Visual and conventional Off-On mode platform for detection of Ofloxacin in water and Eye-Drop using fluorescence enhancement and redshift of Sumac-Derived carbon dots

Ofloxacin (OFL), a broad-spectrum fluoroquinolone antibiotic, is widely utilized for treating bacterial infections. Accurate detection of OFL is essential for pharmaceutical quality control and environmental monitoring, particularly in wastewater. This study introduces a novel fluorescence-based detection method using sumac-derived carbon dots (S-CDs), synthesized via a simple hydrothermal approach. The S-CDs exhibited spherical morphology (20–30 nm) with blue fluorescence emission and a quantum yield of 1.4 %. Upon interaction with OFL, a remarkable fluorescence enhancement was observed, resulting in a 45-fold increase in quantum yield (45.0 %) accompanied by a red shift in the emission. This strong enhancement and red-shift emission enabled to design off–on mode for detection of OFL. The fluorescence intensity showed a strong linear correlation with OFL concentration (R 2  = 0.98) in the range of 1–90 nM, with a limit of detection (LOD) of 0.7 nM and a limit of quantification of 2.3 nM. Furthermore, a smartphone-assisted visual detection method was developed based on an off–on fluorescence mechanism. RGB analysis enabled real-time quantification of OFL, exhibiting a linear detection range of 20–80 µM with an LOD 0.97 µM. The method was successfully applied to detect OFL in eye drop formulations and tap water, demonstrating high accuracy and precision. These findings underscore the potential of S-CDs as a cost-effective, portable, and efficient tool for OFL detection, suitable for pharmaceutical and environmental monitoring applications.