Optimizing Carbon Dots for red/NIR-Fluorescence with Nitrogen and Fluorine Doping*

Carbon dots (CDs) are nano-sized particles with a core-shell structure that utilize quantum confinement to fluoresce, similar to the well-known quantum dots (QDs). Both QDs and CDs have seen implementation in biological applications, such as biomarkers and biosensors, with limited success. Thus, the goal of this project is to investigate how changing the elemental composition, such as nitrogen, fluorine, and other dopants in the system, alters photophysical properties of CDs in a systematic fashion leading to properties such as increased quantum yield or desirable shifting of fluorescence excitation and emission thereby expanding the potential use of CDs as safe yet effective alternatives for biotechnology applications. Unlike QDs, CDs have shown promise as they exhibit enhanced water solubility, low cytotoxicity, and tunable fluorescence. Furthermore, as CDs are based on carbon-based derivatives, they are not limited in terms of toxicity, unlike most QDs. CD fluorescence can be tuned by doping the surface of CDs. Nitrogen and fluorine are commonly used to increase the quantum yield and redshift the excitation/emission spectra. Although CDs show promise in biological applications, further work is needed to enhance their quantum yield for optimal effectiveness.