Low-cost smartphone-assisted dual-readout glucose sensing on rosin-patterned paper using Fe(II)/silane-derived carbon dots

A smartphone-assisted dual-readout paper-based sensor was developed by integrating an Fe(II)/silane-derived carbon dot system (Fe(II)/CDs), a rosin-defined hydrophobic detection zone, and Python-based RGB analysis. Glucose was oxidized by glucose oxidase to generate H 2 O 2 , which subsequently initiated the Fenton reaction. In the fluorescence readout mode, the resulting Fe 3+ interacted with amino and/or oxygen-containing groups on the carbon-dot surface, leading to fluorescence quenching. In the colorimetric readout mode, Fe 3+ and hydroxyl radicals promoted the oxidation of TMB to blue oxTMB, while complexation of Fe 3+ with surface functional groups of the CDs might further facilitate H 2 O 2 activation and enhance the colorimetric response. Images from the two readout modes were separately acquired using a smartphone and quantified using the normalized blue-channel fraction, B/(R + G + B). Under optimized conditions, both modes exhibited linear responses to glucose over 0.01–1.00 mM. The fluorescence and colorimetric modes achieved limits of detection of 2.9 and 2.5 µM and limits of quantification of 9.7 and 8.3 µM, respectively. Spike-recovery analysis in tenfold-diluted human serum produced recoveries of 90.00-91.67% for the fluorescence mode and 95.00-105.00% for the colorimetric mode, with relative standard deviations below 3.40% and 4.29%, respectively. Furthermore, the results were auxiliary verified using fluorescence and ultraviolet instruments. The proposed method provides dual quantitative readouts for glucose determination in diluted human serum samples.