A turn-on fluorescent sensor for relay recognition of two ions: from a F−-selective sensor to highly Zn2+-selective sensor by tuning electronic effects

Abstract

A simple ion sensor bearing quinoline and an amide group was designed and synthesized, which showed both colorimetric detection for F⁻ and a fluorescence turn-on response for Zn²⁺. Moreover, sensor L2 can distinguish F⁻ and Zn²⁺ via different sensing mechanisms (deprotonation for F⁻; inhibition of photo-induced electron transfer (PET) and excited-state intramolecular proton transfer (ESIPT) for Zn²⁺). Meanwhile the distinct color change and the rapid enhancement of fluorescence emission provide naked eye detection. This sensor achieved the detection of two ions which does not need to rely on two different probes: utilization of the innate reactivity of only one probe could achieve a dual recognition purpose in a tandem fashion.