The size-dependent optical properties of 1-phenyl-3-naphthyl-5-((dimethylamino)phenyl)-2-pyrazoline nanoparticles

1-Phenyl-3-naphthyl-5-((dimethylamino)phenyl)-2-pyrazoline nanoparticles with different sizes from 130 to 40 nm were prepared by the re-precipitation method. Their excitonic transitions responsible for absorption and emission, as compared with those of dilute solution, have been investigated as a function of nanoparticle size. We found that pyrazoline nanoparticles possess a special size-dependence in their optical properties. As the nanoparticle size decreased, the absorption and emission peak of pyrazoline nanoparticles were observed to shift to the high-energy side due to the aggregate formation and increased intermolecular interaction in the nanoparticles.