Effect of electronic coupling between CdSe nanocrystals on the photoluminescence spectra

Different types of aggregates of CdSe nanoparticles have been assembled by using bridging molecules such as thiolcarboxylic acids and alkanedithiols as by well as the click reaction involving cycloaddition between azido and acetylenic groups. The aggregates show photoluminescence spectra different from the pristine CdSe nanocrystals. The simplest situation is one where the spectrum has two bands one at longer wavelengths and another at lower wavelengths arising from dimeric units. More complex spectra arise from higher aggregates, but there is always some symmetry in the band positions. Fluorescence decay measurements have been carried out on the different CdSe aggregates. The results are interpreted in terms of electronic coupling between the nanocrystals.