plane(s). However, in a multicomponent system, each electrolyte ion may have its own distance of approach and corresponding electrostatic plane with an ion-specific capacitance. It is preferable to make the capacitance of the compact part of the double layer a general characteristic of the solid-solution interface. A new surface structural approach is presented that may account for variation in size of electrolyte ions. In this approach, the location of the charge of the outersphere surface complexes is described using the concept of charge distribution in which the ion charge is allowed to be distributed over two electrostatic planes. It was shown that the concept can successfully describe the pH dependent proton binding and the shift in the isoelectric point (IEP) in the presence of variety of monovalent electrolyte ions, including Li(+), Na(+), K(+), Cs(+), Cl(-), NO(-)(3), and ClO(-)(4) with a common set of parameters. The new concept also sheds more light on the degree of hydration of the ions when present as outersphere complexes. Interpretation of the charge distribution values obtained shows that Cl(-) ions are located relatively close to the surface. The large alkali ions K(+), Cs(+), and Rb(+) are at the largest distance. Li(+), Na(+), NO(-)(3), and ClO(-)(4) are present at intermediate positions.