Metal-triggered fluorescence enhancement of multicolor carbon dots in sensing and bioimaging

Abstract In this paper, two multicolor CDs have been prepared with eco-friendly folic acid and glucose as precursors by means of a facile hydrothermal strategy. The microscopic and spectroscopic results comprehensively confirmed that both of them exhibited well-defined spherical particles, amorphous structures and similar surface chemistry properties, but with different lateral dimensions and element contents. Moreover, CDs1 and CDs2 show the favorable biocompatibility and low cytotoxicity, in vitro and in vivo CLSM images of HeLa cells and zebrafish larvae tagged with CDs1 and CDs2 revealed multicolor emission (blue, green and red) at different excitation wavelengths. More importantly, the fluorescence of CDs1 could be remarkably enhanced with the increase of Mn 2+ concentration in aqueous solution through the bonding of Mn 2+ with C–OH and N–H groups on the surface of CDs1. A wide linear range was obtained from 0.5 to 90  μ M with a detection limit of 0.42  μ M.