Preparation and optical size-dependent properties of perylene nanocrystals

Optical size-dependent properties of perylene nanocrystals were studied by the addition of polyvinyl alcohol (PVA) to a water suspension of perylene nanocrystals prepared by reprecipitation method. Because PVA could bind with the nanocrystals, it will inhibit the growth of the nanocrystals, so that we could obtain stable nanocrystals with different sizes. By analyzing the absorption and excitation spectra of the nanocrystals with different sizes, it was found that their absorption and excitation peaks underwent red-shift while the size of the nanocrystals increased, which may be due to the change of the interactions between perylene molecules. Also with increasing crystal size, the excimer emission of perylene nanocrystals was weakened and the decay time of the excimer was prolonged.