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• S,N-CDs with excellent photostability and chemo-stability were prepared. • S,N-CDs show fluorometric spectral response to tetracyclines. • S,N-CDs display high sensitivity and selectivity for tetracyclines detection. • The residual tetracycline in fish and pork samples were detected by the S,N-CDs. S,N-doped carbon dots (S,N-CDs) were facilely prepared via a hydrothermal method by using thiourea and citric acid (CA) as precursors. The as-prepared S,N-CDs exhibited high stability in aqueous solution and were applied for fluorometric detection of tetracyclines (TCs). The approach was developed on the basic of the fluorescence of S,N-CDs at 440 nm, which was selectively quenched by TCs through the inner filter effect (IFE) mechanism. Moreover, the fluorescence of TCs with maximum at 600 nm could be used as the internal standard signal, resulting in a fluorometric spectral response. The limit of detection (LOD) was 0.25, 0.39 and 0.26 μM for tetracycline (TC), doxycycline (DC) and oxytetracycline (OTC), respectively. Furthermore, S,N-CDs were successfully utilized for the detection of residual TCs in fish and pork samples with acceptable recovery and good RSD. [ABSTRACT FROM AUTHOR]

A carbon dot (CD)-based fluorometric probe for oxytetracycline (OTC) detection utilizing a Förster resonance energy transfer (FRET) mechanism was firstly developed. Upon addition of OTC, the blue fluorescence of the CDs peaked at 405 nm was quickly quenched, with a new fluorescence peaked at 505 nm attributed to OTC was observed within 30 s. A visual fluorescent color change of the CDs solution from blue to green was discerned under a 365 nm UV light irradiation. The CDs displayed a high sensitivity and selectivity toward OTC with a low detection limit of 0.41 μM. Furthermore, the probe was applied to detect OTC in water, milk, and pork samples with a satisfied recovery. Unlabelled Image • A CD-based fluorometric probe for OTC was developed. • The sensing mechanism is based on FRET. • A low LOD of 0.41 μM was achieved. • Detection OTC in practical samples were demonstrated. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) with blue fluorescence were synthesized through hydrothermal treatment of p -dihydroxybenzene and hydrazine hydrate. The fluorescence of the investigated CDs could be selectively quenched by iron ions (Fe3+) because of the strong metal-ligand coordination and electrostatic interactions between the large amount of hydroxyl, amino, and carboxyl groups on CDs' surface and Fe3+. Interestingly, this non-fluorescent CDs + Fe3+ complex displayed a sensitive and selective turn-on fluorescence toward ampicillin with a limit of detection of 0.70 μM. The sensing process could be observed by naked eyes under the 365 nm UV light irradiation. Importantly, CDs + Fe3+ complex had been successfully applied in the detection of ampicillin in river water. • Fluorescent CDs were synthesized through hydrothermal treatment of p -dihydroxybenzene and hydrazine hydrate. • The fluorescence of CDs was quenched significantly and quickly upon addition of Fe3+. • The quenched fluorescence of CDs could be selectively turned on by the addition of ampicillin. • The CDs-Fe3+ system was successfully applied in the ampicillin detection in river water. [ABSTRACT FROM AUTHOR]