The optical size-dependent properties of pyrazolines nanocrystals

Nanocrystals of 1-phenyl-3-(p-oxymethyl-styryl)-5-(p-oxymethyl-phenyl)-2-pyrazoline (PYB) with different sizes were prepared by the reprecipitation method. The aggregate formation of PYB nanocrystals was found to be J-aggregate, of which the wavelength of absorption peak was observed at about 430 nm. Further, we found that the PYB nanocrystals possess a special optical size-dependent property. As the nanocrystal size decreased, the molecular absorption peak of PYB nanocrystals was observed to shift to the high-energy side due to size effect and at the same time, the J-aggregate absorption peak gradually vanished.