Study On The Fabrication And Electrochemical Biosensor Properties Of TiO₂ Nanotubes Arrays Modified Electrode

Titanium dioxide nanotubes (TNT) are a kind of typical one-dimensional nanomaterials, which possess a unique structure and chemical and physical properties. Several recent studies demonstrated that TNTs have a wide range of applications in photoelectricity, catalysis, chemical sensors and biomedical science, and has been becoming a hot spot in the world. Titanium dioxide nanotubes arrays (TNTs) electrode, which was fabricated by anodization and calcination of the titanium substrate, have higher surface areas, well-aligned nanostructures, favorable electron transfer channel, good biocompatibility and good adhesion to the substrate. So, TNTs electrode are promising functional materials for biosensor substrate. In this paper, we fabricated highly-ordered tinatia nanotube arrays as sensor electrode by anodization. Then, to improve electrocatalysis performance of TNTs electrode, nanomaterials were modified on TNTs electrode by electrochemical method for biosensor. The main research contents of this thesis are as follows:①A novel non-enzymatic glucose biosensor was developed based on the Ni nanoparticles-loaded TiO₂ nanotubes arrays (Ni-NPs/TNTs) electrode. The Ni-NPs/TNTs nanocomposites were prepared by pulsed electrodeposition method (PED). The morphology and phase structure of Ni-NPs/TNTs electrode were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The composition of the samples was analyzed by X-ray photoelectron spectroscopy (XPS). SEM image shows that spherical Ni nanoparticles were well dispersed and embedded in the TNTs. XPS demonstrated that the surface of electrode is composed of Nickel and nickel hydroxide. The effect of different prepared-time on the morphology of Ni-NPs/TNTs electrode is investigated. The deposition times were 20, 25 and 30 minutes respectively. With the increase of deposition time, more and more nickel nanoparticles loaded on TNTs can be observed. At the same time, the average sizes of the nanoparticles become larger and larger increased from about 20 to 85 nm, which is attributed to be inclined to reduce the surface energy of the nanoparticles for the further nucleation and growth of Ni.②Ni-NPs/TNTs electrodes were pretreated in 0.1mol/L NaOH solution by cyclic voltammetry (CV) and its application in nonenzymatic glucose biosensor was investigated. The results indicated are catalyzed by the Ni-based glucose sensors through the formation of a Ni(Ⅱ)/Ni(Ⅲ) redox in alkaline medium. Moreover, the catalysis activity related with the size and quantity of Ni nanoparticles. When Ni nanoparticles under deposition time of 25min are about 40nm, Ni-NPs/TNTs electrode had the highest catalysis activity for glucose. In the optimization of the experimental condition, the glucose biosensor exhibited excellent sensitivity (2043μA/(mmol·cm2)), the detection limit down to 1μmol/L, wide linear range (2μmol/L⁵.5mmol/L), fast response (response time less than 5s) and high selectivity.③A non-enzymatic glucose sensor was developed by nickel hexacyanoferrate nanoparticles modified TiO₂ nanotube arrays (NiHCF/TNTs). Ni nanoparticles on the surface of Ni-NPs/TNTs electrode was converted to nickel hexacyanoferrate nanoparticles (NiHCF) by CV in a solution containing [Fe(CN)6]3-. The electrochemical characteristics of the biosensor were investigated by CV. The non-enzymatic sensor shows significantly higher electrocatalytic activity to the oxidation of glucose in 1mol/L NaOH alkaline solution The sensor response is highly sensitive (663μA/(mM·cm²)) with a wide linear range (up to 23mmol/L). The linear range is 2×10^-3mmol/L¹mmol/L for the low concentration measurement with low detection limit of 0.5μmol/L(S/N=3); it also exhibits high sensitivity, good stability and specificity to glucose. The good analytical performance, low cost and simple preparation method make this novel electrode material promising for the development of effective glucose nonenzymatic glucose biosensor.④TiO₂ nanotubes as a new type of electrode materials used in small biomolecules analysis. TiO₂ nanotubes electrode fabricated by anodic oxidation in 0.2mmol/LKF solution was constructed dopamine biosensor. Compared to TiO₂ nanotubes prepared by anodic oxidation in HF solution, this electrode exhibit higher catalytic effect for dopamine and can selectively detect dopamine under existing ascorbic acid. The dopamine biosensor shows a linear range of detection of 5×10^–6mol/L²×10^-4mol/L with the detection limit of 2×10^–6mol/L. In short, the dopamine sensor has high sensitivity and anti- interference ability, which has great potential application in electrochemical analysis and biosensors.