Analyzing photoluminescence emission quenching effects in colloidal aqueous suspensions of carbon dots

Carbon dots are highly emissive low dimensional carbon nanoparticles with bright and broad photoluminescence emission in colloidal suspensions. The optical features of carbon dot suspensions are strongly influenced by several factors such as the functionalization of the carbon dots, particle aggregation and solids concentration in the dispersion. In this study, we demonstrate that functionalized carbon dots exhibit multiple surface emissive states responsible for localized emission contributions: a bright blue emission at 445 nm governed by electronic transitions involving aromatic carbon sp 2 configurations and long wavelength emission contributions (500, 550, 600 nm) associated to electronic transitions involving C-N and C-O surface groups. Our data shows a strong self-quenching of the photoluminescence emission at short wavelengths, related to the re-absorption of the light emitted by the fluorophores present in the carbon dots (i.e., reduction in the emission intensity and redshift in the main emission peak contribution), with a negligible contribution of quenching effects associated to modification of surface states upon interparticle interactions boosted by aggregation of the nanoparticles in highly concentrated dispersions. • Self-quenching of blue emission due to re-absorption in concentrated suspensions. • Blue to green emission shift related to quenching in concentrated solutions. • Low quenching due to electronic transitions at short interparticle distances. • Blue emission from Csp2 and long wavelength emission from C-N and C-O groups. • Multiple surface emissive states in functionalized carbon dots suspensions.