Gas-phase catalytic growth of single-walled carbon nanotubes from carbon monoxide

Nikolaev, Pavel; Bronikowski, Michael J.; Bradley, Robert S.; Rohmund, F.; Colbert, Daniel T.; Smith, K. A.; Smalley, R. E.

doi:10.1016/s0009-2614(99)01029-5

Cited by 1,733 publications

(1,181 citation statements)

References 13 publications

Supporting

Mentioning

1,133

Contrasting

Unclassified

Order By: Relevance

“…The recent discovery of carbon nanotubes spurred fast-paced research that has resulted in an impressive body of literature: experimental validation of theoretical predictions for onedimensional systems; 85 development of commercially attractive nanotube synthesis methods; 28,86 and the assignment of optical features to specific nanotube structures 87 are examples of such advances. Already, from strong composites and nanoscale electronics to biological tags, these molecules are beginning to find application in commercially relevant avenues.…”

Section: Discussionmentioning

confidence: 99%

“…25,26 Synthesis times vary from a few minutes to several hours, and SWNT growth ceases when the feedstock is discontinued or the catalyst becomes poisoned by amorphous carbon. 27,28 The catalyst lifetime can be extended by using carbon sources containing oxygen 18,24,28 or by introducing water, oxygen, or hydrogen gas during the synthesis. 29,30 Chemical vapor deposition offers a number of advantages over the arc discharge and laser vaporization methods for SWNT synthesis.…”

Section: Synthesis Of Swntsmentioning

confidence: 99%

“…SWNT starting materials were used as-received, and approximately 2 mg of nanotube soot was added to each surfactant solution. For consistency, the same two stock samples of HiPco (Carbon Nanotechnologies, Inc.) 28 and Chemical structures of dispersing agents used in this study. For DNA, the integer n denotes the number of repeating (GT) n units (G is the upper base located at the 5'-end and T is the lower base situated at the 3'-end).…”

Section: Suspension Of Swnts In Dispersing Agentsmentioning

confidence: 99%

See 2 more Smart Citations

Photophysics of Individual Single-Walled Carbon Nanotubes

2008

View full text Add to dashboard Cite

Single-walled carbon nanotubes (SWNTs) are cylindrical graphitic molecules that have remained at the forefront of nanomaterials research since 1991, largely due to their exceptional and unusual mechanical, electrical, and optical properties. The motivation for understanding how nanotubes interact with light (i.e., SWNT photophysics) is both fundamental and applied. Individual nanotubes may someday be used as superior near-infrared fluorophores, biological tags and sensors, and components for ultrahigh-speed optical communications systems. Establishing an understanding of basic nanotube photophysics is intrinsically significant and should enable the rapid development of such innovations. Unlike conventional molecules, carbon nanotubes are synthesized as heterogeneous samples, composed of molecules with different diameters, chiralities, and lengths. Because a nanotube can be either metallic or semiconducting depending on its particular molecular structure, SWNT samples are also mixtures of conductors and semiconductors. Early progress in understanding the optical characteristics of SWNTs was limited because nanotubes aggregate when synthesized, causing a mixing of the energy states of different nanotube structures. Recently, significant improvements in sample preparation have made it possible to isolate individual nanotubes, enabling many advances in characterizing their optical properties. In this Account, single-molecule confocal microscopy and spectroscopy were implemented to study the fluorescence from individual nanotubes. Single-molecule measurements naturally circumvent the difficulties associated with SWNT sample inhomogeneities. Intrinsic SWNT photoluminescence has a simple narrow Lorentzian line shape and a polarization dependence, as expected for a one-dimensional system. Although the local environment heavily influences the optical transition wavelength and intensity, single nanotubes are exceptionally photostable. In fact, they have the unique characteristic that their single molecule fluorescence intensity remains constant over time; SWNTs do not “blink” or photobleach under ambient conditions. In addition, transient absorption spectroscopy was used to examine the relaxation dynamics of photoexcited nanotubes and to elucidate the nature of the SWNT excited state. For metallic SWNTs, very fast initial recovery times (300–500 fs) corresponded to excited-state relaxation. For semiconducting SWNTs, an additional slower decay component was observed (50–100 ps) that corresponded to electron–hole recombination. As the excitation intensity was increased, multiple electron–hole pairs were generated in the SWNT; however, these e−h pairs annihilated each other completely in under 3 ps. Studying the dynamics of this annihilation process revealed the lifetimes for one, two, and three e−h pairs, which further confirmed that the photoexcitation of SWNTs produces not free electrons but rather one-dimensional bound electron–hole pairs (i.e., excitons). In summary, nanotube photophysics is a rapidly developing area o...

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Synthesis Of Swntsmentioning

confidence: 99%

Section: Suspension Of Swnts In Dispersing Agentsmentioning

confidence: 99%

See 1 more Smart Citation

Photophysics of Individual Single-Walled Carbon Nanotubes

2008

View full text Add to dashboard Cite

show abstract

“…3,5 In a fume hood, a 20 mg sample of raw SWCNTs produced in the Rice University HiPco reactor 26,27 was added to a flame-dried 100 mL three neck round bottom flask and approximately 60 mL of NH 3 was condensed into the flask. Granular lithium metal (Sigma-Aldrich, 99% pure) was then added to the flask followed by the addition of 1.90 g of 1-iodododecane (Sigma-Aldrich).…”

Section: Dodecyl Functionalization Of Swcntsmentioning

confidence: 99%

Structure-Dependent Thermal Defunctionalization of Single-Walled Carbon Nanotubes

et al. 2015

View full text Add to dashboard Cite

Covalent sidewall functionalization of single-walled carbon nanotubes (SWCNTs) is an important tool for tailoring their properties for research purposes and applications. In this study, SWCNT samples were first functionalized by reductive alkylation using metallic lithium and 1-iodododecane in liquid ammonia. Samples of the alkyl-functionalized SWCNTs were then pyrolyzed under an inert atmosphere at selected temperatures between 100 and 500 °C to remove the addends. The extent of defunctionalization was assessed using a combination of thermogravimetric analysis, Raman measurements of the RBM, D, and G bands, absorption spectroscopy of the first-and second-order van Hove peaks, and near-IR fluorescence spectroscopy of (n,m)-specific emission bands. These measurements all indicate a substantial dependence of defunctionalization rate on nanotube diameter, with larger diameter nanotubes showing more facile loss of addends. The effective activation energy for defunctionalization is estimated to be a factor of ~1.44 greater for 0.76 nm diameter nanotubes as compared to those with 1.24 nm diameter. The experimental findings also reveal the quantitative variation with functionalization density of the Raman D/G intensity ratio and the relative near-IR 2 fluorescence intensity. Pyrolyzed samples show spectroscopic properties that are equivalent to those of SWCNTs prior to functionalization. The strong structure dependence of defunctionalization rate suggests an approach for scalable diameter-sorting of mixed SWCNT samples.KEYWORDS: covalent functionalization; pyrolysis; dodecylation; D/G ratio; nanotube fluorescence restoration 3 Single-walled carbon nanotubes (SWCNTs) are among the most intensely studied artificial nanomaterials because of their unusual fundamental properties and promise for diverse applications. An essential tool for tailoring the interactions of SWCNTs with their environment is functionalization. 1 Such functionalization may be either noncovalent, for example with coatings of surfactants, synthetic polymers, or biopolymers; 2 or covalent, achieved through chemical reactions that link addends to sidewall carbon atoms of the nanotube. [3][4][5][6] Both noncovalent and covalent functionalization are commonly used to allow SWCNTs to be individually suspended or dissolved in liquid media. In addition, one can sometimes exploit structure-specific interactions that depend on nanotube diameter and roll-up (chiral) angle. As an example, noncovalent interactions between nanotubes and the organic polymeric dye PFO are selective enough that it can extract a subset of SWCNT structures from broadly heterogeneous as-grown samples. 7 Covalent sidewall functionalization offers another possible route to SWCNT sorting, based on structure-dependent reactivity patterns. 8,9 The main such pattern is enhanced reactivity of smaller diameter nanotubes because of their greater sp 2 bond strain. 10 Although previously unexplored, variations in reactivity with structure should also affect the process of covalent defunctio...

show abstract

“…2(b)). Since the average diameter of Hipco SWCNT is 0.8 -1.2 nm 15 Amphiphilic urea groups of CB7 might be adsorbed to SWCNT surface. Generally, amphiphilic polymers such as poly(N-vinyl-2-pyrrolidone) and poly(ethylene glycol) are able to solubilize SWCNTs in aqueous media by wrapping.…”

mentioning

confidence: 99%