Amperometric determination of nanomolar mercury(II) by layered double nanocomposite of zinc/aluminium hydroxide-3(4-methoxyphenyl)propionate modified single-walled carbon nanotube paste electrode

A mercury(II) sensor was developed by using single-walled carbon nanotube (SWCNT) paste electrode modified with layered double Zn/Al hydroxide-3(4-methoxyphenyl)propionate nanocomposite (Zn/Al-LDH-MPP). The cyclic voltammetry was optimised at electrode composition 2.5 % (w/w) of Zn/Al-LDH-MPP/SWCNTs, supporting electrolyte 0.4 M potassium chloride, buffering at pH 4.0 and scan rate of 100 mVs−1. The sensor exhibited a wide linear range from 1 × 10−3 M to 1 × 10−7 M Hg2+ and 1 × 10−7 M to 1 × 10−9 M Hg2+ with a detection limit of 1 × 10−9 M Hg2+. The values of the diffusion coefficients (1.5445 × 10−9 cm2 s−1), surface charge (524.5 μC s−1/2) and surface coverage (4.41 × 10−2 mol cm−2) determined by double potential-step chronocoulometry could probably have contributed to the high sensitivity value obtained. The presence of 25-fold concentration of all metal ions tested showed no influence on the anodic peak current. The electrode was then proposed as the appropriate alternative for the determination of mercury(II).