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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.., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Dual emission quantum dots (QDs) have attracted considerable interest as a novel phosphor for constructing ratiometric optical thermometry because of its self-referencing capability. In this work, the exploration of codoped Zn-In-S QDs with dual emissions at ≈512 and ≈612 nm from intrinsic Cu and Mn dopants for ratiometric temperature sensing is reported. It is found that the dopant emissions can be tailored by adjusting the Mn-to-Cu concentration ratios, enabling the dual emissions in a tunable manner. The energy difference between the conduction band of the host and Cu dopant states is considered as the key for the occurrence of Mn ion emission. The as-constructed QD ratiometric temperature sensor exhibits a totally robust stability with a fluctuation of ≈ ICu/ Itot versus times lower than 1% and almost no hysteresis in cycles over a broad window of 100-320 K. This discovery represents that the present cadmium-free, intrinsic dual-emitting codoped QDs can open a new door for the synthesis of novel QDs with stable dual emissions, which poise them well for challenging applications in optical nanothermometry. [ABSTRACT FROM AUTHOR]

A robust and stable ratiometric temperature sensor based on Zn‐In‐S quantum dots (QDs) with intrinsic dual‐dopant ion emissions is reported by W.Y. Yang, X.S. Fang, and co‐workers on page 7224. The environment‐friendly co‐doped QD sensor exhibits an excellent stability with almost no hysteresis in cycles. The device is promising for challenging applications in future optical nanothermometry. [ABSTRACT FROM AUTHOR]

[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]