Our unique procedure and careful investigation enabled us to observe the fluorescence spectra of pyrene adsorbed onto carbon nanofibers (CNFs) although it is generally very difficult due to strong quenching. In this procedure, CNFs were dispersed throughout the pyrene solution containing water-ethanol by ultrasonic irradiation. The fluorescence spectra of pyrene assigned to those observed in low-polar solvents were clearly found in the suspensions containing pyrene and the CNFs. This fluorescence resulted from the pyrene molecules adsorbed through pi-pi interaction onto graphene sheet of the CNFs and its intensity progressively increased with degree of the CNF dispersion during ultrasonic irradiation. (C) 2007 Elsevier B.V. All rights reserved.