Facile synthesis of bimetallic Ag-Cu nanoparticles for colorimetric detection of mercury ion and catalysis

•Bimetallic Ag-Cu NPs were synthesized by using sodium citrate as protector.•The bimetallic Ag-Cu NPs can be used as colorimetric probe for Hg2+ with detectable minimum concentration of 0.51nM.•The bimetallic colorimetric probe can be expanded the application in from a local campus lake and a natural lake named Chagan lake.•The bimetallic NPs exhibited high catalytic performance in the reduction of nitrophenols and K3Fe(CN)6. Here, we reported on a route to the facile synthesis of bimetallic silver doped copper nanoparticles (Ag-Cu NPs) by AgNO3 and CuSO4 in the presence of sodium borohydride and sodium citrate. The present work described the preparation of the Ag-Cu NPs with sodium citrate and the use of them in colorimetric detection of mercury (II) ions. Ag-Cu NPs with an average diameter of 9.0±0.8nm were prepared via two step reduction at room temperature. The Ag-Cu NPs were thoroughly characterized by using UV–vis spectroscopy and transmission electron microscopy (TEM) techniques. The morphology and constitution of the Ag-Cu NPs were characterized by TEM, and the valence state of Ag-Cu NPs was confirmed by the X-ray photoelectron spectroscopic (XPS) result. The synthesized Ag-Cu NPs were yellow in color due to the intense surface plasmon absorption band centered at 406nm. This high selective sensor allowed a direct quantitative assay of mercury ions (Hg2+) with a detection limited of 0.51nM. The synthesized Ag-Cu NPs also exhibited good catalytic activity in two model reactions, the reduction of the nitrophenols and potassium ferricyanide (III) by sodium borohydride.