Lemon juice-derived nitrogen-doped carbon quantum dots for highly sensitive and selective determination of ferrous ions and cell imaging

Ferrous ion (Fe2+) plays an important role in a large number of chemical and biological processes in living organisms. So, the accurate and rapid determination of Fe2+ in environmental and biological systems is an important issue. In this paper, N-CDs with uniform particle size, outstanding water solubility, favorable stability, high quantum yield (QY, 58.66 %) and excellent photoluminescence performance were prepared by one-step hydrothermal method using biomass lemon and ethylene diamine. The N-CDs showed a bright blue fluorescence under UV light. This new type of N-CDs can be used to effectively detect Fe2+ with high selectivity and sensitivity. It displayed a fine linear relationship in the range of 2-625 & mu;\M with the LOD of 0.063 & mu;M under optimum conditions. The possible fluorescence quenching mechanism can be ascribed to the static quenching (SQ) and internal filtration effect (IFE) for Fe2+. More importantly, the optical imaging performance and cytotoxicity of N-CDs were also demonstrated. The results showed that N-CDs owned low cytotoxicity and glorious biocompatibility, and could be used as a biological imaging agent for labeling Hela cells. Therefore, this study possesses expansive application prospects in environmental monitoring and bioanalysis.