Gold nanostar electrodes for heavy metal detection

Abstract This paper presents a novel application of gold nanostars (AuNSs) for the electrochemical detection of arsenic (As(III)), mercury (Hg(II)), and lead (Pb(II)) in water. The AuNSs were synthesized using the Good’s buffer method, a simple, environmentally friendly procedure. Boiling the AuNS suspension enabled the formation of spherical gold nanoparticles (AuNPs), which were compared to the AuNSs to determine if the shape of the nanoparticle contributed to the functionality of the sensor. When compared to AuNSs, AuNPs exhibited a fourfold increase in specific geometric surface area (per liter) and a threefold increase in electroactive surface area (EASA). The effect of particle loading on charge transfer resistance, R CT , and double layer capacitance, C DL was assessed: as particle loading increased, R CT decreased and C DL increased for both AuNS- and AuNP-modified electrodes; however, R CT was lower for the AuNPs. For the detection of As(III), Hg(II), and Pb(II), square wave stripping voltammetry (SWSV) parameters were individually optimized and peak heights, I p , were obtained for a range of NP loadings. The I p values varied with respect to NP loading and displayed a unique trend for each analyte and particle shape. For As(III), the AuNSs produced higher peak heights than AuNPs of the same loading. I p values for Hg(II) decreased dramatically at high AuNP loadings and decreased minimally at high AuNS loadings. NP loadings did not have a significant influence on I p values associated with Pb(II). These findings suggest that gold nanostructure shape and loading can influence the efficacy of electrochemical heavy metal detection and should be taken into consideration.