Contribution of the loss of nanocrystal ligands to interdot coupling in films of small CdSe/1-thioglycerol nanocrystals

The broadening of the exciton absorption peak in films composed of small, ∼2 nm diameter CdSe nanocrystals capped by 1-thioglycerol has been interpreted as evidence of interdot carrier coupling. This exciton broadening is seen here for 2.1 nm diameter CdSe nanocrystal arrays, and part of it is correlated with the loss of over half of the 1-thioglycerol molecules from the nanocrystal surfaces. These ligands are even more weakly bound in films of 4.1 nm diameter particles, as evidenced by the smaller shift in their ∼2560 cm-1 S−H stretching peak and the faster decay of this peak vis-a-vis that of the smaller particles, but no exciton broadening is observed for these films.