Red dual-emissive carbon dots for ratiometric sensing of veterinary drugs

Carbon dots have been rapidly developed as a kind of luminescent nanomaterials. However, methods for the synthesis of long-wavelength-emissive carbon dots are still not mature enough. Meanwhile, developing a fast and highly sensitive method to detect residual veterinary drugs in food is particularly significant for food safety. Herein, we report the facile fabrication of red-emissive carbon dots (R-CDs) for ratiometric sensing of veterinary drugs. With use of sorbitol and o-phenylenediamine as precursors, R-CDs was prepared via a one-pot solvothermal approach. The resulting R-CDs show mainly excitation-independent and dual-emissive photoluminescence (PL) located at 597 and 645 nm. Meanwhile, the PL quantum yield (QY) of R-CDs without further surface treatment is 33% under 540 nm excitation. Interestingly, the R-CDs exhibit fast fluorescence response to malachite green oxalate (MG oxalate), 1-aminohydantoin hydrochloride (AHD) and pefloxacin, which are abused widely and retained easily in animals. Ratiometric sensing of these veterinary drugs were successfully performed taking the advantage of dual-emissive PL property; the detection limits of MG oxalate, AHD and pefloxacin were 0.79, 0.25 and 0.85 μM, respectively.