A novel photoelectrochemical sensor based on three-dimensional rGO@Au-sensitized cauliflower-like CdS heterojunction for the effective and sensitive detection of copper (II) in pool water.

[Display omitted] • The cauliflower-like CdS with the rough and wide surface was created. • The CdS/rGO@Au/GCE sensor has wide linear range (5 nM − 4 μM). • The detection limit of 2.88 nM is 10,000-fold lower than the WHO guideline. • The sensor has been used to analyze Cu(II) in pool water with great performance. • Material-target interaction is used to solve the selectivity problem of PEC sensors. Copper (II) ion (Cu2+) is a typical heavy metal ion that not only harms the soil and water environment, but also causes neurological disorders, liver cirrhosis and other diseases. Here, we have successfully synthesized three-dimensional CdS/rGO@Au heterojunction using a simple physical mixing technique, characterized the material synthesis by X-ray diffraction spectroscopy (XRD), Transmission electron microscopy (TEM), and finally used it for selective photoelectrochemical detection of Cu2+. In this system, the synergistic interaction of the three creates a channel that is ideal for charge carrier separation and transfer. The cauliflower-shaped CdS possesses a large surface area and acts as a Cu2+ probe. rGO@Au acts as a sensitizer and amplifies the current change. The photocurrent of the CdS/rGO@Au heterojunction is 7 times higher than that of CdS, indicating that CdS/rGO@Au has a good photoresponse intensity. Under the optimized detection conditions, the proposed photoelectrochemical sensor was able to detect Cu2+ concentration in the range of 5 nM to 4 μM with a very low limit of detection (LOD) of 2.88 nM. Moreover, the application feasibility of the developed CdS/rGO@Au heterojunction sensor was verified by the detection of Cu2+ in real water samples. [ABSTRACT FROM AUTHOR]