基于最新势能面的C(1D)+H2反应的环聚合分子动力学研究

本文利用环聚合分子动力学方法对C(¹D)+H₂反应开展了详细的理论研究. 计算中使用了最近构建的Zhang-Ma-Bian(ZMB)从头算势能面,该势能面对锥形交叉附近区域以及范德华区域均有精确的描述. 环聚合分子动力学计算得到的热反应速率常数与最新实验值吻合很好. 与前人计算结果比较,发现在?¹A′电子基态的ZMB-a势能面上获得的反应速率常数远大于前人构建的RKHS势能面上的结果,这是由于ZMB势能面上的范德华鞍具有与之前势能面上的范德华阱完全不同的动态学作用,表明环聚合分子动力学方法能够处理范德华作用引起的势能面拓扑结构所导致的动态学效应. 本文还揭示了b¹A′′电子激发态ZMB-b势能面以及量子效应对反应的重要性.     

基于改进U-Net的量子点STM图像分割

为提升量子点图像分割精度,降低特征识别误差,提出一种基于改进U-Net的量子点图像分割方法.首先,在预处理阶段,设计了以色彩通道为权值的灰度化算法,以提升后续分割效果.其次,在STM图像分割部分,在原始U-Net结构上引入中间过渡层以均衡网络各层特征.而后,建立数据集,并通过实验对比不同分割算法的精确度、召回率、F-measure.最后,将分割算法应用于量子点的特征识别,并测试了不同分割方式对应用的影响.实验结果显示,改进灰度化方法保留细节信息丰富,明显提升了量子点分割精度;改进U-Net的平均精确率、召回率、F-measure相较原始网络分别提升了13.83%、2.16%、8.13%.同时,实验数据表明由于分割精度的提升,量子点数量、纵横比等特征参数的识别更加精确.     

Progress in fluorene-based wide-bandgap steric semiconductors

Molecular bulks are favorable for the thermal and morphological stability in organic wide-bandgap semiconducting polymers with potential applications in both information and energy electronics. In this review, we present our progress in the design of fluorene-based bulky semiconductors with a fractal four-element pattern. Firstly, we established one-pot methods to spirofluorenes, especially spiro[fluorene-9,9′-xanthene](SFX) serving as the next-generation spiro-based semiconductors. Secondly, we observed the supramolecular forces at the bulky groups and discovered the supramolecular steric hindrance(SSH) effect on polymorphisms, nanocrystals as well as device performance. Thus, a synergistically molecular attractor-repulsor theory(SMART) was proposed for the control of nanocrystal morphology, thin film phase and morphology. Thirdly, the third possible type of defects has been identified to generate green band(g-band) emission in widebandgap semiconductors by the introduction of molecular strain design of cyclofluorene. Finally, the first bulky polydiarylfluorene with highly crystalline and β conformation was achieved by an attractor-repulsor design of tadpole-shape monomer, which offered an effective platform to fabricate stable wide-bandgap semiconducting devices. All the discoveries offer the solid basis to break through bottlenecks of organic/polymer wide-bandgap semiconductors by the improvements of overall performances.     

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.