Synthesis of N-Doped Micropore Carbon Quantum Dots with High Quantum Yield and Dual-Wavelength Photoluminescence Emission from Biomass for Cellular Imaging

Pursuit of a simple, fast, and cost-effective method to prepare highly and dual-wavelength fluorescent carbon quantum dots (CQDs) is a persistent objective in recent years. Here, we fabricated N-doped micropore carbon quantum dots (NM-CQDs) with a high quantum yield and dual-wavelength photoluminescence (PL) emission from sustainable biomass using a pulsed laser ablation method. Interestingly, two coexisting indigo–blue photoluminescence (PL) emissions were clearly observed, elucidating that the excited electrons transited from the intrinsic π* orbital to the surface state (SS) formed from the saturation passivation. The quantum yield (QY) and fluorescence lifetime (FL) of the obtained NM-CQDs were as high as 32.4% and 6.56 ns. Further investigations indicated that the emission behaviors of NM-CQDs were still stable and independent in various conditions such as various excitation wavelengths, salt ionic concentrations, pH values, irradiation times, and temperatures. The obtained NM-CQDs are very suitable for cellular staining images due to strong and stable PL emission and show good internalization in different cells. Therefore, we propose a new and cost-effective preparation strategy for highly fluorescent NM-CQDs with great potential in biomedical imaging and engineering.