Xuefeng Qian

Preparation of polychrome silver nanoparticles in different solvents

Polychrome silver nanoparticles have been prepared by a soft solution approach under microwave irradiation from a solution of silver nitrate (AgNO3) in the presence of poly(N-vinyl-2-pyrrolidone) without any other reducing agent. Different morphologies of silver colloids with charming colors could be obtained using different solvents as the reaction medium. The structures of the silver colloids were determined by X-ray powder diffraction. UV-Vis spectroscopy was used to follow the reaction process and to characterize the optical properties of the resultant silver colloids. The influence of the solvent on the morphology of silver was investigated.

Poly(etherimide)/montmorillonite nanocomposites prepared by melt intercalation: morphology, solvent resistance properties and thermal properties

Polyimide-MMT (montmorillonite) nanocomposites has been prepared by melt blending an organo-modified MMT with a thermoplastic poly(etherimide) (PEI) in an internal mixer. The dispersion of the MMT layers within the PEI matrix was verified using X-ray diffraction and transmission electron microscopy, revealing an exfoliation morphology. Owing to the molecular dispersion of the MMT layers and the strong interaction between PEI and MMT, the nanocomposites exhibited a substantial increase at glass transition temperature and thermal decomposition temperature, and a dramatic decrease in solvent uptake compared to the virgin PEI.

Highly Efficient Ag2O/Bi2O2CO3 p-n Heterojunction Photocatalysts with Improved Visible-Light Responsive Activity

Ag2O/Bi2O2CO3 p-n heterojunctions are prepared with commercial Bi2O2CO3 as precursor via a simple photosynthesis process. The obtained Ag2O/Bi2O2CO3 p-n heterojunctions show higher photocatalytic activity than that of pure n-Bi2O2CO3, and the obtained Ag2O/Bi2O2CO3 (AB-4) heterojunction exhibits the best photocatalytic activity under visible light (λ > 400 nm), with which Rhodamine B, methyl blue and methyl orange can be completely degraded within 12 min. Photoluminescent spectra and photoelectrochemical measurement further indicate that the Ag2O/Bi2O2CO3 p-n heterojunctions greatly enhance the charge generation and suppress the charge recombination of photogenerated electron-hole pairs, which would be beneficial to improve their photocatalytic activity.

Hierarchical Bi2O2CO3 microspheres with improved visible-light-driven photocatalytic activity

A high-efficiency Bi2O2CO3 photocatalyst was successfully synthesized using tri-sodium citrate as both the coordinating agent and carbon source through a hydrothermal process. Morphology modulation of the obtained products could be easily realized by tuning the concentration of tri-sodium citrate in sponge-like, rose-like and plate-like shapes. The as-prepared sponge-like Bi2O2CO3 microspheres, owning a narrowed band gap of 2.87 eV and a higher BET surface area of 43.99 m2 g−1, exhibit powerful visible-light-photocatalytic activity for the degradation of dyes under 300 W Xe lamp light irradiation. It is worthy to note that the optimal sponge-like Bi2O2CO3 microspheres also possess superior photocatalytic ability under natural sunlight.

Silver nanocrystals by hyperbranched polyurethane-assisted photochemical reduction of Ag+

Silver nanoparticles in hyperbranched polyurethane (HP) matrix were prepared by means of UV irradiation at room temperature. HP was found to play a key role in the photochemical reduction of silver ions and the formation of nanosized particles. Transmission electron microscopic (TEM) analysis showed that silver nanoparticles were homogeneously dispersed in HP matrix. The absorption peaks due to the surface plasmon resonance of the obtained silver nanoparticles were observed at about 430 nm in the ultraviolet-visible (UV-Vis) absorption spectra. X-ray powder diffraction (XRD) was also used to characterize the obtained nanoparticles.

MnFe2O4–graphene nanocomposites with enhanced performances as anode materials for Li-ion batteries

MnFe(2)O(4)-graphene nanocomposites (MnFe(2)O(4)-GNSs) with enhanced electrochemical performances have been successfully prepared through an ultrasonic method, e.g., approximate 1017 mA h g(-1) and 767 mA h g(-1) reversible capacities are retained even after 90 cycles at a current density of 0.1 A g(-1) and 1 A g(-1), respectively. The remarkable improvement in the reversible capacity, cyclic stability and rate capability of the obtained MnFe(2)O(4)-GNSs nanocomposites can be attributed to the good electrical conductivity and special structure of the graphene nanosheets. On the other hand, MnFe(2)O(4) also plays an important role because it transforms into a nanosized hybrid of Fe(3)O(4)-MnO with a particle size of about 20 nm during discharge-charge process, and the in situ formed hybrid of Fe(3)O(4)-MnO can be combined with GNSs to form a spongy porous structure. Furthermore, the formed hybrid can also act as the matrix of MnO or Fe(3)O(4) to prevent the aggregation of Fe(3)O(4) or MnO, and accommodate the volume change of the active materials during the discharge-charge processes, which is also beneficial to improve the electrochemical performances of the MnFe(2)O(4)-GNSs nanocomposites.

Formation of monodispersed PVP-capped ZnS and CdS nanocrystals under microwave irradiation

Abstract Poly ( N -vinyl-2-pyrrolidone) (PVP)-capped ZnS, CdS nanoparticles were prepared by a microwave method from Zn(Ac) 2 or Cd(Ac) 2 and thiourea in N , N -dimethylformamide (DMF) solution. The reaction process was monitored by the temporal evolution of the absorption spectrum. With PVP as stabilizer, monodispersed semiconductor nanoparticles, which showed high quantum size effect, have been obtained. Further study showed that the microwave irradiation could influence selectively the nucleation and growing rates of different semiconductor nanoparticles.

Formation of silver dendrites under microwave irradiation

Well-defined silver dendrites were successfully prepared in DMF solution containing poly(N-vinly-2-pyrrolidone) (PVP) as the stabilizer under microwave irradiation. Morphology similar to those of the DLA model fractal dimensions around 1.7 has been observed in our systems. It was found that microwave power and the existence of PVP played important roles in the formation of well-defined silver dendrites. The products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The proposed formation mechanism of dendrites was also investigated.

3D-hierarchical SnS2 micro/nano-structures: controlled synthesis, formation mechanism and lithium ion storage performances

Three kinds of 3D-hierarchical SnS2 micro/nano-structures were successfully synthesized through a one-pot hydrothermal method by controlling the ratio of SnCl4 and L-cysteine. It was found that these obtained 3D-hierarchical SnS2 structures had great differences in their chemical composition, crystalline property, building blocks, assembling format and porous structure. The formation processes of the hierarchical structures were studied well and the possible mechanisms were also proposed. The lithium storage properties of these 3D-hierarchical SnS2 structures were carefully studied by charge-discharge test and cyclic voltammetry method. The results indicated that the crystalline properties of the electrode materials could influence the initial electrochemical reactivity and the small size of building blocks could greatly improve the reversibility of electrochemical reaction and rate performances. Furthermore, the large surface area, porous structure and free space derived from the 3D hierarchical structures were beneficial to the long-term cycling stability of electrode materials.

Controlled synthesis of hierarchical Bi2WO6 microspheres with improved visible-light-driven photocatalytic activity

Three-dimensional (3D) hierarchical Bi2WO6 microspheres were successfully synthesized by a simple inorganic salt-assisted hydrothermal process. Morphology modulation of the obtained products could be easily realized by tuning the concentration of the nitrate. It is worthy to note that the obtained hierarchical Bi2WO6 microspheres exhibit powerful visible-light-photocatalytic activity for the degradation of Rhodamine-B (RhB) under 300 W Xe lamp light irradiation. A possible salt-assisted formation mechanism was proposed on the basis of the experimental results. Furthermore, this work might represent a novel synthesis strategy for other photocatalysts with desired photocatalytic activity.