Electrospun iridium oxide nanofibers for direct selective electrochemical detection of ascorbic acid

We report the electrochemical activity of IrOx (0 < x <= 2) nanofibers prepared by electrospinning for the oxidations of biological species including L-ascorbic acid (AA), 4-acetamidophenol (AP), dopamine (DA), glucose, p-nicotinamide adenine dinucleotide (NADH), and uric acid (UA). Compared to bare glassy carbon electrode, IrOx nanofibers show high electroactivity for all the tested species and facilitate AA oxidation most significantly, shifting the oxidation potential to the less positive direction by similar to 485 mV in linear sweep voltammetry while the oxidation of glucose is almost negligible at both electrodes. The amperometric response of IrOx nanofibers at the applied potential of -0.01 V (vs. SCE) is linearly proportional to the AA concentration, exhibiting high sensitivity (194.4 +/- 6.8 mu A mM(-1) cm(-2), n= 5), fast response time (t(95%) = 2.9 +/- 1.2 s, n = 5), low detection limit (<0.4 mu M), and exclusive selectivity over AP, DA, glucose, NADH, and UA at their physiological levels. In addition, excellent potential resolution of IrO2 nanofibers, sufficient to differentiate AA, DA, NADH, and UA, is confirmed by differential pulse voltammetry. This results support that IrOx nanofibers are good potential sensing materials selectively for AA and/or simultaneously for AA, DA, NADH, UA in complex biological samples. (C) 2014 Elsevier B.V. All rights reserved.