Studies On Modified Electrodes Of Ordered Mesoporous Carbons And Their Composite Materials

The ordered mesoporous carbon (OMC) which was first synthesized in 1999 is particularly promising because of the fact that SBA^-15 template is inexpensive and easy to synthesize. And OMC also displays extremely high surface area and well defined pore size as well as high thermal stability, flexible framework composition and chemical inertness, which make OMC potential novel materials for investigating the electrochemical behavior of some biomolecules. Contrary to most porous silica-based materials (for example, SBA^-15) that are electronic insulators, the mesoporous carbons are intrinsically conductors. OMC modified electrodes can promote the electron transfer of some biomolecules. In this work, OMC and the composite materials based on OMC modified electrodes were used to study the electrochemical behaviors of several biomolecular, and electrochemical methods for their determination were proposed. The work was summarized as follows:(1) The electrochemical behavior of quercetin (QUE) was studied at an OMC modified glassy carbon electrode. Quercetin can effectively accumulate at this electrode and produce on anodic peak at about 0.484 V in 0.1 mol·L^-1 PBS (pH 3.0). The experimental parameters were optimized for determination. Under the optimum conditions, the anodic peak current is linear to quercetin concentration over the range of 2.0×10-9 mol·L^-1 - 2.0×10-6 mol·L^-1 and 2.0×10-6 mol·L^-1 - 3.0×10-5 mol·L^-1. The detection limit was 1.0×10-9 mol·L^-1 for 260 s accumulation. The electrode could be easily regenerated and exhibited good stability which make it a promising candidate for sensitive electrochemical sensors for quercetin detection. In addition, some electrochemical parameters about the electrode reaction were determined. The adsorption behavior of quercetin at OMC/GCE was also studied.(2) The voltammetric behavior of uric acid (UA) at an OMC modified glassy carbon electrode was inverstigated by cyclic voltammetry and differential pulse voltammetry. Uric acid can effectively accumulate at this electrode and produce on anodic peak at about 0.353 V in 0.1 mol·L^-1 PBS (pH 7.0). Under the optimum conditions, the anodic peak current is linear to uric acid concentration over the range of 8×10-7 mol·L^-1 to 1×10-4 mol·L^-1. This electrode was successfully applied to the determination of uric acid in human urine sample. The feasibility for simultaneous determination of ascorbic acid and uric acid was discussed, and they did not interfere each other in high concentration. In the presence of 1 mmol·L^-1 ascorbic acid, a linear range of 1×10-6 mol·L^-1 to 1×10-4 mol·L^-1 for uric acid was obtained. In addition, some electrochemical parameters about the electrode reaction were determined.(3) Poly (thionine)/OMC electrode was prepared by cyclic voltammetry in 4.4 mol·L^-1 CH3COOH (pH 1.9) containing 5 mmol·L^-1 thionine on the surface of a ordered mesoporous carbon modified glassy carbon electrode (OMC/GC). Electrochemical behaviors of the resulting electrode were investigated thoroughly with cyclic voltammetry, and a well-defined redox couples was clearly visualized. We also studied the pH influence and dynamical behavior at the modified electrode. Under a lower operation potential of 0 V in 0.1 mol·L^-1 PBS (pH 7.0), NADH could be detected linearly up to a concentration of 3.4×10-6 mol·L^-1 to 8.5×10-4 mol·L^-1 with an extremely lower detection limit of 5.1×10-8 mol·L^-1 estimated at a signal to noise ratio of 3. The feasibility for simultaneous determination of uric acid, ascorbic acid and NADH was discussed. They did not interfere each other in certain concentration. Based on the results, a new NADH sensor was successfully established using the PTH/OMC/GCE.