Dimensionality effects on fluorescence resonance energy transfer between single semiconductor nanocrystals and multiple dye acceptors

Colloidal semiconductor nanocrystals are outstanding donors in energy transfer processes due to their unique size and shape dependent optical properties, their exceptional photostability, and chemical processability. We examine the dimensionality effect in energy transfer between single heterostructure nanocrystals of spherical and rod shape, serving as donors, and multiple dye molecules attached to their surface acting as acceptors. Förster resonant energy transfer (FRET) to individual dyes attached to the surface of a single nanocrystal is identified via step-like changes in both acceptor and donor emission, enabling to calculate the efficiency of energy transfer and distance of each acceptor individually. This offers a unique tool to study the surface chemistry of various nanocrystals. The dimensionality of the nanocrystals is reflected by the acceptors distribution, which enables to study the inner geometry of these heterostructures, such as the location of the seed and shell thickness. Additionally, the nanocrystals serve as an optical antenna that enhances the excitation and emission of the dye molecules through the FRET interaction. These measurements enable to gain deeper understanding of the energy transfer process between semiconductor nanocrystals of various geometries and dye molecules and promote its utilization for extremely sensitive sensing applications at the single molecule level.