Waseem Khan1, Rahul Sharma2, PK Chaudhury3, AM Siddiqui1, Parveen Saini2*
1Department of Physics, Jamia Millia Islamia, New Delhi-110 025, India
2CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi-110 012, India
3Solid State Physics Laboratory, Timarpur, Delhi- 110 054, India
Received: 05 December, 2016; Accepted: 16 December, 2016; Published: 17 December, 2016
Parveen Saini, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi-110 012, India. E-mail:
Khan W, Sharma R, Chaudhury PK, Siddiqui AM, Saini P (2016) Synthesis of Carboxylic Functionalized Multi Wall Carbon Nanotubes and Their Application for Static Charge Dissipative Fibers. Int J Nanomater Nanotechnol Nanomed 2(1): 025-028. DOI: 10.17352/2455-3492.000011
© 2016 Khan W, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Carbon nanotubes (CNTs); Functionalization; Electron microscopy; Raman spectroscopy; Infrared spectroscopy; Electrostatic dissipation (ESD)
In the present study, multi wall carbon nanotubes (CNTs) were chemically functionalized by concentrated nitric acid refluxing for 8 hours to form acid functionalized CNTs (FCNTs). Fourier transformed infrared spectra reveal the formation of carboxylic acid (-COOH) functional groups on the surface of chemically treated CNTs. The increase in intensity of Raman spectra D band relative to G band and enhancement of oxygen to carbon ratio confirm the functionalization and formation of –COOH groups, which in turn increase the dispersibility of CNTs in water, thus rendering them solution processable. The X-ray diffraction pattern and scanning electron microscopy images confirm the structure retention of CNTs even after harsh acid treatment. These functionalized CNTs show good affinity towards cotton fibers and the surface resistivity of FCNTs coated fiber has been found to be ~ 1010 Ω/square making them suitable for use as an anti-static material.
The use of electronic gadgets has become widespread and indispensable in the present technological era. This has given birth to an undesirable effect known as electrostatic dissipation (ESD) effect  . The accumulation of static charge in electronic goods packaging (which are primarily insulating polymeric materials) causes unnecessary damage to their electronics. Therefore, the importance of development of the ESD free materials has been realized for ultimate utility in electronic packaging. As the electrical conductivity is identified as prerequisite for static charge buildup control, several efforts have been made in the past to develop conducting materials based static safe compositions [2–8]. In particular, CNTs with excellent electrical conductivity, low density, high corrosion resistance, outstanding mechanical properties along with high thermal, chemical and environmental stability [6,9–12] is considered as most promising candidate for ESD control applications. However, their hydrophobicity and the inherent inertness of graphitic skeleton pose major challenges for their direct utilization via formation of CNTs filled composites or surface coatings. To solve these issues CNTs are often modified by covalent and non-covalent schemes (known as functionalization) which enhance their hydrophilicity, processability and compatibility [13–16] . The grafting of oxygen containing functional groups at the open ends and sidewalls of CNTs is a useful approach towards the covalent functionalization of CNTs. Particularly, the carboxylic acid group (i.e. –COOH functionality) happens to be the most common functional groups which open up the possibility of further modification of CNTs via suitable solution based chemical routes. It is worth mentioning that functionalized CNTs contain polar groups which enable their dispersion inside solvents, enhances compatibility with polymeric matrices and improves their ability to surface coat the polymeric substrate based packaging materials [16–20].
Here, we have reported the synthesis of covalently functionalized MWCNTs which can be easily coated over cotton fibers and demonstrated the application of these functionalized CNTs coated fibers for anti- static application.
The MWCNTs used in the experiment was purchased from Nanoshel with diameter 10-20 nm, length 3-8 µm and (>99 %) purity. The 70% nitric acid of analytical grade was procured from Merck Specialties Pvt. Ltd. Cellulose nitrate membrane filters with 0.45 μm pore size produced by Millipore were used in this experiment.
About 250 mg of pristine MWCNTs was mixed with 200 mL concentrated nitric acid and the mixture was refluxed for 8 hours followed by its ultracentrifugation at 10000 rpm. The FCNT pulp was dispersed in 500 mL distilled water followed by filtration through a cellulose nitrate membrane filter (0.45 μm pore size) using a vacuum filtration assembly. The sample was repeatedly washed with distilled water till neutral pH of filtrate. The filtered FCNTs bedding was dried in a vacuum oven at 80ºC for 24h and obtained FCNTs powder was characterized using different techniques. Figure 1a,b, show the schematics of pristine CNTs and functionalized CNTs (FCNTs) respectively whereas Figure 1c shows the actual refluxing setup used to carry out the reaction.