Nature-Driven N,S-Highly Fluorescent Carbon Dots as Turn-Off Fluorescent Nanosensors for Determination of Tinidazole in Pharmaceutical Dosage Form and in Biological Fluid.

This work represents a highly sensitive, low-cost, and eco-friendly method that relies on using onion and lemon juices, which are easily available materials. It depends on the synthesis of highly fluorescent carbon dots (λex/em 350.0-430.0 nm) using a one-step microwave-assisted carbonization method. Characterization of the formed carbon dots was performed using transmission electron microscopy (TEM), Fourier transform infrared (FTIR), Zeta potential analysis, fluorescence spectroscopy UV-Visible spectroscopy, and X-ray photoelectron spectroscopy (XPS). The formed carbon dots appeared to be spherical in shape, with a 2.0- to 3.5-nm average particle size. The synthesized carbon dots were used for the determination of tinidazole by static fluorescence quenching mechanism and inner filter effect. The quenching effect on the synthesized carbon dots' fluorescence signal was utilized for the determination of tinidazole in pure form in concentration samples (2.0-30 μM) with a %recovery of 99.86 ± 1.38 in pure form, 100.0 ± 1.67 in tablet and 99.56 ± 4.18 in urine. The validity of the method was assessed according to the recommendations of the International Conference on Harmonization. The greenness of the method was evaluated using different greenness assessment tools. The proposed probe is eco-friendly due to using water as the only solvent in the absence of other organic solvents.