Resistance to surfactant and protein fouling effects at conducting diamond electrodes

Boron-doped diamond thin-film electrodes display negligible fouling effects in the presence of high levels of surface-active materials, including proteins. Dramatic improvements in the stability of the analyte response (compared to common glassy carbon and carbon paste electrodes) are illustrated using bovine serum albumin (BSA), gelatin, and Triton X-100 in connection with repetitive square-wave voltammetric (SWV) measurements. The voltammetric response of ascorbic acid at the diamond electrode exhibits negligible shifts in peak potentials and minimal depressions of current signals over a wide range of surfactant concentrations (0 - 750 ppm). For example, the diamond electrode exhibited 70, 50 and 60 mV potential shifts for 10 repetitive voltammetric scans in the presence of 100 ppm BSA, gelatin and Triton X-100, respectively, compared to 120, 190, and 280 mV shifts observed at the glassy carbon electrode. Furthermore, only 4.3 and 6.2% of the initial current decays were observed in the presence of 100 ppm Triton X-100 and gelatin, respectively (compared to 45.2 and 34.4% diminutions at the glassy carbon electrode). Such improved performance was also confirmed from the SWV measurements of uric acid, dihydroxyphenylacetic acid, and catechol. The greatly improved resistance to surfactant interference reflects the fact that the as-grown diamond thin film, composed of oxide-free and hydrogen-terminated surface, has a relatively lower surface energy and minimal electrostatic attributes, either specific or general, so that little adsorption of surface-active agents occurs. The topographic AFM images of the diamond electrode surface confirm a negligible BSA fouling effect after repetitive SWV measurements. Such enhanced antifouling features make diamond electrodes very attractive for numerous real-life electroanalytical applications.