Nanoporous gold microelectrode arrays using microchips: A highly sensitive and cost-effective platform for electroanalytical applications

Abstract

• Nanoporous gold structures electrochemically formed at the gold microelectrodes. • Increase in electroactive area (4.4-fold), decrease in resistance to charge transfer. • Energy-dispersive X-ray proves the formation of gold oxide nanostructures. • Improved amperometric detection of dipyrone and cysteine by batch-injection analysis. • Stripping voltammetric detection of lead ions was also improved. In this paper, we investigate the effect of electrochemical treatment on the surface of low-cost and disposable devices (microchips) containing gold microelectrode arrays (Au-µE). This procedure consisted of electrode anodization to generate nanoporous gold structures (NPAu-μE), which contributed to 4.4-fold increase in the electroactive area and decrease in the resistance to charge transfer. Energy-dispersive X-ray spectra revealed the formation of gold oxide nanostructures. The electrochemical response of these sensors was properly investigated using dipyrone (DIP), cysteine (CyS) and lead(II) as target species, and for all the analytes, enhanced analytical performances were obtained using the treated surface. NPAu-μE was combined with a batch-injection analysis (BIA) cell for the amperometric determination of DIP and CyS, which resulted in detection limits lower than 1.2 µmol L -1 , adequate precision (RSD > 4.0 %), wide linear ranges (1.0–200.0 and 5.0–150.0 µmol L −1 ), and high sample throughput (148 and 185 analysis per hour) for DIP and CyS, respectively. Moreover, the NPAu-µE sensor proved to be suitable for Pb 2+ detection by square-wave anodic stripping voltammetry (SWASV), with a detection limit of 2.0 nmol L -1 , linear ranges from 24 to 240 nmol L -1 , and 289 to 531 nmol L -1 , and good precision (RSD = 4.3 %), which enabled a good recovery of Pb 2+ added to drinking water at the level corresponding to the WHO allowed threshold limit (48.2 nmol L -1 or 10.0 µg L -1 ). In summary, we demonstrate that NPAu-μE device can be applied for either organic or inorganic species with satisfactory sensing properties.