Zhaoqun Wang

Facile and controlled fabrication of functional gold nanoparticle-coated polystyrene composite particle.

Gold nanoparticles-coated polystyrene (AuNPs-coated PS) composite particles with raspberry-like morphology are successfully prepared with the aid of a unique thermodynamically driving effect. It is of considerable interest that the AuNPs generate and self-assemble with raw, ordinary PS microspheres that preexist in the oxidation-reduction systems. The synthesized AuNPs-coated PS composite particles have been extensively characterized using scanning electron microscope, transmission electron microscope, and UV-Vis-NIR spectroscopy. The results indicate that the morphology of the resultant composite particles is governed by simply changing the amount and type of reductants and the concentration of PS microspheres. The AuNPs-coated PS composite particles also exhibit the good surface-enhanced Raman scattering and catalytic performances.

A facile strategy for controlling the self-assembly of nanocomposite particles based on colloidal steric stabilization theory.

A heterocoagulation strategy based on colloidal steric stabilization theory has been developed, through which polystyrene (PS) and silica (SiO(2)) particles without any surface modification or functionalization self-assembled rapidly via solution to afford nanocomposite particles with raspberry-like morphology. The formation mechanism is fully studied on the basis of a thermodynamic analysis. The soluble stabilizer and the solvent quality are the main determining factors, which have a significant influence on this self-assembly process and the silica coverage of resultant composites. The relative size of PS to SiO(2) candidates also has the effect of control on the extent of self-assembly. Furthermore, this strategy can be applied to fabricate a broad range of composite materials, including PS/TiO(2), PS/AgI, as well as PS/PS composites.

Facile and controllable fabrication of gold nanoparticles-immobilized hollow silica particles and their high catalytic activity

A facile and controllable method of immobilizing gold nanoparticles (AuNPs) on hollow silica particles (SiO2HPs) is proposed and the resultant SiO2HP/AuNP composite particles exhibit high catalytic activity. The carrier SiO2HPs decorated with amino groups are prepared in a W/O inverse emulsion, having a well-defined hollow structure, mesoporous wall and dense bush-like surface morphology. A large number of ultrafine AuNPs are generated via in situ reduction of chloroauric acid by the amino groups and firmly anchored on the bush-like silica shell. The structure and morphology of the composites are governed by changing the weight percentage of 3-aminopropyltriethoxysilane in the total amount of monomers (wa), which have been extensively characterized. Benefiting from the unique multiple structures, the composite particles exhibited outstanding catalytic efficiency and repeatability, which are confirmed by two oxidation–reduction reactions of 2-nitroaniline/NaBH4 and 4-nitrophenol/NaBH4.

The toxicity of cadmium to three aquatic organisms (Photobacterium phosphoreum, Daphnia magna and Carassius auratus) under different pH levels

This study investigated the effect of pH on cadmium toxicity to three aquatic organisms: Photobacterium phosphoreum, Daphnia magna and Carassius auratus. The acute toxicity of Cd(2+) to P. phosphoreum and D. magna at five pH values (5.0, 6.0, 7.0, 8.0, and 9.0) was assessed by calculating EC50 values. We determined that Cd(2+) was least toxic under acidic conditions, and D. magna was more sensitive to the toxicity of Cd than P. phosphoreum. To evaluate Cd(2+)-induced hepatic oxidative stress in C. auratus at three pH levels (5.0, 7.25, 9.0), the activity of antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase), the level of glutathione and the malondialdehyde content in the liver were measured. Oxidative damage was observed after 7d Cd exposure at pH 9.0. An important finding of the current research was that Cd(2+) was generally more toxic to the three test organisms in alkaline environments than in acidic environments.

Colloid Thermodynamic Effect as the Universal Driving Force for Fabricating Various Functional Composite Particles

The design and fabrication of functional nanocomposites is an active area of research because composite particles have significantly improved physical and chemical properties over those of their single-component counterparts. Traditionally, chemical pretreatments of the components were used to enhance their physicochemical or chemical interactions. Here, we propose a novel approach to taking advantage of the beauty of thermodynamics. A series of functional materials, including graphene nanosheets, carbon nanotubes, noble metals, magnetic materials, conducting polymers, attapulgite, and etc. were incorporated with polystyrene particles by a thermodynamic driving force. This unique approach is facile and versatile and shows the considerable significance of developments in both scientific methodology and particle engineering.

A facile and environmentally friendly method for the synthesis of hollow silica particles in a self-stable dispersion

The fabrication of hollow silica particles is of interest from both academic and application viewpoints. In this paper, we propose a distinctly novel method by which hollow silica particles are successfully fabricated in a self-stable system without any surfactants during a self-consumptive templated process. In detail, it was carried out by adopting a two-step feeding of tetraethoxysilane including initial dropping and subsequent addition of residual TEOS in one batch. The synthesized hollow particles have been extensively characterized using a scanning electron microscope, transmission electron microscope and N2 sorption analysis. The results indicated that the morphology of the resultant hollow silica particles was governed by simply changing the volume ratio of the precursor added in two steps, the reaction temperature and the concentration of ammonia. Additionally, the mechanism governing the formation of the hollow silica particles is discussed.

PS Microspheres Coated by AuNPs via Thermodynamic Driving Heterocoagulation and Their High Catalytic Activity

A unique method of fabricating PS/AuNPs composite particles in ex situ mode is proposed on the basis of thermodynamically driving mechanism. It is facile and versatile as it eliminates the need for surface functionalizations and modifications of both PS microspheres and AuNPs. The PS/AuNPs composite particles take on a raspberry-like morphology with controllable coverage according to some thermodynamic factors, which have been extensively characterized by scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis. More importantly, the PS/AuNPs composite particles hold higher catalytic efficiency and better repeatability than the previously reported results, which are confirmed in two oxidation-reduction reactions of 2-nitroaniline/NaBH(4) and rhodamine B/NaBH(4).

One-step synthesis of silica hollow particles in a W/O inverse emulsion

Porous silica hollow particles have been fabricated by a one-step approach in water in oil (W/O) inverse emulsion. Ammonia water droplets stabilized by alkyl-phenol polyoxyethylene ether (TX-4) in tetraethoxysilane (TEOS)/cyclohexane solution act as soft templates for constructing the silica hollow particles. The formation mechanism is discussed in detail from the equilibrium between the diffusion and reactions of TEOS and its products (hydrolysates and polycondensates) on the W/O interface. The structure and morphology of the resultant silica hollow particles are well controlled by changing the parameters involving the concentration of TX-4, TEOS, and ammonia. The synthesized products have been characterized using transmission electron microscopy, scanning electron microscopy, solid state NMR, and nitrogen adsorption–desorption measurements.

Controlled preparation of core–shell polystyrene/polypyrrole nanocomposite particles by a swelling–diffusion–interfacial polymerization method

Polystyrene/polypyrrole (PS/PPy) core–shell nanocomposite particles with uniform and tailored morphology have been successfully synthesized using the “naked” PS particulate substrate with the aid of a proposed strategy, the so-called swelling–diffusion–interfacial polymerization method. After initially forming pyrrole-swollen PS particles, diffusion of the monomer toward the aqueous phase was controlled through the addition of hydrochloric acid, eventually leading to its polymerization on the substrate particle surface. This process allows the nanocomposite particles to possess uniform and intact PPy overlayer and affords much more effective control over the structure and morphology of the resultant nanocomposites by simply changing the PS/pyrrole weight ratio or the addition amount of the doping acid. In particular, the nanocomposite particles with a thin, uniform, and intact PPy overlayer and their corresponding PPy hollow particles were obtained at a low addition amount of pyrrole. The resultant nanocomposite particles have been extensively characterized using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and thermogravimetry.

Facile and Controllable Assembly of Multiwalled Carbon Nanotubes on Polystyrene Microspheres

Herein a facile and controllable heterocoagulation between polystyrene (PS) microspheres and multiwalled carbon nanotubes (MWCNTs) is introduced based on colloid thermodynamics. The MWCNTs play the role of steric stabilizer for stabilizing the metastable PS microspheres and thus immobilize spontaneously on the surface of PS microspheres. The synthesized MWCNTs-coated PS composite particles have been extensively characterized by scanning electron microscopy, transmission electron microscopy, thermogravimetry and Raman spectroscopy. The results indicate that the structure and morphology of the resultant MWCNTs-coated PS composite particles are significantly affected by the weight ratio of PS and MWNCTs and the amount of poly(vinylpyrrolidone) that is injected into PS dispersion before they are mixed with MWCNTs. Therefore, these composite particles have the potential to produce MWCNTs-based composite materials with controllable mass loading and dispersity of MWCNTs.