Electrochemical Glucose Biosensor Research Oxide Based Nanomaterials

1. A novel mesoporous silica nanosphere matrix for the immobilization of proteins and their applications as electrochemical biosensorA mesoporous silica nanoshpere (MSN) was proposed to modify glassy carbon electrode (GCE) for the immobilization of protein. Using glucose oxidase (GOD) as a model, direct electrochemistry of protein and biosensing at the MSN modified GCE was studied for the first time. The MNS had large surface area and offered a favorable microenvironment for facilitating the direct electron transfer between enzyme and electrode surface. Scanning electron microscopy, transmission electron microscopy, UV-vis spectroscopy and cyclic voltammetry were used to examine the interaction between GOD and the MSN matrix. The results demonstrated that the immobilized enzyme on the MSN retained its native structure and bioactivity. In addition, the electrochemical reaction showed a surface controlled, reversible two-proton and two-electron transfer process with the apparent electron transferrate constant of3.96s-1. The MNS-based glucose biosensor exhibited the two linear ranges of0.04-2.0mM and2.0-4.8mM, a high sensitivity of14.5mA M-1cm-2and a low detection limit of0.02mM at signal-to-noise of3. The proposed biosensor showed excellent selectivity, good reproducibility, acceptable stability and could be successfully applied in the reagentless detection of glucose in real samples at-0.45V. The work displayed that mesoporous silica nanosphere provided a promising approach for immobilizing proteins and fabrication of excellent biosensors.2. Porous Fe3O4NPs-Chitosan based electrochemical glucose biosensorThe porous Fe3O4nanoparticles were synthesized by solvothermal method. The surface morphology and size of the microspheres were estimated by transmission electron microscopy (TEM), scanning electron microscope (FE-SEM), X-ray diffraction and N2adsorption-desorption technique. The porous Fe3O4NPs were dispersed in Chitosan (CS) solution and were used as a novel electrochemical platform for glucose biosensing based on the Fe3O4-CS nanocomposition modified the glassy carbon electrode (GCE). In this paper, the electrochemical performance influence of sweep speed, pH and other conditions was studied. The Fe3O4-CS based glucose biosensor exhibited the linear range of0.04-1.6mM, a high sensitivity of25.1mA M-1cm-2and a low detection limit of1.4X10-2mM at signal-to-noise of3, the surface coverage fraction of3.094×10-11mol cm-2, the apparent Michaelis-Menten constant (KM) of13.37mM. The results showed that the electrode reaction is a surface process controled and two-electron transfer process. The biosensor exhibited direct electrochemical reaction and showed good stability, selectivity and fast electron transfer rate.3. A nonenzymatic glucose sensor based on the CuO nanorodsThe CuO nanorods were synthesized by the simple hydrothermal method. Transmission electron microscopy, scanning electron microscopy, the energy spectrum, X-ray diffraction were used to characterize the CuO nanorods. The CuO nanorods were dispersed in the ethanol and were dropped on the surface of the glassy carbon electrode (GCE), then the electrochemical non-enzymatic glucose biosensor was obtained after drying. In this paper, the biosensor’s electrochemical impedance, the influence of applied potential and the interference to the glucose renponse were studied. The electrochemical test results show that the CuO biosensor’s impedance is very small, with good electron transfer, large glucose response current and small interference. The biosensor has a glucose linear detection range of5μM-8.6mM, sensitivity of231.7mA M-1cm-2, low detection limit of9×10-4mM (S/N=3). The practical detection results of serum sample shows that the CuO nanorods based biosensor has excellent potential in enzyme-free glucose sensoring.4. CuO-Au nanocomposites for enzyme-free glucose sensing with enhanced performancesThis chapter has synthesized good dispersivity Au nanoparticles, and mixed with CuO nanorods synthesized by simple hydrothermal method in the previous chapter to form mixture of different proportion, modified the mixture on the glassy carbon electrode surface. Then an electrochemical non-enzymatic glucose biosensor was obtained after drying. In this paper, the effect of the content of colloidal gold, electrolyte concentration of sodium hydroxide, applied potential and the interference to the sensor response were studied. Electrochemical tests show that the biosensor’s performance has improved greatly after dopping with CuO-Au nanoparticles which may be drived from the polarization effect provided by Au nanoparticles. As we can see the linear glucose detection range (0.5mM to21.0mM) has been wider obviously compared to the only CuO nanorods modified electrode.In addition, the biosensor has good electron transfer rate, large glucose response current while small of interference at+0.5V, good sensitivity of70.57mA M-1cm-2, low detection limit of2.7×10-6mM (S/N=3). As-prepared CuO-Au nanocomposites have great potential in enzyme-free glucose sensoring.