In this study, we investigate the upconversion properties of graphene quantum dots (GQDs) doped with Nd³⁺ ions, utilizing benzoate and terephthalate ligands as alternatives to citrate. These ligands enhance the upconversion efficiency of the Nd³⁺-doped GQDs by improving energy transfer processes. We analyze the electronic and band structures of these modified GQDs using density functional theory (DFT) calculations, revealing significant changes in energy band alignment following ligand exchange. Experimentally, we characterize the optical properties of the synthesized GQDs through UV-Vis absorption and photoluminescence spectroscopy. Our results demonstrate an increase in upconversion efficiency, attributed to the electron-donor properties of the ligands and enhancements in energy transfer mechanisms. This study highlights the potential of ligand engineering to optimize the optical performance of GQD-based materials for applications in photonics, sensing, and bioimaging.

up conversion,graphene,Quantum dots,Doping