Elucidation of Two Giants: Challenges to Thick-s

Elucidation of Two Giants: Challenges to Thick-shell Synthesis in CdSe/ZnSe and ZnSe/CdS Core/Shell Quantum Dots.

J Am Chem Soc 2015 Mar 6. Epub 2015 Mar 6.

Krishna P Acharya, Hue M Nguyen, Melissa Paulite, Andrei Piryatinski, Jun Zhang, Joanna L Casson, Hongwu Xu, Han Htoon, Jennifer A Hollingsworth


Core/thick-shell "giant" quantum dots (gQDs) possessing type II electronic structures exhibit suppressed blinking and diminished nonradiative Auger recombination. We investigate CdSe/ZnSe and ZnSe/CdS as potential new gQDs. We show theoretically and experimentally that both can exhibit partial or complete spatial separation of an excited-state electron-hole pair (i.e., type II behavior). However, we reveal that thick-shell growth is challenged by competing processes: alloying and cation exchange, respectively. We demonstrate that these can be largely avoided by choice of shelling conditions (e.g., time, temperature, QD core identity). The resulting CdSe/ZnSe gQDs exhibit unusual single-QD properties, principally emitting from dim ?gray? states but having high two-exciton (biexciton) emission efficiencies, while ZnSe/CdS gQDs show characteristic gQD blinking suppression, though only if shelling is accompanied by partial cation exchange.
http://www.pubfacts.com/detail/25746140/Eluci...Shell-Quan