cathodic signal-on photoelectrochemical sensor for Hg2+ detection based on ion-exchange with ZnS quantum dots

A cathodic signal-on method was developed for the photoelectrochemical detection of Hg2+ ions. Here, ZnS quantum dots (QDs) capped with mercaptoacetic acid was assembled on the surface of an indium tin oxide (ITO) electrode through electrostatic interaction between poly dimethyl diallyl ammonium chloride (PDDA) and the ZnS QDs. HgS was formed on the ZnS surface by ion -exchange in the presence of Hg2+ ions in solution. The cathodic photocurrent increased under visible light irradiation with a light emitting diode lamp. This novel strategy exhibits high sensitivity and good selectivity owing to the low background signal and the benefits of ion -exchange technology. The cathodic photocurrent increases linearly with Hg2+ concentration in the range 1 x 10(-11)-1 x 10(-6) M, providing a detection limit of 2 pM (SIN = 3). This sensor provides a promising new strategy for the detection of trace heavy metal ions. (C) 2017 Elsevier B.V. All rights reserved.