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Pyrene crystals were grown on carbon nanofibers (CNFs) by dispersing pyrene polycrystals and CNFs in water during ultrasonic irradiation, and they were characterized by scanning electron microscopy, X-ray diffractometry (XRD) and spectroscopy. The XRD measurements indicated that the orientation and size of the pyrene crystals on the CNF aggregates were different from that of the added pyrene polycrystals. Based on the spectroscopic properties of the pyrene crystals on the CNFs, the pyrene crystals on the CNF aggregates and on the individual CNFs were determined to be polycrystals and single crystals, respectively. These results indicate that pyrene crystals are produced on the CNFs by recrystallization of the added pyrene polycrystals and their crystal states depend on the aggregation state of the CNFs. [Copyright &y& Elsevier]

Abstract: Acidic functional groups produced on the surface of acid-treated carbon nanofibers (CNFs) were characterized by fluorescence measurements using 1-aminopyrene (1-AP) as an in situ probe molecule. The 1-AP molecules only slightly interacted with the untreated CNF surface, whereas the 1-AP cation-like bands were observed on the HNO3-treated and HNO3/H2SO4 treated CNF surfaces. These results indicate that 1-AP was tightly immobilized by the hydrogen bonding interaction between its amino group and the Brönsted-acidic groups on the CNF surface. A stronger acid treatment (with HNO3/H2SO4 mixture) caused the chemical modification to generate higher amounts of the acidic functional groups on the CNF surface. [Copyright &y& Elsevier]