Solution-grown CdTe nanowires: Self-assembly, optical properties and strong temperature dependent electronic coupling

CdTe nanowires have been self-assembled in solution from the individual CdTe nanocrystal building blocks. Individual wires preserve the bright luminescence of CdTe nanocrystals and have been studied by photoluminescence measurements at variable temperature and by fluorescence lifetime imaging microscopy. The wires represent quantum dot solids with a strong degree of electronic coupling between the constituting semiconductor nanocrystals. Upon cooling to low temperatures the emission surprisingly red shifts in the strong coupling regime (nanowires) while for weaker coupling (closed packed and isolated nanocrystals) it blue shifts. A temperature dependent exchange interaction between the nanocrystals in the nanowires is proposed as explanation.