Biomass-based carbon dots with strong solid-state emission for fingerprint recognition and high-color-rendering WLEDs (CRI > 90)

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Effective suppression of π-π interactions between graphitic carbon cores is crucial for solid-state fluorescence emission by carbon dots. In this study, biomass-based solid-state fluorescent carbon dots (Bio-SSF-CDs) were prepared by a one-step hydrothermal method using dehydroabietic acid as a raw material. The Bio-SSF-CDs consist of a graphitic carbon core and tricyclic phenanthrene moieties on its surface. The Bio-SSF-CDs show concentration-dependent emission and aggregated solid-state fluorescence emission. Femtosecond transient absorption spectroscopy and density functional theory calculations indicated that, as the concentration of Bio-SSF-CDs increases, resonance energy transfer occurs between the graphitic carbon cores and surface groups, leading to a decrease in the band gap energy and thereby promoting long-wavelength emission. When aggregated into the solid state, steric hindrance between tricyclic phenanthrene moieties on the surface of the carbon dots inhibits π-π interactions between the carbon cores. This prevents aggregation-caused quenching and promotes solid-state fluorescence. Exploration of potential optical applications of the Bio-SSF-CDs showed that they can be used in fluorescent inks, for highly sensitive, user-friendly fingerprint recognition, and also to produce a white light-emitting diode with a color rendering index >90.