Surface modification of nitrogen-doped carbon quantum dots for enhanced functionalities
Pham Van Duong, Le Anh Thi, M. D. Hieu, Thi Thu Huong Le, Duc Toan Nguyen, Hong Minh Pham, Trong Tuyen Nguyen, Nguyễn Đình Lâm, Minh Hoa Nguyễn, Thanh Binh Nguyen
Abstract
A facile and controllable one-step atmospheric pressure microplasma method was employed to synthesize nitrogen-doped carbon quantum dots (N-CQDs) with tunable optical properties. The N-CQDs were characterized using Fourier transform infrared spectroscopy, high-resolution transmission electron microscopy, UV‒Vis absorption spectroscopy, and photoluminescence spectroscopy. HRTEM revealed uniformly distributed spherical nanoparticles with a graphite-like structure. FTIR confirmed effective nitrogen doping, enhancing chemical stability. UV‒Vis spectroscopy revealed redshifted absorption peaks, indicating improved electronic interactions and a reduced bandgap (4.05 eV) compared to those of undoped CQDs (4.18 eV). PL analysis revealed excitation-dependent emission and a significantly higher photoluminescence quantum yield (PLQY) of 33.09%. These results suggest that N-CQDs hold promise for applications in optoelectronics and bioimaging, providing a foundation for further optimization in future studies.