Gold Nanoparticle Modified Transparent Carbon Ultramicroelectrode Arrays for the Selective and Sensitive Electroanalytical Detection of Nitric Oxide.

Transparent carbon ultramicroelectrode arrays (T-CUAs) were made using a previously reported facile fabrication method (Duay et al. Anal. Chem. 2015, 87, 10109). Two modifications introduced to the T-CUAs were examined for their analytical response to nitric oxide (NO•). The first modification was the application of a cellulose acetate (CA) gas permeable membrane. Its selectivity to NO• was extensively characterized via chronoamperometry, electrochemical impedance spectroscopy (EIS), and atomic force microscopy (AFM). The thickness of the CA membrane was determined to be 100 nm and 88 ± 15 nm using AFM and EIS, respectively. Furthermore, the partition and diffusion coefficients of NO• within the CA membrane were determined to be 0.0500 and 2.44 × 10-13 m2/s using EIS measurements. The second modification to the 1.54T-CUA was the introduction of chitosan and gold nanoparticles (CS/GNPs) to enhance its catalytic activity, sensitivity, and limit of detection (LOD) to NO•. Square wave voltammetry was used to quantify the NO• concentration at the CA membrane covered 1.54T-CUA with and without CS/GNPs; the LODs were determined to be 0.2 ± 0.1 and 0.44 ± 0.02 μM (S/N = 3), with sensitivities of 9 ± 9 and 1.2 ± 0.4 nA/μM, respectively. Our results indicate that this modification to the arrays results in a significant catalytic enhancement to the electrochemical oxidation of NO•. Hence, these electrodes allow for the in situ mechanistic and kinetic characterization of electrochemical reactions with high electroanalytical sensitivity.