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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.

The self-assembly of amorphous three-dimensional arrays of CdSe nanocrystals is probed in real time using multiple-reflection, infrared attenuated total reflection spectroscopy by following the solvent and the organic ligands that passivate the nanocrystal surface. During the self-assembly of a 250 ML array from pyridine-capped CdSe nanocrystals in pyridine solvent, the solvent molecules evaporate in ∼30–40 min and the pyridine-capping molecules leave the array very slowly, apparently limited by diffusion, with ∼30±8% remaining after three days.

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