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Featured researches published by Jingwen Zhao.


Journal of the American Chemical Society | 2012

Preparation of Fe3O4@SiO2@Layered Double Hydroxide Core–Shell Microspheres for Magnetic Separation of Proteins

Mingfei Shao; Fanyu Ning; Jingwen Zhao; Min Wei; David G. Evans; Xue Duan

Three-component microspheres containing an SiO(2)-coated Fe(3)O(4) magnetite core and a layered double hydroxide (LDH) nanoplatelet shell have been synthesized via an in situ growth method. The resulting Fe(3)O(4)@SiO(2)@NiAl-LDH microspheres display three-dimensional core-shell architecture with flowerlike morphology, large surface area (83 m(2)/g), and uniform mesochannels (4.3 nm). The Ni(2+) cations in the NiAl-LDH shell provide docking sites for histidine and the materials exhibit excellent performance in the separation of a histidine (His)-tagged green fluorescent protein, with a binding capacity as high as 239 μg/mg. The microspheres show highly selective adsorption of the His-tagged protein from Escherichia coli lysate, demonstrating their practical applicability. Moreover, the microspheres possess superparamagnetism and high saturation magnetization (36.8 emu/g), which allows them to be easily separated from solution by means of an external magnetic field and subsequently reused. The high stability and selectivity of the Fe(3)O(4)@SiO(2)@NiAl-LDH microspheres for the His-tagged protein were retained over several separation cycles. Therefore, this work provides a promising approach for the design and synthesis of multifunctional LDH microspheres, which can be used for the practical purification of recombinant proteins, as well as having other potential applications in a variety of biomedical fields including drug delivery and biosensors.


Small | 2013

Flexible CoAl LDH@PEDOT Core/Shell Nanoplatelet Array for High‐Performance Energy Storage

Jingbin Han; Yibo Dou; Jingwen Zhao; Min Wei; David G. Evans; Xue Duan

A CoAl-layered double hydroxide (LDH)@poly(3,4-ethylenedioxythiophene) (PEDOT) core/shell nanoplatelet array (NPA) is grown on a flexible Ni foil substrate as a high-performance pseudocapacitor. The LDH@PEDOT core/shell NPA shows a maximum specific capacitance of 649 F/g (based on the total mass) by cyclic voltammetry (scan rate: 2 mV/s) and 672 F/g by galvanostatic discharge (current density: 1 A/g). Furthermore, the hybrid NPA electrode also exhibits excellent rate capability with a specific energy of 39.4 Wh/kg at a current density of 40 A/g, as well as good long-term cycling stability (92.5% of its original capacitance is retained after 5000 cycles). These performances are superior to those of conventional supercapacitors and LDH NPA without the PEDOT coating. The largely enhanced pseudocapacitor behavior of the LDH@PEDOT NPA electrode is related to the synergistic effect of its individual components: the LDH nanoplatelet core provides abundant energy-storage capacity, while the highly conductive PEDOT shell and porous architecture facilitate the electron/mass transport in the redox reaction.


Journal of Materials Chemistry | 2013

CoMn-layered double hydroxide nanowalls supported on carbon fibers for high-performance flexible energy storage devices

Jingwen Zhao; Jiale Chen; Simin Xu; Mingfei Shao; Dongpeng Yan; Min Wei; David G. Evans; Xue Duan

CoMn-layered double hydroxide (LDH) nanowalls were supported on flexible carbon fibers (CFs) via an in situ growth approach; the resulting CoMn-LDH/CF electrode delivers a high specific capacitance (1079 F g−1 at 2.1 A g−1 normalized to the weight of the active LDH material) with excellent rate capability even at high current densities (82.5% capacitance retention at 42.0 A g−1). A combined experimental and theoretical study reveals that the dramatic performance enhancement is mainly attributed to the homogeneous and ordered dispersion of metal units within the LDH framework, which enriches the redox reactions associated with charge storage by both Co and Mn. The hierarchical configuration further improves the exposure of active sites and enables a fast charge transfer to the electrode/electrolyte interface, with CFs serving as both the current collector and binderless electrode. In addition, a solid-state supercapacitor device with good flexibility was fabricated using the CoMn-LDH/CFs, which achieves a specific energy up to 126.1 W h kg−1 and a specific power of 65.6 kW kg−1. By virtue of rational design of the chemical composition and architecture, this work demonstrates a facile strategy for the fabrication of a hierarchical configuration based on CoMn-LDH nanowalls anchored to CFs, which can be potentially used in wearable and miniaturized devices for energy storage.


Journal of Materials Chemistry | 2013

A hierarchical heterostructure based on Pd nanoparticles/layered double hydroxide nanowalls for enhanced ethanol electrooxidation

Jingwen Zhao; Mingfei Shao; Dongpeng Yan; Shitong Zhang; Zhenzhi Lu; Zhuoxin Li; Xingzhong Cao; Baoyi Wang; Min Wei; David G. Evans; Xue Duan

Finely dispersed Pd nanoparticles (PdNPs) anchored to CoAl layered double hydroxide nanowalls (LDH-NWs) have been fabricated via a facile in situ redox reaction between the LDH-NWs and the PdCl42− precursor. The integrated LDH-NWs play the roles of both a hierarchical support and a reductant without any external agent, ensuring the cleanness of the metal–support interface. Based on the effective exposure of the Pd active sites and the elaborate network architecture, the Pd/LDH-NW heterogenous material yields a largely improved catalytic activity as well as robust durability towards ethanol electrooxidation in comparison with the commercial Pd/C catalyst. Moreover, a density functional theory (DFT) calculation indicates that the enhancement in the electrocatalytic properties originates from the synergistic effect between the metal and support, in which the LDH support stabilizes the PdNPs via the formation of a Pd–HO bond which is accompanied by an electron transfer from the LDH to the PdNPs. This work provides a promising approach for the design and fabrication of highly efficient metal-supported nanocatalysts which can be used in fuel cells and other related catalytic reactions.


Journal of Materials Chemistry | 2011

Self-assembly of layered double hydroxide nanosheets/Au nanoparticles ultrathin films for enzyme-free electrocatalysis of glucose†

Jingwen Zhao; Xianggui Kong; Wenying Shi; Mingfei Shao; Jingbin Han; Min Wei; David G. Evans; Xue Duan

This paper reports the fabrication of layered double hydroxide nanosheets (LDH nanosheets)/Au nanoparticles (AuNPs) ultrathin films (UTFs) via the layer-by-layer (LBL) assembly technique, and their electrocatalytic performance for the oxidation of glucose was demonstrated. UV-vis absorption spectra show the uniform growth of the UTFs and the enhancement of interlayer plasmon coupling of AuNPs upon increasing deposition cycle. The XRD results indicate that the (LDH/AuNPs)n UTFs possess long-range order stacking in the normal direction of the substrate, with AuNPs accommodated between the LDH nanosheets as a monolayer arrangement. SEM, TEM and AFM images reveal a high dispersion of AuNPs on the surface of the LDH nanosheets without aggregation. The electrochemical behavior of the UTF modified fluorine-doped tin oxide (FTO) electrode was studied by cyclic voltammetry and electrochemical impedance spectroscopy. The (LDH/AuNPs)n UTF shows improved electron transfer kinetics, owing to the formation of electron tunneling junctions resulting from the interlayer plasmon coupling. This leads to new channels for facilitating electron transfer within the UTFs. In addition, the (LDH/AuNPs)8electrode displays significant electrocatalytic performance for glucose with a linear response range (50 μM–20 mM), low detection limit (10.8 μM), high sensitivity (343 μA mM−1 cm−2), good stability and reproducibility. Therefore, this work provides a feasible method to immobilize metal nanoparticles using the LDH nanosheet as a 2D matrix, which is promising for the development of enzyme-free sensors.


RSC Advances | 2013

Flexible hierarchical nanocomposites based on MnO2 nanowires/CoAl hydrotalcite/carbon fibers for high-performance supercapacitors

Jingwen Zhao; Zhenzhi Lu; Mingfei Shao; Dongpeng Yan; Min Wei; David G. Evans; Xue Duan

A hierarchical nanocomposite based on MnO2 nanowire/CoAl layered double hydroxide/carbon fibers is fabricated by a facile two-step method as a high-performance supercapacitor. The CoAl-LDH nanocrystals grown on flexible carbon fibers were prepared via an in situ hydrothermal method, followed by loading of MnO2 nanowires through a direct redox reaction between the Co2+ species and MnO4−. The hierarchical MnO2/LDH/CFs electrode as a supercapacitor displays a high specific capacitance (944 F g−1 at 1 A g−1) and rate capability, good stability and excellent long-term cycling life.


Catalysis Science & Technology | 2013

Catalytic conversion of syngas to mixed alcohols over CuFe-based catalysts derived from layered double hydroxides

Wa Gao; Yufei Zhao; Junmin Liu; Qianwen Huang; Shan He; Changming Li; Jingwen Zhao; Min Wei

A uniform and highly dispersed CuFe-based catalyst was obtained via a calcination–reduction process of a CuFeMg-layered double hydroxide (LDH) precursor, which exhibits good activity and selectivity towards catalytic conversion of syngas to mixed alcohols. X-ray diffraction (XRD) and scanning electron microscopy (SEM) reveal that the CuFeMg-LDH precursor possesses high crystallinity with a particle size of 40–60 nm. High resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy (STEM) demonstrate a high dispersion of copper and iron species on the catalyst surface. The CuFe-based catalyst derived from CuFeMg-LDHs shows high CO conversion (56.89%) and the total alcohol yield (0.28 g mLcat.−1 h−1), as a result of the high dispersion of active species as well as the synergistic effect between the copper and the iron species revealed by X-ray photoelectron spectra (XPS) and H2 temperature-programmed reduction (H2-TPR) techniques. Therefore, this work provides a facile and effective method for the preparation of CuFe-based catalysts with high catalytic activity, which can be potentially used in syngas conversion to mixed alcohols.


Langmuir | 2011

Magnetic-Field-Assisted Assembly of Layered Double Hydroxide/Metal Porphyrin Ultrathin Films and Their Application for Glucose Sensors

Mingfei Shao; Xiangyu Xu; Jingbin Han; Jingwen Zhao; Wenying Shi; Xianggui Kong; Min Wei; David G. Evans; Xue Duan

The ordered ultrathin films (UTFs) based on CoFe-LDH (layered double hydroxide) nanoplatelets and manganese porphyrin (Mn-TPPS) have been fabricated on ITO substrates via a magnetic-field-assisted (MFA) layer-by-layer (LBL) method and were demonstrated as an electrochemical sensor for glucose. The XRD pattern for the film indicates a long-range stacking order in the normal direction of the substrate. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images of the MFA LDH/Mn-TPPS UTFs reveal a continuous and uniform surface morphology. Cyclic voltammetry, impedance spectroscopy, and chronoamperometry were used to evaluate the electrochemical performance of the film, and the results show that the MFA-0.5 (0.5 T magnetic field) CoFe-LDH/Mn-TPPS-modified electrode displays the strongest redox current peaks and fastest electron transfer process compared with those of MFA-0 (without magnetic-field) and MFA-0.15 (0.15 T magnetic field). Furthermore, the MFA-0.5 CoFe-LDH/Mn-TPPS exhibits remarkable electrocatalytic activity toward the oxidation of glucose with a linear response range (0.1-15 mM; R(2) = 0.999), low detection limit (0.79 μM) and high sensitivity (66.3 μA mM(-1) cm(-2)). In addition, the glucose sensor prepared by the MFA LBL method also shows good selectivity and reproducibility as well as resistance to poisoning in a chloride ion solution. Therefore, the novel strategy in this work creates new opportunities for the fabrication of nonenzyme sensors with prospective applications in practical detection.


Journal of Materials Chemistry C | 2013

Organic-inorganic hybrid fluorescent ultrathin films and their sensor application for nitroaromatic explosives

Hanyue Ma; Rui Gao; Dongpeng Yan; Jingwen Zhao; Min Wei

The luminescent film materials sensitive to external stimuli are important to develop new types of optical sensors and switches. Herein we report organic–inorganic hybrid ultrathin films (UTFs) with reversible luminescence response to nitroaromatic explosive compounds by the use of layer-by-layer assembly of optical brightener BBU and Mg–Al-layered double hydroxide (LDH) nanosheets. UV-Visible absorption and fluorescence spectroscopy showed an orderly growth of the BBU/LDH films upon increasing the number of deposition cycle. XRD, AFM and SEM measurements indicated that the films feature periodic layered structure with a period of ca. 2 nm as well as uniform surface morphology. The BBU/LDH UTFs exhibit well-defined one/two-photon polarized photoemission with the anisotropy as high as 0.38. Moreover, the UTFs show a fast, selective and reversible luminescence response to different nitroaromatic explosives with the most significant luminescent red-shift occurring for picric acid; in addition, by combining suitable luminescent building blocks, the films can also be extended to other dual-color luminescence systems, which exhibit changes in both luminescence intensity and ratiometric fluorescence upon interaction with explosives, enlightening that these films can serve as new types of selective solid luminescent sensors towards nitroaromatic compounds.


Journal of Materials Chemistry | 2013

Binary Cu–Co catalysts derived from hydrotalcites with excellent activity and recyclability towards NH3BH3 dehydrogenation

Changming Li; Junyao Zhou; Wa Gao; Jingwen Zhao; Jie Liu; Yufei Zhao; Min Wei; David G. Evans; Xue Duan

The “Hydrogen economy” as an energy solution has received worldwide attention. Development of efficient, economic and recyclable catalysts for hydrogen generation from hydrogen storage materials (e.g., NH3BH3, AB) under moderate conditions has been one of the most active research areas. In the well-studied transition metals, cobalt (Co) and copper (Cu) are very efficient catalysts towards NH3BH3 dehydrogenation. In this work, we demonstrate the preparation of binary Cu–Co catalysts via the LDH precursor approach, which exhibit largely enhanced catalytic activity towards dehydrogenation of AB. The catalyst with a Cu/Co molar ratio of 1/1 yields a hydrolysis completion time less than 4.0 min at a rate of ∼1000 mL (min−1 gcat) under the ambient conditions, comparable to the most reported noble metal catalysts (e.g., Ru, Pt). XRD, H2-TPR, XPS and HRTEM measurements verify that the synergistic effect between highly dispersive metallic Cu and Co3O4 species plays a key role in the significantly enhanced activity of the Cu–Co catalyst. In addition, a monolithic Cu–Co film catalyst was fabricated by an in situ growth-reduction method, which displays further enhanced catalytic activity, recyclability and long-term reusability. This work provides an effective strategy for the fabrication of excellent Cu–Co catalysts for NH3BH3 decomposition, which can be used as promising candidates in pursuit of practical implementation of AB as a hydrogen storage material.

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Min Wei

Beijing University of Chemical Technology

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Xue Duan

Beijing University of Chemical Technology

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David G. Evans

Beijing University of Chemical Technology

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Mingfei Shao

Beijing University of Chemical Technology

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Xianggui Kong

Beijing University of Chemical Technology

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Jingbin Han

Beijing University of Chemical Technology

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Wenying Shi

Beijing University of Chemical Technology

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Dongpeng Yan

Beijing University of Chemical Technology

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Yufei Zhao

Chinese Academy of Sciences

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Fanyu Ning

Beijing University of Chemical Technology

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