Charge overlap interaction in quantum dot films: Time dependence and suppression by cyanide adsorption

Chemical bath deposited films of CdSe nanocrystals (< 4 nm) are shown to exhibit time-dependent spectral red shifts, caused by increasing overlap of the electron wave functions in adjacent nanocrystals. Treatment of these '' aggregated '' films with aqueous KCN solution results in repulsion of the wave functions due to the strongly adsorbed negatively charged cyanide and thus electronic decoupling of the physically connected nanocrystals. The previously reported band gap increase due to cyanide adsorption on nominally uncoupled nanocrystals is also described here in more detail.