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[Display omitted] • An amine-response visual fluorescent tag was prepared by physical deposition. • Quantum dots with aggregation-induced emission effect acted as internal reference. • The tag can realize non-contact detection of biogenic amines. • The tag can be used for real-time and visual monitoring of seafood freshness. The method of monitoring the freshness of seafood is not satisfactory for ensuring food safety. Here, we develop a filter membrane-based smart fluorescent tag with excellent biogenic amine response, which can monitor the freshness of seafood in real time and visually. We use green fluorescent fluorescein as an indicator and red fluorescent carbon quantum dots (RQDs) with aggregation-induced emission property as an internal reference. After simple mixing, they are deposited on the commercial filter membrane by physical deposition method to prepare the fluorescent tag. When amine molecules are present, the molecular conformation of fluorescein changes and the fluorescence increases rapidly, while RQDs have no obvious response, thus achieving a clear fluorescence color response to biogenic amines. Under UV light of 254 nm and 365 nm, the fluorescent tag showed sensitive, rapid, and color-responsive to ammonia in a wide range of 250–2.5 × 104 ppm. To further verify the practical application potential, the fluorescent tag was used to monitor the freshness of shrimp and crab in situ in real time, and satisfactory results were achieved. More importantly, owing to the reversible conformational change of fluorescein, the fluorescent tag can be reused and manufactured at low cost, making it a more attractive platform for freshness monitoring in the field of food safety. [ABSTRACT FROM AUTHOR]

• A novel fluorescent probe based on red emission carbon dots was fabricated. • It was applied colorimetric and fluorometric dual-mode detection of nitrite. • It had a high sensitivity and a low detection limit. • It was successfully applied in detecting nitrite in meat products with satisfactory recoveries. • This dual-mode probe presented great advantages for detection of nitrite in food samples. Nitrite (NO 2 –) is widely present in the human environment and accurate, sensitive and selective detecting of nitrite is of vital significance for food safety and water quality. Herein, a novel red emission carbon dots (r-CDs) fluorescent probe was fabricated for dual-mode detection of nitrite, which was capable of both convenient colorimetric analysis and accurate fluorometric detection. When NO 2 – is added to the rose-red r-CDs solution, NO 2 – interacts with the amino groups which on the surface of r-CDs to form diazotized substance, resulting in that the colorimetric color of r-CDs solution realizes the transition from rose red to light purple, and the red fluorescence is gradually quenched. The detection limits of colorimetric and fluorescence for NO 2 – were 0.193 μM and 0.149 μM, respectively. Furthermore, the dual-readout probe revealed satisfactory recovery and reliability when analyzing the concentration of NO 2 – in ham and bacon samples.. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel bimetallic organic framework based fluorescent aptamer probe was designed. • Aptamer was combined with Cu/UiO-66 by electrostatic force and van der Waals force. • Aptamer's fluorescence was quenched by the photoinduced electron transfer effect. • The probe realized sensitive detection of zearalenone in cereal and their products. • A detection limit of 0.048 ng/mL was achieved with a linear range of 0.5–60 ng/mL. In this work, a bimetallic organic framework (Cu/UiO-66) based "turn on" fluorescent aptamer probe was designed for the high-efficiency detection of zearalenone (ZEN). In the probe, the 6-carboxyfluorescein-labeled aptamer (FAM-Apt) was used as the recognition element, and the electrostatic interaction, coordination effect, and photoinduced electron transfer effect between FAM-Apt and Cu/UiO-66 caused fluorescence quenching. When ZEN existed, FAM-Apt recognized ZEN specifically, causing FAM-Apt to separate from the surface of Cu/UiO-66 and recovery of fluorescence. Under the optimal conditions, the probe had a linear detection range of 0.5 ng/mL–60 ng/mL, and the detection limit was 0.048 ng/mL. The application potential of the probe was verified by real detection of various cereals and their products, with a standard recovery from 83.67 %–106.8 %. The development of this efficient, rapid, and sensitive ZEN detection method provides a new platform for the quality control of cereals and their products. [ABSTRACT FROM AUTHOR]

[Display omitted] • An enzyme-mediated ratiometric fluorescent probe was developed. • Ru@UiO-66 acted as a reference signal and thiamine acted as a response signal. • It integrated quenching effect, enzyme-like activity and enzyme inhibition. • It exhibited excellent analytical performance against dichlorvos and chlorpyrifos. • Ratiometric fluorescent hydrogels were developed for portable visual detection. In view of the potential hazards of organophosphorus pesticides (OPs), this paper constructed a ratiometric fluorescent probe utilizing a functionalized metal–organic framework to detect OPs. Ru(bpy) 3 Cl 2 was encapsulated inside UiO-66 as a reference signal, and MnO 2 nanosheets (MnO 2 NSs) were grown on the surface to obtain Ru@UiO-66@MnO 2 NSs. Acetylcholinesterase catalyzed the decomposition of acetylcholine into reductive thiocholine, which consumed MnO 2 NSs, thus restoring the Ru@UiO-66 fluorescence. Due to the enzymatic inhibition of OPs and the redox reaction between MnO 2 NSs and thiamine, this probe emitted blue fluorescence in the presence of OPs. The probe achieved linear responses to dichlorvos and chlorpyrifos with LODs of 9.99 × 10-6 μg mL−1 and 9.99 × 10-5 μg mL−1. The probe exhibited a satisfactory recovery rate for OPs in green tea. Furthermore, a hydrogel detection platform was developed by embedding the probe into sodium alginate. Overall, this work provides a visual approach to detect OPs in agricultural products. [ABSTRACT FROM AUTHOR]

The valorization, resource generation and the functional characteristic exploration of domestic waste still face enormous challenges. Kiwi peels, a common kind of fruit waste, contain a large amount of phenolic substances, including polyphenols, flavonoids, etc., which can be explored and reused in food and biomedical fields. By ultrasonic assisted extraction technology, we obtained conversional fluorescence kiwi peel phenolic extracts (PE) which possessed gradient magenta fluorescence relying on the content of ethanol in the solution, as well as strong antioxidant activity. Besides, metal ions sensing assay revealed that PE can specifically sense Hg2+ and Cu2+ (LOD: 1.16 and 0.17 μM, respectively) accompanied with a fluorescence conversion from magenta fluorescence to blue. Moreover, employing the prepared PE as fluorescent probes, imaging of HeLa cells can be easily achieved with satisfactory resolution. Additionally, PE was incorporated into the gelatin matrix, successfully fabricating a green, edible degradable film with excellent antioxidant activity. Unlabelled Image • Ultrasound treatment accelerated the escape of kiwi peel phenolic extracts. • Phenolic extracts exhibited a gradient magenta fluorescence relying on the solvent effects. • Phenolic extracts sense Hg2+ and Cu2+ with a fluorescence conversion from magenta to blue. • Phenolic extracts were successfully applied to fluorescent imaging of HeLa cells. • Phenolic extracts improved the antioxidant capacity of gelatin-based films. [ABSTRACT FROM AUTHOR]