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 Cu2+ in the fluorescence switching, the nanolamp could be reversibly turned on and off through the alternate regulation of CN- and Cu2+, displaying potential for developing reusable nanosensors and constructing optical molecular logic circuits.