Integrated all-diamond ultramicroelectrode arrays: Optimization of faradaic and capacitive currents

Integrated all-diamond ultramicroelectrode arrays (UMEAs) were fabricated using standard photolithography processes. The array consisted of typically 45 ultramicroelectrodes with a diameter of 10 ?m and with a center-to-center spacing of 60 ?m. The quasi-reference and counter electrodes were made from conductive diamond and were integrated on a 5 \'03 5 mm2 chip. On the UMEA, a high ratio of faradaic current to capacitive current was achieved on heavily boron-doped and hydrogen-terminated diamond surfaces at slow scan rates and in high concentration of supporting electrolyte. A sensitive and reproducible detection of dopamine was achieved on hydrogen-terminated diamond UMEA at slow scan rates. The detection limit of dopamine in the presence of ascorbic acid was 1.0 nM, which is 50\'01100 times lower than that obtained on the macrosized boron-doped diamond electrodes. This array is promising for sensitive and reproducible detection of analytes in solutions with low detection limits.