miao Li

A novel nonenzymatic hydrogen peroxide sensor based on MnO2/graphene oxide nanocomposite

A new electrocatalyst, MnO(2)/graphene oxide hybrid nanostructure was successfully synthesized for the nonenzymatic detection of H(2)O(2). The morphological characterization was examined by scanning electron microscopy and transmission electron microscopy. The MnO(2)/graphene oxide based electrodes showed high electrochemical activity for the detection of H(2)O(2) in alkaline medium. The nonenzymatic biosensors displayed good performance along with low working potential, high sensitivity, low detection limit, and long-term stability, which could be attributed to the high surface area of graphene oxide providing for the deposition of MnO(2) nanoparticles. These results demonstrate that this new nanocomposite with the high surface area and electrocatalytic activity offers great promise for new class of nanostructured electrode for nonenzymatic biosensor and energy conversion applications.

Surface-depletion controlled gas sensing of ZnO nanorods grown at room temperature

The authors report on surface-depletion controlled gas sensing ZnO nanorods. These nanorods were synthesized through a simple wet chemical route at room temperature. The diameter of nanorods is about 15nm, which is close to two times of the Debye length of ZnO. In contrast to the previous report, the sensing is surface-depletion controlled rather than contact controlled and the sensitivity is up to 29.7 against 100ppm ethanol. Such high sensitivity is due to an almost complete depletion of the rods in air, which is confirmed from photoluminescence spectrum and x-ray photoelectron spectroscopy. The gas sensing mechanism controlled by surface depletion provides another approach to realize high-performance gas sensors.

A novel amperometric biosensor based on NiO hollow nanospheres for biosensing glucose

NiO hollow nanospheres were synthesized by controlled precipitation of metal ions with urea using carbon microspheres as templates, which were for the first time adopted to construct a novel amperometric glucose biosensor. Glucose oxidase was immobilized on the surface of hollow nanospheres through chitosan-assisted cross-linking technique. Due to the high specific active sites and high electrocatalytic activity of NiO hollow nanospheres, the constructed glucose biosensors exhibited a high sensitivity of 3.43 microA/mM. The low detection limit was estimated to be 47 microM (S/N=3), and the Michaelis-Menten constant was found to be 7.76 mM, indicating the high affinity of enzyme on NiO hollow nanospheres to glucose. These results show that the NiO hollow nanospheres are a promising material to construct enzyme biosensors.

Flexible morphology-controlled synthesis of mesoporous hierarchical α-Fe2O3 architectures and their gas-sensing properties

Mesoporous flower-like and urchin-like α-Fe2O3 nanostructures have been successfully synthesized by a simple solution-based reaction and sequential calcination. Detailed experiments demonstrated that the morphology of the hierarchical α-FeOOH precursors could be easily controlled by adjusting the experimental conditions including reactant concentration, solvent composition, reaction time, and reaction temperature. On the basis of time-dependent experiments, a multistage growth mechanism for the formation of the α-FeOOH super-architectures was proposed. In addition, by virtue of the unique hierarchical mesoporous structure and comparative high specific surface area, these obtained α-Fe2O3 nanostructures exhibited enhanced sensing performances to ethanol. This method is expected to be a useful technique for controlling the diverse morphologies of iron oxide superstructures that could meet the demands of a variety of applications, such as gas sensors, lithium-ion batteries, catalysis, waste-water treatment, and pigments.

An excellent enzyme biosensor based on Sb-doped SnO2 nanowires

Sb-doped SnO(2) nanowires were synthesized via thermal evaporation. Scanning electron microscopic, transmission electron microscopic, X-ray diffraction, current-voltage, and electrochemical impedance spectroscopy experiments have been used to characterize the structural and electrical behaviors of the nanowires. A mediator-free horseradish peroxidase-based H(2)O(2) biosensor was constructed through the Sb-doped SnO(2) nanowires used as the immobilization matrix for the enzymes. In comparison with the undoped SnO(2) nanowires, Sb-doped SnO(2) nanowires exhibited excellent electron transfer properties for the enzymes and higher electroactivity toward H(2)O(2). The biosensors displayed good performance along with high sensitivity, wide linear range, and long-term stability. Those can be attributed to the enhanced carrier density arising from Sb doping and biocompatible microenvironment provided by the Sb-doped SnO(2) nanowires. This study demonstrated that Sb-doped SnO(2) nanowires were promising platform for the construction of mediator-free biosensors and provided new further fundamental insights into the study of nanoscience and nanodevices.

A novel non-enzymatic hydrogen peroxide sensor based on Mn-nitrilotriacetate acid (Mn-NTA) nanowires

A novel non-enzymatic hydrogen peroxide sensor was realized from Mn-nitrilotriacetate acid (Mn-NTA) nanowires, which were successfully fabricated via a facile hydrothermal route. Cyclic voltammetry (CV) revealed that the Mn-NTA nanowires exhibited direct electrocatalytic activity for the oxidation of H(2)O(2) in phosphate buffer solution. The sensor showed linear response to H(2)O(2) at the concentrations range from 5 x 10(-6)M to 2.5 x 10(-3)M with a detection limit of 2 x 10(-7)M. The sensitivity was up to 78.9 microA mM(-1)cm(-2). These results indicated that the Mn-NTA nanowires were promising in realizing non-enzymatic H(2)O(2) detection.

Electrocatalytic activity of horseradish peroxidase/chitosan/carbon microsphere microbiocomposites to hydrogen peroxide.

Colloidal carbon microspheres (CMS) are dispersed in chitosan (CHIT) solution to form an organic-inorganic hybrid with excellent micro-environment for the immobilization of biomolecules. A novel amperometric biosensor for the determination of hydrogen peroxide (H(2)O(2)) has been constructed by entrapping horseradish peroxidase (HRP) in as-synthesized CMS/CHIT hybrid. The modification of glassy carbon electrode is made by a simple solution-evaporation method. The electrochemical properties of the biosensor are characterized in electrochemical methods. The proposed biosensor shows high sensitive determination and fast response to H(2)O(2) at -0.15 V. The constructed HRP/CHIT/CMS/GC electrode also exhibits a fine linear correlation with H(2)O(2) concentration. The calculated value of the apparent Michaelis-Menten constant, 2.33 mM, suggests that the HRP in CMS/CHIT hybrid keeps its native bioactivity and has high affinity for H(2)O(2).

Electrografted Poly(N-mercaptoethyl acrylamide) and Au Nanoparticles-Based Organic/Inorganic Film: A Platform for the High-Performance Electrochemical Biosensors

In this study, we describe the use of the combination of eletrografting poly(N-mercaptoethyl acrylamide) and Au nanoparticles in the construction of high-performance biosensors. The poly(N-mercaptoethyl acrylamide) was electrografted onto the glassy carbon electrode surface, which provided a strongly adhering primer film for the stable attachment of Au nanoparticles and horseradish peroxidase (HRP) enzymes. The performances of the biosensors based on the HRP immobilized in the Au/poly(N-mercaptoethyl acrylamide) composite film were investigated. A couple of redox peaks were obtained, indicating that the Au nanoparticles could facilitate the direct-electron transfer between HRP and the underlying electrode. The biosensor showed an excellent electrocatalytic activity toward the reduction of hydrogen oxide and long-term stability, owing to the stable electrografted film and biocompatible Au nanoparticles. Our results demonstrate that the combination of electrografting and Au nanoparticles provides a promising platform for the immobilization of biomolecules and analysis of redox enzymes for their sensing applications.