pH-Responsive Nanovesicles with Enhanced Emission Co-Assembled by Ag(I) Nanoclusters and Polyethyleneimine as a Superior Sensor for Al.

Metal nanoclusters (NCs) have been engineered as a new kind of luminescent material, whereas the application of metal NCs in aqueous solution was subjected to great limitations owing to their poor solubility, stability, and strong luminescence quenching in a single-molecule state. Herein, facile supramolecular self-assembly strategy was carried out to enhance the luminescence of Ag(I) NCs (Ag-NCs) through multiple electrostatic interactions with polyethyleneimine (PEI). Functional colloid aggregates of Ag-NCs such as nanospheres and nanovesicles were formed along with the enhanced emission because of the formation of compact-ordered self-assemblies, which effectively restricted intramolecular vibration of the capping ligands on Ag-NCs to diminish the nonradiative decay. All those could block energy loss and facilitated the radiative relaxation of excited states which ultimately induced an aggregation-induced emission (AIE) phenomenon. Furthermore, the luminescent Ag-NCs/PEI nanovesicles are pH-responsive and show a superior fluorescent sensing behavior for the detection of Al with a limit of detection low to 3 μM. This is the first report about AIE of silver NCs with polymers in aqueous solution. This work sheds light on the controlled NCs-based supramolecular self-assembly and the NCs-based functional materials, which will be well-established candidates in controllable drug delivery, biomarkers, and sensors in aqueous solution.