Atomically Dispersed Zn-N 5 Sites immobilized on g-C 3 N 4 Nanosheets for Ultrasensitive Selective Detection of Phenanthrene by Dual Ratiometric Fluorescence.

Ultrasensitively selective detection of trace polycyclic aromatic hydrocarbons (PAHs) like phenanthrene (PHE) is critical but remains challenging. Herein, for the first time, atomically-dispersed Zn sites on g-C 3 N 4 nanosheets (sZn-CN) are constructed by thermal polymerization of Zn-cyanuric acid-melamine supramolecular precursor for the fluorescence detection of PHE. The high-amount (1.6 wt%) sZn is grafted in the cave of CN with one N vacancy in the form of unique Zn(II)-N 5 coordination. The optimized sZn-CN achieves a wide detection range (1 ng·L -1 ∼ 5 mg·L -1 ), ultralow detection limit (0.35 ng·L -1 , with 5-order magnitude improvement over CN), and ultrahigh selectivity towards PHE even among typical PAHs based on the built PHE-CN dual ratiometric fluorescence method. By means of the in-situ Fourier transform infrared spectra, time-resolved absorption and fluorescence spectra, and theoretical calculation, the resulting superior detection performance is attributed to the favorable selective adsorption of PHE on as-constructed atomic Zn(II)-N 5 sites via the ionic cation-π interactions (Zn δ+ -C 2 δ- type), and the fluorescence quenching is dominated by the inner filter effect (IFE) from the multilayer adsorption of PHE at low concentrations, while it is done by the protruded photogenerated electron transfer (PET) process as well as IFE from the monolayer adsorption of PHE at ultralow concentration. This article is protected by copyright. All rights reserved.