3D porous nanostructured reduced graphene oxide and nafion composite as an ultrasensitive interface for rapid and nanomolar determination of a flavonoid, galangin

Graphene-based nanostructures are considered ideal modifiers for electrochemical sensors owing to their unique structural, conductive, and catalytic properties. Given this, herein we have developed a three-dimensional reduced porous graphene oxide-nafion nanocomposite film modified glassy carbon electrode (p-rGO/NAF/ GCE) for electrochemical determination of a flavonoid, galangin (GAL) for the first time. A simple, almost instantaneous, and environmentally benign "low-temperature solution combustion" method was used for the preparation of p-rGO using glycine as a fuel and green reducing agent simultaneously, followed by compositing it with nafion and coating on GCE to form an electrochemical sensor. The p-rGO/NAF/GCE promoted the mass transfer of GAL to the electrode surface and exhibited excellent electrocatalytic activity towards the oxidation of GAL with a significant enhancement (similar to 70-fold) in the peak current. The enhanced electrocatalytic activity was attributed to the synergistic contribution from p-rGO and nafion, which provided higher active surface area, porous network structure, feasible cation exchangeability, and strong adsorption capacity. The two anodic peaks exhibited by GAL at p-rGO/NAF/GCE involved an equal number of protons and electrons via diffusion-controlled (peak a1) and adsorption-controlled (peak a(2)) processes. Linear response over concentration range of 1.99 x 10(-8) - 4.5 x 10(-5) mol L-1 of GAL was established with the lowest limit of detection value of 1.11 nM by square wave voltammetric (SWV) method. Importantly, the fabricated sensor demonstrated repeatability, high stability, and potential anti-interference properties with practical utility for the analysis of analyte-fortified biological samples and pharmaceutical formulations with good recoveries.