Enzyme Free Amperometric Sensing Of Hydrogen Peroxide And Glucose Based On Novel Nanostructure Materials

Detecting glucose and hydrogen peroxide levels in foods and blood by electrochemical method is of great importance for many years in chemical, clinical, and environmental communities. Despite positive attributes of enzymatic biosensors, such as high selectivity and sensitivity, the main drawbacks associated with their applications are the insufficient stability originated from the nature of the enzymes and the complexity of enzyme immobilization process, regardless of the employment of artificial mediator or direct electron transfer. In recent years, the electrode modification with nanostructured inorganic materials has attracted much attention due to their advantages such as fast response, low cost and reusability. In this thesis, particulate copper and its corresponding oxide were prepared and applied to modify glass carbon electrode to fabricate an enzymeless electrode for detecting hydrogen peroxide and glucose. The main results are summarized as follows:1. Fine powders of copper were prepared by liquid phase reduction process and the effects of synthesis conditions on size and morphologies of products were systematically investigated. It is found that the synthesis reaction occurs only in acid solutions with pH value lower than3. And the average particle size decreases when prepared at solutions at a lower pH. Increasing temperature is favorable for producing the copper particles. Surfactant has inconspicuous effect in this experiment. Sensors prepared with the as-obtained Cu powders shows relatively high electrocatalytic properties, though its stability is low because the modifying Cu powders can be oxidized easily during detecting test.2. Fine copper powders were oxidized using cold oxygen plasma to obtain core-shell structured particles. XRD analysis reveals that the products contain a small fraction of Cu2O. Electrochemical measurement for detecting H2O2showed similar ability with copper powders before oxidation.3. Monodispersed Cu2O nanoparticles with average diameter of200nm were prepared in DMF solvent when NaBH4serving as reduction agent. TEM image reveals the Cu2O nanospheres are the results of self-assembly of smaller Cu2O nanocrystals. BET specific surface area via nitrogen sorption analysis of the as-synthesized Cu2O is13.1m2/g. Enzymeless sensors were constructed by modifying glass carbon with the Cu2O nanoparticles and Nafion solution, which showed excellent sensibility toward H2O2and glucose. Detection limit, sensitivity and response time for detecting H2O2are0.039μM,3.693A/M and less than0.5s, respectively. And detection limit and response time for detecting glucose are47.2μM and less than4s, respectively.4. Submicro-sized Cu2O particles of various shapes were prepared from Benedict solution. With increasing reaction time, the shape of the particle turns from cubic to convex polyhedron. The Cu2O/Nf electrode modified by Cu2O powders prepared by this method showed high sensitivity at a narrow working range.