Oriented contraction: a facile nonequilibrium heat-treatment approach for fabrication of maghemite fiber-in-tube and tube-in-tube nanostructures.

We present a simple and effective nonequilibrium heat-treatment approach that allows for the facile fabrication of maghemite (γ-Fe(2)O(3)) fiber-in-tube and tube-in-tube nanostructures by heat-treating electrospun precursor fibers composed of polyvinylpyrrolidone (PVP) and iron citrate with a carefully devised heating rate (R). In this nonequilibrium heat-treatment procedure, R can be easily utilized to tune the temperature gradient established in the inner portion of the fibers and the difference between the cohesive force and the adhesive force at the interface layer between the inner gel and the dense rigid shell generated in situ by a high R. Therefore, the contraction direction of the precursor nanofibers and the final morphology of the resultant γ-Fe(2)O(3) fibers ranging from a simple tube to a fiber in tube to a tube in tube are realized for control. The nonequilibrium heat-treatment approach reported here can be readily extended to the fabrication of other materials with controllable interior structures by fast heating their corresponding gel precursors, which may be fabricated on the basis of electrospinning techniques and others. The resultant γ-Fe(2)O(3) fiber-in-tube and tube-in-tube nanostructures may have important applications in a number of areas, such as magnetic separable catalysts or catalyst supporting materials, sensors, absorbents, microreactors, and so forth, because of their structural characteristics and good magnetic properties.

Prussian blue modified amperometric FIA biosensor: one-step immunoassay for alpha-fetoprotein.

The aim of this study was to develop a rapid method to measure alpha-fetoprotein (AFP) in human serum by use of one-step sandwich enzyme-linked immunosorbent assay (ELISA)-based immunobiosensor with disposable screen-printed carbon electrode technology. Prussian blue (PB) was deposited using cyclic voltammetry (CV) on the surface of electrode to catalyze H202 from the reaction of glucose oxidase. It took only about 30 min to complete the whole experimental procedure through flow injection analysis (FIA). A detection range obtained is in the range from 5 to 500 ng/ml AFP. This detection seems to be quick, reliable and practical.

Impedimetric biosensors.

Electrochemical impedance spectroscopy (EIS) is a sensitive indicator of a wide variety of chemical and physical properties. An increasing trend towards the development of impedimetric biosensors is being currently observed. Impedimetric techniques have been performed to characterize the fabrication of the biosensors and to monitor the catalyzed reactions of enzymes or the biomolecular recognition events of specific binding proteins, lectins, receptors, nucleic acids, whole cells, antibodies or antibody-related substances. However, little attention has been paid to reviewing this interesting research area. Herein, impedimetric biosensors are reviewed and many novel designs are discussed.

Polymorphous ZnO complex architectures: selective synthesis, mechanism, surface area and Zn-polar plane-codetermining antibacterial activity.

Complex ZnO architectures with tunable morphologies and structures were obtained by modulating only the base type and molar ratio of base to Zn2+ (α) using an easy one-pot hydrothermal approach without any template or organic additive. Characterizations by X-ray diffraction, Fourier-transform infrared spectrometry, scanning electron microscopy, transmission electron microscopy, and surface area analysis were performed. The effect of the base type and base/Zn2+ molar ratio on the morphology and corresponding mechanism were determined. The correlations between the microstructure and properties were established. The antibacterial effect of the ZnO samples was probably due to a combination of variable factors. Better antibacterial activity is derived from more effective antibacterial surfaces, which are mainly associated with the specific surface area and Zn-polar plane. Thus, flower-like architectures with larger specific surface areas and more highly exposed (0001) Zn-polar surfaces outwards are promising structures for ZnO antibacterial agents. This work provides a guide for devising and synthesizing highly efficient antibacterial materials.