Uniform Fe3O4 nanospheres with a diameter of 100 nm were rapidly prepared using a microwave solvothermal method. Then Fe304/polypyrrole (PPy) composite nanospheres with well-defined core/shell structures were obtained through chemical oxidative polymerization of pyrrole in the presence of Fe3O4; the average thickness of the coating shell was about 25 nm. Furthermore, by means of electrostatic interactions, plentiful gold nanoparticles with a diameter of 15 nm were assembled on the surface of Fe3O4/PPy to get Fe3O4/PPy/Au core/shell/shell structure. The morphology, structure, and composition of the products were characterized by transmission electronic microscopy (TEM), scanning electronic microscopy (SEM), X-ray powder diffraction (XRD), and Fourier transform infrared (FT-IR) spectroscopy. The resultant nanocomposites not only have the magnetism of Fe3O4 nanoparticles that make the nanocomposites easily controlled by an external magnetic field but also have the good conductivity and excellent electrochemical and catalytic properties of PPy and Au nanoparticles. Furthermore, the nanocomposites showed excellent electrocatalytic activities to biospecies such as ascorbic acid (AA).

A newly developed electrochemical cell sensor for the determination of K562 leukemia cells using 3‐aminophenylboronic acid (APBA)‐functionalized multiwalled carbon nanotubes (MWCNTs) films is demonstrated. The films are generated by the covalent coupling between the NH2 groups in APBA and the COOH group in the acid‐oxidized MWCNTs. As a result of the sugar‐specific affinity interactions, the K562 leukemia cells are firmly bound to the APBA‐functionalized MWCNTs film via boronic acid groups. Compared to electropolymerized APBA films, the presence of MWCNTs not only provides abundant boronic acid domains for cell capture, their high electrical conductivity also makes the film suitable for electrochemical sensing applications. The resulting modified electrodes are tested as cell detection sensors. This work presents a promising platform for effective cell capture and constructing reusable cytosensors.

A nanocomposite with poly(diallyldimethylammonium), PDDA, intercalated between manganese oxide layers is constructed on a graphite electrode surface through one-step electrodeposition and used to adsorb glucose oxidase (GOD). The immobilized GOD displays a pair of stable and quasireversible redox peaks with a formal potential of À 468 mV in pH 7.0 buffer solutions and exhibits excellent electrocatalysis to the reduction of oxygen. In the presence of dissolved oxygen, the reduction peak current decreased gradually with the addition of glucose, indicating that the immobilized GOD kept its bioactivity. Thus a reagentless biosensor for glucose at a low detection potential was established. The linear concentration range is from 0.02 to 2.78 mM with a detection limit of 9.8 mM. The proposed glucose biosensor was insensitive to common interferences such as ascorbic and uric acids etc.

In this paper, an interface constructed with fibronectin (Fn) functionalized multiple-walled carbon nanotubes (MWNTs) was prepared which can efficiently capture cells. The acid-treated MWNTs were covalently coupled with Fn in the presence of a coupling agent, thus realizing the efficient immobilization of Fn, and it was proven by infrared spectroscopy. Due to the specific binding of integrin receptor on cells and the arginineglycine-aspartic acid amino acids (RGD) peptide contained in Fn, this interface not only has a property for capturing SMMC 7721 cells, but also efficiently retains viability of immobilized cells. The presence of MWNTs not only increases the surface area of the electrode but also promotes the electrochemical behavior of SMMC 7721 cells. In addition, we applied homemade heated glassy carbon electrodes to cell detection, which were indirectly heated by direct current. Profiting from the heat convection generated by the joule heat from direct current, the sensitivity of the detection of cell concentration was clearly meliorated. The biosensor based on heated electrode modified with Fn-MWNTs, presents a promising platform for sensitive cell detection.

Oxidation behaviors of ZrHx(x=0~2) in O2at 600°C were investigated. The influences of temperature and oxidation time on mass gain of the oxide film were studied. The phase structure and morphology of the oxide film were analyzed by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The result indicates that the oxidation behavior of zirconium is greatly changed after absorbing hydrogen. The oxidation rate of zirconium hydride decreased with increasing of hydrogen content. The thickness of the oxide film decreases and the uniformity of oxide film declined with increasing of x value. Some holes and creaks present in the oxide films when x value is 1.8 and 2. The similar textured oxide film on the surface of ZrHx(x=0~2) is found and the main phase of the oxide films is monoclinic ZrO2of the baddeleyite structure. A detectable amount of tetragonal ZrO2appeal in all the samples. A protective textured oxide film can be formed on the surface of ZrHx(x=0~2), making it ingerate and thick is important to reduce hydrogen loss.