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Particularly in recent years, fluorescence carbon dots (CDs) were in the central point of scientist's focus. However, some difficulties may exist concerning CDs. For example, their targeting by other analytes usually goes wrong due to the absence of specific recognition groups on the surface of CDs. Furthermore, due to low quantum yield, they cannot be conducive to bioimaging. Additionally, they do not have biological functionality that originated from poor interaction with biological agents. For improvement of the luminescence properties and extending of new applications for CDs, the functionalisation of CDs has attracted many interests. Functionalised CDs have promising applications. The present paper has reviewed different published reports considering applications of functionalised CDs. In this comprehensive article, first the functionalisation mechanisms of CDs are discussed. Then, the functionalised CDs for detection applications including biochemical and chemical detections are reviewed. After that, functionalised CDs for diagnostic applications are reviewed. In this part functionalised CDs for fluorescence imaging probes, functionalised CDs for surface-enhanced Raman scattering (SERS) imaging and functionalised CDs for photoacoustic imaging probes are discussed. Later, functionalised CDs for disease treatment including drug delivery and photothermal therapy applications are reviewed to elucidate the importance of their function in cancer treatment. Finally, the applications of functionalised CDs for water desalination are reviewed.

No abstract

Carbon dots (CDs) are an emerging family of nanostructures due to their unique optical properties, high chemical stability, biocompatibility, and low toxicity, they have been able to attract a lot of attention and cause significant changes in various scientific fields. In this study, the green synthesis of stable CDs by hydrothermal and pyrolysis methods (H-CDs and P-CDs) is performed from Nigella sativa seeds as a natural precursor. Using these methods, the formation and the surface passivation of the CDs are done simultaneously, resulting in the intrinsic fluorescence emission. The as-prepared CDs are characterised by UV-vis spectroscopy, fluorescence spectroscopy, elemental analysis, dynamic light scattering, Fourier transform infrared spectroscopy, and transmission electron microscopy, from which their structural information and property are interpreted. The fluorescence intensity graph of H-CDs and P-CDs, with excitation wavelengths in 360 nm, shows the highest emissions at 430 and 410 nm, respectively. Particle size distribution was obtained at about 4 nm. The fluorescent quantum yield (QY) of H-CDs and P-CDs was measured to be 7% and 2%, respectively. The synthesised CDs showed good photoluminescence (PL) responses to acetone solution. Acetone had a different effect on the PL properties of CDs obtained from pyrolysis and hydrothermal methods so that in P-CDs, it increased the intensity of PL, and in H-CDs; it decreased the intensity of PL.