New progress in controlling optical properties of graphene quantum dots based on strong magnetic fields

[ Instrument Network Instrument R & D ] Graphene quantum dots (GQDs) are two-dimensional nanomaterials with small size. In recent years, due to its stability, biocompatibility, fluorescence tunability, and easy removal by the kidney, it has been widely used in cancer diagnosis and treatment integration, and has attracted great attention in the field of biomedicine. The optical absorption of GQDs currently used in photothermal therapy is mainly concentrated in the near infrared region. However, the absorption and scattering of skin and tissue make the laser penetration depth of the near-infrared region and the light intensity reaching the target area greatly reduced. Existing methods for adjusting the optical absorption of GQDs (doping, passivation, and other surface post-treatments) are difficult to adjust to the near-infrared region.
Recently, researcher Wang Hui from the High Magnetic Field Science Center of the Chinese Academy of Sciences, Professor Chen Qianwang of the University of Science and Technology of China, and Professor Nie Rongrong of Nanjing University, etc., started with the control of the optical absorption performance of GQDs, using phenol as the precursor and hydrogen peroxide as the oxidant. GQDs-9T-GQDs with near-infrared two-zone optical absorption performance were developed. Compared with GQDs synthesized under non-magnetic field (0T-GQDs), 9T-GQDs showed obvious near-infrared two-zone optical absorption performance (1070 nm). At the same time, 9T-GQDs has a fluorescence quantum yield of 16.67% and a photothermal conversion efficiency of 33.45%.
In vivo realization proves that 9T-GQDs has a significant inhibitory effect on tumor growth in mice in the near-infrared two-zone photothermal cancer therapy guided by fluorescence imaging. The relevant results were published in the international journal Biomaterials under the title "Magnetic-induced graphene quantum dots for imaging-guided photothermal therapy in the second near-infrared window".
The research work was supported by the National Natural Science Foundation of China, Hefei Research Institute Start-up Fund, Hefei University Science Center Collaborative Innovation Cultivation Fund, Chinese Academy of Sciences Key Laboratory of Photovoltaic Materials and Energy Saving, and Anhui Key Laboratory of Medical Physics and Technology. The experimental data under the relevant magnetic field were collected on a steady-state strong magnetic field experimental device.
Schematic diagram of the mechanism of GQDs formation in the presence or absence of a magnetic field

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