Photoluminescent lignin hybridized carbon quantum dots composites for bioimaging applications

Carbon quantum dots (CQDs) have attracted considerable interests because of their unique luminescence properties and promising applications in bioimaging. Lignin hybridized CQDs (L-CQDs) are facilely synthesized by one-pot hydrothermal method with different molar ratios of citric acid and ethanediamine. The morphology and chemical structures of L-CQDs are investigated by TEM, FT-IR, XPS, 2D-HSQC NMR spectra. The resultant L-CQDs with near spherical morphology are less than 10 nm in diameter, which are essentially composed of main interunit linkages and aromatic ring structures. The L-CQDs exhibit the excitation-dependent photoluminescence behavior with emission maximum ranging from 454 to 535 nm under excitation at 375-460 nm. The maximum emission of the L-CQDs red-shift to a longer wavelength with a decrease in intensity as the excitation wavelengths are gradually increased. L-CQDs show the low cytotoxicity and good cellular biocompatibility, demonstrating the great potential of the L-CQDs for bioimaging applications.