Covalent organic framework-encapsulated europium clusters for convenient detection of Ag+ released by nanosilver

Abstract

Accurate determination of Ag⁺ released by silver nanoparticles (AgNPs) is vital for elucidating the environmental behaviors and defining exposure risks of nanosilver. However, this remains challenging due to limitations in in situ Ag⁺ concentration assessment within AgNPs, along with complex pretreatment processes, low throughput, reliance on expensive instrumentation, and the need for specialized operators. Herein, a novel europium composite (EuCs@TD) was prepared through encapsulating europium clusters (EuCs) into the one-dimensional nanochannels of a 1,2,4,5-tetra(4-aminophenyl)benzene (TPB) and dimethyl succinylo succinate (DMSS)-based covalent organic framework (termed as TD). Secondary micropores were formed between the walls of the nanochannels and the orderly aligned EuCs therein, which function as molecular sieves for selective analysis of Ag⁺. EuCs@TD showed excellent selectivity, rapid response (within 20 s), and high sensitivity (detection limit, 0.35 nM) for Ag⁺ due to a great enhancement of the Eu³⁺ luminescence. Taking advantages of the robust performance of EuCs@TD, the contents of Ag⁺ in AgNPs were conveniently determined, which avoided cumbersome post-processing steps as nanofiltration and centrifugation. Furthermore, long-term evaluation of the activity of commercialized nanosilver products was successfully performed by using the EuCs@TD probe. This work presents an effective strategy for creating ultraselective fluorescent probes for application in complex systems.