Step‐Mediated Anisotropic Adsorption and Condensation of tert‐Butylamine on Cu(111)

Scanning tunneling microscopy (STM) combined with density functional theory (DFT) calculations were applied in studying the anisotropic adsorption and condensation of tert‐butylamine (t‐BA) molecules in the vicinity of the steps on the Cu(111) surface. The preferential adsorption at the upper step edges and uneven distribution of t‐BA in the vicinity of the steps illustrate the asymmetric electronic structure of the surface steps. Our observation demonstrates that the adsorption and diffusion of a polar molecule would be significantly mediated by steps on metal surfaces due to the molecule–step interaction and the intermolecular interactions.     

Simultaneous stacking of cationic and anionic compounds in single run capillary zone electrophoresis by two-end field amplified sample injection

In order to extend the application of field amplified sample injection (FASI) in high throughput analysis, a convenient and simple procedure, namely two-end field amplified sample injection (TE-FASI), was developed for the simultaneous stacking of cationic and anionic compounds in a single run capillary zone electrophoresis (CZE). Following the capillary-filling with a buffer of high conductivity, water plug was loaded into each end of the capillary; and two high-field strength zones were generated at both heads of the column when high voltage was applied. Therefore, under suppressed EOF cations and anions can be selectively FASI stacked at anode and cathode head, respectively. After separation, the stacked anions and cations are detected by a common detector placed in the center of the capillary. Under the optimized conditions, the limits of detection for the model cationic (matrine and oxymatrine) and anionic (5-sulfosalicylic acid) compounds were determined as 0.2, 0.2 and 0.06 ng/mL, respectively. Compared with non-stacking conditions, the sensitivities of these compounds were enhanced 1003-, 1330- and 1380-fold, respectively. The results of reproducibility, linearity and real sample analysis show that the proposed procedure is promising to be applied for the simultaneous quantification detection of trace cationic and anionic analytes.     

A simple and convenient synthesis of 2-(perfluoroalkyl)-4H-chromenes from salicyl N-tosylimines or salicylaldehydes and methyl 2-perfluoroalkynoates

Et₃N-catalyzed reactions of salicyl N-tosylimines or salicylaldehydes with methyl 2-perfluoroalkynoates proceed smoothly at room temperature in dichloromethane (DCM) or dimethyl sulfoxide (DMSO) to give the corresponding fluorinated chromenes in good to excellent yields with high regioselectivity.     

Study of valence state of iodine in simulated fuel solution of medical isotope production reactor

The effects of temperature, heating-time, concentration of HNO₃ and γ-ray irradiation on the valence states of iodine in a simulated fuel solution of a medical isotope production reactor (MIPR) were investigated. About 83% of I⁻ was oxidized to IO₃ ⁻ and 10% of I⁻ was oxidized to I₂ in uranyl nitrate solution after heating at 70 °C for 6 hours. Heating and existence of oxidant, U and ionizing radiation accelerate the oxidation process of iodine, and results in most of the iodine being produced in high oxidation states such as in IO₃ ⁻ and IO₄ ⁻. The results indicate that the production of ¹³¹I by MIPR can be carried out by extraction of iodine in high oxidation states from the fuel solution.     

Electrospinning and characterization of poly(vinyl alcohol)/chitosan oligosaccharide/clay nanocomposite nanofibers in aqueous solutions

Submicron fibers of the composite of poly(vinyl alcohol) (PVA), chitosan oligosaccharide [COS, (1→4)2-amino-2-deoxy-β-d-glucose], and montmorillonite clay (MMT) were prepared using electrospinning method with aqueous solutions. Scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), thermal gravimetric analyzer, and tensile strength testing machine (Zwick) were utilized to characterize the PVA/COS/MMT nanofiber mats morphology and properties. The PVA/COS ratio and MMT concentration play important roles in nanofiber mat properties. XRD and TEM data demonstrated that exfoliated MMT layers were well-distributed within nanofiber. It was also found that the mechanical property and thermal stability were increased with COS and MMT contents.     

卟啉－苝酰亚胺分子阵列的合成及应用进展

由于卟啉与苝酰亚胺基元之间存在高效的能量转移或电子转移过程, 卟啉-苝酰亚胺分子阵列表现出优良的光电性能, 在有机分子器件、有机太阳能电池和光收集材料等高新技术领域展示出广阔的应用前景. 综述了近十几年来卟啉-苝酰亚胺分子阵列的合成及应用研究进展, 并展望了其发展前景.     

Development of a highly sensitive and specific monoclonal antibody-based enzyme-linked immunosorbent assay (ELISA) for detection of Sudan I in food samples

The use of Sudan I as an additive in food products has been prohibited in the European Union and many other countries. In this study, a highly sensitive and specific monoclonal antibody (mAb)-based indirect competitive enzyme-linked immunosorbent assay (ELISA) for the detection of Sudan I in food samples was developed. The hapten derivative with a three-carbon-atom length of carboxylic spacer at the azobound para-position was synthesized and coupled to carrier proteins. The hapten-bovine serum albumin (BSA) conjugate was used as an immunogen, while the hapten-ovalbumin (OVA) conjugate was applied as a coating antigen. The mAb against Sudan I was produced by hybridoma technique and the corresponding ELISA was characterized in terms of sensitivity, specificity, precision and accuracy. At optimal experimental conditions, the standard curve was constructed in concentrations of 0.1-100 ng mL⁻¹. The values of IC₅₀ for nine standard curves were in the range of 1.1-2.0 ng mL⁻¹ and the LOD at a signal-to-noise ratio of 3 (S/N = 3) was 0.07-0.14 ng mL⁻¹. The cross-reactivity values of the mAb with Sudan II, III and IV were 9.5%, 33.9% and 0.95%; no cross-reactivity was found with other six edible colorants: Lemon yellow, Bright blue, Indigotin, Kermes, Amarant and Sunset yellow, indicating the assay displays not only high sensitivity but also high specificity as well. The organic solvent effect on the assay was tested. It was observed that the ELISA was tolerated to 30% of methanol and 10% of acetonitrile without significant loss of IC₅₀ value. Six food samples were spiked with Sudan I and the methanolic extracts after appropriate dilution were analyzed by ELISA. Acceptable recovery rates of 88.2-110.5% and coefficients of variation of 2.5-17.4% were obtained. The ELISA for nine spiked samples was confirmed by high-performance liquid chromatography (HPLC) with a high correlation coefficient of 0.9840 (n = 9). The mAb-based ELISA proven to be a feasible quantitative/screening method for Sudan I analysis in food samples with the properties of high sensitivity, specificity, simplicity of sample pretreatment, high sample throughput and low expense.     

β-氨基酸的合成: 等当体方法的应用

β-氨基酸是一类在药物开发和生物研究中有广泛应用的中间体. 由等当体合成β-氨基酸的方法具有结构定制、合成产物丰富、直观等特点, 是β-氨基酸合成领域中不可或缺的合成方法. 重点介绍近年来该领域具有代表性的工作.     

Molecular dynamics of CO in few-cycle laser fields

We experimentally study the ionization, fragmentation and Coulomb explosion of CO using 6 fs laser pulses. Different from previous observations in tens or hundreds of femtoseconds laser pulses, strong charge asymmetric dissociation and CO²⁺ are observed in the current intense few-cycle laser field.