The spectral heterogeneity and size distribution of the carbon dots derived from time-resolved fluorescence studies

We performed comprehensive studies on the photoluminescence properties of the carbon dots prepared from citric acid (C-dots^CA) and citric acid + ethylenediamine (C-dots^CA+EDA). The cryogenic experiment confirmed that the excitation dependent fluorescence and the spectral relaxation dynamics of the C-dots are associated with the presence of multiple emissive states/species in the C-dots instead of solvation dynamics. Moreover, we also compared the size of the C-dots estimated from the TEM/AFM images and fluorescence anisotropy methods. The experimental results indicate that the fluorescence anisotropy method not only avoids the formation of aggregates during the sample preparation processes, but also selectively detects the size of emissive C-dots in the solution. Therefore, the fluorescence anisotropy method is ideal for studying the size dependent optical properties of the C-dots.