Single precursor-based luminescent nitrogen-doped carbon dots and their application for iron (III) sensing

Iron III (Fe3+) sensing is of great importance for monitoring its levels in different environmental and biological systems since its levels are tightly associated with many environmental concerns and serious diseases. Compared to the ordinary Fe3+ detection methods involving the sophisticated and expensive instruments, the use of fluorescent materials with short response time and low cost attracts much attention. Amongst a variety of fluorescent materials, a nitrogen-doped carbon dot (N-CD) is emerging as promising luminescent materials for biosensing due to their superior photoluminescent properties, good water solubility, and biocompatibility. Herein, N-CD prepared via a green and cost-effective one-pot hydrothermal method using a new single precursor N-(2-hydroxyethyl) ethylenediamine triacetic acid (HEDTA) as both the carbon and nitrogen sources is reported. The blue fluorescent emission of N-CDs is quenched by the addition of Fe3+, and the quenching intensity is concentration dependent in the wide range (0.76–400 μM) with a detection limit of 0.16 μM. The quantum yield for the as prepared N-CDs is 14.17%. The N-CDs also show a high selectivity for Fe3+ chelation amongst a range of biological metal ions. The fluorescent quenching is attributed to the formation of the coordinate covalent bonds between the Fe3+ and N-CDs, and the mechanism is proved to be a static type on the basis of the photoluminescence lifetime and the temperature-dependent fluorescent intensity change. Our eco-friendly and simple strategy will benefit the application of CDs in various fields. Keywords: N-(2-hydroxyethyl) ethylenediamine triacetic acid (HEDTA), Nitrogen-doped carbon dot (N-CD), Metal sensing, Iron III, Quenching mechanism