Preparation of\nRed-Emitting CDs for Glioma Imaging\nand Fe<sup>3+</sup> Sensing

Red-emitting fluorescent carbon dots (CDs) have garnered\nsignificant\nattention due to their wide-ranging applications in biological fields.\nHowever, challenges such as complex precursors, labor-intensive preparation\nprocesses, and low quantum yields have hindered their broader utilization.\nIn this study, we developed a simple and efficient solvothermal method\nto synthesize fluorescent CDs with tunable emission wavelengths using\naniline derivatives as precursors. The emission wavelengths of the\nsynthesized CDs were influenced by the functional groups at the <i>para</i>-position of the aniline derivatives with stronger electron-donating\neffects leading to a red shift in emissions. Notably, bright red-emitting\nCDs with a quantum yield of 19.42% and excellent photobleaching resistance\nwere obtained by using <i>p</i>-phenylenediamine as the\nsole precursor. These CDs exhibited sensitivity to Fe<sup>3+</sup> ions, demonstrating a strong linear detection range (<i>R</i><sup>2</sup> = 0.999) from 0 to 50 μM. Additionally, the CDs\nwere uniform in size (2–5 nm), emitted stable red fluorescence\nin pH conditions ranging from 4 to 10, and were successfully internalized\nby glioma cells, enabling precise fluorescence imaging of gliomas\nboth in vitro and in vivo.