Exciton dynamics in cadmium selenide/zinc selenide core/core-shell nanocrystals as effected by surface ligand modification using femtosecond fluorescence upconversion

Femtosecond fluorescence upconversion has been utilized to study the band edge dynamics of cadmium selenide and cadmium selenide/zinc selenide core-shell nanocrystals. Improvements in the methodology for synthesis of CdSe, through the addition of dodecylphosphonic acid and hexadecylamine as a co-solvent, have led to distinct changes in the band edge dynamics when compared to the traditional trioctylphosphine oxide (TOPO) synthesis. Further modification of the surface with a shell of ZnSe further perturbs the ultrafast dynamics. Increases in static quantum yield and changes to both the fast and slow components of the kinetics are observed. Interaction of the amine hydrogen with the core and core-shell surface is strongly implicated for the changes in the static and ultrafast luminescence. All of these changes have a profound impact on quantum dots used in electronic devices and the design of such devices.