A MOF/hydrogel film-based array sensor for discriminative detection of nitrophenol isomers

Abstract

Nitrophenol is a common industrial intermediate with a potential threat to human health. Luminescent metal–organic frameworks (LMOFs) make it possible to detect nitrophenol rapidly and sensitively, but this method still suffers from the confusion of nitrophenol analogs and the lack of portability. In this paper, by loading two lanthanide metal ions Eu³⁺ and Tb³⁺ into mixed-ligand LMOF Uio-66-(COOH)₂/NDC, a multiple-emissive luminescent sensor array for three nitrophenol isomers was obtained. Through the diverse response of the three luminescence centers to the three nitrophenol isomers and the linear discriminant analysis method, nanoscale Eu³⁺/Tb³⁺@Uio-66-(COOH)₂/NDC exhibits excellent capability to recognize three nitrophenol isomers at concentrations ranging from 40 to 100 μM, distinguish binary or ternary mixtures at 60 μM and achieve semi-quantification in concentrations ranging from 0 to 80 μM. Furthermore, as a proof of concept, a film-based array sensor is prepared by doping Eu³⁺/Tb³⁺@Uio-66-(COOH)₂/NDC nanoparticles in sodium alginate hydrogel, which shows excellent portability and optical stability while maintaining the distinguishing performance to nitrophenol. Considering the diversity of LMOFs and hydrogels, the strategy of constructing the MOF/hydrogel film-based array sensor is expected to provide new ideas for the distinction of more analogs and make the application of LMOFs in real life full of possibilities.