The Construction And Property Of One Demensional TiO₂Nanotube Arrays Based Glucose Biosensor

In recent years, various efforts have been made to improve the sensitivity of glucosedetection since the first glucose enzyme biosensor was constructed in1962, such asimproving detection instrument, ameliorating enzyme immobilization method,searching for suitable substrate and so on. Nanostructure material owns large specificarea which benefits for loading large amount of biomolecules, and its excellentbiocompatibility can maintain the activity of biomolecules and guarantee its ownelectrochemical property and stability as an electrode of biosensors at the same time.Therefore, nanomaterial has been wildly used in construction of biosensors. In thisstudy main efforts was focused on constructing glucose sensors based on TiO2nanotubearrays substrate and its modification in order to enhance the sensitivity of biosensor. Themian works carried out are listed as following:1) A GOx/Ag/TiO2glucose biosensor was constructed by photo-reduced of Agnanoparticles on the highly ordered TiO2nanotube arrays (NTAs) made with anodicoxidation method followed with adsorption of GOx. The morphology, structure andelement component of Ag/TiO2NTAs were characterized by scanning electronmicroscope (SEM), transmission electron microscope (TEM) and X-ray photoelectronspectrum (XPS). Results indicate that the size of Ag nanoparticles changes from15to40nm with increasing immersion time of TiO2NTAs in AgNO3aqueous solution, andthe Ag species exist in metallic state. The uniform distribution of Ag nanoparticles isobtained with an immersion time of30min. The GOx/Ag/TiO2NTAs biosensor madewith optimum conditions achieves a sensitivity of0.39μA·mM-1·cm-2and a linerresponse range of0.1to4mM for glucose detection.2) As the biosensors based on Ag modified TiO2NTAs has a rather small linear rangefor glucose detection, Pt modification is taken into consideration. Pt nanoparticlesmodification was performed with pulse electro-deposition process, in which thedistribution was controlled by changing the deposition potential. The morphology,structure and elemental components of Pt/TiO2NTAs were characterized by SEM, TEMand XPS, and electrochemical properties were investigated by cyclic voltammetry andamperometry. Results reveal that: Pt deposition at a potential of-0.35V can achieveuniform distributed nanoparticles and demonstrate excellent electrochemical properties;the sensor constructed on the above Pt/TiO2NTAs obtains a sensitivity of0.45μA·mM-1·cm-2and a linear response range of0.1to14mM for glucose detection, both of which are higher than that of the sensor contructed on Ag/TiO2NTAs.3) In order to further improve the sensitivity of TiO2NTAs based biosensors,co-deposition of graphene and Pt nanoparticles on TiO2NTAs was carried out.GOx/Pt/Gr/TiO2NTAs electrode was prepared by graphene and Pt nanoparticlesco-deposition on TiO2NTAs with electrochemical deposition method followed withGOx immobilization. The distinct effects of co-deposition of graphene and Ptnanoparticles on promoting the electrochemical performance of the sensor werediscussed in detail by comparing the cyclic voltammograms of TiO2, Gr/TiO2, Pt/TiO2and Pt/Gr/TiO2NTAs electrodes measured in buffer,10mM H2O2and glucose with andwithout GOx immobilization. Results show that larger surface area and more dissolvedoxygen, which is benefit to the enzymatic reaction, are provided due to the graphenemodification, and the catalytic oxidation of H2O2is improved after Pt deposition, bothof which greatly enhance the sensitivity of the electrode for glucose detection. Theamperometric response of GOx/Pt/Gr/TiO2NTAs electrode to glucose is linearlyproportional to the glucose concentration in the range of0.1to8mM. And a muchhigher sensitivity of0.94μA·mM-1·cm-2is achieved.4) Enzyme biosensor was construted on TiO2nanotube arrays(TiO2NTAs) anneallingat different temperature without any modification followed by glucose oxidase (GOx)immobilization. The morphology, structure and bio-electrochemical properties ofcrystallized TiO2NTAs electrodes were studied by SEM, XRD and chemical workingstation, respectively. The electrochemical properties of TiO2NTAs electrodes with andwithout heat-treatment were compared, and works were performed to determine theoptimum heat-treatment temperature for crystallied TiO2NTAs electrode basedbiosensor. Results indicate that crystallied TiO2NTAs due to annealling increasesignificantly the electrochemical properties and do not cause any structure damage atthe same time. Moreover,400℃is determined to be the optinum crystallizingtemperature for the heat-treatment of TiO2NTAs, at which crystallized TiO2NTAsachieve the highest sensitivity of1.91μA·mM1·cm2and the widest linear responserange of0.1to9.5mM in addition to excellent stabilityafter enzyme immobilization inthis study regard.