Electrocatalytic Investigations On 1-D Copper Oxide Nanofiber-based Materials

Great efforts have been made recently to fabricate one dimensional (1-D) nanomaterials due to their special morphologies, compositions, chemical and physical properties. A variety of methods including electrochemical deposition, hydrothermal process, electrospinning, vapor phase growth and solution phase growth have been developed for preparation of 1-D nanomaterials. In the meantime, a large quantity of 1-D nanomaterials with different components and varied structures, such as nanowires, nanobelts, nanotubes, nanorings and nanofibers, have been reported. However, most reports limited the scope to their experimental production and characterization, only few reports recently emerged concerning the applications of 1-D in catalysis and electroanalysis.Reliable and fast determination of glucose is of considerable importance in clinical diagnostics, biotechnology and food industry. Various techniques such as chemiluminescence, chromatography and electrochemistry were applied in glucose determination. Electrochemical methods, especially amperometry with the advantages of high sensitivity, quick response, simple detection procedures, board detection range and high accuracy, have been proved to be powerful approaches and attracted much attention. Two major types of amperometric glucose sensors, i.e., enzymatic and nonenzymatic sensors, receive keen interests and are developed rapidly in the last several decades. Enzymatic glucose sensors based on the immobilization of glucose oxidase on various substrates are the tipics of the most previous studies on this subject. However, the short life time of enzymes, the difficulties in miniaturization and poor reproducibility of enzymatic glucose sensors limited their application. In recent years, more and more attempts have been made to determine glucose concentration without using enzymes. Most enzymeless electrochemical glucose sensors are direct amperometric ones that rely on the current response of glucose oxidation directly at the electrode surface (such as: metal, metal oxide, nanomaterials, polymer films). Among which, Pt and Au are widely used electrode materials for glucose electrooxidation. However, most of these electrodes have drawbacks of low sensitivity and poor selectivity, attributed to the surface poisoning resulted from the adsorbed intermediates and chloride. Transition metals with the high sensitivity for glucose determination and can oxidize carbohydrates directly without surface poisoning attracted much attention over the last two decades.Copper oxide nanofibers (CuO-NFs) prepared by electrospinning and subsequent thermal treatment processes were demonstrated for the first time for glucose non-enzymatic determination. The high surface-to-volume ratio, complex pore structure, extremely long length of the as-prepared CuO-NFs and the excellent three-dimensional network structure on immobilization were well-characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Eletrochemistry and catalysis of the film electrode towards glucose oxidation were evaluated by cyclic voltammetry (CV) and chronoamperometry (I–t). Results revealed a high electrocatalytic activities to glucose. Different dispersants were utilized for the suspension preparation and effects of ultrasonic time on the film electrode fabrication were investigated in detail for fabrication of enzymeless glucose sensors. Under optimal conditions, the electrocatalytic response of the sensor revealed a high sensitivity, fast response, wide linear range, low detection limit and excellent resistance towards electrode fouling. Results in this study suggest that electrospun CuO-NFs is a promising 1-D nanomaterial for glucose non-enzymatic determination.Copper oxide nanofibers doped with others have been successfully prepared via electrospinning. The structures and morphologies of the materials were characterized by SEM and XRD. These materials were exploited to fabricate the enzymeless glucose sensors, and their assay performances to glucose were evaluated by conventional electrochemical techniques. Results revealed that cobalt oxide doped copper oxide materials exhibted a wide linear range, CNT or nickel oxide doped copper oxide showed a low applied potential in glucose determination. These results suggested that novel electrode materials for glucose sensing can be obtained by tuning the ratio of doping materials into the copper oxide NFs.1-D Copper oxide NFs and the doping materials for direct electrocatalytic oxidation of fructose were demonstrated in the third part. Cobalt oxide doped copper oxide NFs electrode exhibted the superiorities of high sensitivity, wide linear range towards fructose detection. Carbon and nickel oxide doped copper oxide NFs electrode showed significantly lower overvoltage in fructose detection. All these results suggest that copper oxide NFs and the doping materials are promising electrode materials for fabrication of amperometric fructose enzymeless sensors.