Competitive coordination-triggered fluorescence turn-on in NU-1000 for selective tricresyl phosphate detection

Abstract

Tricresyl phosphate (TCP), a typical aryl-organophosphorus flame retardant, has been shown to exhibit neurotoxicity, genotoxicity, and reproductive and developmental toxicity. The release of TCP into the environment through human activities has raised significant global concerns, creating a demand for efficient, rapid, and portable TCP detection methods. In this study, a fluorescence turn-on sensor based on NU-1000 was developed for the selective detection of TCP. The fluorescence intensity of NU-1000 is significantly lower than that of the corresponding organic ligand (H₄TBAPy) due to the ligand–metal charge transfer (LMCT) effect. Following the introduction of TCP, under the π–π stacking effect, the phosphate group of TCP competed with the carboxyl group of the ligand for coordination with Zr–O clusters in NU-1000, forming Zr–O–P bonds, inhibiting the LMCT effect, and triggering the metal-enhanced fluorescence (MEF) effect. This subsequently promoted the fluorescence enhancement of NU-1000. The sensor exhibited excellent linearity over the range of 0.30 to 10.0 μmol L⁻¹, with a response time of just 2 min. This work not only expands the optical applications of NU-1000 but also lays a foundation for rapid fluorescence analysis of organophosphorus flame retardants in aquatic systems.