Ofloxacin-Mediated Fluorescence Enhancement of Carbon Quantum Dots for Sensitive and Selective Detection in...

This study introduces an innovative fluorescence enhancement strategy utilizing carbon quantum dots (CQDs) for the ultrasensitive and selective detection of Ofloxacin in pharmaceutical formulations. Synthesized hydrothermally from ascorbic acid, a green, non-toxic precursor, the CQDs exhibit a unique "turn-on" response upon interaction with Ofloxacin, contrasting conventional quenching-based mechanisms. The fluorescence enhancement (22.4% quantum yield) arises from Ofloxacin-induced surface passivation of CQDs, which reduces non-radiative decay pathways, as evidenced by lifetime studies and spectroscopic characterization. Optimized synthesis conditions (180 °C, 8 h) yielded monodisperse CQDs (17-30 nm) with tailored optical properties, validated via TEM, FTIR, XPS, and XRD. Under optimal detection parameters (pH 8.0, 40 °C, 800 µL CQDs), the method achieved a wide linear dynamic range of 0.5-120 µM (y = 0.0186x + 1.0023, R² = 0.9987), with detection and quantification limits of 75 nM and 248 nM (3σ/S and 10σ/S criteria), surpassing HPLC sensitivity by twofold. The quantum yield increased from 22.4% (pristine CQDs) to 28.9% upon Ofloxacin binding, confirming the turn-on mechanism. Rigorous validation per United States Pharmacopeia guidelines demonstrated high accuracy (mean recovery: 100.5 ± 3.4%; range: 96.2-104.8%) and precision (intra-day RSD < 1.8%, inter-day RSD < 2.5%, n = 6). The eco-friendly protocol eliminates organic solvents, aligning with green chemistry principles, while maintaining stability for four weeks at 4 °C. By pioneering a cost-effective, sustainable "turn-on" fluorescence platform, this work addresses critical challenges in pharmaceutical quality control and extends potential applications to clinical diagnostics and environmental monitoring of antibiotic residues.