Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 8, Issue 38, Pages 25454-25460Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.6b08315
Keywords
carbon nanodots (CDs); excitation-independent; amplified spontaneous emission (ASE); lasing; planar waveguide
Funding
- CAS Innovation Program
- National Natural Science Foundation of China [6140031454]
- Jilin Province Science and Technology Research Project [20140520119JH, 20150101039JC]
- State Key Laboratory of Luminescence and Applications
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Carbon nanodots (CDs) are known to be a superior type of lasing material due to their low cost, low toxicity, high photostability, and photobleaching resistance. Significant attention has been paid to synthesizing CDs with high fluorescence quantum yields (FLQYs) to achieve higher optical gains. In this report, we reveal that excitation wavelength-independent (lambda ex-independent) photoluminescence (PL) characteristics, rather than high FLQYs, should be given priority to realize CD-based light amplification. CDs with excitation wavelength-dependent (lambda ex-dependent) PL characteristics and FLQYs as high as 99% and 96% were found not to exhibit amplified spontaneous emission (ASE), while those with lambda ex-independent PL characteristics and FLQYs of only 38% and 82% realized ASE with low thresholds. The difficulty of achieving ASE using CDs with lambda ex-dependent PL characteristics is likely attributable to their high contents of C-O-H or C-O-C groups. These groups can induce numerous localized electronic states within the n-p* gap, which could decentralize the excited electrons, thus increasing the difficulty of population inversion. In addition, the radiative transition rates and stimulated emission cross sections of CDs with lambda ex-independent PL characteristics were found to be significantly higher than those of CDs with lambda ex-dependent PL characteristics. ASE in a planar waveguide structure, which is a practical structure for solid-state lasing devices, was also demonstrated for the first time using CDs with lambda ex-independent PL characteristics. These results provide simple and effective guidelines for synthesizing and selecting CDs for low-threshold lasing devices.
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