Generalized Einstein relation and the Metzler-Klafter conjecture in a composite-subdiffusive regime

In this paper, a generalized diffusion model driven by the composite-subdiffusive fractional Brownian motion (FBM) is employed. Based on this stochastic process, we derive a fractional Fokker-Planck equation (FFPE) and obtain its solution. It is proved that the Generalized Einstein Relation (GER) and the Metzler and Klafter conjecture on the asymptotic behavior of stretched Gaussian hold the FFPE in a composite-subdiffusive regime.     

Effect of annealing temperature on photocatalytic activity of ZnO thin films prepared by sol-gel method

Zinc oxide thin films are deposited on Si and quartz substrates using the sol-gel method. The thin films, annealed at 400, 600 and 800 °C respectively, are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), ultraviolet-visible spectrophotometer (UV-Vis), fluorescence spectrometer (FL) and the photocatalytic activity is tested by the decomposition of methyl orange dye under UV illumination. The results show that the mean grain size, surface-to-volume ratio, rms roughness and degradation efficiency of the thin films increases with increasing annealing temperature. In particular, ZnO thin film annealed at 800 °C exhibits the highest photocatalytic activity, degrading methyl orange by almost 88% in 180 min. Photocatalytic reaction mechanism of the ZnO thin films is discussed in detail, and the oxygen defects are proposed to be the active sites of the ZnO photocatalyst.     

First-principles study of structural, electronic and elastic properties of single crystal CuZr

Investigations into the structural, electronic and elastic properties of intermetallic CuZr compound had been conducted by the plane-wave pseudopotential method. The calculated lattice constant was consistent well with the experimental value. The absence of band gap and finite value of the density of states (DOS) at the Fermi level reveal the metallic behavior of CuZr crystal, and Zr 4d states give rise to the electrical conductivity. The calculated elastic constants for single crystal CuZr at zero pressure obey the cubic mechanical stability condition, which indicates that the cubic CuZr crystal is mechanical stable at zero pressure. By analyzing the ratio between the bulk and shear moduli, we conclude that CuZr crystal is ductile in nature. The present theoretical investigations might give prediction to polycrystalline CuZr system.     

Programming resistive switching memory by a charged capacitor

The performances of bulk-heterojunction (BHJ) solar cells are investigated for time-dependent thermal annealing with different morphology evolution scales, having special consideration for the diffusion and aggregation of fullerene derivative molecules based on blends of poly(3-hexylthiophene):[6,6]-phenyl-C₆₁-butyric acid methyl ester (P3HT:PCBM). Meaningfully, rapid formation of dot-like and needle-like crystalline PCBM structures of a few micrometers up to 60 μm in size is obtained with thermal annealing treatment from 2 to 15 min, which dynamically reflects a fast process of PCBM molecule and cluster aggregation. Upon ultrasonic-assisted processing and annealing treatment, the scale of P3HT crystals is drastically increased in view of X-ray diffraction (XRD) patterns, leading to a high hole mobility. And, the P3HT domains can be gradually converted into larger P3HT crystals approved by the decreased full width at half-maximum in the XRD patterns. Corresponding current–voltage curves are measured in quantity and we propose a model to explain the effect of the crystalline degree of P3HT domains and aggregation of PCBM molecules and clusters on the phase segregation, expressing a viewpoint towards high performance of BHJ solar cells.     

Preferred structures of the atomic Ag islands on silicone oil surfaces

Varying the substrate temperature T(s) from 285 to 353 K, both the aggregation behavior of Ag atoms and the preferred structures of the atomic Ag islands on silicone oil surfaces are investigated. After deposition, the deposited Ag atoms form isolated islands with a preferred height. Our observations reveal that, as T(s) increases, the preferred island height increases from 20.0 to 33.0 nm, which results in the decrease of the Ag apparent coverage, from 9.6 ± 0.1% to 6.5 ± 0.3%. Further, the crystal structure of the Ag islands changes from amorphous to polycrystalline as the substrate temperature T(s) goes up. Subsequently a 3D aggregation mechanism of the Ag atoms on the liquid substrates is proposed.     

Theoretical study on the solvent effect of the nitrosyl cation (NO+) generating reaction

Nitrosyl cation (NO⁺) generating reaction HONO + H⁺ → NO⁺ + H₂O has been theoretically investigated by B3LYP and high‐electron‐correlation QCISD methods with 6‐31G (d,p) basis set. The solvent effects on the geometries, reaction path properties, energies, thermodynamic, and kinetic characters in four solvents (benzene, tetrahydrofuran, acetonitrile, and water) have been calculated using self‐consistent reaction field (SCRF) approach with the polarizable continuum model (PCM). The results show that the activation energy barriers and the relative energies of the products are decreased with increase of the polarities of the solvents, and the reaction is favored in polar solvents thermodynamically and kinetically. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Selective substitution reactions of methoxycarbonylamino‐1‐(1‐benzotriazolyl)alkanes with active methylene compounds

Benzotriazole adducts methoxycarbonylamino‐1‐(1‐benzotriazolyl)alkanes 1 were derived from the condensation of an aldehyde, benzotriazole, and methylcarbamate. The leaving tendency of methoxycarbonylamino group (MeOCONH) and benzotriazole group (Bt) was investigated by treatment of the adducts with active methylene compounds under either Lewis acid‐catalyzed or basic conditions. In the presence of SmI₃, MeOCONH take priority over Bt in the leaving process, whereas in the presence of MeONa, the Bt was substituted in preference. Thus, the tunable substitution of the two leaving groups could be used for different synthetic purposes. J. Heterocyclic Chem., 00 , 00 (2011).     

Brønsted acid-catalyzed decarboxylative redox amination: formation of N-alkylindoles from azomethine ylides by isomerization

A Br?nsted acid-catalyzed decarboxylative redox amination involving aldehydes with 2-carboxyindoline for the synthesis of N-alkylindoles is described. The decarboxylative condensations of aldehydes with 2-carboxyindoline produce azomethine ylides in situ, which then transform into N-alkylindoles by isomerization.     

Ultrasensitive fluorescence detection of glutaraldehyde in water samples with bovine serum albumin-Au nanoclusters

Based on the cross-linking nature of BSA in the presence of glutaraldehyde (GA), the fluorescence of BSA-stabilized Au nanoclusters was effectively quenched by GA. A new method for ultrasensitive GA detection in water samples was thus developed with fluorescent BSA-stabilized Au nanoclusters. The fluorescence quenching of BSA-stabilized Au nanoclusters in the presence of GA fitted to Stern-Volmer equation. In the GA concentration range of 0.8–6 μM, a linear relationship of F₀/F versus GA concentration was obtained with a limit of detection (LOD) of 0.2 μM. The relative standard deviation of 5 replicate measurements of 4 μM GA is 1.3%. This method shows good selectivity over other organics in water samples. The feasibility of the new sensor for GA in different water samples was demonstrated.     

Polycyclic aromatic hydrocarbons (PAHs) pollution recorded in annual rings of gingko (Gingko biloba L.): Determination of PAHs by GC/MS after accelerated solvent extraction

Retrospective monitoring of polycyclic aromatic hydrocarbons (PAHs) pollution levels was demonstrated by analyzing the annual rings of gingko (Gingko biloba L.) sampled from the Chengdu plain of southwest China. The samples of gingko trunk section, leaf, bark and its host soil were analyzed for PAHs by gas chromatography/mass spectrometry (GC/MS) after optimized accelerated solvent extraction (ASE). Compared to ultrasonic or soxhlet, ASE has high extraction efficiency thus meaningful contamination information contained in trunk tissue. The distribution of PAHs in gingko trunk, leaf and its host soil indicates that the main uptake pathway might be gaseous and particles-bound deposition via foliage with the exception of two-ring compounds from root, such as Nap and 2-methyl-Nap. PAHs in gingko trunk could be used to reveal the regional and historical contamination information, which is consistent with the environmental history of events (straw incineration) in Chengdu.