Study of an AuNPs functionalized electrode using different diazonium salts for the ultra-fast detection of Hg(II) traces in water

Chemically-prepared gold nanoparticles (AuNPs) were drop-casted onto bare glassy carbon (GC) and on GC functionalized by two different diazonium salts bearing either nitro (NO2) or thiol (SH) groups. The resulting interfaces were characterized by field emission gun scanning electron microscopy (FEG-SEM) and cyclic voltammetry in H2SO4. The micrographs evidenced different densities of AuNPs depending on the substrate, bare GC affording denser deposits than diazonium-functionalized GC. The stability of the interfaces was evaluated over one month and showed higher recovery of active surface area (up to 91% depending on the storage conditions) for AuNPs deposited on diazonium-functionalized GC than on bare GC. The three electrodes were also tested for Hg(II) trace detection by using Square Wave Anodic Stripping Voltammetry (SWASV) and a preconcentration time shortened from 300 s to 30 s. In such conditions, a linear response was obtained in the range 1-10 nmoll−1 together with a normalized sensitivity up to 17 times higher than that reported in our previous works dealing with electrodeposited AuNPs.