An amino-appended asymmetry salamo-type ratiometric fluorescent probe for efficient relay detection of B4O72−/HCHO in real samples

Abstract

Development of fluorescent chemical sensors for ratiometric detection of multiple metal ions or anions are highly demanded, but there are still many challenges. Herein, an asymmetry salamo-type ratiometric fluorescent probe G1 were designed and synthesized for highly selective and sensitive detection of B4O72− and formaldehyde (HCHO). The introduction of B4O72− anion into salamo-type fluorescent probe solution induces a significant turn-off fluorescence behavior. Meanwhile, a strong fluorescence feature was again observed when HCHO was successively injected into the formed G1-B probe solution with turn-on style. 1H NMR titration and theoretical calculation proved that the B4O72- coordinates with phenolic oxygen and oxime nitrogen in fluorescent probe G1. B4O72− combination with probe G1 destroys the excited-state intramolecular proton transfer (ESIPT) process and causes fluorescence quenching effect. However, the addition of HCHO leads to a Cannizzaro disproportionation reaction occurred with the G1-B probe, resulting in the fluorescence recovery of the primitive probe molecule. Such probes have excellent selectivity and sensitivity for B4O72− and HCHO, in which the detection limit of sensor towards B4O72− and HCHO was 9.65×10−6 M and 4.66×10−11 M, respectively. Moreover, such sensor was successfully used for monitoring the concentration levels of B4O72− and HCHO in actual sample.