Affiliation: | 1. Department of Chemistry, Yonsei University, Seoul, 03722 Republic of Korea These authors contributed equally to this work.;2. Department of Chemistry, University of Kentucky, 505 Rose Street, Lexington, Kentucky, 40506-0055 United States These authors contributed equally to this work.;3. Department of Chemistry, University of Kentucky, 505 Rose Street, Lexington, Kentucky, 40506-0055 United States;4. Department of Chemistry, Yonsei University, Seoul, 03722 Republic of Korea Department of Chemical Engineering (BK21 FOUR), Dong-A University, Busan, 49315 Republic of Korea;5. Samsung Advanced Institute of Technology (SAIT), Samsung Electronics Co. Ltd., Suwon, 16678 Republic of Korea;6. Data and Information Technology (DIT) Center, Samsung Electronics, Hwaseong, 18448 Republic of Korea;7. Department of Chemistry, Yonsei University, Seoul, 03722 Republic of Korea |
Abstract: | Fluorescent carbon nanodots (CDs) have been highlighted as promising semiconducting materials due to their outstanding chemical and optical properties. However, the intrinsic heterogeneity of CDs has impeded a clear understanding of the mechanisms behind their photophysical properties. In this study, as-prepared CDs are fractionated via chromatography to reduce their structural and chemical heterogeneity and analyzed through ensemble and single-particle spectroscopies. Many single particles reveal fluorescence intensity fluctuations between two or more discrete levels with bi-exponential decays. While the intrinsic τ1 components are uniform among single particles, the τ2 components from molecule-like emissions spans a wider range of lifetimes, reflecting the inhomogeneity of the surface states. Furthermore, it is concluded that the relative population and chemical states of surface functional groups in CDs have a significant impact on emissive states, brightness, blinking, stability, and lifetime distribution of photoluminescence. |