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Simple and Precise Quantification of Iron Catalyst Content in Carbon Nanotubes Using UV/Visible Spectroscopy.

Agustina E, Goak J, Lee S, Seo Y, Park JY, Lee N - ChemistryOpen (2015)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Hybrid Materials Center, HMC), Department of Nanotechnology and Advanced Materials Engineering, Sejong University 209 Neungdong-ro, Gwangjin-gu, Seoul, 143-747, Republic of Korea.

ABSTRACT
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.

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SEM images of a) CNT-B and b) CNT-C. TEM images of c) CNT-B and d) CNT-C show that multiple graphitic layers encase catalyst particles. The ashes, produced by oxidizing CNTs at 900 °C, have a grey color for both e) CNT-B and f) CNT-C. g) Fe concentrations measured by UV/Vis spectroscopy and ICP-OES for CNT-B and CNT-C. Data are the average ±SD of three independent measurements.
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fig04: SEM images of a) CNT-B and b) CNT-C. TEM images of c) CNT-B and d) CNT-C show that multiple graphitic layers encase catalyst particles. The ashes, produced by oxidizing CNTs at 900 °C, have a grey color for both e) CNT-B and f) CNT-C. g) Fe concentrations measured by UV/Vis spectroscopy and ICP-OES for CNT-B and CNT-C. Data are the average ±SD of three independent measurements.

Mentions: In an attempt to demonstrate its reliability, this method was applied to other CNT samples, namely CNT-B and CNT-C. Both CNTs were synthesized using Fe and Co catalysts on alumina supports by catalytic chemical vapor deposition (CCVD). In Figure 4 a–d, CNTs occurred entangled, and metal catalysts were enclosed by CNTs for both CNT-B and -C. The ashes, obtained by burning at 900 °C in air, appeared grey because Fe and Co were used as catalysts (Figure 4 e,f). Fe measurements were made three times for each CNT sample using UV/Vis spectroscopy and ICP-OES (Figure 4 g). Fe concentrations measured by both methods closely match each other within the average differences of 1.66 and 0.38 % for CNT-B and -C, respectively, supporting that the UV/Vis spectroscopic method is comparable to the widely used ICP-OES technique in assessing the Fe content of CNTs. Measurement precision, as indicated by the small error bars, illustrates the reliability of this method.


Simple and Precise Quantification of Iron Catalyst Content in Carbon Nanotubes Using UV/Visible Spectroscopy.

Agustina E, Goak J, Lee S, Seo Y, Park JY, Lee N - ChemistryOpen (2015)

SEM images of a) CNT-B and b) CNT-C. TEM images of c) CNT-B and d) CNT-C show that multiple graphitic layers encase catalyst particles. The ashes, produced by oxidizing CNTs at 900 °C, have a grey color for both e) CNT-B and f) CNT-C. g) Fe concentrations measured by UV/Vis spectroscopy and ICP-OES for CNT-B and CNT-C. Data are the average ±SD of three independent measurements.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4608529&req=5

fig04: SEM images of a) CNT-B and b) CNT-C. TEM images of c) CNT-B and d) CNT-C show that multiple graphitic layers encase catalyst particles. The ashes, produced by oxidizing CNTs at 900 °C, have a grey color for both e) CNT-B and f) CNT-C. g) Fe concentrations measured by UV/Vis spectroscopy and ICP-OES for CNT-B and CNT-C. Data are the average ±SD of three independent measurements.
Mentions: In an attempt to demonstrate its reliability, this method was applied to other CNT samples, namely CNT-B and CNT-C. Both CNTs were synthesized using Fe and Co catalysts on alumina supports by catalytic chemical vapor deposition (CCVD). In Figure 4 a–d, CNTs occurred entangled, and metal catalysts were enclosed by CNTs for both CNT-B and -C. The ashes, obtained by burning at 900 °C in air, appeared grey because Fe and Co were used as catalysts (Figure 4 e,f). Fe measurements were made three times for each CNT sample using UV/Vis spectroscopy and ICP-OES (Figure 4 g). Fe concentrations measured by both methods closely match each other within the average differences of 1.66 and 0.38 % for CNT-B and -C, respectively, supporting that the UV/Vis spectroscopic method is comparable to the widely used ICP-OES technique in assessing the Fe content of CNTs. Measurement precision, as indicated by the small error bars, illustrates the reliability of this method.

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Hybrid Materials Center, HMC), Department of Nanotechnology and Advanced Materials Engineering, Sejong University 209 Neungdong-ro, Gwangjin-gu, Seoul, 143-747, Republic of Korea.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus