Ultrasensitive electrochemical sensor with renewable ratio signal for real-time monitoring of cyanide in Baijiu.

Although electrochemical sensors offer a convenient approach for cyanide detection, they often require multiple components or complex instrumentation. To address this limitation, we designed a covalent organic framework-encapsulated thionine-modified silver‑gold composite (Ag-Au@COF-Thi) sensor that integrates sensitivity and simplicity into a single platform. AgAu nanoparticles are embedded within a COF matrix, with Thi stably adsorbed on the Au surface to provide an internal reference. The sensor is integrated into a miniaturized electrochemical platform, enabling point-of-care cyanide detection via dual-signal readout: target (ICN-) and reference (IThi). After each cycle, the sensor breaks down the silver-cyanide complex and restores the electrode surface, ensuring repeatable performance. Under optimal conditions, the ICN-/ IThi signal ratio correlates linearly with cyanide concentration from 1 ng/mL to 0.5 μg/mL, achieving a detection limit of 0.82 ng/mL. This sensor effectively quantifies cyanide in Baijiu and fermented grains, offering a promising method for food contamination monitoring.