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Jénnifer Gómez, Manuel Vázquez Sulleiro, Anna Dolečková, Naděžda Pizúrová, Jiřina Medalová, Antonín Bednařík, Jan Preisler, David Nečas, Lenka Zajíčková

Structure elucidation of multicolor emissive graphene quantum dots towards cell guidance

Materials Chemistry Frontiers 6 (2022) 145-154

Graphene quantum dots (GQDs) can become excellent bioimaging tools when tuned to emit at larger wavelengths due to the minimal tissue absorbance and emission in this range. Tuning the GQDs structure can help, but understanding the chemical structure responsible for their properties remains challenging. Herein, we concluded on the structure of GQDs synthesized from glucose and ammonium hydroxide by fast microwave-assisted hydrothermal protocol. Remarkably, these GQDs exhibited emission from the NUV-Vis up to the NIR range. The structure and chemical composition was elucidated with advanced NMR techniques, such as dimensional nuclear magnetic resonance, combined with the traditional spectroscopies and electron microscopies. The graphitic core composed of pyrazines presented localized defects and lower rotation mobility compared with their edges that mainly were formed by hydroxyls, acids, and amines functional groups, which paved the way for the multicolor red-shift observed fluorescence emission. Confocal laser scanning microscopy revealed functioning cell imaging in a wide spectral range from bright purple to red fluorescence, confirming the uptake of GQDs by the cells without any observable toxicity. The non-cytotoxicity was further proved by the chemiluminescent cell viability adenosine triphosphate (ATP) assay. Combined with the tunable GQDs emission, it gives them the potential as bioimaging carriers starting a new phase for their use in vivo.

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DOI: 10.1039/D1QM01126J

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