We vary the mixing ratio of 1% Sn and 6% Sn ITO nanocrystals in superlattices continuously, changing the fraction of 6% Sn nanocrystals, x 6% , from 0 to 1. Qualitatively, the normal incidence extinction spectra of the mixed superlattices evolve systematically between the spectra of the two single-component assemblies, but neither the peak positions nor the heights reflect simple linear mixing (Fig. ). Electron transfer is not expected to occur between nanocrystals, but LSPR coupling between neighboring nanocrystals should depend on their % Sn.