Phosphorus and chlorine co-doped carbon dots with strong photoluminescence as a fluorescent probe for ferric ions

Usually, carbon dots (CDs) display a relatively weak fluorescence quantum yield (QY). In order to obtain brighter CDs, phosphorus and chlorine co-doped CDs (P,Cl-CDs) were prepared via hydrothermal treatment of maltose in the presence of phosphoric and hydrochloric acids. The new CDs are highly monodispersed in water solution, have high fractions of P (14.4 atomic%) and Cl (8.9 atomic%), and exhibited yellow fluorescence with a QY of 15%. This is higher than that of monoatomic doped CDs (8.7 and 9.3% for P-CDs and Cl-CDs, respectively). The P,Cl-CDs are highly photostable, and fluorescence is strongly (statically) quenched by Fe(III). Fluorescence decreases with increasing concentration of Fe(III) in the range from 0.1-8.0 μmol⋅L^-1, with a 60 nmol⋅L^-1 detection limit. The doped CDs are shown to be a viable nanoprobe for the fluorometric determination of Fe(III) in spiked serum and water samples. Graphical abstract Schematic presentation of one-step synthesis of phosphorus and chlorine co-doped carbon dots with high photoluminescence for the detection of ferric ions.