SERS Sensor for Cu²⁺ Detection Based on Etching Reactions.

The presence of copper ions (Cu2+) in excessive amounts can pose significant health risks. Therefore, the development of a rapid and highly sensitive technique for detecting even trace quantities of Cu2+ 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 Cu2+ and I− took place, leading to the generation of I2, 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 Cu2+ 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 Cu2+ not only in tap water but also in various other water sources. [ABSTRACT FROM AUTHOR]

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