Purification strategies and purity visualization techniques for single-walled carbon nanotubes

Park, Tae‐Jin; Banerjee, Sarbajit; Hemraj‐Benny, Tirandai; Wong, Stanislaus S.

doi:10.1039/b510858f

Cited by 215 publications

(173 citation statements)

References 101 publications

Supporting

Mentioning

169

Contrasting

Order By: Relevance

“…Many commercial carbon nanotube samples have been post-processed to reduce metal and/or amorphous carbon, and to increase the nanotube fraction, but even these "purified" samples typically contain significant quantities (1.2-14.3%) of residual metal [1,2]. Nanotube purification technologies continue to improve [3][4][5][6][7][8][9], but deep purification can damage tube structure [10][11][12] and for the foreseeable future, most CNT samples will contain metals.…”

Section: Introductionmentioning

confidence: 99%

Targeted removal of bioavailable metal as a detoxification strategy for carbon nanotubes

Liu

Guo

Morris

et al. 2008

Carbon

124

110

View full text Add to dashboard Cite

There is substantial evidence for toxicity and/or carcinogenicity upon inhalation of pure transition metals in fine particulate form. Carbon nanotube catalyst residues may trigger similar metal-mediated toxicity, but only if the metal is bioavailable and not fully encapsulated within fluid-protective carbon shells. Recent studies have documented the presence of bioavailable iron and nickel in a variety of commercial as-produced and vendor "purified" nanotubes, and the present article examines techniques to avoid or remove this bioavailable metal. First, data are presented on the mechanisms potentially responsible for free metal in "purified" samples, including kinetic limitations during metal dissolution, the re-deposition or adsorption of metal on nanotube outer surfaces, and carbon shell damage during last-step oxidation or one-pot purification. Optimized acid treatment protocols are presented for targeting the free metal, considering the effects of acid strength, composition, time, and conditions for post-treatment water washing. Finally, after optimized acid treatment, it is shown that the remaining, non-bioavailable (encapsulated) metal persists in a stable and biologically unavailable form up to two months in an in vitro biopersistence assay, suggesting that simple removal of bioavailable (free) metal is a promising strategy for reducing nanotube health risks.

show abstract

Section: Introductionmentioning

confidence: 99%

Targeted removal of bioavailable metal as a detoxification strategy for carbon nanotubes

Liu

Guo

Morris

et al. 2008

Carbon

124

110

View full text Add to dashboard Cite

show abstract

“…Therefore, removing the metallic catalyst (typically Fe, Co and/or Ni) used in the growth of CNTs and other carbonaceous components is one of the fundamental challenges for the application of CNTs in many fields. 13 Many types of purification methods have been developed, including chemical, physical and chromatographic purification. 14,15 Because some of the metallic particles are protected by a graphitic shell, rigorous purification procedures might damage the tube structure of CNTs.…”

Section: Introductionmentioning

confidence: 99%

The contributions of metal impurities and tube structure to the toxicity of carbon nanotube materials

et al. 2012

View full text Add to dashboard Cite

Due to the existence of considerable quantities of metallic and carbonaceous impurities, the key factor and mechanism for the reported toxicity of carbon nanotubes (CNTs) are unclear. Here, we first quantify the contribution of metal residues and fiber structure to the toxicity of CNTs. Significant quantities of metal particles could be mobilized from CNTs into surrounding fluids, depending on the properties and constituents of the biological microenvironment, as well as the properties of metal particles. Furthermore, electron spin resonance measurements confirm that hydroxyl radicals can be generated by both CNTs containing metal impurities and acid-leachable metals from CNTs. Several biomolecules facilitate the generation of free radicals, which might be due to the participation of these biomolecules in redox cycling influenced by pH. Among several major metal residues, Fe has a critical role in generating hydroxyl radicals, reducing cell viability and promoting intracellular reactive oxidative species. Cell viability is highly dependent on the amount of metal residues and iron in particular, but not tube structure, while the negative effect of CNTs themselves on cell viability is very limited in a certain concentration range below 80 lg ml À1 . It is crucial to systematically understand how these exogenous and endogenous factors influence the toxicity of CNTs to avoid their undesirable toxicity. Keywords: biological microenvironments; carbon nanotube; metal impurities; reactive oxygen species; toxicity INTRODUCTION Engineered nanomaterials possess novel properties and have been used worldwide in numerous consumer products, for example, food, clothes, pharmaceuticals and cleaning products. Estimates suggest that by 2015 nanotechnology will have a trillion-plus dollar global economic impact. 1 Therefore, ensuring the safety of nanomaterials is of great importance to the tremendous commercial applications of nanotechnology. Safety evaluation of nanomaterials should consider their behaviors in various aspects, including their interaction with proteins, DNA, lipids, membranes, organelles, cells, tissues, biological fluids and even the dissolution of metal constituents. [2][3][4] Carbon nanotubes (CNTs) have attracted great interest from both scientists and the industry because their high aspect ratios, strength and remarkable physical properties make them a unique material with a wide range of promising applications. Many applications of CNTs in biomedicine have been proposed, including nanoelectronics, 4 biosensors, 5 biomolecular recognition devices and molecular transporters, 6 artificial water channels, 7 cancer therapy 8,9 and photoacoustic molecular imaging. 10 Because transitional metals are often used as catalysts during CNT synthesis, 11 it is unavoidable that as-received CNTs are contaminated by catalyst residues. 12 The catalyst precursor (such as iron carbonyl) decomposes, and nanometer-sized metal particles form from the decomposition products. Therefore,

show abstract

“…These methods are used in the mass synthesis of CNTs in which the CNTs are obtained as soot adhered on the wall of the production chambers. Since the as-synthesized soot contains amorphous carbons, multi-shelled graphites, fullerenes, and/or catalyst metal particles as impurities, a purification process is generally required prior to use (Bandow et al, 1998;Bai et al, 2004;Chiang et al, 2001;Colomer et al, 1999;Morishita & Takarada, 1999;Park et al, 2006). The high pressure carbon mono-oxide (HiPco) method (Nikolaev et al, 1999) has been one of the commercialized fabrication methods for the mass production of CNTs.…”

Section: Carbon Nanotubes Fabrication Methodsmentioning

confidence: 99%

Optical Deposition of Carbon Nanotubes for Fiber-based Device Fabrication

Kashiwagi¹,

Yamashita²

2010

Frontiers in Guided Wave Optics and Optoelectronics

View full text Add to dashboard Cite

Purification strategies and purity visualization techniques for single-walled carbon nanotubes

Cited by 215 publications

References 101 publications

Targeted removal of bioavailable metal as a detoxification strategy for carbon nanotubes

Targeted removal of bioavailable metal as a detoxification strategy for carbon nanotubes

The contributions of metal impurities and tube structure to the toxicity of carbon nanotube materials

Optical Deposition of Carbon Nanotubes for Fiber-based Device Fabrication

Contact Info

Product

Resources

About