SERS Sensor for Cu2+ Detection Based on Etching Reactions

The presence of copper ions (Cu 2+ ) in excessive amounts can pose significant health risks. Therefore, the development of a rapid and highly sensitive technique for detecting even trace quantities of Cu 2+ is of paramount importance. The proposed detection approach leverages the core-shell design of Au@Ag NPs functioning as the sensing substrate. The substrates were coupled with Raman probe molecules, namely, 4-mercaptobenzoic acid (4-MBA) and iodine ions (I − ), resulting in the formation of the Au@Ag NPs-4-MBA-I − detection system. In this system, interactions between Cu 2+ and I − took place, leading to the generation of I 2 , which in turn initiated the etching process of the Ag shell layer. Consequently, the thickness of the Ag shell decreased gradually. This reduction in the shell layer impaired the surface-enhanced Raman scattering (SERS) enhancement effect, causing a gradual decrease in the Raman signal intensity at 1586 cm −1 which was attributed to the characteristic peak of 4-MBA. Notably, a linear correlation existed between the thickness of the Ag shell and the intensity of the Raman signal. The proposed method for Cu 2+ detection exhibits robust resistance to interference and high reproducibility under optimal SERS testing conditions. It boasted a wide linear detection range from 10 −9 to 10 −4 M and achieves a low detection limit (LOD) of 1.108 10 −9 M. Moreover, this sensor was environmentally friendly, offered rapid recognition capabilities, and incurred minimal detection costs. Its versatility extended to diverse water systems, making it suitable for detecting Cu 2+ not only in tap water but also in various other water sources.