Bingjun Ding

Synthesis of colloidal metal and metal alloy nanoparticles for electrochemical energy applications

This Review is focused on the recent progresses in the synthetic approaches to the precise control of structure, size, shape, composition and multi-functionality of metal and metal alloy nanoparticles. Many of these strategies have been developed based on colloidal methods, and to limited extent, the galvanic and other methods. The shape, size and composition often govern the chemical and catalytic properties that are important for electrochemical energy applications. The structure-property relationship and the design in controllable structures and morphologies for specific reactions such as oxygen reduction reaction (ORR) are emphasized.

Nanoparticle-aggregated 3D monocrystalline gold dendritic nanostructures

In this paper, through a simple and fast electroless metal deposition route, gold dendritic nanostructures are synthesized in aqueous conditions. The gold dendrites with a threefold symmetric characteristic were built up of numerous nanoparticles roughly 5–10 nm in size. The aggregated nanoparticles spontaneously experience a self-assembly process along crystallographic orientations and finally form a monocrystalline dendrite. An oriented attachment mechanism can be used to explain the nanoparticle-aggregated self-assembly process.

Electrochemical synthesis of leaf-like CuO mesocrystals and their lithium storage properties

We have developed an electrochemical approach for the synthesis of leaf-like CuO mesocrystals. The oriented attachment mechanism is responsible for the formation of CuO mesocrystals. As anode materials for lithium ion batteries, the high reversible capacity and enhanced cycle performance were demonstrated.

Preparation of copper nanoparticles by chemical reduction method using potassium borohydride

High dispersive copper nanoparticles were prepared by chemical reduction method using potassium borohydride as reducing agent. The effects of reactant ratio, concentration of CuSO4, reaction temperature, and dispersant on the size of product and conversion rate were studied. The morphologies of copper nanoparticles were characterized by scanning electron microscopy. The results show that the optimum process conditions are as follows: the molar ratio of KBH4 to CuSO4 is 0.75 (3:4), concentration of CuSO4 is 0.4 mol/L, reaction temperature is 30 °C, and dispersant is n-butyl alcohol. The average particles size of copper powders with spherical shape gained is about 100 nm.

The preparation and the properties of microcrystalline and nanocrystalline CuCr contact materials

The microcrystalline and nanocrystalline CuCr alloys prepared by high-energy ball milling and hot pressing were investigated in this paper. The experimental results show that the nanocrystalline Cu-Cr alloy powders are obtained by high energy ball milling, and the milled powders appear flaked or equiaxed morphology with or without liquid medium addition. The grain size of near fully dense alloys consolidated at 850 and 1200 K from milled powders is less than 100 nm and about 2-3 /spl mu/m, respectively. The ability to withstand high voltage of the nanocrystalline CuCr materials in vacuum is much higher than that of microcrystalline materials. The breakdown first takes place on the Cu-rich phase in the microcrystalline CuCr materials. For nanocrystalline CuCr materials, the breakdown exhibits a diffusional feature, in which the arc can move to the whole contact surface in a breakdown.

Interface synthesis of gold mesocrystals with highly roughened surfaces for surface-enhanced Raman spectroscopy

Local electromagnetic enhancement excited from collective oscillations of free electrons on a highly roughened mental surface can induce greatly enhanced Raman scattering. Herein gold mesoparticles with various morphologies and highly roughened surfaces, including sea urchin-like, flower-like, star-like, meatball-like, and dendritic nanostructures are prepared using pentanol/water interface as a growth “bed”. The morphologies of the prepared gold mesoparticles are well controlled by varying the concentrations of additives such as gold ions, ascorbic acid (AA) and cetyltrimethylammonium bromide (CTAB). Due to the unique structures such as rough surface, high internal porosity as well as complex morphology, these as-prepared mesocrystals exhibit a remarkable performance in surface-enhanced Raman scattering (SERS) compared with polyhedral mesoparticles.

Nanoparticle attachment on silver corrugated-wire nanoantenna for large increases of surface-enhanced Raman scattering.

Using three-dimensional finite-difference time-domain (FDTD) simulation, we described a systematic investigation on the electric field enhancement of the silver corrugated nanowires. The enhancement factor (EF) of surface-enhanced Raman scattering (SERS) for corrugated nanowires can be markedly increased by 1 or 2 orders of magnitude as compared with the smooth nanowires. Moreover, the EF can be further increased with nanoparticle attachment on the corrugated Ag nanowires owing to the coupling between the discrete plasmon state of the nanoparticles and continuum plasmon states of the corrugated nanowire or the crossed corrugated nanowires. The surface plasmonic field distribution of Ag nanowires can be effectively controlled by the polarization of the incident light. Raman spectrum measurements show that the relatively dense corrugated nanowires exhibit a relatively high reproducibility and SERS enhancement attributed to the elimination of polarization-dependent SERS-anisotropic enhancement via the overlapping of randomly distributed Ag nanowires. Such nanostructures as potential nanoantennas offer a route to optimize plasmon coupling for designing miniaturization integration.

Highly symmetric polyhedral Cu2O crystals with controllable-index planes

Novel highly symmetric multi-faceted polyhedral Cu2O crystals enclosed by controllable high-index facets and different low-index facets have been synthesized via a template-free complex-precursor solution route. The formation and evolution of these polyhedral shapes can be attributed to the aggregation and ripening mechanism with face-selective adsorption. The appearance of these novel polyhedral architectures further enriches the current morphologies of Cu2O crystals, and might become useful for the fundamental study of crystals design.

A route to increase the enhancement factor of surface enhanced Raman scattering (SERS) via a high density Ag flower-like pattern

We explored a route to prepare a high enhancement factor of SERS substrate via a high density of Ag flowerlike pattern. The finite difference time domain (FDTD) calculations indicate that the Ag flowerlike pattern may demonstrate a high quality SERS property owing to the high density and abundant hot spot characteristic. Using an unusually high overpotential with electrodeposition system, the fractal flowerlike patterns and the high density nanoparticle arrays were experimental synthesized. The SERS measurement of above different Ag nanostructures verified the predications from the FDTD calculation.

Sodium Chloride Template Synthesis of Cubic Tin Dioxide Hollow Particles for Lithium Ion Battery Applications

This paper describes a new synthesis and lithium ion charge-discharge property of tin dioxide (SnO(2)) hollow nanocubes. SnO(2) is one of the best-known anode materials for lithium-ion battery application because of its high lithiation-delithiation capacity. Hollow nanostructures with high surface area are preferred, because they accommodate large volume changes and maintain the structural stability of electrode materials during charge-discharge cycles. The SnO(2) hollow cubes made in this study had a discharge capacity of up to 1783 mA h g(-1) for the initial cycle and 546 mA h g(-1) after 30 cycles at a current density of 0.2 C between 0.02 and 2.0 V (vs Li/Li(+)).