Functionalization and Dissolution of Nitric Acid Treated Single-Walled Carbon Nanotubes

Abstract

We report an investigation of the nature and chemical functionalization of nitric acid treated single-walled carbon nanotubes (SWNTs). SWNTs washed with diluted sodium hydroxide solutions were characterized by near-IR, mid-IR, and Raman spectroscopy as well as TEM, and the remaining carboxylic acid content was determined to assess the effect of base washing on the removal of carboxylated carbon fractions, which are generated by the nitric acid treatment. It was found that even after exhaustive washing with aqueous base the purified SWNTs contain carboxylic acid groups in sufficient quantity to prepare high quality soluble SWNT materials by covalent functionalization with octadecylamine.

Deposition of Pristine and Functionalized MWCNTs in Alumina Matrix by Sol-Gel Technique and Investigation of their Ammonia Sensing Properties

“…These results support the fact that ammonia interaction with p-MWCNTs is dominated by physisorption which can easily be overcome at room temperature by nitrogen flow [9]. While ammonia interaction with f-CNTs where oxygen containing functional groups are present on CNTs surface chemisorptions is dominated and due to the strong chemical bonding chemisorbed molecules are hardly removed from CNTs upon air exposure [8][9], resulting in slow recovery of functionalized CNTs based ammonia sensors [16][17]. Hence it is clear that some external energy is needed to break the strong chemical bonds between ammonia molecule and oxygen containing groups of f-MWCNTs to achieve complete recovery.…”

“…This process was repeated several times until the pH of the solution reached up to neutral value. The acid treatment removed all the metallic impurities and greatly enhanced the solubility of MWCNTs in polar solvents by introducing carboxylic (-COOH) functional groups to the sidewalls and ends of MWCNTs [8],that is further confirmed by FTIR characterization as shown in Fig.2. …”

“…To enhance the solubility of CNTs several methods of chemical functionalization have been developed. The most widely used approach, is wet chemical oxidation process which is initiated by mixing CNTs with strong acids such nitric acid, sulfuric acid or a mixture of the two [8].…”

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

“…7,8 Among the different approaches for covalent modification, acid treatments are the most reported in literature, generally using nitric acid (HNO 3 ) or a mixture of HNO 3 and sulfuric acid (H 2 SO 4 ). [9][10][11][12] The acid treatments introduce oxygen functional groups on the surface of the CNTs, especially carboxyls, phenolic hydroxyls and lactones/lactols. 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. 14,23,[29][30][31] Most documents that describe the use of ultrasonic bath does not cite any heating or occasionally mention the temperature of 40 °C, 17 which can be naturally achieved due to the ultrasonic power delivered from some equipment.…”