Tuning Optical Properties of Carbon Dots by Co-doping Strategy for Versatile Applications

Graphical A green one-step hydrothermal method has been successfully used to prepare carbon dots (CDs) by selectively co-doping nitrogen, phosphorus and sulphur elements. For the sensitive detection of iron ions, a fluorescence quencher sensor based on nitrogen- and sulphur-doped carbon dots (red NS-CDs) has been developed, because of the good optical properties and bio-histocompatibility of green NPS-CDs and blue NP-CDs, They are observed to penetrate NCl−H292 cells, fluorescing green and localizing in the cytoplasm. Carbon dots (CDs) with tunable photoluminescence was successfully prepared via selective co-doping of three elements, including nitrogen, phosphorus and sulfur element by green one-step hydrothermal method. Nitrogen-sulfur-doped CDs (red NS-CDs), which emitted red fluorescence under UV excitation, were used to detect iron ions in the linear range 1–50 μM, yielding detectable limits as low as 94 nM. The nitrogen-phosphorus-doped CDs (blue NP-CDs) exhibited blue fluorescence with quantum yields up to 34.5 %. When the concentration is 800 μg/mL, it showed excellent anticancer effect in vitro. The nitrogen-sulfur-phosphorus-doped CDs (green NPS-CDs) emitting green fluorescence showed a low cytotoxicity at a high concentration of 800 μg/mL and were used for intracelluar imaging of NCl−H292 cells. This study demonstrated the photoluminescent characteristics of carbon dots (CDs) and highlighted the ability to modify their peak fluorescence emission wavelengths through the flexible combination of specific reagents under comparable hydrothermal conditions. Additionally, it provided valuable insights into the efficient methodologies for synthesizing CDs suitable for various application scenarios.