  The design of large-scale colloidal quantum dots (QDs) assemblies and the
investigation of their interaction with their close environment are of great
interest for improving QD-based optoelectronic devices' performances.
Understanding the interaction mechanisms taking place when only a few QDs are
assembled at a short interparticle distance is relevant to better promote the
charge or energy transfer processes. Here, small hetero-assemblies formed of a
few CdSe QDs of two different sizes, connected by alkyl dithiols, are
fabricated in solution. The interparticle distance is tuned by varying the
linear alkyl chain length of the bifunctional spacer from nanometer to
sub-nanometer range. The crystallographic analysis highlights that the nearest
surfaces involved in the linkage between the QDs are the (101) faces. The
thorough spectroscopic investigation enables a sound rationalization of the
coupling mechanism between the interacting nanoparticles, ranging from charge
transfer/wavefunction delocalization to energy transfer, depending on their
separation distance.
