Exploring the Role of Surface States in Emissive Carbon Nanodots: Analysis at Single‐Particle Level

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. We explored the chemical and optical properties of carbon nanodots by using single particle analysis. To reduce the intrinsic heterogeneity of carbon nanodots, we controlled the surface states of carbon nanodots with chromatographic separation. This effort reveals the correlation between surface states of carbon nanodots and their photophysical and chemical properties, investigating the changes of emissive states in a single‐particle level.