Red and Blue Emissive Graphene Quantum Dots for Biomedical Applications

Graphene quantum dots (GQDs) are a promising class of carbon nanomaterials characterized by unique photophysical and photochemical properties, which can be adjusted by using adapt preparation methods. 1 Despite the wide range of synthesis routes suitable for GQDs production, achieving reproducible and properly controllable synthesis remains a challenging task. 2,3 GQDs are characterized by high solubility in water, high biocompatibility, and low toxicity, which determine their wide application in bioimaging, biosensing, drug delivery, diagnosis, and therapy of cancer, and other more. 4-7 Their synthesis was carried out by ultrasonic top-down technique starting from graphene oxide or using a bottom up approach starting from different precursors, including melamine and its polymer, or a mixture of citric acid, boric acid, and urea. The synthesis conditions, as well as ratios of the reagents, were varied to get control over the structure, size, and composition and, as a consequence, their photophysical properties. The nanomaterials from GO presented excitation wavelength-independent photoluminescent behavior in the red region when excited in the range from UV till yellow light (300-550 nm). The emission maximum was observed at 647 nm when irradiated at 400 nm, while the one diriving from the bottom up strategies showed different fluorescence properties, with very interesting quantum yield. These properties let us consider these nanomaterials promising for investigating biological systems both in vitro and in vivo. References 1) Tian et al. Mater. Today Chem. 2018, 10, 221–258. 2) Miao Nano Today. 2020, 33, 100879. 3) Moon et al. Nat. Commun. 2021,12, 5879. 4) Hadad et al. Nano Research, 2021, 14, 674-683. 5) Bayda et al. Nanoscale Adv., 2021, 3, 5183-5221. 6) Ding et al. Carbon, 2020, 167, 322-344. 7) She et al. Carbon, 2022, 191, 636-645.