Photoluminescence Quenching of Single CdSe Nanocrystals by Ligand Adsorption

We study the effects of octadecanethiol on the photoluminescence intensity and blinking dynamics of single CdSe nanocrystal quantum dots. The number of luminescent nanocrystals per unit area, the intensity histograms of the luminescent nanocrystals, and the single nanocrystal blinking behavior are analyzed in samples with and without added octadecanethiol. We find that the individual nanocrystals within an ensemble do not quench uniformly with thiol addition. The data suggest that the binding of a single octadecanethiol molecule to a CdSe nanocrystal can decrease the photoluminescence quantum yield of that single nanocrystal by at least 50%. These results are important for interpreting photoluminescence-based studies of nanocrystal−ligand binding constants and surface chemistry.