Simple and Precise Quantification of Iron Catalyst Content in Carbon Nanotubes Using UV/Visible Spectroscopy.
Iron catalysts have been used widely for the mass production of carbon nanotubes (CNTs) with high yield. In this study, UV/visible spectroscopy was used to determine the Fe catalyst content in CNTs using a colorimetric technique. Fe ions in solution form red-orange complexes with 1,10-phenanthroline, producing an absorption peak at λ=510 nm, the intensity of which is proportional to the solution Fe concentration. A series of standard Fe solutions were formulated to establish the relationship between optical absorbance and Fe concentration. Many Fe catalysts were microscopically observed to be encased by graphitic layers, thus preventing their extraction. Fe catalyst dissolution from CNTs was investigated with various single and mixed acids, and Fe concentration was found to be highest with CNTs being held at reflux in HClO4/HNO3 and H2SO4/HNO3 mixtures. This novel colorimetric method to measure Fe concentrations by UV/Vis spectroscopy was validated by inductively coupled plasma optical emission spectroscopy, indicating its reliability and applicability to asses Fe content in CNTs.
Hybrid Materials Center, HMC), Department of Nanotechnology and Advanced Materials Engineering, Sejong University 209 Neungdong-ro, Gwangjin-gu, Seoul, 143-747, Republic of Korea.
Elsye
E
Agustina
Hybrid Materials Center, HMC), Department of Nanotechnology and Advanced Materials Engineering, Sejong University 209 Neungdong-ro, Gwangjin-gu, Seoul, 143-747, Republic of Korea.
Jeungchoon
J
Goak
Hybrid Materials Center, HMC), Department of Nanotechnology and Advanced Materials Engineering, Sejong University 209 Neungdong-ro, Gwangjin-gu, Seoul, 143-747, Republic of Korea.
Suntae
S
Lee
Hybrid Materials Center, HMC), Department of Nanotechnology and Advanced Materials Engineering, Sejong University 209 Neungdong-ro, Gwangjin-gu, Seoul, 143-747, Republic of Korea.
Youngho
Y
Seo
Hybrid Materials Center, HMC), Department of Nanotechnology and Advanced Materials Engineering, Sejong University 209 Neungdong-ro, Gwangjin-gu, Seoul, 143-747, Republic of Korea.
Jun-Young
JY
Park
Hybrid Materials Center, HMC), Department of Nanotechnology and Advanced Materials Engineering, Sejong University 209 Neungdong-ro, Gwangjin-gu, Seoul, 143-747, Republic of Korea.
Naesung
N
Lee
UV/Vis spectroscopy; acid treatment; iron catalysts; nanotubes; phenanthroline