Analysis of Functional Group Sited on Multi-Wall Carbon Nanotube Surface

Abstract

Functionalization of Carbon Nanotube (CNT) plays an important role in creating CNT hybride material. In this study, integrated analysis of functional group sites on the pristine and modified Multi-Wall Carbon Nanotube (MWCNT) surface was comparably conducted to know the effect of acid solution on the surface after purification and functionalization process. Acid treatment removed rest of graphitic and residual catalytic metal particles and suffered degradation, such as nanotube shortening and additional defect generation in the graphitic network. Defects on the side wall due to functionalized group clearly shown in Transmission Electron Image (TEM) images cause a reduction in thermal stability. Functional group sited on the side wall was detected by Attenuated Total Reflectance (ATR) -Fourier Transform Infra Red (FTIR) with the relative concentration of oxygen-containing functional groups determined by Boehm titration.

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“…The intensity of the peak at the D band is due to structural defects or impurities. The G band indicates the longitudinal stretching vibrations of the sp2 carbons of semiconducting SWCNTs (Yudianti et al, 2011). The ratio of D and G peak intensities (I D / I G ) determines the structure of SWCNTs, and a comparison indicates an increase in the D band after sulfonation due to the strong damage to the sidewalls of SWCNTs or the formation of fragments caused by the functionalization .…”

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“…[33] No further decay in mass was observed after 700 C, as beyond this point the remaining residue consisted essentially of thermally stable carbon. [22] Since enzyme molecules tend to decompose at lower temperatures than other chemical groups [22] introduced onto the MWCNTs in this study, the loss of mass (19%) for CRL-MWCNTs that occurred at lower temperatures (150 ¡450 C) (Figure 2(c)) may be accredited to the decomposition of the CRL protein. Hence, the results showed that physical adsorption had succeeded in attaching approximately 19% of CRL protein to the surface of the F-MWCNTs.…”

“…[22] Functionalization of the MWCNTs was performed according to the method described by Yudianti et al [22] The purified MWCNTs were refluxed in a mixture of concentrated H 2 SO 4 : HNO 3 (3:1, v/v) for 6 h at 100 C and the suspension was left overnight to ensure deposition of the functionalized MWCNTs (F-MWCNTs). Then the suspension was diluted and rinsed with distilled water, until no residual acid was detected, and subsequently dried at 80 C.…”

“…[29] Following the acid functionalization process, a peak appearing in the region of 1730À1650 cm ¡1 was expected to indicate the development of carboxylic groups on the MWCNTs. [22] Appearance of peak at 1742 cm ¡1 assigns carbonyl (C D O) stretching vibration of carboxyl groups, [30,31] indicating the expansion of carboxylation on the surfaces of F-MWCNTs. On the other hand, for the CRL-MWCNT spectrum (Figure 1(c)), strong peaks at 1634 cm ¡1 were characteristic of the C D O stretching of amide of the polypeptide chains of CRL.…”

“…The F-MWCNTs were observably shorter and the fibres remained relatively defected (Figure 3(b)) than the as-synthesized MWCNTs (Figure 3(a)) as a result of a stronger acid treatment (H 2 SO 4 :HNO 3 ) during the functionalization process. [22,34] The open-ended pipes on the F-MWCNTs hypothetically increase the surface area for the attachment of carboxylic groups at the open ends, [35] thereby rendering the surface accessible for biological and chemical reactions. [22] The TEM image of the CRL-MWCNTs (Figure 3(c)) depicted a layer of lipase protein that coated the surface of the MWCNTs, confirming the successful immobilization of CRL.…”