Perylene nanocrystals with different sizes(10-250 nm) were prepared by reprecipitation. Compared with the absorption spectrum of perylene acetone solution, a new J aggregate absorption peak appeared in the absorption spectra of nanocrystals. With the decrease of perylene nanocrystals size, it shows a blue shift in the absorption spectra. This blue shift is due to the size dependent property. The perylene concentration of initial acetone solution or the amount of solution injected into water, the aging time of organic nanocrystal dispersion and the adding of surfactant were the influencing factors of nanocrystal growth. We can gain the required microcrystals of different sizes by controlling the conditions of growth.
