A sensitive bromate sensor based on a gold nanoparticle-poly(diallyldimethylammonium chloride)-reduced graphene oxide nanocomposite modified glassy carbon electrode

A nanocomposite consisting of gold nanoparticles (AuNPs), poly(diallyldimethylammonium chloride) (PDDA), and reduced graphene oxide (rGO) was fabricated by a two-step chemical reduction method. Firstly, a PDDA-rGO composite was prepared by using hydrazine hydrate as a reducing agent. Subsequently, the AuNP-PDDA-rGO composite was prepared in ethylene glycol with PDDA-rGO and HAuCl₄ as raw materials using sodium citrate as a reduction agent. The resulting composite was characterized using X-ray powder diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), and electrochemical methods. This composite was then modified on a glassy carbon electrode (GCE) by the dropping method. The electrochemical behavior of bromate on this modified electrode was investigated. The results showed that PDDA-rGO can be used as a good carrier to obtain AuNPs with small particle sizes and good dispersion. The AuNPs and PDDA-rGO in composite enhanced the electrochemical activity of the electrode. Under the synergistic action of each component, the resulting electrode exhibited high activity for the electrochemical reduction of bromate. Based on this, an amperometric bromate sensor was fabricated in N₂-saturated 0.10 mol/L HCl with attractive features including a wide linear range of 1.0 × 10^-7-1.7 × 10^-3 mol/L, a low detection limit (3s_b) of 3.2 × 10^-8 mol/L, and a high sensitivity of 2317 µA/mM/cm². The sensor was successively used for the determination of bromate in drinking water.