Chuanxin Zhai

Porous ZnCo2O4 nanowires synthesis via sacrificial templates: high-performance anode materials of Li-ion batteries.

A simple microemulsion-based method has been developed to synthesize ZnCo(2)(C(2)O(4))(3) nanowires that can be transformed to porous ZnCo(2)O(4) nanowires under annealing conditions. The morphology of porous ZnCo(2)O(4) nanowires can be tuned by the initial ZnCo(2)(C(2)O(4))(3) nanowires and the annealing temperatures. The as-synthesized porous ZnCo(2)O(4) nanowires have been applied as anode materials of Li-ion batteries, which show superior capacity and cycling performance. The porous one-dimensional (1D) nanostructures and large surface area are responsible for the superior performance. Moreover, it is indicated that porous ZnCo(2)O(4) nanowires synthesized at low annealing temperature (500 °C) show larger capacity and better cycling performance than that prepared at high annealing temperature (700 °C), because of their higher porosity and larger surface area.

Multiwalled Carbon Nanotubes Anchored with SnS2 Nanosheets as High-Performance Anode Materials of Lithium-Ion Batteries

A nanocomposite of multiwalled carbon nanotubes (MWCNTs) anchored with SnS(2) nanosheets (NS) (SnS(2) NS@MWCNTs coaxial nanocables) has been synthesized through a simple solution-based method at room temperature. The synthetic mechanism of these intriguing nanocomposites is proposed as electrostatic attraction between tin ions and MWCNTs, followed by the nucleation and two-dimensional growth of SnS(2). The as-synthesized SnS(2) NS@MWCNTs coaxial nanocables have been applied as anode materials for lithium-ion batteries, which show better lithium storage performance compared to pure SnS(2) nanosheets and MWCNTs. The combination of MWCNTs that can hinder the agglomeration and enhance electronic conductivity of the active materials might be responsible for the enhanced cyclic performance.

Self-templating synthesis of SnO2-carbon hybrid hollow spheres for superior reversible lithium ion storage.

This paper reports a novel self-templating methodology for the formation of SnO(2)-carbon hybrid hollow spheres by using Sn spheres as sacrificing templates. The time-sequenced structural evolution of the templates indicates that the nanoscale Kirkendall effect plays a critical role in the transformation from Sn spheres to the hybrid hollow spheres. Moreover, the as-synthesized SnO(2)-carbon hybrid hollow spheres have been applied as anode materials for lithium-ion batteries, which exhibit a much higher initial Coulombic efficiency and better cycling performance than pure SnO(2) hollow spheres.

Selective Synthesis of Fe2O3 and Fe3O4 Nanowires Via a Single Precursor: A General Method for Metal Oxide Nanowires

Hematite (α-Fe2O3) and magnetite (Fe3O4) nanowires with the diameter of about 100 nm and the length of tens of micrometers have been selectively synthesized by a microemulsion-based method in combination of the calcinations under different atmosphere. The effects of the precursors, annealing temperature, and atmosphere on the morphology and the structure of the products have been investigated. Moreover, Co3O4 nanowires have been fabricated to confirm the versatility of the method for metal oxide nanowires.

From ZnO nanorods to 3D hollow microhemispheres: solvothermal synthesis, photoluminescence and gas sensor properties

A novel solvothermal process using ethylene glycol (EG) as solvent has been employed to synthesize 3D ZnO hollow microhemispheres consisting of numerous orderly and radical nanorods with diameter of about 50 nm and length of several hundred nanometers. The glycol such as EG and the solvothermal process play the critical role in the synthesis of the 3D ZnO hollow microhemispheres by the primary formation of glycolate precursors and subsequent transformation into ZnO. The morphology, structure and optical property of the 3D ZnO hollow microhemispheres have been characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), x-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL). Furthermore, the 3D ZnO hollow microhemisphere based gas sensor exhibits high sensitivity for ethanol and ammonia as well as quick response and recovery time at room temperature due to the high surface-to-volume ratio.

Carbon nanotube-based magnetic-fluorescent nanohybrids as highly efficient contrast agents for multimodal cellular imaging

We developed a simple and novel layer-by-layer (LBL) assembly in combination with covalent connection strategy for the synthesis of multifunctional carbon nanotubes (CNTs)-based magnetic-fluorescent nanohybrids as multimodal cellular imaging agents for detecting human embryonic kidney (HEK) 293T cells via magnetic resonance (MRI) and confocal fluorescence imaging. Superparamagnetic iron oxide nanoparticles (SPIO) and near-infrared fluorescent CdTe quantum dots (QDs) were covalently coupled on the surface of CNTs in sequence via LBL assembly. It was indicated that the SPIO layer acted not only as a contrast agent for MRI, but also as a spacer between CdTe QDs and CNTs for prohibiting fluorescence quenching of QDs on the surface of the CNTs. The multifunctional CNT-based magnetic-fluorescent nanohybrids showed an enhanced MRI signal as contrast agent for detecting 293T cells in comparison with the pure SPIO. This is due to the magnetic coupling between the orderly arrayed SPIO, the function of CNTs for lowering the transverse relaxation and the ability of CNTs for penetrating into cells. Moreover, the multifunctional CNT-based magnetic-fluorescent nanohybrids exhibited the higher intracellular labeling efficiency due to the ability of CNTs for penetrating into cells in comparison with pure SPIO-CdTe nanoparticles.

Labeling transplanted mice islet with polyvinylpyrrolidone coated superparamagnetic iron oxide nanoparticles for in vivo detection by magnetic resonance imaging

Superparamagnetic iron oxide nanoparticles (SPIO) are emerging as a novel probe for noninvasive cell tracking with magnetic resonance imaging (MRI) and have potential wide usage in medical research. In this study, we have developed a method using high-temperature hydrolysis of chelate metal alkoxide complexes to synthesize polyvinylpyrrolidone coated iron oxide nanoparticles (PVP-SPIO), as a biocompatible magnetic agent that can efficiently label mice islet beta-cells. The size, crystal structure and magnetic properties of the as-synthesized nanoparticles have been characterized. The newly synthesized PVP-SPIO with high stability, crystallinity and saturation magnetization can be efficiently internalized into beta-cells, without affecting viability and function. The imaging of 100 PVP-SPIO-labeled mice islets in the syngeneic renal subcapsular model of transplantation under a clinical 3.0 T MR imager showed high spatial resolution in vivo. These results indicated the great potential application of the PVP-SPIO as an MRI contrast agent for monitoring transplanted islet grafts in the clinical management of diabetes in the near future.

Synthesis of Co3O4@SnO2@C core-shell nanorods with superior reversible lithium-ion storage

This paper describes a facile hydrothermal and subsequent carbonization approach for the synthesis of Co3O4@SnO2@C core-shell nanorods. The as-synthesized Co3O4@SnO2@C nanorods have been applied as anode materials for lithium-ion batteries, which exhibit improved cyclic performance and enhanced power capability. Both Co3O4 and SnO2 are electrochemically active materials, and the hybridization of Co3O4 and SnO2 into an integrated core-shell nanorod structure makes them an elegant synergistic effect when participating in the lithium-ion charge-discharge process. In addition, the carbon matrix has good volume buffering effect and high electronic conductivity, which may be responsible for the improved electrochemical performance.

Assembling CoSn3 nanoparticles on multiwalled carbon nanotubes with enhanced lithium storage properties

CoSn(3) nanoparticles have been successfully assembled on noncovalently poly(diallyldimethylammonium chloride)-functionalized multiwalled carbon nanotubes (MWCNTs) via a chemical reduction method in a polyol system. The influences of the surface functionality and the reaction temperature on the synthesis of uniform CoSn(3)-MWCNTs nanohybrids have been investigated. The as-synthesized CoSn(3)-MWCNTs nanohybrids have been applied as anodes for lithium-ion batteries, and show better lithium storage performance compared to the bare CoSn(3) nanoparticles and MWCNTs. The combining of MWCNTs that can hinder the agglomeration and enhance the electronic conductivity of the active materials is responsible for the enhanced cyclic performance.

Cobalt ferrite nanorings: Ostwald ripening dictated synthesis and magnetic properties

CoFe(2)O(4) nanorings were synthesized by a simple solvothermal process, in which Ostwald ripening was definitely responsible for the formation of hollow structures, and their ferromagnetic behavior at room temperature was observed.