A Double‐Stimuli‐Responsive Fluorescent Center for Monitoring of Food Spoilage based on Dye Covalently Modified EuMOFs: From Sensory Hydrogels to Logic Devices

Abstract

Unsafe food is a huge threat to human health and the economy, and detecting food spoilage early is an ongoing and imperative need. Herein, a simple and effective strategy combining a fluorescence sensor and one-to-two logic operation is designed for monitoring biogenic amines, indicators of food spoilage. Sensors (methyl red@lanthanide metal-organic frameworks (MR@EuMOFs)) are created by covalently modifying MR into NH -rich EuMOFs, which have a high quantum yield (48%). A double-stimuli-responsive fluorescence center is produced via energy transfer from the ligands to Eu and MR. Portable sensory hydrogels are obtained by dispersing and solidifying MR@EuMOFs in water-phase sodium salt of carboxy methyl cellulose (CMC-Na). The hydrogels exhibit a color transition upon "smelling" histamine (HI) vapor. This transition and shift in the MR-based emission peak are closely related to the HI concentration. Using the HI concentration as the input signal and the two fluorescence emissions as output signals, an advanced analytical device based on a one-to-two logic gate is constructed. The four output combinations, NOT (0, 1), YES (1, 0), PASS 1 (1, 1), and PASS 0 (0, 0), allow the direct analysis of HI levels, which can be used for real-time food-freshness evaluation. The novel strategy suggested here may be a new application for a molecular logic system in the sensing field.

Loading Photochromic Molecules into a Luminescent Metal–Organic Framework for Information Anticounterfeiting

“…On the other hand, some of these responses are irreversible. [8] As ar esult, the quenched luminescence cannot be recovered anymore. [2a] Theencoded information is irreversibly destroyed, rather than temporarily hided.…”

Functionalization of Metal–Organic Frameworks for Photoactive Materials

“…Moreover, compared to amorphous materials, the highly ordered crystalline nature of MOFs allows for precise structural determinations and specific knowledge of structural changes that occur during the detection of an analyte and the detail sensing mechanism. To date, a wide range of luminescent MOFs, particularly lanthanide‐based MOFs, have been realized and reported as sensors for ions, small molecules, gas/vapors, temperature, pH values, and moisture …”

“…In the past few years, some luminescent MOFs have also been explored for sensing gas‐phase analytes, including common gases and vapors of solids/liquids …”

Concurrent Modulation of Competitive Mechanisms to Design Stimuli‐Responsive Ln‐MOFs: A Light‐Operated Dual‐Mode Assay for Oxidative DNA Damage

“…As a new type of luminescent material, lanthanide metal‐organic frameworks (Ln‐MOFs) provide an effective platform for chemical recognition by virtue of both the excellent, stimuli‐responsive photoluminescent characteristics of lanthanides through an “antenna effect” and the guest‐binding abilities of MOFs for analytes pre‐concentration . Indeed, considerable progress has been made in exploring Ln‐MOFs as luminescent sensors to detect various species and conditions, such as ions, organic small molecules/VOCs, gases, explosives, antibiotics, humidity, and temperature . Nevertheless, few studies on exploiting such materials for assessing DNA damage or 8‐oxo‐dG levels have been reported thus far, and the multimodal MOF‐based assay for a specific analyte is also particularly rare.…”