Innovative fluorescent ratiometric probe from Oolong tea dreg for highly sensitive bilirubin detection

• Fluorescent ratiometric sensor from Oolong tea dreg for bilirubin detection. • Partial transformation of biomass-sourced chlorophyll into carbon dots. • Low detection threshold, heightened accuracy, and selectivity in bilirubin assessment. • Satisfactory recovery rates when tested with artificial urine and human urine. Bilirubin, a crucial component in heme degradation, is formed during the breakdown of red blood cells in the liver and spleen. Elevated bilirubin levels are closely associated with jaundice and serve as markers for various blood and liver-related disorders. Detection of BR has been approached through various methods with fluorescent methods gaining prominence due to their exceptional sensitivity, rapid response, and precision. Among the fluorescence methods, carbon dots have emerged as versatile optical probes, known for their unique optical properties, low toxicity, and ease of synthesis. However, carbon dots typically exhibit a single emission peak, limiting accuracy due to vulnerability to external interferences. To overcome this limitation, probes featuring multiple independent emission signals are preferred. Chlorophyll, abundant in nature and sourced from biomass, is recognized for its safe and fluorescent properties, making it a secure choice for fluorescence-based sensing. This study introduces an innovative approach utilizing Oolong tea dreg as a source of chlorophyll for creating a fluorescent probe to detect bilirubin. Chlorophyll was partially converted into carbon dots using a combination of extraction and hydrothermal techniques, producing a ratiometric probe with two emission signals. The fluorescence of the probe was quenched in the presence of the bilirubin through the inner filter effect. The proposed probe exhibited outstanding selectivity and a low limit of detection (0.8 µM) for bilirubin. Furthermore, the probe demonstrated satisfactory recovery rates when tested with artificial urine and human urine samples.