Förster transfer in coupled colloidal type-II and type-I quantum dots

We examine theoretically resonant non-radiative exciton (Förster) transfer in the system of colloidal coreshell quantum dots (QDs) of different types. We show that when the type-I QD (acceptor) is coupled with the type-II QD (donor), the electron-hole pair optically excited in the type-II QD can be transferred to the type-I QD nonradiatively, if the recombination time of the former is larger than the time of the exciton transfer. Correspondingly, the time-resolved photoluminescence signal from the type-I QDs would be modified both quantitatively and qualitatively. We also discuss the feasibility to use this effect in a pathogen detection platform aimed at a single molecule level. With the QDs functionalized with antibodies to target pathogens, their presence will manifest itself by allowing or disallowing the Förster transfer by either bringing QDs closer to each other or changing electrostatic environmental properties, respectively. This “On-or-Off” scheme can work in both liquids and gases.