Square voltammetric sensing of mercury at very low working potential by using oligomer-functionalized Ag@Au core-shell nanoparticles

The authors describe a material for the sensitive and selective voltammetric determination of mercury(II). Core-shell nanoparticles (NPs) of the type Ag@Au were prepared and modified with an oligoner with the sequence 5′-CCC CCC CCC CCC TTC TTT CTT CCC CTT GTT TGT T-3′. The NPs were characterized by transmission electron microscopy, UV-vis spectroscopy and electrochemical impedance spectroscopy. The modified NPs were examined by cyclic voltammetry (CV) and square wave voltammetry (SWV). It is shown that the material, if placed on a screen printed carbon electrode, is a viable sensor for Hg(II). If operated at a voltage as low as 10 mV (vs Ag/AgCl), it has a linear response that convers the 10 to 160 pM concentration range and a 6 pM detection limit (at an S/N ratio of 3). The sensor is rapid, convenient, inexpensive and selective. It was applied successfully to the determination of Hg(II) in spiked wastewater samples. Its low working potential makes it a highly attractive sensing tool that is not readily interfered by other redox-active species. [Figure not available: see fulltext.].