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Abstract

In this work, a carbon nanotube microelectrode set (CNT µ-ES) was modified, in which three electrodes based on highly densified carbon nanotube fiber (HD-CNTf) cross-sections (length ~40 µm) were embedded in an inert polymer matrix with exposed open-ended CNTs at the interface. An HD-CNTf cross-section (∼40 µm diameter) electrochemically modified with copper nanoparticles (CuNPs) was used as the working electrode; a bare HD-CNTf cross-section (∼94 µm diameter) was used as the counter electrode; and an HD-CNTf cross-section (∼94 µm diameter) electroplated with Ag/AgCl and then coated with Nafion™ was used as a quasi-reference electrode. The electrochemical activity of the CuNPs/HD-CNTf microsensor for glucose electrooxidation was examined by cyclic voltammetry and amperometry in 0.1 M NaOH solution. As shown by amperometry studies, the proposed nonenzymatic CuNPs/HD-CNTf microsensor had a remarkably low limit of detection (28 nM) and a wide linear quantification range with an excellent sensitivity (1942 nA·µM−1·cm−2). This sensitivity can be attributed to the synergetic effect of electrocatalytic CuNPs and aligned HD-CNTf, which provide excellent conductivity. The electrooxidation of glucose on the developed microsensor was free from chloride poisoning and independent of the oxygen concentration. The developed microsensor demonstrated insignificant interference from the oxidation of common interfering species and carbohydrate compounds at their physiological concentrations. Finally, the CuNPs/ HD-CNTf microsensor was successfully applied for the quantification of glucose in normal human serum and diabetic patient urine samples, demonstrating the applicability of this strategy for commercial nonenzymatic glucose sensors.