A colorimetric sensor of functionalized gold nanoparticles for the identification of copper and magnesium ions based on SPR and Gaussian calculations

Due to the serious threat of excessive copper and magnesium ions to human health, it is crucial to detect copper and magnesium ions in aquatic environments. In this study, we propose a colorimetric strategy – gold nanoparticles (AuNPs) modified by 5-(3-aminophenyl)-1H-tetrazole (TA@AuNPs) for the rapid and portable identification of copper and magnesium ions in water. As the concentration of the target metal ions increases, the colorimetric principle (TA@AuNPs) causes the aggregation of the AuNPs system, shifts of the surface plasma resonance (SPR) absorption peak, and a change of system colors (wine-red to gray-blue). The advantages of this work: 1) the detection process is simple without complex pretreatment; 2) the concentration of the target ions could be quickly detected within 3 min by Standard Color Cards; 3) it can selectively detect two kinds of metal ions (Cu 2+ and Mg 2+ ) with high specificity in the presence of other interfering ions; 4) It eliminates the interference of calcium ions in the detection of magnesium ions; 5) It has excellent linearity and low detection limit (for Cu 2+ : R 2  = 0.94, LOD = 30.0 μM by the naked eye and 0.229 μM through ultraviolet–visible spectroscopy; for Mg 2+ : R 2  = 0.96, LOD = 300 μM by the naked eye and 0.653 μM through ultraviolet–visible spectroscopy). Furthermore, the colorimetric mechanism of the present work has been comprehensively demonstrated through DLS, TEM, zeta potential analysis, FT-IR, UV–vis and Gaussian calculations.