Sesame-derived ions co-doped fluorescent carbon nanoparticles for bio-imaging, sensing and patterning applications

Fluorescent carbon nanoparticles (FCNPs) are promising fluorescence probes with potential applications in sensors, bio-imaging, photo-catalysis, ion detection, fluorescent inks and other areas, mainly due to their high stability, low toxicity and cost-effectiveness. However, the relatively low quantum yield (QY) and complex synthesis routes usually hinder their applications. Here, highly efficient FCNPs doped with N, P and Ca ions have been prepared via a simple hydrothermal process using green natural raw materials of sesame as precursors. The products emit strong blue fluorescence with QY as high as 48.5% under 360 nm excitation due to the improved electronic characteristics and abundant defect sites induced by natural N, P and Ca ions co-doping. The bright fluorescence, high photostability, ultralow toxicity and good biocompatibility endow as-prepared FCNPs with great potential applicatios in bio-imaging and patterning. Most importantly, as-prepared FCNPs exhibit an extraordinarily high sensitivity and selectivity to Fe³⁺ ions compared to other metal ions in aqueous solution. The fluorescence intensity is inversely proportional to the concentration of Fe³⁺ ions, and the calibration curve displays linear regions over the range of 0–90 nM with a low limit of detection (LOD) of 1.5 nM. Meanwhile, it shows a “turn-on” fluorescence response to F⁻ with good linearity at 10–60 nM and a LOD of 2.4 nM. These results indicate that FCNPs, as a fluorescent sensing platform, could meet the selective requirements for biomedical analysis and environmental monitoring.