Colorimetric/fluorescent/SERS triple-readout sensing of Mercury(II) via in-situ growth of AgNPs in phenanthroline-functionalized covalent organic framework

Targeted design of new covalent organic frameworks (COFs) with specific functions to build multi-readout platform for environmental pollutant monitoring has been gaining increasing interest. Herein, a fluorescent phenanthroline-functionalized COF (PA-COF) with favorable pore structure and reactive nitrogen-containing functional groups is designed and synthesized, and in-situ growth of silver nanoparticles (AgNPs) in PA-COF is achieved to produce PA-COF-based nanocomposite (PA-COF@AgNPs). Phenanthroline facilitates the anchoring of Ag+ in the skeleton of COF material via strong coordination interaction, and the confinement of in -situ grown AgNPs on PA-COF structure provides excellent dispersibility. The formed silver amalgam in the skeleton of PA-COF@AgNPs with the presence of Mercury(II) can oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue product (oxTMB) quickly, inducing obvious absorbance/SERS signal enhancement and fluores-cence quenching of PA-COF@AgNPs. A colorimetric/fluorescence/SERS triple-readout strategy is thus developed for Hg2+ sensing with high sensitivity and excellent accuracy. The present study offers a promising strategy to develop a multi-readout assay platform for monitoring hazardous pollutants based on the targeted fabricating of novel COFs with specific functions.

Automated summary

This study presents the design and synthesis of a fluorescent phenanthroline-functionalized COF (PA-COF) with in-situ grown silver nanoparticles (AgNPs) to form a PA-COF@AgNPs nanocomposite. The PA-COF@AgNPs exhibit high sensitivity and excellent accuracy in detecting Hg2+ through a colorimetric/fluorescence/SERS triple-readout strategy.