Preparation of an ammonia-responsive sensor based on bacterial cellulose film with enhanced AIE/ESIPT emission of fluorescent molecules bound to europium-based metal–organic framework

Abstract

At present, selecting suitable fluorescent molecules to design low-cost, stable and sensitive ammonia response sensors is an important topic in the field of meat quality detection. In this work, a solid–liquid applicable ammonia-responsive fluorescent molecule (2-(benzo[d]thiazol-2-yl)-4-chlorophenol acetate, BTCP-Ac), was designed by enhancing the aggregation-induced emission (AIE)/excited state intramolecular proton transfer (ESIPT) luminescence properties of 2-(Benzo[d]thiazol-2-yl) phenol (HBT) molecules. BTCP-Ac combined the advantages of the red luminescence (colorimetric intrinsic parameter) and the confinement effect (enhanced aggregation of fluorescent molecules) of the metal–organic framework (Eu-MOF) to prepare fluorescent probes (BTCP-Ac@Eu-MOF). The sensor (BTCP-Ac@Eu-MOF film) was prepared using bacterial cellulose (BC) as a fluorescent probe loading platform. The sensor achieves specific detection of amines by “switching: the intramolecular proton transfer process of fluorescent molecules. The experimental results showed that the sensor reacted significantly with ammonia compared to BTCP-Ac (LOD = 2.24 ppm), with a low detection limit (LOD = 0.68 ppm) and stable luminescence (no decay for 30 d). The sensor with high temperature resistance and strong hydrophobicity (121.64°) successfully monitored the freshness of chicken meat, which changed color from red to blue-green and was easily visible to the consumer’s eye. This method encapsulates specially designed AIE molecules in a luminescent metal–organic framework to prepare ammonia-responsive sensors with selectivity, high sensitivity and stability, providing a novel and practical strategy for designing gas-responsive solid-state sensors.