Green one-pot synthesis of nitrogen and sulfur co-doped carbon quantum dots as new fluorescent nanosensors for determination of salinomycin and maduramicin in food samples

•The first direct spectrofluorimetric analysis of SAL and MAD without pre-derivatization.•A simple hydrothermal synthesis and characterization of highly fluorescent N,S-CQDs.•N,S-CQDs as fluorescent nanosensors for analysis of SAL and MAD in six raw matrices.•Determination of cited drugs based on quantitative fluorescence quenching of N,S-CQDs.•Method validation in accordance to ICH guidelines was performed. A simple green hydrothermal method was proposed for synthesis of highly fluorescent nitrogen and sulfur co-doped carbon quantum dots (N,S-CQDs) using citric acid and thiosemicarbazide. The produced N,S-CQDs were subjected to extensive spectroscopic characterization and applied as fluorescent nanosensors for the sensitive spectrofluorimetric determination of salinomycin and maduramicin directly without prior derivatization for the first time. The obtained N,S-CQDs showed strong emission band at 430 nm after excitation at 360 nm. The native fluorescence of N,S-CQDs was found to be quenched by the addition of increased concentrations of each drug. Method validation revealed a wide linear relationship between the fluorescence quenching of N,S-CQDs and the concentration of each drug in the range of 10.0–300.0 μM with detection limits of 2.07 μM and 1.34 μM for salinomycin and maduramicin, respectively. The developed method has been efficiently applied for estimation of analytes in six raw matrices with high recoveries.