Dual-mode SERS and colorimetric detection of cyanide in baijiu (Chinese distilled liquor)

In recent years, the issue of excessive cyanide levels in fermented alcoholic beverages has raised widespread public concern regarding food safety. Technologies enabling rapid detection of cyanide ions (CN-) in alcoholic matrices have consequently emerged as a key research focus. This study presents a novel dual-mode sensing platform based on Au@Ag nanocubes and Au@Ag-graphene oxide (GO) nanocomposites for ultrasensitive and selective cyanide detection in Chinese baijiu (traditional Chinese distilled liquor with multiple types and flavours). The hybrid substrates exploit the strong localized surface plasmon resonance of noble metals combined with cyanide-induced etching of the silver shell, enabling both surface-enhanced Raman spectroscopy (SERS) and colorimetric detection. SERS analysis achieved limits of detection of 1 ppm in aqueous solution and 1.25 ppm in alcoholic matrices, well below the national safety standard of 8 ppm. In authentic baijiu samples spiked with cyanide, reliable detection was achieved at 500 ppb-2.5 ppm depending on baijiu aroma type. Simultaneously, a distinct color transition from yellow to gray was observed at concentrations as low as 0.1 ppm, providing a rapid, instrument-free screening capability. RGB analysis was introduced to quantify the colorimetric response. Compared with Au@Ag nanocubes, the Au@Ag-GO substrate demonstrated superior reproducibility and more robust colorimetric performance in complex liquor matrices. This work offers a practical tool for on-site cyanide monitoring in alcoholic beverages, addressing a critical need in food safety assurance.