In this work, we developed a tetrapod-shaped ZnO nanostructure (T-ZnO) biosensor to determine uric acid (UA), which is the primary end product of purine metabolism. The as-fabricated UA sensor presents a higher performance than that of the reported biosensors based on ZnO nanorods and ZnS quantum dots, etc. High-quality ZnO nanotetrapods were characterized by field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectra (EDX), X-ray diffraction (XRD) and Raman spectroscopy, respectively. A high affinity of uricase/ZnO to UA was revealed by cyclic voltammograms. The biosensor performance has been systematically investigated by amperometric response measurements. A fast current response time is within 9 s. It was also found that the uricase/T-ZnO biosensor presented a high and reproducible sensitivity of 80.0 microA cm(-2) mM(-1) and an experiment limit of detection of 0.8 microM. This study provides an insight utilizing the unique ZnO nanostructure to develop the highly sensitive and rapidly responsive nano-bio devices.

An amperometric biosensor based on zinc oxide (ZnO) nanotetrapods was designed to detect L-lactic acid. The lactate oxidase was immobilized on the surface of ZnO nanotetrapods by electrostatic adsorption. Unlike traditional detectors, the special four-leg individual ZnO nanostructure, as an adsorption layer, provides multiterminal charge transfer channels. Furthermore, a large amount of ZnO tetrapods are randomly stacked to form a three-dimensional network naturally that facilitates the exchange of electrons and ions in the phosphate buffer solution. Utilizing amperometric response measurements, the prepared ZnO nanotetrapod L-lactic acid biosensor displayed a detection limit of 1.2 μM, a low apparent Michaelis-Menten constant of 0.58 mM, a high sensitivity of 28.0 μA cm(-2) mM(-1) and a good linear relationship in the range of 3.6 μM-0.6 mM for the L-lactic acid detection. This study shows that the biosensor based on ZnO tetrapod nanostructures is highly sensitive and able to respond rapidly in detecting lactic acid.

ZnO nanotetrapod electrochemical biosensor is demonstrated for the quantitative detection of an extremely small amount of glucose. The tetrapod-like ZnO nanostructures possess good electron communication and positively charged surface, where negatively charged glucose oxidase was immobilized through electrostatic interaction. The as-fabricated biosensor presented a reproducible sensitivity of 25.3 μA/mM cm2 with a low detection limit of 4 μM for glucose. The high performance is attributed to the ZnO tetrapods with multiterminal charge conduction, larger specific surface area and three-dimensional (3D) spatial network structure of their random accumulation. Our work provides a wide insight utilizing the multiterminal ZnO nanostructure as an adsorption material to construct highly sensitive and rapidly responsive biosensors.

We constructed the transferred ZnO biosensor and the grown ZnO biosensor by two different nano-ZnO immobilization approaches. And the influence of different assembly processes on the biosensor performance has been systematically investigated and compared. An enhanced sensitivity of the grown ZnO biosensor is found to be 52% higher than that of the transferred ZnO biosensor. Correspondingly, the other properties are also better in the grown ZnO biosensor, including the response time, the detection limit and the linear range. These results are well consistent with the fact that more glucose oxidase is immobilized on the well-aligned ZnO arrays, which have higher specific surface area and more direct electron communication path, in the grown sensor than the randomly distributed and stacked ZnO nanorods in the transferred sensor. The nano-ZnO grown directly has been demonstrated more desirable for enzymatic immobilization and signal transduction in the high performance biosensors.

A simple method was developed to directly deposit silver nanoparticles on the surface of silica spheres. The photochemical reduction was carried out by ultraviolet irradiation in air atmosphere at room temperature. The [Ag(NH3)2]+was reduced to silver atoms upon ultraviolet irradiation. Silver atoms subsequently deposited on the surface of silica spheres and agglomerated into silver nanoparticles. Silica spheres with silver nanoparticles of different size and density can be simply controlled by adjusting the UV-light irradiation time. The silver nanoparticles deposited on silica spheres were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, and field emission scanning electron microscopy.

Polyimide/silica/silver hybrid films were prepared via the combination of sol-gel method and in situ single-stage self-metallization technique. The structure of polyimide films in the thermal curing process and the influence of silica content on the transfer and aggregation of silver particles to the surface of hybrid films were investigated. Films were characterized by transmission electron microscopy, dynamic mechanical thermal analysis Fourier transform infrared spectroscopy, ultraviolet visible spectroscopy and mechanical measurements. The results indicated that there was no degradation of polyimide matrix after the formation of silica and silver particles. Silica acted as the nucleus for the silver particles. With increasing the content of silica, more and more silver particles keep in the hybrid films instead of transferring onto the surface of the hybrid films, and the reflections of hybrid films decreased gradually.

Polyimide/silica/silver hybrid films were prepared by the sol-gel method combined with in situ single-stage self-metallization technique. The structure of polyimide films in the thermal curing process and the influence of silica content on the migration and aggregation of silver particles to the surface of hybrid films were investigated. The hybrid films were characterized by transmission electron microscopy, dynamic mechanical thermal analysis, Fourier transform infrared spectroscopy, ultraviolet visible spectroscopy and mechanical measurements. The results indicated that there was no degradation of the polyimide matrix after the formation of silica and silver particles. Silica acted as the nucleus for the silver particles. With increasing silica content, more and more silver particles were kept in the hybrid films instead of being migrated onto the surface of the hybrid films and the reflections of hybrid films decreased gradually.

采用溶胶-凝胶法(Sol-Gel)制备了二氧化硅不同质量分数的聚酰亚胺/二氧化硅(PI/SiO2)纳米复合薄膜.并用TEM、力学性能、吸水性能及介电性能测试等方法研究了薄膜的结构与性能.结果表明,SiO2微粒均匀分散在PI基体中,粒径随着SiO2含量的增加而增大;当SiO2质量分数在20%以内时对PI基体有增强作用,且在10%左右拉伸强度达到最大,而吸水率逐渐减小,介电常数则变化不大.