Exploitation of carbon surface functionality toward additive‐free formation of gold nanocuboids suitable for sensitive assay of N‐acetylcysteine in pharmaceutical formulations

Abstract

Chemical additive and physical template‐free electrochemical methods to prepare carbon‐supported nanostructures of catalyst metals represent an emerging technology. Formation of the metal nano/microstructures depends not only on the electrochemical method/parameters but also on the nature of the underlying carbon material. Here, we present a comparative evolution of unevenly distributed coral‐like aggregates of nanocuboid‐shaped gold nanostructures (AuNCBs) on the oxidised form of boron, nitrogen‐doped carbon nanoonions (oxi‐B,N‐CNO) compared to evenly distributed bud‐like aggregates of cubic shaped gold nanostructures on bare glassy carbon electrode under a similar electrochemical approach. The synthesis method provided the best availability of the surface active sites, whereas the shape of the structures showed a direct influence of both outer‐sphere and inner‐sphere electron transfer reactions. The higher sensitivity of AuNCBs@oxi‐B,N‐CNO compared to individual components and bare carbon/gold electrodes toward the inner‐sphere oxidative reaction of N‐acetyl‐L‐cysteine (NAC) was exploited in order to develop an electrochemical assay method with sensitivity and linear dynamic range of (4.70 ± 0.25) × 10−4 C∙cm−2∙mM−1 and 0.2–2.5 mM, respectively in acetate buffer (pH 4.45). Furthermore, the sensor design was deployed in the quantitation of NAC in pharmaceutical preparations, resulting in 89%–106% recovery.