Highly Sensitive EQCM Sensor for Mercury Determination by Coupled Stripping Voltammetry

An electrochemical quartz crystal microbalance (EQCM) can be used as electrochemical stripping sensor for mercury (II) detection. Due to the frequency changes of EQCM electrode were used as analytical signal instead of currents, the influence of interference current would not be considered. To improve the sensitivity and signal response range, a QCM electrode, modified with Nafion film and Au-nanoparticles (Au-NPs), was employed as a stripping detector for mercury (II) determination in 0.1 M perchloric acid. The cooperation of Au-NPs and Nafion on the gold electrode surface provided an environment for the enhanced electrodeposition of mercury (II). The prepared sensor exhibited a wide linear response to mercury (II) in the concentration range of 3-300 nM (correlation coefficient of 0.9968), with a detection limit of 0.15 nM. The Nafion film was placed between the Au-NPs and the QCM gold-based electrode, which prevented the direct deposition of mercury onto the QCM gold-based electrode surface, and resulted in the easier regeneration of composites modified electrodes. On the other hand, the roughness of electrode surface increased owing to the modification of Nafion film, which would provide much more area for the immobilization of Au-NPs.