Dual-lanthanide urea metal-organic framework based fluorescent traffic light microsensor for solvent decoding and visual trace water assay

Abstract

A rapid and sensitive sensor for organic solvent decoding and water assay is crucial for human health and chemical industry. Herein, a dual-lanthanide metal-organic framework (Ln-MOF) Eu0.2Tb0.8-UL (UL: urea-containing ligand) was fabricated for 3-dimensional solvent decoding and ratiometric on-off water assay in organic solvents. According to innovative multiple response mechanisms including ligand protonation and -OH oscillation, the energy transfer of ligand to Ln3+ and Tb3+ to Eu3+ is precisely regulated by water content. Ultra-low limit of detection (0.004% v/v), broad response range (0–100%) and high-efficacy fluorescence color changing from red to green are achieved. A one-to-two logic device with single input (water content) and dual outputs (Eu3+ and Tb3+ emissions) was designed for the facile intelligent water detection, which is realized by 3 output results: YES (1, 0), PASS (0, 0) and NOT (0, 1), just like a smart traffic light sensor (red-yellow-green). The MOF-loaded paper microsensor was constructed for real-time and sensitive detection of trace water in organic solvents, coupled with a smartphone-assisted visual portable device. To our knowledge, this is the first case of Ln-MOF-based 3-dimensional solvent decoder, and traffic light-like logic analytical device and paper microsensor for real-time visual water assay in organic solvents.