Helin Niu

Hierarchical structured bismuth oxychlorides: self-assembly from nanoplates to nanoflowers via a solvothermal route and their photocatalytic properties

A simple solvothermal route was explored to prepare hierarchical, nanostructured flower-like bismuth oxychlorides (BiOCl) by employing pyridine as the solvent. The volume ratios of distilled water to pyridine play an important role in the assembly of the BiOCl nanostructure from nanoplates to nanoflowers. The as-prepared BiOCl nanoflowers were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and nitrogen sorption. The resulting BiOCl nanoflowers with high specific surface area were phase-pure and self-assembled from thin nanoplates during the reaction process. In addition, the photocatalytic properties of the as-prepared samples were further investigated by photocatalytic decomposition of methyl orange (MO) dye, and it was found that the BiOCl nanoflowers showed a higher photocatalytic activity than that of TiO2 (Degussa, P25) under modeling sunlight.

Magnetic field-induced growth and self-assembly of cobalt nanocrystallites

The growth and assembly behavior of cobalt magnetic nanocrystallites under an external magnetic field were studied. Co polycrystalline wires with an average length of 2 mm and diameter of 13 µm were formed by the self-assembly of Co nanocrystallites (15 nm on average) under the induction of a 0.25 T external magnetic field. The wires were nearly parallel because their axes were all parallel to the magnetic line of force. The Ms and Hc values of the sample, 111 emu g−1 and 389 Oe, are higher than those of the sample prepared without an external magnetic field applied (91 emu g−1 and 375 Oe), which might be associated with the special nanostructure in which Co nanocrystallites were arranged in polycrystalline wires acting as permanent magnetic dipoles. The process could be used to fabricate large arrays of uniform wires of some magnetic materials and improve the magnetic properties of nanoscale magnetic materials.

Enhanced electrochemiluminescence of CdSe quantum dots composited with graphene oxide and chitosan for sensitive sensor.

A novel strategy for the enhancement of electrochemiluminescence (ECL) was developed by combining CdSe quantum dots (QDs) with graphene oxide-chitosan (GO-CHIT). The ECL sensor fabricated with CdSe QDs/GO-CHIT composite exhibited high ECL intensity, good biocompatibility and long-term stability, and was used to detect of cytochrome C (Cyt C). The results show that the ECL sensor has high sensitivity for Cyt C with the linear range from 4.0 to 324 μM and the detection limit of 1.5 μM. Furthermore, the ECL sensor can selectively sense Cyt C from glucose and bovine serum albumin (BSA).

Preparation and characterization of single-crystalline bismuth nanowires by a low-temperature solvothermal process

Abstract Single-crystalline metallic bismuth nanowires have been successfully prepared by a solvothermal process at low temperatures, using aqueous bismuth nitrate [Bi(NO3)3·5H2O] and ethylene diamine (H2NCH2CH2NH2) as starting materials. Characterizations have been carried out by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The diameter of the nanowires is about 20–30 nm and lengths range from 0.2 to 2.5 μ m. The reduction of bismuth ions (Bi3+) and formation mechanism of nanowire were discussed based on the characteristic of the reaction system employed.

Fabrication of GO/PANi/CdSe nanocomposites for sensitive electrochemiluminescence biosensor.

A novel graphene oxide sheets/polyaniline/CdSe quantum dots (GO/PANi/CdSe) nanocomposites were successfully synthesized and used for the sensitive electrochemiluminescence (ECL) biosensing. The GO/PANi/CdSe nanocomposites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), ultraviolet-visible (UV-vis) absorption spectroscopy, photoluminescence (PL) spectroscopy and Fourier transform infrared (FTIR) spectroscopy. Finally, the nanocomposites were employed to construct the biosensor via layer-by-layer assembly for the ECL detection of Cytochrome C (Cyt C). The whole process was characterized by cyclic voltammogram (CV) and electrochemical impedance spectroscopy (EIS). Experimental parameters such as the ratio of GO/PANi, the K(2)S(4)O(8) concentration and the pH value of electrolyte solution were studied to investigate the effect on the ECL intensity. Under the optimized conditions, the ECL intensity decreased linearly with the Cyt C concentrations in the range from 5.0×10(-8) to 1.0×10(-4) M with detection limit of 2.0×10(-8) M. Besides, the as-proposed biosensor exhibits high specificity, good reproducibility, and stability, and may be applied in more bioanalytical systems.

Core–shell CeO2@C nanospheres as enhanced anode materials for lithium ion batteries

In this work, novel CeCO3OH@C nanocomposites were prepared via a one-pot approach by hydrothermal carbonization of a solution of glucose as a carbon precursor in the presence of Ce(NO3)3·6H2O and urea. It was found that glucose not only facilitates the formation of CeCO3OH nanoparticles, but also leads to a uniform, glucose-derived, carbon-rich polysaccharide (GCP) overlayer on the CeCO3OH nanocomposites. By adjusting the concentrations of glucose, the morphology of the samples was transformed from spindle nanoparticles to uniform spherical particles. CeO2@C with a core–shell structure was fabricated after calcining the CeCO3OH@C nanospheres under an N2 atmosphere. The obtained products were characterized by SEM, TEM, XRD, TG-DSC, FT-IR and charge–discharge test. The electrochemical performance test showed that these CeO2@C core–shell spheres as an anode material for lithium ion batteries exhibited an initial discharge specific capacity of 863.0 mA h g−1 in the potential range of 3.0–0.0 V. After 50 cycles, the capacity of the CeO2@C core–shell spheres was stabilized reversibly at about 355.0 mA h g−1. The improved cycling performance was attributed to the carbon shells, which can enhance the conductivity of the CeO2 core and suppress the aggregation of active particles during cycling. These CeO2@C core–shell spheres are promising anode materials for lithium ion batteries.

A novel enzymatic hydrogen peroxide biosensor based on Ag/C nanocables.

A novel enzymatic hydrogen peroxide sensor was successfully fabricated based on the nanocomposites containing of Ag/C nanocables and gold nanoparticles (AuNPs). Ag/C nanocables have been synthesized by a hydrothermal method and then AuNPs were assembled on the surface of Ag/C nanocables. The nanocomposites were confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDS). The above nanocomposites have satisfactory chemical stability and excellent biocompatibility. Cyclic voltammetry (CV) was used to evaluate the electrochemical performance of the Ag/C/Au nanocomposites at glassy carbon electrode (GCE). The results indicated that the Ag/C/Au nanocomposites exhibited excellent electrocatalytic activity to the reduction of H(2)O(2). It offered a linear range of 6.7×10(-9) to 8.0×10(-6) M, with a detection limit of 2.2×10(-9) M. The apparent Michaelis-Menten constant of the biosensor was 51.7×10(-6) M. These results indicated that Ag/C/Au nanocomposites have potential for constructing of a variety of electrochemical biosensors.

Graphene-like cobalt selenide nanostructures: template-free solvothermal synthesis, characterization and wastewater treatment

Hexagonal Co0.85Se with Ni0.85Se-type structure has been successfully synthesized without any surfactants by a solvothermal reduction route. SEM observation indicated that the obtained Co0.85Se nanostructures were of graphene-like morphology with a thickness less than 10 nm. The influence of the reaction temperature and the molar ratios of reactants has been studied in detail, and the results reveal the two reaction conditions play a crucial role in determining the final morphologies of the samples. The as-prepared product is determined to be ferromagnetic at room temperature from magnetic measurements. And the product with high specific surface area could be used as an adsorbent in wastewater treatment, which may be very useful for the environment.

Visible-Light Active and Magnetically Recyclable Nanocomposites for the Degradation of Organic Dye

Recyclable visible-light photocatalyst Fe3O4@TiO2 with core-shell structure was prepared by a simple synthetic strategy using solvothermal crystallization of titanium precursor on preformed Fe3O4 nanopartiles. The photo-degradation reaction of neutral red aqueous solution was tested to evaluate the visible-light photocatalytic activity of the as prepared Fe3O4@TiO2 nanoparticles, which show excellent photocatalytic activity compared with commercial P25 catalyst. Moreover, the Fe3O4@TiO2 nanocomposites can be easily separated from the reaction mixture, and maintain favorable photocatalytic activity after five cycles. The high visible light absorption of the Fe3O4@TiO2 nanocomposites may originate from the absence of electronic heterojunction, excellently dispersity and the high specific surface area of the as-synthesized Fe3O4@TiO2 samples.

Electrochemical biosensor for Ni(2+) detection based on a DNAzyme-CdSe nanocomposite.

The detection and speciation analysis of metal-ion is very important for environmental monitoring. A novel electrochemical biosensor for Nickel(II) detection based on a DNAzyme-CdSe nanocomposite was developed. We firstly hybridized with capture probe (DNA1) and sequentially with DNA (DNA2) on the gold electrode. Then CdSe QDs were incorporated the specific recognition of DNA2 by covalent assembling. Upon addition of nickel ion into the above system, the substrate strand of the immobilized DNAzyme was catalytically cleaved by target Ni(2+), resulting in disassociation of the shorter DNA fragments containing CdSe QDs. The remaining CdSe QDs on the electrode surface detected by differential pulse anodic stripping voltammetry (DPASV). Under optimal conditions, the as-prepared sensor exhibited high sensitivity and fast response to Ni(2+) with the linear range from 20 nM to 0.2mM and a low detection limit of 6.67 nM. The prepared biosensor also shows good stability and good reproducibility and high selectivity toward target Ni(2+) against other metal ions because of highly specific Ni(2+)-dependent DNAzyme. Thus, our strategy has a good potential in the environment surveys.