Electrooxidation of nitrite based on green synthesis of gold nanoparticles using Hibiscus sabdariffa leaves

Abstract In this study, gold nanoparticles (Au-NPs) were synthesized through green biosynthetic route using water extract of Hibiscus sabdariffa leaves ( H. sabdariffa L.) which acted as both reductant and stabilizer agents. The synthesized Au-NPs were characterized by UV–vis spectroscopy, XRD, TEM, FESEM, EDX, zeta potential, and FTIR spectroscopy. By analyzing the UV–vis, FTIR and HPLC data, and comparing with previous studies, the presence of chlorogenic acid in H. sabdariffa L. was identified as the major antioxidant compound involved in the reduction of Au 3+ ions. The FESEM micrograph and TEM images visualized that Au-NPs were formed with a narrow distribution and an average particle size of 7 ± 2 nm at stirring time of 80 min. As for application, the electrooxidation of nitrite was studied with Au-NPs. The electrocatalytic activity of bare GCE and Au-NPs/GCE towards the electrooxidation of nitrite was examined and compared via cyclic voltammetry. Higher electrooxidation of nitrite ions for the synthesized Au-NPs was observed at a stirring time of 80 min. The prepared material showed a linearity of 0.37–10 mM towards nitrite electrooxidation, with the limit of detection (LOD) of 0.11 mM (S/N = 3). Moreover, the prepared electrode presented acceptable stability, repeatability and reproducibility.