Smartphone-based sensing and and imaging of Mn() based on nitrogen-doped red fluorescent carbon dots

Smartphone-assisted visual assay platform provides novel insight for the real-time in-field quantitation of intended analytes in resource-insufficient areas. Herein, nitrogen-doped red fluorescent (FL) carbon dots (R-CDs) were developed for the timely on-site quantitation of Mn( vii ) using the smartphone-assisted assay platform. R-CDs, possessing a desirable bright red FL at 616 nm under a 470 nm excitation, were fabricated through hydrothermal treatment adopting passion fruit and neutral red as precursors. Interestingly, bright red FL at 616 nm are gradually quenched upon introducing Mn( vii ) based on the inner filter effect, concurrently accompanying with significant FL color variation from bright red to dark red. Inspired by the above-mentioned phenomena, hue-saturation-values (HSV) of real-time captured images could be precisely quantified through a color recognition APP within the smartphone, of which the V/S values could be employed to quantify Mn( vii ) with a linear range of 50-400 μM. Furthermore, confocal fluorescence imaging of HeLa cells and zebrafish larvae demonstrates that R-CDs could be employed for the visual determination of Mn( vii ) in vivo and in vitro , illustrating that R-CDs possess powerful practical application prospect in biosystem. Schematic diagram of synthesis and application of R-CDs for visual quantification and bioimaging of Mn( vii ).