Development of boron-doped diamond thin-films as voltammetric and amperometric detectors.

摘要

The utilization of boron-doped diamond thin-films for applications in electroanalysis was investigated. Voltammetric analysis in static solution, and amperometric detection coupled with flow injection analysis and HPLC were performed. The results were compared to those for glassy carbon. The electroactivity, the merit of detection figures, the adsorption of polar organic molecules, and the resistance to fouling were studied. Surface characterization was performed to elucidate the surface property-electroacticvity relationship.; The results showed that diamond thin-films, compared with glassy carbon, had comparable electroactivity to simple electron transfer processes (e.g., Ru(NH3)6+2/+3, Fe(CN)6 -3/-4, IrCl6-2/-3, azide, chlorpromazine), but had lower electroactivity for the electron transfer processes involving surface-confined intermediate (e.g., hydrogen evolution, oxygen evolution, 4-methyl catechol, hydrazine). The diamond thin-films had a wide working potential up to 4.0 V in aqueous media. They also had small double layer capacitance, voltammetric background current, and amperometric residual current. These properties had leaded to higher signal-to-background ratios and signal-to-noise ratios. The diamond thin-films had lower limits of detection in voltammetric measurements of several analytes, and had lower limits of detection in amperometric measurements of all compounds studied.; The diamond thin-films had negligible adsorption of polar organic molecules (e.g., anthraquinone 2,6-disulfonate, chlorpromazine), compared to glassy carbon. This is due to the fact that the diamond surfaces are primarily composed of sp3 carbon and hydrogen terminated. This leaded to less decay of the electroactivity by storage and operation, and higher resistance to fouling.; The surface property-electroactivity relationship depends on the specific mechanism for electron transfer. The extent of non-diamond impurities (e.g., oxygen evolution), diamond crystalline size, surface termination (e.g., azide), and surface boron sites (hydrazine) could all affect the electroactivity for diamond thin-films.