Fluorescent nanoprobe for detection of naproxen based on doped carbon dots prepared in choline chloride-thiourea deep eutectic solvent

Choline chloride-thiourea deep eutectic solvent (DES) was prepared and used to microwave-assisted synthesis of nitrogen, sulfur, and chloride doped carbon dots (N, S, Cl-CDs). In this innovative approach, DES is a solvent and a doping agent. The synthesized carbon dots (CDs) were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), transmission electron microscopy (TEM), ultraviolet-visible (UV-Vis), and fluorescence spectroscopy. The average size of N, S, Cl-CDs was 7 nm. The N, S, Cl-CDs had a quantum yield of 26.5% as the result of heteroatoms doping in CDs. The method was based on quenching of the fluorescence intensity by Fe3+ interaction with CDs and then N, S, Cl/CDs + Fe3+ system displayed a sensitive and selective turn-on fluorescence in the presence of naproxen. Linear range and detection limit for naproxen were 0.05-70 mu M and 25 nM, respectively. Applicability of this nanoprobe was tested in naproxen determination in pharmaceutical tablets and the method was validated by high-performance liquid chromatography. The mechanism was also studied.

Automated summary

Choline chloride-thiourea deep eutectic solvent (DES) was used to synthesize N, S, Cl-doped carbon dots (CDs) through a microwave-assisted method. The synthesized CDs were characterized by various techniques and had an average size of 7 nm. The doping of heteroatoms resulted in a quantum yield of 26.5%. The CDs exhibited sensitive and selective turn-on fluorescence in the presence of naproxen, with a linear range of 0.05-70 μM and a detection limit of 25 nM. The applicability of this nanoprobe was validated in the determination of naproxen in pharmaceutical tablets.