Nitrogen-doped graphene quantum dots (N-GQDs) are promising biocompatible nanomaterial which has received much attention for biological application. However, the effect of the engineered electronic structure of N-GQDs to the fluorescence of GQDs applied for bio-imaging is still under debate. In this study, N-GQDs were synthesized by a facile one-step hydrothermal method for 10 hours at 180°C and theoretical calculation of electronic structure using density functional theory (DFT) by GAUSSIAN 09, were compared. Single to multilayer of N-GQDs with the particle size of 3.2 nm in average were obtained from hydrothermal synthesis. The optical properties of N-GQDs emitted green photoluminescence (PL) at 525 nm (2.36 eV) with PL excitation (PLE) at 367 nm (3.38 eV). From DFT calculation, the optoelectronic properties of GQDs from HOMO to LUMO differ between edge functionalization and graphitic nitrogen doping. Furthermore, cells cytotoxity showed that N-GQDs possess non-toxic property, and the cells were presented with high viability. In summary, by comparing experimental and theoretical calculations, the electronic properties of N-GQDs could enhance their reactivity in photo-electronics for biological application.

氮掺杂石墨烯量子点（N-GQDs）是有前途的生物相容性纳米材料，在生物应用中受到了广泛关注。然而，N-GQD的工程电子结构对应用于生物成像的GQD荧光的影响仍在争论中。在这项研究中，N-GQDs通过一种简便的一步水热法在180°C下合成10小时，并使用高斯09的密度泛函理论（DFT）对电子结构的理论计算进行了比较。通过水热合成获得平均粒径为3.2 nm的单层至多层N-GQD。N-GQD的光学特性在525 nm（2.36 eV）下发出绿色光致发光（PL），在367 nm（3.38 eV）下发出PL激发（PLE）。根据DFT计算，在边缘官能化和石墨氮掺杂之间，从HOMO到LUMO的GQD的光电性能有所不同。此外，细胞的细胞毒性表明N-GQD具有无毒特性，并且细胞具有高生存力。总之，通过比较实验和理论计算，N-GQD的电子性质可以增强其在生物应用光电学中的反应性。