para-Sulfonatocalix[6]arene-modified silver nanoparticles electrodeposited on glassy carbon electrode: Preparation and electrochemical sensing of methyl parathion

In this paper, a new electrochemical sensor, based on modified silver nanoparticles, was fabricated using one-step electrodeposition approach. The para-sulfonatocalix[6]arene-modified silver nanoparticles coated on glassy carbon electrode (pSC₆-Ag NPs/GCE) was characterized by attenuated total reflection IR spectroscopy (ATR-IR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), etc. The pSC₆ as the host are highly efficient to capture organophosphates (OPs), which dramatically facilitates the enrichment of nitroaromatic OPs onto the electrochemical sensor surface. The combination of the host-guest supramolecular structure and the excellent electrochemical catalytic activities of the pSC₆-Ag NPs/GCE provides a fast, simple, and sensitive electrochemical method for detecting nitroaromatic OPs. In this work, methyl parathion (MP) was used as a nitroaromatic OP model for testing the proposed sensor. In comparison with Ag NPs-modified electrode, the cathodic peak current of MP was amplified significantly. Differential pulse voltammetry was used for the simultaneous determination of MP. Under optimum conditions, the current increased linearly with the increasing concentration of MP in the range of 0.01-80 μM, with a detection limit of 4.0 nM (S/N = 3). The fabrication reproducibility and stability of the sensor is better than that of enzyme-based electrodes. The possible underlying mechanism is discussed.     

Transition metal complexes as linkages for assembly of supertetrahedral T4 clusters

Tn clusters are usually connected into frameworks by sulfur bridges. A new type of T4 compounds in which the clusters are linked by both sulfur bridges and transition metal complexes are described.     

Theoretical study of the inhibitive properties of a group of benzimidazoles

In this work, a group of benzimidazoles, namely benzimidazole (BIM), 2‐hexyl benzimidazole (2‐HBIM), and 2‐benzyl chloride benzimidazole (2‐ClBBIM), have been studied using density functional theory (DFT) at the level of B3LYP with the 6‐31G (d) and 6‐311G (d, p) base sets in order to elucidate the different inhibition efficiencies and reactive sites of these compounds as corrosion inhibitors. Based on the calculated results, the studied molecules interact with Fe‐atoms mainly in their stable pyridine‐N protonated forms. It is found that the inhibition efficiencies of the stable protonated molecules involved in this study have a certain relation with some parameters, such as the highest occupied molecular orbital energy (E_HOMO) and the global hardness (η). The results indicate that the C (7) atoms, as the reactive sites, receive electrons from Fe‐atoms, benzene ring denote electrons to vacant orbital of Fe‐atoms. Additionally, Fukui indices and the orbital analyses suggest that 2‐ClBBIM has the highest reaction activity among the three molecules, the efficiency order of three inhibitors is found to be 2‐ClBBIM > 2‐HBIM > BIM, which accords with experimental results. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Electrochemical Behavior of Herbal Antitumor Drug Aloe‐Emodin at Carbon‐Coated Nickel Magnetic Nanoparticles Modified Glassy Carbon Electrode

The electrochemical behavior of aloe‐emodin (AE), an important herbal antitumor drug, was investigated at a carbon‐coated nickel magnetic nanoparticles modified glassy carbon electrode (CNN/GCE). A couple of well‐defined redox peaks was obtained. Some electrochemical parameters of AE at a CNN/GCE, such as the charge number, exchange current density, standard heterogeneous rate constant, were measured. The square wave voltammetry (SWV) response of AE was linear with the concentration over two concentration intervals viz. 6.24×10^?9?1.13×10^?6 M and 1.13×10^?6?1.23×10^?5 M, with a detection limit of 2.08 nM. A fast, simple and sensitive detection and analysis of AE was developed.     

Solvothermal synthesis of well-defined TiO(2) mesoporous nanotubes with enhanced photocatalytic activity

High efficiency TiO(2) photocatalyst in porous nanotubes were prepared by solvothermal alcoholysis of TiOSO(4) in the presence of carbon nanotube template.     

Development of fluorescent FeIII sensor based on chalcone

In this paper, 4-dimethylamino 2,5-dihydroxy chalcone (DMADHC), which exhibits excited state intramolecular charge transfer (ICT) characteristics, was synthesized and characterized. A sensitive optochemical sensor for Fe³⁺ ion was developed using DMADHC as fluorescence receptor. The fluorescence of DMADHC was gradually quenched with the addition of Fe³⁺ ion, which attributed to the formation of 1:1 complex between DMADHC and Fe³⁺ ion. The sensor exhibited excellent selectivity for Fe³⁺ ion over a large number of cation ions such as alkali, alkaline earth and transitional metal ions with a linear range of 3.984×10⁻⁷-1.135×10⁻⁵ and a limit of detection of 8.223×10⁻⁸ mol/L. On this basis, the sensor was preliminary applied to the determination of the content of iron ions in multi-vitamin tablet with satisfied results and the recoveries were in the 95-100% interval, and precision (n=5) was better than 5%.     

Visualizing electronic chirality and Berry phases in graphene systems using photoemission with circularly polarized light

Electronic chirality near the Dirac point is a key property of graphene systems, which is revealed by the spectral intensity patterns as measured by angle-resolved photoemission spectroscopy under various polarization conditions. Specifically, the strongly modulated circular patterns for monolayer (bilayer) graphene rotate by ±90° (±45°) in changing from linearly to circularly polarized light; these angles are directly related to the phases of the wave functions and thus visually confirm the Berry's phase of π (2π) around the Dirac point. The details are verified by calculations.     

Combining clustering and classification for remote-sensing images using unlabeled data

A joint clustering and classification approach is proposed.This approach exploits unlabeled data for efficient clustering,which is applied in the classification with support vector machine(SVM) in the case of small-size training samples.The proposed method requires no prior information on data labels,and yields better cluster structures.Through cluster assumption and the notions of support vectors,the most confident k cluster centers and data points near the cluster boundaries are labeled and used to train a reliable SVM classifier.Our method gains better estimation of data distributions and mitigates the unrepresentative problem of small-size training samples.The data set collected from Landsat Thematic Mapper(Landsat TM-5) validates the effectiveness of the proposed approach.     

X射线荧光光谱研究粮食中生命有机碳与碳化学循环

采用X射线荧光光谱(XRF)方法测定六种粮食:稻谷(大米)、小麦(面粉)、黄豆、小米、高粱和玉米中生命有机碳含量和化学元素组成,建立一种新方法测定它们的蛋白质含量.粮食中生命有机碳平均含量约为44%.黄豆中的蛋白质含量最高(42.74%),小米蛋白质含量28.56%,麦子蛋白质含量27.57%,玉米蛋白质含量24.99...     

SEM-EDXA分析不同生长应力木材细胞壁微区木质素沉积

选取具不同生长应力水平的人工林尾巨桉(Eucalyptus uroph ylla×E.grandis)正常木为研究对象,借助场发射环境扫描电子显微镜系统,结合以溴元素做标记的X射线能谱分析技术,分析了尾巨桉细胞壁微区木质素沉积与生长应力的关系.研究结果表明,木纤维细胞壁各微区间木质素含量的大小关系与生长应力高低无关,其...