Single-particle fluorescence intensity fluctuations of carbon nanodots.

Fluorescent carbon nanodots (CNDs) were synthesized in oxidized and reduced forms and were analyzed at the single-particle level. Images of single CNDs at different excitation energies revealed significant heterogeneity in the lower energy trap sites between particles. We observed that a high percentage of reduced CND particles transitioned between multiple fluorescence intensity levels indicative of multichromophoric systems. Despite this behavior, individual CNDs exhibit single-step photobleaching and transient blinking to the background level suggesting single-molecule behavior.