Smartphone-based fluorescence detection of bilirubin using yellow emissive carbon dots

-phenylenediamine (oPDA) as a precursor. The fluorescence of Y-CDs was quenched with the addition of bilirubin due to the inner filter effect mechanism. The fluorescence intensity of Y-CDs decreases as bilirubin concentration increases and can be completely quenched with approximately 90 μM bilirubin. Over other coexisting interferents (26 interferents), the Y-CD probe exhibited great selectivity for bilirubin. More crucially, a smartphone can capture the visible color intensity change of the Y-CD probe under a 365 nm UV lamp and later with the aid of computer software, RGB (red/green/blue) analysis was performed for the quantification of colors. This provides computer vision-based detection and sensitive bilirubin assay with a linear range of 4.0-225 μM and a limit of detection of 1.37 μM. Furthermore, the proposed fluorescent probe was applied in real samples (newborn serum, serum and urine of adults with hyperbilirubinemia) with satisfactory recoveries (96-102%). Based on the validation findings, solution and computer vision-based methods have the potential to be used as fast detection methods for bilirubin in biological samples at the bedside. For the first time, a fluorescent probe based on yellow emissive CDs and RGB analysis for bilirubin recognition has been reported.