Metal Nanoclusters–Based Ratiometric Fluorescent Probes from Design to Sensing Applications

Ratiometric fluorescent probes have many advantages including improved sensitivity, high reliability and accuracy, visualization sensing, etc. Herein, the development of metal nanoclusters (NCs)‐based ratiometric fluorescent probes in the recent years is summarized. NCs, an emerging new class of fluorescent nanomaterials, have demonstrated excellent optical properties, good biocompatibility, great aqueous solubility, low cost, and simple synthesis, and NCs‐based ratiometric fluorescent probes have attracted much attention. In this progress report, the preparation and properties of NCs and the design of ratiometric fluorescent probes are summarized. Sensing of a broad range of analytes including cations, gas, small molecules, macromolecules, temperature, and pH is discussed. In addition, the challenges and future directions for NCs‐based ratiometric fluorescent probes are also presented.     

Incorporating Copper Nanoclusters into Metal‐Organic Frameworks: Confinement‐Assisted Emission Enhancement and Application for Trinitrotoluene Detection

Herein, a strategy for improving both the stability and the emission intensity of Cu nanoclusters based on their entrapment into metal‐organic frameworks (MOFs) is demonstrated. The latter effect reaches 20 times and is ascribed to a confinement‐assisted emission enhancement similar to the aggregation induced emission of fluorescent species in solution, evidenced by the prolonged emission lifetime. Cu nanoclusters are distributed homogeneously over the entire MOFs structure, as confirmed by combination of structural and elemental mapping studies. Toward potential applications of Cu nanocluster/MOF composites as chemical sensors, the authors demonstrate the selective quenching of their emission by 2,4,6‐trinitrotoluene attributed to specific electron‐withdrawing interactions with glutathione ligands on Cu clusters.