Er3+/Yb3+ doped graphene quantum dots: an upconversion strategy for photodetection of glioblastoma

This study focused on optimizing the doping of GQDs with rare-earth to obtain nanoparticles that can permeate the brain and be excited in the red or infrared region. Apart from the structural characterization, the absorption spectra show the characteristic band of the π-π* transitions in the graphene structure, with a maximum around 430 nm. The luminescence spectra confirmed that doping with the Er³⁺/Y³⁺ pair at different ratios results in fluorescence emission via upconversion effect, starting from excitation at 980 nm. These findings reinforce the potential use of rare-earth-doped quantum dots as photodiagnostic agents, ensuring excitation in a region of high tissue penetration. Preliminary cytotoxicity tests in 2D and 3D models using healthy cells (NIH-3T3) and glioblastoma cells (U87MG) showed that both pure and doped NQGDs exhibited no intrinsic cytotoxicity up to a concentration of 500 μg/mL.