Study on size-dependent optical property of 4,4′-dibromobiphenyl nanocrystals

4,4^′-dibromobiphenyl nanocrystals with different sizes in the range from 20 nm to 300 nm were prepared by the reprecipitation method. It was found that their absorption peaks experienced a red shift while the size of the nanocrystals increased. Through analyzing these spectra of the nanocrystals with different sizes, it is suggested that this size-dependent optical property is contributed by two factors, the size effect and the J-aggregate formation. Received: 28 August 2000 / Accepted: 2 March 2001 / Published online: 23 May 2001