| Chemically modified electrodes (CMEs) are a kind of artificially modified electrode which possesses some characteristics of modified substances on its surface. As an important application of CMEs in analysis, electrocatalysis has been extensively concerned, since CMEs can reduce the free energy and speed the reaction rate as well as improve the reaction reversibility when some chemicals are electrocatalysed. Dopamine and ascorbic acid are two kinds of familiar organic molecules. Their metabolic equilibriums are important for maintaining the normal operation of human enginery. The research of electrocatalysis and quantitative analysis to these two molecules are significant in both theory research and actual application of CMEs electrocatalysis.1. We immobilized redox organic molecule onto the surface of electrode for the obtaining of the simple and effective electrocatalysis CMEs. The obtained electrode exhibited good electrocatalysis characteristics to DA, namely,M-aminophenol was electrochemically modified onto glassy carbon electrode (GCE) to fabricate an electrochemical dopamine sensor. The resulting sensor exhibited improved electrocatalysis towards dopamine. Compared to bare GC, the anodic peak potential was shifted negatively about 200 mV; the cathodic peak was shifted positively about 90 mV; the redox and response also enhanced. The anodic peak current of DA was proportional to the concentration over two concentration intervals of DA, viz 1.2×10-7-9.1×10-6 and 9.1×10-6-1.2×10-4 mol/L, with the correlation coefficient, 0.998(n=22) and 0.998(n=16), respectively, and a detection limit (S/N=3) of 3.2×10-8mol/L.2. Recently, the application of Nanomaterials in CMEs has been deepening and widening. We overcastted the electrodes by carbon tubes-electron mediator complex to prepare the CMEs with good characteristics to AA, for the integrating the excellent catalysis of carbon tubes and strong electron transfer ability of electron mediator, namely,A glassy carbon electrode was modified by multi-walled carbon nanotubes-thionine complex to prepare chemically modified electrode (MWNTs-Thi/GCE) for aseorbie acid. The electrochemical characteristics of MWNTs-Thi/GCE were studied by cyclic voltammetry. It also had been found that MWNTs-Thi/GCE exhibited good electrocatalytic activity for the oxidation of AA. The oxidation current response of the MWNTs-Thi/GCE is in the range of 5.0×10-7-1.1×10-3 mol/L AA with a correlation coefficient of 0.999 (n=17). The detection limit of the electrode was found to be 1.0×10-7 mol/L (S/N=3).The research of amperometric biosensors is also an important research and application field in CMEs. The biosensors have many advantages such as: good selectivity, high sensitivity, fast analysis speed, low cost, available for continuously testing in complex system and so on. The important aspects of preparing biosensor are materials of electrode modification and immobilization of biomolecule.1. Self-assembly is simple,ordered,controllable and biocompatible. Gold nanoparticles (GNPs) are good conductor of electrons and have good biocompatibility as well as loading ability of biomolecule. We self-assemble sulfhydryl compound onto the surface of gold electrode and immobilization of GNPs and biomolecule, successively, namely,A novel amperometric hydrogen peroxide biosensor based on self-assembly of L-cysteine and Nano-Au has been constructed. The electrochemical characteristics of biosensor was characterized by cyclic voltammetry, which shown good linear range between 2.1×10-6 and 3.6×10-3 (R=0.999, n=28) mol/L with a detection limit of 8.9×10-7mol/L (S/N=3 ) to H2O2. The resulting biosensor exhibited good stability, wide linear range and lower detection limit as well as certain anti-interference ability. 2. The preparation of orderly membrane on carbon electrode is a rising research field. The using of carbon electrode as matrix can get over the drawbacks of the narrow potential window and the poor tolerance of metal electodes. We prepared the CMEs with orderly diamine compound membrane, which can further immobilize GNPs and biomolecule to obtain biosensors, namely,A facile strategy of amperometric biosensor for hydrogen peroxide based on direct electrocatalysis of hemoglobin (Hb) immobilized on gold nanoparticles (GNPs) /1, 6-diaminohexane (DAH) modified glassy carbon electrode (GCE) has been described. A uniform monolayer film of DAH was initially covalently bound on GCE surface by virtue of electrooxidation of one amino group of DAH, and another amino group was modified with GNPs and Hb, successively. The proposed biosensor exhibited an effective and fast catalytic response to the reduction of H202 with good reproducibility and stability. The linear relationship existed between the catalytic current and the H2O2 concentration in the range of 1.5×10-6 to 5.1×10-3 mol/L with a correlation coefficient of 0.999 (n = 24). The detection limit (S/N = 3) was 2.8×10-7 mol/L. |
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