Sustainable-biomass-derived multifunctional carbon dots as fluorescent probes for multi-purpose advanced imaging, migration and security solutions

초록

Multifunctional tunable-emissive carbon dots (ME-CDs) were hydrothermally synthesized and characterized for their structural, morphological, and optical properties, as well as their applications in biological imaging and anti-counterfeiting. Scanning electron microscopy revealed uniformly dispersed wrinkle-shaped particles, while high-resolution transmission electron microscopy confirmed sizes below 5 nm. Energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy validated the carbon-dominant composition, with functional groups essential for biological interactions. Raman spectroscopy showed a partially disordered graphite-like structure with a 0.72 D/G intensity ratio, and Fourier-transform infrared spectroscopy identified surface functionalities. The UV-vis absorption spectrum exhibited characteristic pi-pi* and n-pi* transitions at 280 nm and 340 nm, while fluorescence studies demonstrated strong excitation-dependent emission suitable for imaging. ME-CDs showed remarkable stability, maintaining fluorescence intensity over 200 days and under UV irradiation. As fluorescent ink, they displayed clear visibility under UV light and prolonged durability. Biocompatibility studies confirmed non-toxicity, enabling effective labeling of fibroblasts and human mesenchymal stem cells (HMSCs) with confocal visualization. ME-CDs also penetrated 3D HMSC spheroids, providing multicolor fluorescence without affecting cell viability, and efficiently tracked macrophage migration. The robust optical properties, biocompatibility, and durability of ME-CDs underscore their potential for long-term applications in bioimaging and anti-counterfeiting.

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