Portable smartphone-based detection integrated with paper based device functionalised with green emissive carbon dots for selective determination of Fe3+ ions

Abstract

ABSTRACT In this paper, a smartphone-assisted detection integrated with paper-based analytical device (PAD) functionalised with green emissive carbon dot (g-CDs) has been designed for on-site selective detection of Fe3+ ions. g-CDs have been prepared by one-step hydrothermal process using 4-aminophenol and ethylenediamine (EDA) as precursors. g-CDs were highly stable for more than three months in aqueous solution with a strong green emission, λem at 513 nm and 30.33% as a fluorescence quantum yield. Interestingly, Fe3+ selectively quenched the fluorescence intensity of the g-CDs and the quenching mechanism can be attributed to static quenching. Furthermore, under the optimal conditions, using conventional fluorimetry, the g-CDs could detect Fe3+ ions with a linear relationship from 0 to 90 μM (R2 = 0.9970) and the limit of detection was 0.35 μM. Visual mode integrated with smartphone detection on PAD was successfully prepared after loading g-CDs on the paper. The fluorescent colour variations of g-CDs on PAD were monitored under the UV lamp using smartphone for capturing images. The green channel intensities of images of the circle zones were processed using Colour Grab App for the RGB analysis. A linear working range was obtained from 0 to 0.8 mM, and the limit of detection was 0.05 mM. The PAD was used successfully for the detection of Fe3+ ions in human serum with a recovery from 87.93% to 96.86%.