Surface properties of oxidized and aminated multi-walled carbon nanotubes

Abstract

A influência de modificação química (por tratamento ácido seguido de funcionalização com trietilenotetramina, TETA) sobre a superfície de nanotubos de carbono de paredes múltiplas (MWCNT) foi estudada qualitativa e quantitativamente. A análise termogravimétrica (TGA) mostrou que, no caso do nanotubo funcionalizado com amina, 29% de perda de massa pode ser atribuída a -C(=O)TETA e grupos funcionais residuais que contêm oxigênio. A espectroscopia de fotoelétrons excitados por raios X (XPS) foi utilizada para observar as funções aminadas e oxigenadas ligadas covalentemente à superfície do nanotubo. As imagens de microscopia de força elétrica (EFM) indicaram que, à medida que se modifica a química superficial dos nanotubos em presença de ar, estes mostram respostas diferentes em função do potencial da ponta. Deslocamentos nos sinais de fase de EFM decrescem quando se modifica a superfície dos tubos com grupos funcionais contendo oxigênio e amina. Em atmosfera seca e inerte de N 2 , as três diferentes superfícies mostraram a mesma resposta à EFM. Além disso, o caráter hidrofílico dos "buckypapers" cresceu na ordem MWCNT < MWCNT-aminado < MWCNT-oxidado.The influence of chemical modification by acid treatment followed by triethylenetetramine (TETA) functionalization on the surface of multi-walled carbon nanotubes (MWCNT) was evaluated, both qualitative and quantitatively. Thermogravimetric analysis (TGA) showed that, in the case of amine-functionalized nanotubes, 29% of mass loss can be attributed to -C(=O)TETA and residual oxygen-containing functional groups. X-ray photoelectron spectroscopy (XPS) was used to observe the oxygenated and aminated functions covalently linked to the nanotube surface. Electric force microscopy (EFM) images indicated that the nanotubes with diverse surface chemistry showed distinct responses to the tip potential in the presence of air. Shifts in EFM phase images decreased when the nanotube surface was modified with oxygen and amine-containing functional groups. In dry and inert N 2 atmosphere, however, the three different surfaces showed the same response to EFM. In addition, the hydrophilic character of the buckypapers increased in the order MWCNT < aminated-MWCNT < oxidized-MWCNT.Keywords: multi-walled carbon nanotubes, triethylenetetramine, surface chemical modification, spectroscopic characterization, electric force microscopy IntroductionAn important historical reference about carbon nanotube (CNT) synthesis is the work of Oberlin et al. in 1976. 1 However, it was not until Iijima's work, in 1991, 2 that CNTs emerged as a key material in the field of nanotechnology due to their extraordinary thermal, electrical and mechanical properties.2-4 However, low dispersibility in organic and inorganic solvents, combined with poor chemical compatibility, has become a major issue. 5,6 Functionalization or chemical modification of CNT, that is, the covalent attachment of atoms or molecules to the surface, has been used to introduce chemical specificity and processability in different environments...

Production of TiO2 Coated Multiwall Carbon Nanotubes by the Sol-Gel Technique

“…It is known that the intensity of the bands D and G are associated respectively to structural disorder and to the graphitic nature of the MWCNT, related to the tangential stretching mode of the C=C bond 31,32 . The ratio between the intensities of D and G bands (I D /I G ratio) is expected to increase after the MWCNT functionalization, as surface defects are created in the nanotubes.…”

Tailored Degree of Functionalization and Length Preservation of Multiwalled Carbon Nanotubes by an Optimized Acid Treatment Process

“…Thermogravimetric analysis TGA provides useful information about functionalized CNTs and is usually performed in air 11,12,15,18,32 or nitrogen. 11,17,19,32 The analyses in both atmospheres are relevant, but the evaluation in air has the advantage of also exhibit the decomposition of CNTs.…”

“…The temperature defined for the end of water removal and the initial decomposition of functional groups (especially carboxyl groups) is generally in the range between 100 and 150 °C. 15,21,26 An usual range to analyze the degree of functionalization is from 120 to 400 °C, 15 which was used in this work once no weight loss was observed in this temperature range for the pristine MWCNTs.…”

“…7,10,13,14 The inserted functional groups, particularly carboxyls, are also basis for subsequent functionalization, such as amidation, alkylation, esterification and thiolation. 6,7,15,16 SO 4 , which are based on a single step treatment or a two-step sequence. The most common processes use ultrasonic bath, [17][18][19][20] reflux at high temperatures 9,12,13,[20][21][22][23][24][25][26] (occasionally under magnetic stirring) 10,27,28 or ultrasonic bath followed by reflux.…”

Methane decomposition for carbon nanotube production: Optimization of the reaction parameters using response surface methodology

“…A c c e p t e d M a n u s c r i p t 28 1350 cm -1 , 2650 cm -1 , and 2930 cm -1 corresponding to the G band, D band,G' band, and the G+D band (or G"), respectively . The D-band is recognized as the disorder features of the hexagonal graphitic layers, while the G and G' bands are assigned to the tangential stretching mode of the graphite C=C bond, and acknowledged as the two most prominent original graphite structures, respectively (Robertson, 1986;Silva et al, 2012;Tuinstra and Koenig, 1970). The presence of G and G' bands confirms the formation of graphitic nanotubes.…”