Bimodal ratiometric fluorescence and colorimetric sensing of paraoxon based on trifunctional Ce,Tb co-coordinated polymers

Abstract

Here we develop a ‘three functions-in-one’ platform based on Ce,Tb co-coordinated isophthalic acid (IPA) polymers (Ce/Tb-IPA) with acid phosphatase (ACP) loading, switchable luminescence and oxidase-mimicking activity, enabling the dual-mode ratiometric fluorescence and colorimetric quantification of paraoxon. The Ce4+/Ce3+ nodes make ACP@Ce/Tb-IPA exhibit oxidase-like activity to catalyze the 3,3′,5,5′-tetramethylbenzidine (TMB) chromogenic reaction, and the Ce3+ and Tb3+ species endow it with a weak fluorescence at 358 nm and a strong one at 496 nm, respectively. The ACP loaded on Ce/Tb-IPA can catalyze ascorbic acid 2-phosphate (AAP) hydrolysis to generate ascorbic acid, which chemically reduces Ce4+ to Ce3+, resulting in an obvious enhancement of the Ce3+ signal and a decrease of the Tb3+ signal. Meanwhile, the oxidase-mimetic activity of ACP@Ce/Tb-IPA is restrained due to the decreased Ce4+/Ce3+ ratio, leading to a suppression of the TMB color reaction. When paraoxon exists, it poisons ACP against AAP hydrolysis, and such that the Tb3+ signal restores and the Ce3+ one is restrained again, together with the restoration of the catalyzed TMB oxidation signal. Consequently, bimodal ratiometric fluorescence and colorimetric determination of paraoxon with excellent reliability was realized using the developed platform. Also, it was successfully employed to monitor the pesticide residue in spinach.