PH-TUNABLE DUAL-TARGET FLUORESCENT SENSOR FOR SELECTIVE DETECTION OF TARTRAZINE AND ASCORBIC ACID USING N/O-DOPED CARBON QUANTUM DOTS

Abstract

Fluorescent detection of multiple analytes requires dual-target fluorescent sensors in complex environments for precise monitoring. The synthesize nitrogen/oxygen-doped carbon quantum dots (N/O-CQDs) under hydrothermal conditions by incorporating cranberry extract with urea and citric acid as a sustainable precursor effective surface passivation. N/O-CQDs produced by optimized conditions reached an 18.6% quantum yield and maintained strong chemical stability while showing excellent photostability. The successful passivation of functional groups (-NH₂, -OH, -COOH) were confirmed on the surface through analysis by UV-Vis spectroscopy, fluorescence spectroscopy, X-ray photoelectron spectroscopy (XPS), N/O-CQDs functioned as a dual-target fluorescent sensor at different pH levels to selectively detect TZ and AA while displaying reversible fluorescence quenching. Fluorescence quenching triggered by tartrazine occurred via electrostatic interactions, while ascorbic acid facilitated fluorescence restoration through reduction processes. N/O-CQDs exhibited high sensitivity in quantifying Tartrazine at 32 nm and Ascorbic acid at 86nm, with detection capabilities ranging from 0.5 to 10 μM and 0.5 to 15μM respectively. The study introduces a cost-effective, environmentally sustainable approach for the large-scale production of dual-sensing functionalized carbon quantum dots. N/O-CQDs exhibit exceptional selectivity and sensitivity, indicating significant promise for the development of enhanced monitoring systems in food quality control, environmental protection, and biomedical applications.