A generalized in situ electrodeposition of Zn doped CdS-based photoelectrochemical strategy for the detection of two metal ions on the same sensing platform

An efficient strategy for the sensitive detection of Cd(2+) and Cu(2+) on the same sensing platform was first developed based on the photocurrents generated from the electrodeposited Zn doped CdS (CdZnS) film. The enhancement of the photocurrents, which was directly obtained from the in situ electrodeposited CdZnS on ITO with the gradual addition of Cd(2+), was used an indicator for the content of Cd(2+) with theoretical and technical simplicity. Moreover, the electrodeposited CdZnS was further applied to sensing of Cu(2+) based on the interaction between Cu(2+) and S(2-) by immersing the hetero-structural film electrode into a Cu(2+)-containing sample for an appropriate time, leading to decrease the photocurrent of CdZnS. The decrease extent of photocurrent was depended on the concentration of Cu(2+) in the sample solution. Due to the sensitivity of the photoelectrochemical (PEC) sensor was enhanced obviously through the doping of Zn, the present electrodeposited PEC method demonstrated acceptable linear range of 10(-9)-10(-2)M and 10(-8)-10(-4)M, with low detection limit down to 0.35 nM and 3 nM for Cd(2+) and Cu(2+) respectively, which were lower than the Environmental Protection Agency (EPA) and World Health Organization (WHO) guidelines. The proposed CdZnS-based PEC strategy achieved two metal ions detection on the same sensing platform, which had positive and significant effect on solving the common problems, such as time-consuming, high cost, complex operation and high detection limit in the detection of metal ions. In addition, the proposed PEC device was further successfully applied to an assay of Cd(2+) and Cu(2+) in water sample.