Lanthanide ion-sensitized hydrogen-bonded organic framework as a fluorescent sensing platform for ultra-low concentration breath ammonia detection

Abstract

As ammonia (NH₃) is a biomarker of liver and kidney lesions, developing precise and credible exhaled ammonia fluorescence sensors is of major importance to replace time-consuming blood tests; however, their insufficient sensitivity and weak response for low-concentration analytes in expiratory breath restrict their generalization and application. Herein, we adopt a “ligand-to-metal charge transfer-induced energy transfer (LMCT-ET)” strategy to enhance luminescence, through coordination post-synthetic modification, target introduction terbium(III) ions (Tb³⁺) into hydrogen-bonded organic framework (HOF). With the charge rearrangement and energy transfer between photoluminescence HOF-16 and lanthanide metal, a ratiometric fluorescence sensor is successfully constructed and achieved significant amplification of the response signal. Tb@HOF-16 realizes sensitive sensing of ultra-low concentration of ammonia with a limit of detection of 36 ppb. Notably, Tb@HOF-16 is able to accurately quantify ammonia concentrations in exhaled components of patients, and the analysis results have substantial positive correlation with blood ammonia testing. The visible fluorescent platform developed in this work provides a productive method for early diagnosis of liver and kidney lesions.