Unveiling the photoluminescence mechanisms of carbon dots through tunable near-infrared dual-wavelength lasing

Multi-wavelength lasers are urgently required for integrated multi-channel optoelectronic applications. Carbon dots (CDs) show promise as laser devices due to their multiple photoluminescence centers, modifiable structure, and exceptional gain performance. In this study, we achieved reversible switchable dual-wavelength laser emission in the near-infrared (NIR) regions using o-phenylenediamine (OPD)-derived CDs with fine-tuning capabilities through concentration or pH regulation. Additionally, by comparing the laser properties of its fluorophore 5,14-dihydroquinoxalino[2,3-b] phenazine (DHQP), we established a model for the CDs. DHQP confined on the surface of CDs provides aggregation sites, conjugated carbon nuclei promote multiple scattering and enhance light amplification, and whole CDs exhibit a cross-linked confined enhanced emission effect with higher photoluminescence (PL) quantum yield (PLQY), more stable laser emission, and lower laser threshold. This study not only offers valuable insights into the PL mechanisms of CDs but also demonstrates a promising direction for rational design of tunable multi-wavelength laser gain materials.