Samarium Doped ZnO Nanorods Anchored on Graphitic Carbon Nitride Sheets as a Fluorometric Sensor for Sunset Yellow and Tartrazine

Azo dyes such as Tartrazine (Tz) and Sunset Yellow (SY) are extensively used in food and consumer products, but their overuse poses significant health and environmental risks. Developing simple and reliable detection methods for dyes is, therefore, crucial. In the present study, Samarium-doped zinc oxide (Sm-ZnO) nanorods anchored on graphitic carbon nitride (gCN) sheets were synthesized via a hydrothermal route and further applied as a fluorometric sensor for Tz and SY. The gCN/Sm-ZnO hybrid showed strong blue fluorescence, which underwent pronounced quenching upon interaction with the dyes through a combination of the inner filter effect (IFE) and static quenching mechanisms. The probe showed excellent photostability and long-term thermal stability, retaining its fluorescence intensity even after prolonged irradiation and storage under varied temperature conditions. The sensor exhibited remarkable sensitivity, achieving detection limits of 0.164 µM for Tz and 0.305 µM for SY. To exemplify its practical utility, the probe was successfully applied to real-world matrices such as turmeric powder, soft drinks, cosmetics (face wash), and jellies, yielding high recovery rates of 93.33%-105.42% with good reusability. The synergistic combination of Sm-ZnO nanorods and gCN sheets enhanced charge transfer and amplified the fluorescence quenching response, offering a cost-effective and robust approach for monitoring synthetic colorants in complex samples.