Nitrogen-doped carbon dots as a fluorescence probe suitable for sensing Fe3+ under acidic conditions

To obtain nitrogen-doped carbon dots (N-CDs) for sensing Fe3+ under acidic conditions, robust and highly fluorescent N-CDs were prepared by one-pot hydrothermal treatment of dopamine and ethylenediamine. The N-CDs have a relatively uniform size of approximately 4.9 nm and good water dispersibility. The N-CDs exhibit strong visible fluorescence (ca. 497 nm) and high stability at low pH (i.e. 2–3). The FTIR spectra and the XPS analyses indicated that primary amines and distinctive catechol groups exist on the surface of the N-CDs. The FTIR spectra further prove that the catechol groups on their surfaces can be oxidized to the quinone species by Fe3+, contributing to fluorescence response to Fe3+. Thus, the N-CDs as fluorescence probes allowed the detection of Fe3+ under acidic conditions, which has been verified in this work.