Intriguing pH-modulated Luminescence Chameleon System based on Postsynthetic Modified Dual-emitting Eu@Mn-MOF and Its Application for Histidine Chemosensor.

Due to the disruption by other nonanalyte factors, single-emission probes have been limited in complicated detecting systems. In this work, a pH-modulated luminescence chameleon system based on lanthanide-based MOF (Eu@Mn-MOF), with stable structure and miraculous dual-emitting fluorescent properties, was synthesized by a postsynthetic modification (PSM) strategy of a simple hydrothermal and agitation method. Amazingly, not only can the Eu@Mn-MOF emit a broad emission at 500 nm attributed to the ligand-based fluorescence emission but it can also exhibit the characteristic emission of Eu ions responding to the antenna effect. Moreover, the Eu@Mn-MOF displays an interesting luminescence color transition between acidic and basic solutions. Inspired by this phenomenon, a pH-modulated luminescence chameleon system was first constructed and employed to detect histidine, a kind of basic amino acid for a variety of biological matters, causing a unique fluorescence signal of the ratio-dependent color to change from yellow to light pink which differs from the color change of other water-soluble amino acids. Therefore, Eu@Mn-MOF can be as a practical pH-modulated luminescence chameleon system chemsensor for sensing histidine with low detection limit, high sensitivity, and rapid sensing time. In conclusion, the postsynthetic modified Eu@Mn-MOF has outstanding applications in the fields of chemical detection and human health.