Study On Fabrication And Electrochemical Property Of Nonenzymatic Biosensor Based On Carbon Nanospheres/ CuO Nanocrystals

Recently, there has been rapid development in the research and application of biosensors. Enzymatic biosensors, which can detect analytes using the specific reaction of bioactive materials such as the enzyme-substrate, enzyme-coenzyme, antigen-antibody, incretion-acceptor and so on, have attracted much attentions due to their good selectivity. Howerver, these sensors are limited by the stability of the enzyme to both PH value and temperature. As such recent effort has been put into producing nonenzymatic biosensors.In this paper, we have synthesized carbon nanospheres and CuO nanocrystals, and used them to fabricate nonenzymatic biosensors for H2O2 and glucose, respectively. The main results are summarized as follows:1. Nonenzymatic H2O2 sensor based on carbon nanospheres①Carbon nanospheres have been synthesized from analytically pure glucose at 200℃for 24h by hydrothermal synthesis and a composite-molten-salt (CMS) method, respectively. Scanning electron microscopy (SEM) images show that diameters of the nanospheres synthesized by hydrothermal synthesis and the CMS method are about 350 and 200 nm, respectively.②Carbon nanospheres obtained via the CMS method have been further investigated by transmission electron microscopy (TEM), Raman and Fourier transformation infra-red (FTIR) spectroscopy, indicating those carbon nanospheres are solid, bond hybridisation (sp2/sp3) and with many functional groups on their surfaces.③Amperometric sensors based on the as-synthesized carbon nanospheres have been fabricated without pretreatment or modification. The detection of hydrogen peroxide (H2O2) by the CMS carbon nanosphere electrode exhibits high sensitivity, good selectivity and excellent reproducibility. The electrochemical measurement of these nanospheres demonstrates much superior performance to those of the carbon nanospheres synthesized by hydrothermal method.2. Nonenzymatic glucose sensor based on CuO nanocrystals①Flower-shaped CuO nanostructures and CuO nanorods have been synthesized by the composite-hydroxide-mediated (CHM) method and the composite-molten-salt (CMS) method, respectively. Both of the two products have been characterized by X-ray powder diffraction (XRD),scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results indicate that both samples are monoclinic phase CuO crystal, the sample synthesized by the CHM methode is flower-shaped structure consisting of high-density CuO nanosheet petals with typical thicknesses around 20–50 nm, while the full array of one flower is about 3.5μm; The product obtained via the CMS approach is tiny nanorods with 50–80 nm in length and 20–40 nm in width.②Both of the two products have been applied to modify the graphite substrates for sensitive nonenzymatic glucose detection. The CuO nanostructures modified electrodes, compared to the Nafion modified graphite electrode, exhibit enhanced electrocatalytic properties for direct glucose oxidation and show high sensitivities and excellent slectivities. And in contrast, the CuO nanorods/ Nafion electrode shows much better linear amperometric response towards glucose.