Kaifeng, China
Kaifeng, China

Henan University is a public university in Kaifeng, Henan, China. Wikipedia.

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Han X.,National University of Singapore | Zhong F.,National University of Singapore | Wang Y.,Henan University | Lu Y.,National University of Singapore
Angewandte Chemie - International Edition | Year: 2012

A fast one: The title reaction proceeds in the presence of 5 mol % of the catalyst 1, and is complete within an hour. The 2-alkyl- and 2-aryl-substituted 3-pyrroline products are obtained in good yield and with high enantioselectivity. The application of the method to the concise formal synthesis of (+)-trachelanthamidine is also demonstrated. Boc=tert- butoxycarbonyl, M.S.=molecular sieves, TBDPS=tert-butyldiphenylsilyl. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhong F.,National University of Singapore | Han X.,National University of Singapore | Wang Y.,Henan University | Lu Y.,National University of Singapore
Angewandte Chemie - International Edition | Year: 2011

Spiral bound: The Morita-Baylis-Hillman adducts were employed as C 3 synthons in the asymmetric [3+2] annulation with malonitrile substrates using L-threonine-derived 1 as the catalyst (see scheme). The reaction is highly regioselective and stereoselective, and affords optically enriched 3-spirocyclopentene-2-oxindoles containing two contiguous quaternary centers. Boc=tert-butoxycarbonyl, PMB=para-methoxybenzyl, TIPS= triisopropylsilyl. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhong F.,National University of Singapore | Han X.,National University of Singapore | Wang Y.,Henan University | Lu Y.,National University of Singapore
Chemical Science | Year: 2012

Highly enantioselective [4 + 2] annulation of activated alkenes with α-substituted allenoates catalyzed by amino acid-based bifunctional phosphines has been developed for the first time, which provides an easy access to optically enriched functionalized cyclohexenes. In particular, 3-spirocyclohexene-2-oxindoles were prepared in high yields and with excellent enantioselectivities. This journal is © 2012 The Royal Society of Chemistry.

Han X.,National University of Singapore | Wang Y.,Henan University | Zhong F.,National University of Singapore | Lu Y.,National University of Singapore
Journal of the American Chemical Society | Year: 2011

A new family of dipeptide-based chiral phosphines was designed and prepared. d-Thr-l-tert-Leu-derived catalyst 4c promoted [3 + 2] cycloaddition of allenoates to α-substituted acrylates in a regiospecific and stereoselective manner, furnishing functionalized cyclopentenes with quaternary stereogenic centers in high yields and with excellent enantioselectivities. © 2011 American Chemical Society.

Wu T.-J.,Henan University
Chinese Journal of Applied Ecology | Year: 2013

Terrestrial ecosystem consists of aboveground and belowground components, whose interaction affects the ecosystem processes and functions. Soil fauna plays an important role in biogeochemical cycles. With the recognizing of the significance of soil fauna in ecosystem processes, increasing evidences demonstrated that global change has profound effects on soil fauna diversity. The alternation of land use type, the increasing temperature, and the changes in precipitation pattern can directly affect soil fauna diversity, while the increase of atmospheric CO2 concentration and nitrogen deposition can indirectly affect the soil fauna diversity by altering plant community composition, diversity, and nutrient contents. The interactions of different environmental factors can co-affect the soil fauna diversity. To understand the effects of different driving factors on soil fauna diversity under the background of climate change would facilitate us better predicting how the soil fauna diversity and related ecological processes changed in the future.

Liu W.,Henan University | Zhang Y.,Henan University
Journal of Materials Chemistry A | Year: 2014

TiO2/CH3NH3PbI3 heterojunction solar cells were fabricated by spin-coating and characterized by current-voltage measurements, impedance spectroscopy and capacitance-voltage measurements. It was demonstrated that the TiO2/CH3NH3PbI 3 layers form an ideal p-n heterojunction suitable for the photovoltaic applications. The active acceptor concentration of 9.67 × 1015 cm-3 in the CH3NH3PbI 3 layer and the built-in potential of 0.67 eV in the TiO 2/CH3NH3PbI3 heterojunction were derived by the Mott-Schottky relationship. Numerical simulations showed that the acceptor concentration in the CH3NH3PbI3 layer greatly influenced the electron potential barrier height at the junction interface. The degradation of TiO2/CH3NH 3PbI3 heterojunction solar cells showed that the efficiency remained 35.5% after storage under ambient laboratory conditions for 15 days. These results indicated that the oriented TiO2 layers provide a possible route to fabricate stable perovskite-based photovoltaic devices without hole transporting materials. 2014 This journal is © the Partner Organisations.

Fabrication of intrinsically fluorescent porous nanocarriers that are simultaneously stable in aqueous solutions and photostable is critical for their application in drug delivery and optical imaging but remains a challenge. In this study, fluorescent porous zinc sulfide nanospheres were synthesized by a facile gum arabic-assisted hydrothermal procedure. The morphology, composition and properties of the nanospheres have been characterized by field-emission scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, N 2 adsorption-desorption analysis, thermal gravimetric analysis, fourier transform infrared spectrograph, optical measurement, dynamic light scattering, and cytotoxicity assay. They exhibit larger surface area, excellent colloidal stability, photostable fluorescent signals, and good biocompatibility, which makes them promising hosts for drug delivery and cellular imaging. The fluorescent dye safranine-T was employed as a drug model and loaded into the porous nanospheres, which were delivered to human cervical cancer HeLa cells in vitro for live cell imaging. © 2012 The Royal Society of Chemistry.

Tang X.,Henan University | Li G.,Henan University | Zhou S.,Henan University
Nano Letters | Year: 2013

We present successful fabrication of single n-ZnO/p-AlGaN heterojunction nanowires with excellent optoelectronic properties. Because of the formation of high-quality interfacial structure, heterojunction nanowire showed a diodelike rectification behavior and an electroluminescence (EL) ultraviolet (UV) emission centered at 394 nm from a single nanowire was observed when the injection current is 4 μA due to high exciton efficiency in the interfacial layer between ZnO and AlGaN. With the increase of the applied current, the EL peak at 5 μA becomes weaker revealing an optimal injection current of less than 5 μA. These results are expected to open up new application possibilities in nanoscale UV light-emitting devices based on single ZnO heterostructure. © 2013 American Chemical Society.

Direct electron transfer of hemoglobin (Hb) was realized by immobilizing Hb on a carboxyl functionalized multi-walled carbon nanotubes (FMWCNTs) and gold nanoparticles (AuNPs) nanocomplex-modified glassy carbon electrode. The ultraviolet-visible absorption spectrometry (UV-Vis), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) methods were utilized for additional characterization of the AuNPs and FMWCNTs. The cyclic voltammogram of the modified electrode has a pair of well-defined quasi-reversible redox peaks with a formal potential of -0.270 ± 0.002 V (vs. Ag/AgCl) at a scan rate of 0.05 V/s. The heterogeneous electron transfer constant (ks) was evaluated to be 4.0 ± 0.2 s(-1). The average surface concentration of electro-active Hb on the surface of the modified glassy carbon electrode was calculated to be 6.8 ± 0.3 × 10(-10) mol cm(-2). The cathodic peak current of the modified electrode increased linearly with increasing concentration of hydrogen peroxide (from 0.05 nM to 1 nM) with a detection limit of 0.05 ± 0.01 nM. The apparent Michaelis-Menten constant (K(m)(app)) was calculated to be 0.85 ± 0.1 nM. Thus, the modified electrode could be applied as a third generation biosensor with high sensitivity, long-term stability and low detection limit.

Yan Y.L.,Henan University | Wang Y.X.,Henan University
Journal of Materials Chemistry | Year: 2011

The electronic structure and transport properties of Ca5Al 2Sb6 are investigated by using first-principles calculations and Boltzmann transport theory, respectively. The results show that the partially filled valence band induces a high carrier concentration of about n = 5 × 1019 cm-3. There is a combination of heavy and light bands at the conduction band edge, which may lead to a combination of high Seebeck coefficient and reasonable conductivity. At mid-and-high temperature, the thermoelectric powerfactor, with respect to relaxation time of p-type Ca5Al2Sb6, is higher than that of the n-type within the carrier concentration ranging from -10 × 1021 cm-3 to 10 × 1021 cm-3, without considering the kinds of doping. But with decreasing temperature, the thermoelectric powerfactor with respect to relaxation time of n-type Ca 5Al2Sb6 is higher than that of the p-type. The thermoelectric coefficient is increasingly sensitive to carrier concentration with the decreasing temperature. Most strikingly, at 30 K, the thermoelectric powerfactor, with respect to relaxation time, is nearly thirty-five times larger than that of conventional n-type thermoelectric materials. At 300 K, the thermoelectric powerfactor with respect to relaxation time of Ca 5Al2Sb6 is equal to that of the conventional p-type thermoelectric materials. Our theoretical calculations give valuable insight on how to improve the thermoelectric performance of Ca 5Al2Sb6 under different temperature and doping conditions. © 2011 The Royal Society of Chemistry.

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