In situ creation of ZnO@CdS nanoflowers on ITO electrodes for sensitive photoelectrochemical detection of copper ions in blood.

A highly selective and sensitive photoelectrochemical (PEC) detection method has been developed for the analysis of copper (Cu2+) ions using nanoflower-like ZnO@CdS heterojunctions, of which ZnO was first in situ grown onto the indium tin oxide electrodes by a hydrothermal method and then coated with CdS through the chemical bath deposition route. It was discovered that the ZnO@CdS heterojunction so formed could serve as a photosensitive catalyst with improved charge separation for visible-light-driven PEC responses. Enhanced visible-light harvesting of nanocomposites could also be expected with CdS as the visible-light sensitizer. Furthermore, the introduction of Cu2+ ions could cause a rational decrease in the photocurrents of nanocomposites through the specific interaction between CdS and Cu2+ ions. A ZnO@CdS heterojunction-based PEC sensor was thereby developed for the detection of Cu2+ ions in blood in the linear concentrations ranging from 0.50 to 80 nM, with a limit of detection of 0.18 nM. Such a heterojunction-based PEC detection platform constructed using two photocatalytic materials with matched band structures are promising for a wide range of applications for sensing Cu2+ ions in clinical diagnostics, food monitoring, and environmental analysis.