Green synthesis and multifunctional applications of nitrogen-doped carbon quantum dots via one-step hydrothermal carbonization of Curcuma zedoaria.

Low-dimensional (<10 nm) semiconductor carbon quantum dots (CQDs) have been widely used in metal ion sensing and bioimaging. Here, we used the renewable resource Curcuma zedoaria as a carbon source and prepared green carbon quantum dots with good water solubility by a hydrothermal method without any chemical reagent. At different pH values (4-6) and high NaCl concentrations, the photoluminescence of the CQDs was very stable, which indicated that they were suitable for a wide range of applications even under harsh conditions. The CQDs exhibited fluorescence quenching in the presence of Fe3+ ions, indicating their application potential as fluorescence probes for the sensitive and selective detection of Fe3+ ions. The CQDs showed high photostability, low cytotoxicity, and good hemolytic activity, and were successfully applied to bioimaging experiments, i.e. multicolor cell imaging in L-02 (human normal hepatocytes) and CHL (Chinese hamster lung) cells with and without Fe3+, as well as wash-free labeling imaging of Staphylococcus aureus and Escherichia coli. The CQDs also showed good free radical scavenging activity and demonstrated a protective effect against photooxidative damage to L-02 cells. These results indicate that CQDs obtained from medicinal herb sources have multiple potential applications in the fields of sensing, bioimaging, and even disease diagnosis.

Nitrogen-doped carbon dots/curcumin nanocomposite for combined Photodynamic/photothermal dual-mode antibacterial therapy.

Due to their excellent photophysical properties, carbon quantum dots have great potential in biomedical and drug delivery fields. In this study, nitrogen-doped carbon quantum dots with good water solubility were prepared using citric acid and ethylenediamine as precursors, and compounded with curcumin, a photosensitive component, to produce composite nanomaterials with photodynamic therapy and synergistic photothermal therapy. The formation of nitrogen-doped carbon quantum dots and composite nanomaterials was verified using physical and optical means. In addition, the composite nanomaterials produced single-linear oxygen and exacerbated the increase of solution temperature under blue (405 nm) and near-infrared (808 nm) light irradiation, respectively. The plate counting method showed that the composite nanomaterials exhibited good photodynamic synergistic photothermal antibacterial properties against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus under dual light source (405+808 nm) irradiation, which improved the photoinactivation of curcumin against bacteria. In addition, the composite nanomaterials exhibited low toxicity and good hemocompatibility. These experimental results suggested that the composite nanomaterials showed great potential in a multimodal photodynamic therapy synergistic photothermal treatment platform.