High quantum yield nitrogen-doped carbon quantum dots: Green synthesis and application as “on-off” fluorescent sensors for specific Fe3+ ions detection and cell imaging

A nitrogen-doped carbon quantum dots (N-CQDs)-based “on-off” fluorescent nanosensor was profitably synthesized through one-pot hydrothermal treatment of citric acid and o-phenylenediamine for the determination of Fe3+ and imaging towards cancerous cells in vitro. The synthesized N-CQDs exhibited excellent photoluminescence and favorable biocompatibility. The excitation-dependent fluorescence emission spectra were observed and the maximum emission wavelength was 483 nm at the excitation wavelength of 420 nm. The fluorescent N-CQDs had a selective and sensitive response to Fe3+ with a limit of detection of 0.177 μM and an allowable detection range of 0–110 μM. The sensor was applied for the determination of Fe3+ ions in tap water with satisfactory results. Moreover, the N-CQDs provide a practical and promising method for cellular imaging due to their excellent fluorescence potency and negligible cytotoxicity.