Fabrication And Application Of Electrodes Modified By Functionalized Materials

In recent years,chemically modified electrodes (CMEs) attract wide attentions. CMEs exhibited excellent and special functions because some particular chemical groups or materials could be introduced in modifying their surfaces by covalent bond, strong adsorption or casting polymers. The chemical sensors based on different CMEs presented great advantages, such as convenient manipulation, low cost, quick response and high sensitivity etc. Our study focused on the fabrication of CMEs with ionic liquid, mesoporous material and nano metal oxides and their uses in detecting environmental pollutants, so as to establish simple, fast, stable and sensitive electrochemical methods. The main points of our thesis were shown as follows.1. Hydrophobic ionic liquid-functionalized SBA-15 modified carbon paste electrode (CPSPE) was fabricated and its electrochemical performance was investigated by cyclic voltammetry, electrochemical impedance spectra and chronocoulometry in K₃Fe(CN)₆/K4_Fe(CN)₆ solution. Compared with carbon paste electrode (CPE) and SBA-15 modified carbon paste electrode (CSPE), the electron transfer ability was in the sequence: CPSPE>CSPE>CPE. Meanwhile, the electrocatalytic activity of CPSPE to catechol and hydroquinone was also evaluated. It was found that CPSPE significantly improved their reversibility, sensitivity and selectivity, while their peak potential separation was large enough for simultaneous determination. In the amperometric detection, the linear concentration ranges were 2.0×10-5 to 3.2×10-4 M for catechol and 5.0×10-5 to 5.5×10-4 M for hydroquinone, with the detection limits of 5.0×10-7 M and 6.0×10-7 M, respectively. Furthermore, the presented method was applied to the determination of catechol and hydroquinone in artificial wastewater sample and the results were satisfactory.2. Hydrophilic ionic liquid-functionalized ordered mesoporous silica SBA-15 modified carbon paste electrode (CBSPE) was fabricated and its electrochemical performance was investigated by cyclic voltammetry, electrochemical impedance spectra. The electrochemical behavior of Cd²⁺, Pb²⁺, Cu²⁺ and Hg²⁺ at CBSPE was studied by differential pulse anodic stripping voltammetry (DPASV). Compared with carbon paste electrode, the stripping peak currents had a significant increase at CBSPE. Under the optimized conditions, the detection limits were 8.0×10-8 M (Cd²⁺), 4.0×10-8 M (Pb²⁺), 6.0×10-8 M (Cu²⁺), 1.0×10-8 M (Hg²⁺), respectively. Furthermore, the presented method was applied to the determination of Cd²⁺, Pb²⁺, Cu²⁺ and Hg²⁺ in water samples and people hair sample.3. Flowerlike, spherical, and walnutlike NiO microspheres were respectively mixed with ionic liquid (IL) to form three stable composite films, which were used to immobilize hemoglobin (Hb) on carbon paste electrodes. Spectroscopic and electrochemical examinations revealed that the three NiO/IL composites were biocompatible matrix for immobilizing Hb with good stability and bioactivity. However, electrochemical studies demonstrated that flowerlike NiO microspheres were far more effective than the other two in adsorbing Hb and facilitating the electron transfer between Hb and underlying electrode, which resulted from its unique flower architecture and large surface area. With advantages of flowerlike NiO and ionic liquid, a pair of stable and well-defined quasi-reversible redox peaks of Hb were obtained with a formal potential of -0.275 V (vs. Ag/AgCl) in pH 7.0 buffer. Meantime, flowerlike NiO modified electrode showed better electrocatalytic activity toward hydrogen peroxide reduction with a high sensitivity (15.7μA mM-1), low detection limit (0.68μM) and small apparent Michaelis-Menten constant KM (0.18 mM). Flowerlike NiO could be a promising matrix for the fabrication of direct electrochemical biosensors in biomedical analysis.