Self-assembly of S,N-codoped Ce/Cu bimetallic nanoparticles for fluorescence and visual detection of hexavalent chromium

Ce₂(SO₄)₃ was doped into 4,6-diamino-2-mercaptopyrimidine (DAMP)-encapsulated copper nanoclusters (CuNCs) via a facile, rapid, low-temperature, and green self-assembly synthesis method to obtain fluorescent S,N-codoped Cu/Ce-DAMP nanoparticles (S,N-codoped Cu/CeNPs) for the detection of Cr(VI). The prepared Cu/CeNPs exhibit double emission peaks at 470 nm and 610 nm. The fluorescence emission at 610 nm is significantly enhanced due to the aggregation-induced emission (AIE) effect, and the quantum yield is as high as 20.19%. The fluorescence emission at 610 nm can be selectively quenched by Cr(VI) due to the internal filter effect (IFE) and dynamic quenching, whereas the weak fluorescence at 470 nm remains almost stable. On this basis, a fluorescence assay method for Cr(VI) was established, with good linearity in the concentration range 0.5–120 µM and a detection limit (LOD) of 134 nM. Using a smartphone to take photos of the fluorescence signals changes caused by Cr(VI) rapid visual detection is achieved with a linear range of 10–130 μM and a LOD of 2.35 μM. The proposed method was successfully applied to the detection of Cr(VI) in actual water samples.