A Reversible Nanolamp for Instantaneous Monitoring of Cyanide Based on an Elsner-Like Reaction.

It is well-known that cyanide ion (CN) is a hypertoxic anion, which can cause adverse effects in both the environment and living beings; thus, it is highly desirable to develop strategies for detecting CN, especially in water and food. However, due to the short half-life of free cyanide, long analysis time and/or interference from other competitive ions are general challenges for accurate monitoring of CN. In this work, through the investigation on the sequence-dependent optical interaction of DNA-CuNPs with the fluorophore (e.g., EBMVC-B), we found, for the first time, that DNA-CuNPs were an ideal alternative as fluorescence quencher in constructing a sensor which could be illuminated by CN based on an Elsner-like reaction and that the signal switching was dependent on poly(AT/TA) dsDNA sequence. By virtue of CuNPs' small size and its high chemical reactivity with cyanide, the lighting of fluorescence was ultrarapid and similar to the hairtrigger "turn-on" of a lamp, which is significant for accurately monitoring a target of short half-life (e.g., cyanide). Attributed to the unique Elsner-like reaction between CN and the Cu atoms, high selectivity was achieved for CN monitoring by the nanolamp, with practical applications in real water and food samples. In addition, because of the highly efficient in situ formation of DNA-CuNPs and the approximative stoichiometry between CN and Cu in the fluorescence switching, the nanolamp could be reversibly turned on and off through the alternate regulation of CN and Cu, displaying potential for developing reusable nanosensors and constructing optical molecular logic circuits.