Investigation Of Electrochemical Biosensor Based On Boron-Doped Diamond And Newly Nanocomposites

1. Boron-doped diamond (BDD) electrodes have recently attracted considerable interest, especially for electrochemical analysis due to its outstanding characteristics: (1) very low background current density; (2) a wide potential window in aqueous solution; (3) good activity toward some redox analytes without any pretreatment; (4) long term response stability.We fully utilized the characteristics of the deficient electron structure (carbon sp3 and boron) and easy oxidation introducing -OH on BDD electrode surface to preparation of biosensors, which were used to investigate the electrochemistry of biological molecules and be rapid, sensitive.(1) The electrochemical assay of bromide and iodide ions at a boron-doped diamond (BDD) electrode was investigated (In chapter 2). The BDD electrode exhibited well-resolved and irreversible reduction voltammograms, while the GC electrode provided only ill-defined response. Cyclic voltammetric signals at BDD electrode for Br- and I- were observed at 561 mV and 125 mV vs SCE; the values shifted negatively for 228.7 mV and 187.5 mV respectively, comparing to those at GC electrode. Sensitive amperometric responses for Br- and I- were obtained covering linear range 6.7×10^-7～1.0×10^-3 mol/L and 1.3×10^-8～1.0×10^-3 mol/L with 5.3×10^-7 mol/L and 1.7×10^-9 mol/L, respectively, under the optimum pH and applied potential. The amperometric response was very reproducible and stable with satisfactory recovery results.(2) We fully utilized the characteristics of the deficient electron structure (carbon sp3 and boron) and easy oxidation introducing -OH on BDD electrode surface to preparation of biosensors, which were used to investigate the electrochemistry of uric acid at a BDD electrode modified with poly(L-cysteine) and be rapid, sensitive. In the presence of major interference from ascorbic acid or dopamine, the peak potential of uric acid shifts less than 15 mV and the peak current changes slightly obtained square wave voltammetric (SWV) response at the modified BDD electrode. Moreover, the effects of scan rate, working potential of SWV response and pH are investigated; under the optimum conditions, Sensitive SWV response were obtained covering linear range 1.5×10^-9 1.2×10^-6mol/L. The determination of nephropathy patients'urine sample using this method shows satisfactory results.