Chemically Modified Electrode And Its Application

Chemically modified electrodes (CMEs) have had a dominant position in many electrochemical studies since the 1970's. The distinguishing feature of a CME is that a generally thin film of a selected chemical is bonded or coated onto the electrode surface to endow the electrode with the chemical, electrochemical, optical, electrical, transport, and other desirable properties of the film in a rational, chemically designed manner. For analytical applications, CMEs should possess certain properties; good mechanical and chemical stability of electrode surface, good short-term reproducibility and long-term stability of the modifiers activity towards the analyte, wide dynamic range of responds, low and stable background currents over the potential range reguired, simple and reliable fabrication that results in consistency of the response from one electrode to another. In this work, one of the principal researches is about the preparation of the CEM and its application in electroanalysis.The primary research work is as follows:1. Research of 2,5-dimercapto-l,3,4-thiadiazol (DMTD ) self-assembled monolayer modified electrode and its application in the determination of metal ionThe fabrication and electrochemical characteristics of the DMTD self-assembled monolayer (SAM)-modified gold electrode were investigated. The DMTD SAM electrode exhibited selective voltammetric response to Cu(II). The effects of various parameters, such as the pH values of the preconcentration solution and measurement solution, the accumulation potential, and the accumulation time, were investigated. The proposed voltammetric method was utilized successfully to detect the concentration of Cu(II) ions in tap water samples.2. Research of poly(acridine red) modified electrode and its applicationA stable electroactive thin film of poly(acridine red) has been deposited on the surface of a glassy carbon electrode by potentiostatic technique in a pH 7.0 phosphate buffer containing acridine red. The poly(acridine red)/glassy carbon electrode is easy to be prepared with good stability and reproducibility. The voltammetric behavior of uric acid (UA) at the modified glassy carbon electrode was studied by cyclic voltammetry and different pulse voltammetry. The modified electrode exhibited a high stability in phosphate buffer. The proposed voltammetric method was utilized successfully to detect the concentration of UA in urine samples.3. Research of meso-2, 3-dimercaptosuccinic acid self-assembled monolayer modified electrode and its application in ion-channel sensorsSelf-assembled monolayers (SAMs) of meso-2, 3-dimercaptosuccinic acid (DMSA) on gold electrodes were used for ion-channel mimetic sensing of cationic surfactants. The SAMs on gold electrodes were characterized with reductive-desorption and electrochemical impedance measurements. The pH dependence of the cyclic voltammograms (CVs) of K₃[Fe(CN)₆] and [Ru(NH₃)₆]Cl₃ as electroactive markers suggested an electrostatic repulsion between charged head groups of the SAMs and the equally charged marker ions with the half current values in the plot reflecting the apparent pKa of the SAMs. In the presence of cationic surfactants as the analyte and [Fe(CN)₆]^3- anions as the marker ions, the self-assembled monolayers channel was open and exhibited distinct channel current.4. Research of gold colloid modified electrode and its applicationColloidal gold modified glass carbon electrode was prepared by electrodeposit. The modified electrode showed an obvious electrocatalytic activity for the oxidation of nitrite at 0.850 V vs. the Ag/AgCl electrode in 0.05 mol L^-1 H₂SO₄ solution and for the oxidation of serotonin (5-HT). Under the optimum conditions, the possible reaction mechanism has also been discussed. The NG/GC electrode has a high stability and can be applied to the determination of nitrite in rain water and of 5-HT in human blood sample with simplicity, rapidness and accurate results.5. Research of the interaction of colloid gold and serotonin in optical labelsIn pH 7.0 Britton-Robinson buffer solution, binding of colloidal gold with serotonin was discussed by resonance light scattering (RLS) spectrum, fluorescence emission spectrum, ultraviolet-visible (UV-Vis) absorption spectrum, and transmission electron microscopy (TEM). The optimum conditions of the binding interaction and the influencing factors have been investigated. Based on the study, we proposed a highly sensitive gold colloid-based assay using RLS spectrum to detect serotonin for the first time. The mechanism of binding interaction between Au colloid and serotonin was also discussed.