@article{oai:soar-ir.repo.nii.ac.jp:00012330,
 author = {Nishikiori,  Hiromasa and Tanigaki,  Taku and Endo,  Morinobu and Fujii,  Tsuneo},
 journal = {CARBON},
 month = {Jan},
 note = {Acidic functional groups produced on the surface of acid-treated multi-walled carbon nanotubes (MWCNTs) were quantified by fluorescence measurements using 1-aminopyrene (1-AP) as an in situ probe molecule. The 1-AP cation-like bands were observed on the HNO3/H2SO4 mixture-treated MWCNT surfaces because the 1-AP molecule was tightly immobilized by the hydrogen bonding interaction between its amino group and the Bronsted-acidic groups on the MWCNT surface. The fluorescence measurement, allowed us to confirm the Langmuir-type adsorption of 1-AP on the functional groups of the MWCNTs, and estimate their amount of the functional groups and adsorption equilibrium constant. A longer acid treatment caused the chemical modification to generate higher amounts of the Bronsted-acidic functional groups and improve the adsorption ability on the MWCNT surface. About 2% of carbon in the MWCNTs was oxidized by the 24 h acid treatment. This value corresponded to 15-22% of carbon in the surface layer., Article, CARBON. 66:560-566 (2014)},
 pages = {560--566},
 title = {Quantitative characterization of acidic groups on acid-treated multi-walled carbon nanotubes using 1-aminopyrene as a fluorescent probe},
 volume = {66},
 year = {2014}
}