Nankai University

About: Nankai University is a education organization based out in Tianjin, China. It is known for research contribution in the topics: Catalysis & Enantioselective synthesis. The organization has 42964 authors who have published 51866 publications receiving 1127896 citations. The organization is also known as: Nánkāi Dàxué.

Vibrational properties of graphene and graphene layers

Abstract: The phonon dispersions of graphene and graphene layers are theoretically investigated within fifth-nearest-neighbor force-constant approach. Based on their symmetry groups, the number of Raman- and infrared-active modes at the Γ point is given. Interatomic force constants are recalculated by fitting them to experimental phonon energy dispersion curves. Wavenumbers of optically active modes are presented as a function of number of layers (n). Our calculated results reproduce well the experimental data of G peak for graphene (1587 cm−1) and graphite (1581.6 cm−1) and clearly give the relation that ωG = 1581.6 + 11/(1 + n1.6). Copyright © 2009 John Wiley & Sons, Ltd.

Nonparametric Profile Monitoring by Mixed Effects Modeling

Abstract: In some applications, the quality of a process is characterized by the functional relationship between a response variable and one or more explanatory variables. Profile monitoring is for checking the stability of this relationship over time. Control charts for monitoring nonparametric profiles are useful when the relationship is too complicated to be described parametrically. Most existing control charts in the literature are for monitoring parametric profiles. They require the assumption that within-profile measurements are independent of each other, which is often invalid in practice. This article focuses on nonparametric profile monitoring when within-profile data are correlated. A novel control chart is suggested, which incorporates local linear kernel smoothing into the exponentially weighted moving average (EWMA) control scheme. In this method, within-profile correlation is described by a nonparametric mixed-effects model. Our proposed control chart is fast to compute and convenient to use. Numeric...

CdTe Quantum Dots (QDs) Based Kinetic Discrimination of Fe2+ and Fe3+, and CdTe QDs-Fenton Hybrid System for Sensitive Photoluminescent Detection of Fe2+

Abstract: A method based on the quenching kinetics for the fluorescence of glutathione capped CdTe quantum dots (GSH-CdTe QDs) was developed for discriminating Fe2+ and Fe3+, and a GSH-CdTe QDs-Fenton hybrid system was constructed for sensitive and selective determination of trace Fe2+. Although both Fe2+ and Fe3+ could quench the fluorescence of GSH-CdTe QDs, the quenching kinetics was quite different for Fe2+ and Fe3+. The fluorescence of the GSH-CdTe QDs (30 nM) was quenched by about 18% in 1 min after the addition of Fe3+ (10 μM), and remained unchanged with further increase of reaction time. In contrast, the fluorescence intensity of the GSH-CdTe QDs decreased by about 65% in the first 5 min after the addition of Fe2+ (10 μM), then slowly decreased by 15% in the next 25 minutes. Other transition metal ions like Cu2+, Ni2+ and Co2+, Zn2+, and Mn2+ also gave very different quenching kinetics of the GSH-CdTe QDs from Fe2+. No significant effect of the capping agents (GSH, thioglycolic acid, and mercaptopropionic ...

Operational calixarene-based fluorescent sensing systems for choline and acetylcholine and their application to enzymatic reactions

Abstract: Electron-rich anionic calixarenes and resorcinarenes are known receptors for trimethylammonium-containing neurotransmitters, but the development of practical sensor applications has been impeded by the lack of suitable supramolecular sensing ensembles as well as the low selectivity and sensitivity of the macrocyclic cation-receptor hosts. The host–guest complexes between p-sulfonatocalix[n]arenes (n = 4–5) and the cationic aromatic fluorescent dye lucigenin (LCG) have been characterised by optical spectroscopic techniques, NMR, cyclic voltammetry, isothermal titration calorimetry, and X-ray crystallography. The dye is complexed with binding constants of the order of 107 M−1 and undergoes a strong static fluorescence quenching (factor 140) upon complexation as a consequence of exergonic electron transfer within the complex. LCG has been utilised in combination with p-sulfonatocalix[4]arene to set-up a refined reporter pair for label-free continuous real-time enzyme assays according to the supramolecular tandem assay principle. This affords product-selective tandem assays for amino acid decarboxylases with a one order of magnitude higher sensitivity and a 3 orders of magnitude lower host/dye concentration range, a convenient substrate-selective tandem assay for direct monitoring of choline oxidase, and a conceptually novel substrate-selective enzyme-coupled tandem assay for acetylcholinesterase. The applicability of the method to the measurement of enzyme-kinetic parameters, the screening for inhibitors of acetylcholinesterase, and the highly selective determination of absolute, low micromolar concentrations of both choline and acetylcholine by simple fluorescence measurements has been demonstrated. A domino tandem assay can be employed to measure the two analytes in the same sample. The described applications bypass problems related to the unselective binding of the macrocycle by coupling the signalling event with highly specific enzymatic transformations.

A Planar Small Molecule with Dithienosilole Core for High Efficiency Solution-Processed Organic Photovoltaic Cells

Abstract: An electron-withdrawing terminal small molecule with dithienosilole core shows high photovoltaic performance. The DCAO3TSi:PC61BM based solar cell exhibits a power conversion efficiency of 5.84%, w...