In situ probing of acidic groups on acid-treated carbon nanofibers using 1-aminopyrene

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.