Shiwen Li

Facile Synthesis of Au-Nanoparticle/Polyoxometalate/Graphene Tricomponent Nanohybrids: An Enzyme-Free Electrochemical Biosensor for Hydrogen Peroxide

A green, facile, one-pot synthesis of well-defined Au NPs@POM-GNSs tricomponent nanohybrids is reported (POM stands for polyoxometalate and GNSs for graphene nanosheets). The synthesis is convenient, rapid and environmentally friendly. The POMs serve as both reducing, encapsulating molecules, and bridging molecules; this avoids the introduction of other organic toxic molecules. Characterization using transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy analysis is performed, and the structure of the prepared nanohybrids of Au NPs@POM-GNSs is verified. Most importantly, the amperometric measurements show the Au NPs@POM-GNSs nanohybrids have high catalytic activity with good sensitivity, good long-term stability, wide linear range, low detection limit, and fast response towards H(2)O(2) detection for application as an enzyme-free biosensor. Transformation of the POMs during H(2)O(2) detection does not affect the catalytic activities of the nanohybrids. Thus, the synergistic effect of Au NPs and GNSs in the nanohybrids leads to the enhanced catalytic property.

Green chemical decoration of multiwalled carbon nanotubes with polyoxometalate-encapsulated gold nanoparticles: visible light photocatalytic activities

A green, facile, one-pot synthesis of well-defined Au NPs@POM-CNTs tri-component nanohybrids is reported in this paper. The synthesis is convenient, rapid and environmentally friendly. The POMs serve as both reducing, encapsulating molecules and bridging molecules, and avoid introducing other organic toxic molecules. Most importantly, the prepared nanohybrids have been found to have enhanced photocatalytic activities under visible light irradiation. The synergistic effect of the three components in the nanohybrids leads to the enhanced photocatalytic property.

Facile synthesis of a Ag nanoparticle/polyoxometalate/carbon nanotube tri-component hybrid and its activity in the electrocatalysis of oxygen reduction

The facile, one-pot synthesis of Ag nanoparticle-decorated carbon nanotubes (CNTs) is reported. Polyoxometalates (POMs) were used to serve as both reducing and bridging molecules, which avoids the step of introducing other organic toxic molecules. Characterization using transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) analysis, etc. was performed and the structure of the prepared nanohybrid of Ag NPs@POM-CNTs was verified. The nanohybrid showed a high electrocatalytic activity towards oxygen reduction reaction because of the synergistic effect of Ag NPs and CNTs. The POM is removable in the nanohybrid without affecting the catalytic activities.

A general green strategy for fabricating metal nanoparticles/polyoxometalate/graphene tri-component nanohybrids: enhanced electrocatalytic properties

The well-defined metal NPs@POM–GNS tri-component nanohybrids were synthesized by a green, facile, one-pot method. The obtained nanohybrids exhibited exciting electrocatalytic activity for methanol and formic acid oxidation.

ε-Keggin-based coordination networks: Synthesis, structure and application toward green synthesis of polyoxometalate@graphene hybrids

Four coordination networks based on the {ε-PMo(V)(8)Mo(VI)(4)O(40)(OH)(4)Zn(4)} Keggin unit (εZn) have been synthesized under hydrothermal conditions. (TBA)(3){PMo(V)(8)Mo(VI)(4)O(36)(OH)(4)Zn(4)}[C(6)H(4)(COO)(2)](2) (ε(isop)(2)) is a 2D material with monomeric εZn units connected via 1,3 benzenedicarboxylate (isop) linkers and tetrabutylammonium (TBA) counter-cations lying between the planes. In (TPA)(3){PMo(V)(8)Mo(VI)(4)O(37)(OH)(3)Zn(4)}[C(6)H(3)(COO)(3)] (TPA[ε(trim)](∞)), 1D inorganic chains formed by the connection of εZn POMs, via Zn-O bonds, are linked via 1,3,5 benzenetricarboxylate (trim) ligands into a 2D compound with tetrapropylammonium (TPA) cations as counter-cations. (TBA){PMo(V)(8)Mo(VI)(4)O(40)Zn(4)}(C(7)H(4)N(2))(2)(C(7)H(5)N(2))(2)·12H(2)O (ε(bim)(4)) is a molecular material with monomeric εZn POMs bound to terminal benzimidazole (bim) ligands. Finally, (TBA)(C(10)H(10)N(4))(2)(HPO(3)){PMo(V)(8)Mo(VI)(4)O(40)Zn(4)}(2)(C(10)H(9)N(4))(3)(C(10)H(8)N(4)) (ε(2)(pazo)(4)) is a 1D compound with dimeric (εZn)(2) POMs connected by HPO(3)(2-) ions and terminal para-azobipyridine (pazo) ligands. In this compound an unusual bond cleavage of the central N[double bond, length as m-dash]N bond of the pazo ligand is observed. We report also a green chemistry-type one-step synthesis method carried out in water at room temperature using ε(2)(pazo)(4) and ε(isop)(2) as reducing agent of graphite oxide (GO) to obtain graphene (G). The POM@G hybrids were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, powder X-ray diffraction, energy dispersive X-ray analysis, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and cyclic voltammetry.

Polyoxometalate-Mediated Green Synthesis of Graphene and Metal Nanohybrids: High-Performance Electrocatalysts

This report focuses on our recent achievements relevant to the development of facile, green and low cost synthetic approaches leading to high-nuclearity polyoxometalate/graphene (POM/G), POM/poly(ionic liquid)/G, POM-based metal organic framework/G (POMOF/G) and Metal (Ag, Au, Pd, Pt) nano-object/POM/G (Metal/POM/G) hybrids aimed at effective photo-electro-catalysis of challenging reactions. All the synthetic routes yield hybrids with high quality G, improved electrochemical properties, huge surface area, and remarkable stability under various conditions. Well-defined metal nanoparticles were generated for Au, Pd and Pt nanostructures whereas a 2D Ag nanonet was observed for that of Ag. Moreover, the synergistic effect of the three components of these hybrids induces significant enhancement of their electrocatalytic activity. In particular, the Au NPs/POM-G hybrids can be used as remarkably effective enzyme-free biosensor for H2O2. They disclose salient electrocatalytic performance with high sensitivity and selectivity, good long-term stability, large detection range, low detection limit and fast current response for H2O2 detection. Outstanding electrocatalytic activity was also demonstrated for the Ag NN/POM-G hybrids towards the oxygen reduction reaction in alkaline medium. Owing to their higher durability compared to that of commercial Pt/Carbon nanocomposites, the Ag NN/POM-G hybrids are new promising low cost cathode materials for alkaline fuel cells.Graphical Abstract

Ratio of shear viscosity to entropy density in multifragmentation of Au + Au

The ratio of the shear viscosity (eta) to entropy density (s) for the intermediate energy heavy-ion collisions has been calculated by using the Green-Kubo method in the framework of the quantum molecular dynamics model. The theoretical curve of eta/s as a function of the incident energy for the head-on Au + Au collisions displays that a minimum region of eta/s has been approached at higher incident energies, where the minimum eta/s value is about 7 times Kovtun-Son-Starinets (KSS) bound (1/4 pi). We argue that the onset of minimum eta/s region at higher incident energies corresponds to the nuclear liquid gas phase transition in nuclear multifragmentation. Copyright (C) EPLA, 2012

Simple and efficient polyoxomolybdate-mediated synthesis of novel graphene and metal nanohybrids for versatile applications

The application of nanohybrids based on polyoxomolybdates, reduced graphene oxide (rGO) and/or metal nanoparticles (NPs) high-performance electrode materials in electrocatalysis and energy storage devices is promising but still limited due to the complexity and the cost of the synthesis. Here we introduce a simple polyoxomolybdate, [MoV4O8(OH)2(H2O)2(C4O4)2]2- (MoS), as reducing and stabilizing agent for the facile and one-pot syntheses of large quantity of highly stable MoS/rGO and MoS/Au NPs nanohybrids in aqueous solution without any catalyst or toxic co-solvent. They were characterized by various physical techniques and electrochemistry which confirm strong interaction between MoS and rGO sheets. We also used DFT calculations to investigate the affinity between MoS or its neutral form with graphene. The adsorption energy for the most stable configuration is -1.97 eV, indicating a strong adsorption process of MoS, which can also be confirmed by the distance (3.04 Å) and the charge transfer (0.86 e) between MoS and graphene. These observations are also consistent with the electrochemical results which underscore the excellent redox properties and high stability of MoS/rGO. Importantly, the MoS/rGO nanohybrids are excellent noble metal-free electrocatalysts for hydrogen peroxide reduction with high sensitivity, large detection range and low detection limit. Finally, the preliminary tests reveal that the electrode materials based on MoS/rGO and a low-cost carbon cloth (CC) composite MoS/rGO/CC may have a potential for an application in energy storage as performant and flexible supercapacitor, showing specific capacitance as high as 870 F g-1 at 10 mV s-1 and excellent stability after 5000 cycles.