S,N-Doped carbon dots for tetracyclines sensing with a fluorometric spectral response

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.