Cu2+-Assisted Synthesis of Au@AgI Core/Shell Nanorods via In Situ Oxidation of Iodide:A Strategy for Colorimetric Iodide Sensing

Colorimetric nanoprobes are frequently employed to construct sensitive sensors via various strategies.In this work,a novel strategy for simple and ultrasensitive sensing of iodide(I-) was constructed based on Cu2+-assisted generation of Au@AgI core/shell nanorods(NRs),by etching silver-coated gold nanorods(Ag@Au NRs).Ag@AuNRs were first prepared and characterized with UV–visible spectroscopy,transmission electron microscopy,high-angle annular dark-field scanning transmission electron microscopy,and energy-dispersive X-ray spectroscopy before and after iodide treatment.The mechanism of detection was based on the generation of AgI shells via etching Ag shells by I2,which was produced from the oxidation of I-with Cu2+,resulting in the peak shift of localized surface plasmon resonance(LSPR) while the color changed from green,blue to light-violet.The red-shift of the longitudinal LSPR peak had a linear relationship with I-concentration in the range of 0–50 μmol/L with a correlation coe fficient of 0.982.Furthermore,the proposed method was used for the quantitative detection of I-in real samples and outstanding recoveries in the range of 91–106% with relative standard deviations lower than 2.5% were observed.