Preparation Of Nanostructured Materials And Their Application For The Construction Of Electrochemical Bisensors

Electrochemical biosensors have valuable applications in chemistry, biology, environmental science, food industry, and medicine because of its excellent selectivity, high sensitivity, rapid response, low cost, continuous detection, easy to be miniaturized. Nanostructured materials are attractive in the developement of biosensors due to their novel optical, electrical, electrocatalytic and biocompatible properties. The performance of the resulting biosensors could be greatly improved with the apllication of nanomaterials. In this thesis, nanomaterials with different morphologies were synthesized using different methods and applied for the preparation of electrochemical biosensors. The developed biosensors foe glucose and hydrogen peroxide show high sensitivity, low detection limit and rapid response. The details are described as follows:(1) The large surface area of these nanostructures can increase the amount of enzyme loading and provide a friendly microenvironment for the enzymes. It would be a significant advancement if perpendicularly aligned nanowires could be formed as sensing materials because the well-defined surface could facilitate enzyme-substrate contact and improve the performance of the resulting biosensor. Ruthenium purple nanowire array (RPNWA) was synthesized using a polycarbonate (PC) membrane template via a direct electrodeposition technique on the glassy carbon electrode (GCE). The RPNWA electrode as prepared was demonstrated to have high catalytic activity for the electrochemical reduction of hydrogen peroxide at -0.1 V in neutral media. Through the crosslinking of glucose oxidase (GOx) on the nanoelectrode array surface, a biosensor for glucose is constructed. The results show that the biosensor displays rapid response and expanded linear response range besides excellent repeatability and stability (in chapter 2).(2) Recently, graphene has been considered as a very promising carbon material that attracs enormous interest. Due to the specific two-dimensional structure of graphene, the electrons in graphene obey a linear dispersion relation and behave like massless relativistic particles, resulting in the observation of a number of very peculiar electronic properties such as the quantum Hall effect, transport via relativistic Dirac fermions and unusual electronic and robust transport properties. In present study, grapheme (GR) was synthesized by chemical method. Scanning electron microscopy (SEM), X-ray diffraction (XRD), UV and FT-IR spectra were employed to characterize the graphene. By using layer-by-layer assembly method, grapheme and horseradish peroxidase (HRP) were alternately assembled into multilayer films. The HRP-GRs multilayer structures were then immobilized on the glassy carbon electrode surface followed by the coating with chitosan (CHIT). The biosensor exhibited an ideal response behavior to hydrogen peroxide with a detection limit of 0.1μM and a linear range of 1.0μM～2.6 mM (in chapter 3).(3)α-ZrP is a well-characterized layered material with hydrophilic hydroxyl function groups present on its two-dimensional lamellar surface. The advantages ofα-ZrP for protein immobilization are that the host has a layered structure and can be readily expanded to accommodate guest molecules of varying sizes ranging from protons to proteins. Also,α-ZrP is thermally stable and chemically inert in neutral/acidic media. In additioal,α-ZrP provides a large surface area upon exfoliation of the lamellae and affords anionic surfaces for protein binding. In the prsent paper, a facile protocol was described for immobilizing glucose oxidase in the interlayer regions of the layeredα-zirconium phosphate (α-ZrP) under ambient conditions at pH 7.0. Then, the GOx/α-ZrPs complex as prepared were dispersed in chitosan and immobilized on the glassy carbon electrode surface. The biosensor could be used for the detection of glucose, and the linear range was 0.01 mM～20.0 mM with a related coefficient was 0.996. The sensitivity was 4.74μA mM-1 and the detection limit was 0.01 mM (in chapter 4).