Chemistry of Single-Walled Carbon Nanotubes

Niyogi, Sandip; Hamon, Mark A.; Hu, Haoquan; Zhao, Bin; Bhowmik, Paragranjita; Sen, Rahul; Itkis, Mikhail E.; Haddon, Robert C.

doi:10.1021/ar010155r

Cited by 1,462 publications

(973 citation statements)

References 127 publications

(335 reference statements)

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“…126 As a result, SWNTs are insoluble in water and nearly all common organic solvents, with the exception of N-methylpyrrolidone. 127,128 It is desirable to solubilize SWNTs in aqueous environments to accommodate both ease of sample processing and compatibility for biological applications.…”

Section: Motivationmentioning

confidence: 99%

Photophysics of Individual Single-Walled Carbon Nanotubes

2008

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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...

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Section: Motivationmentioning

confidence: 99%

Photophysics of Individual Single-Walled Carbon Nanotubes

2008

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“…of CNTs with aryldiazonium salts, first demonstrated by Bahr et al [23] This reaction which occurs at room temperature has been used extensively to attach various organic compounds to CNTs [24,25,26,27]. For the selective placement of nanotubes on metal oxides we combine it with the hydroxamic acid functionality.…”

Section: Figmentioning

confidence: 99%

Field-Effect Transistors Assembled from Functionalized Carbon Nanotubes

Klinke¹,

Hannon²,

Afzali³

et al. 2006

Nano Lett.

136

127

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We have fabricated field effect transistors from carbon nanotubes using a novel selective placement scheme. We use carbon nanotubes that are covalently bound to molecules containing hydroxamic acid functionality. The functionalized nanotubes bind strongly to basic metal oxide surfaces, but not to silicon dioxide. Upon annealing, the functionalization is removed, restoring the electronic properties of the nanotubes. The devices we have fabricated show excellent electrical characteristics.One-dimensional nanostructures, such as nanowires [1] and carbon nanotubes [2,3] (CNTs) have excellent electrical properties making them attractive for applications in nanotechnology [4,5,6,7]. Semiconducting nanotubes, in particular, are receiving considerable attention due to their very promising performance as channels of field effect transistors (FETs) [8,9,10,11,12]. However, in order for the large-scale integration of CNTs in electronics to take place, many challenges must be overcome. One particularly important problem is selectively positioning CNTs on a substrate. Although considerable progress has been made for nanoclusters [13,14,15] and nanowires [16,17,18] it remains a difficult task for CNTs. Several approaches have been demonstrated based on the chemical patterning of the substrate (typically SiO2) [19,20,21]. In these approaches surfaces are patterned with molecules that either promote or prevent nanotube adhesion. For example, amine-terminated compounds have been shown to enhance nanotube binding while hydrophobic compounds prevent it [22]. Nevertheless, these methods remain unsatisfactory because of the adverse influence of the functionalization on the electrical performance of the devices.Here we propose a new approach that allows to selectively position CNTs based on their functionalization rather than the modification of the substrate. The complete fabrication sequence of chemical functionalization, selective placement, fabrication of multiple devices and defunctionalization is demostrated. High-performance devices can thus be directly assembled. Specifically, we covalently bound molecules to the CNTs that contain the hydroxamic acid functionality (Fig. 1). The functionalized tubes bind strongly to Al2O3 (and other basic metal oxides), but not to SiO2. Upon heating to 600 • C, the functionalization is removed, and the electrical properties of the tube are restored. We exploited the selective bonding to position nanotubes at precise locations on a SiO2 substrate patterned with Al2O3. Using this approach we fabricated FETs with high yield and excellent electrical properties.Our functionalization strategy is based on the reaction * Electronic address: klinke@chemie.uni-hamburg.de; Present address:

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“…[1][2][3] In the field of biotechnology, CNTs-based biomaterials have also proved quite versatile with applications as diverse as prosthesis, biomolecular recognition and drug delivery systems. 4 Nonetheless, strong intermolecular π-π interactions between the nanotube walls and their high aspect ratio lead to a bundle-like arrangement, which represents a major drawback for their processability and application.…”

Section: Introductionmentioning

confidence: 99%

Poly(ethylene oxide)-b-poly(l-lactide) Diblock Copolymer/Carbon Nanotube-Based Nanocomposites: LiCl as Supramolecular Structure-Directing Agent

et al. 2011

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(2011). Poly(ethylene oxide)-b-poly(l-lactide) Diblock Copolymer/Carbon Nanotube-Based Nanocomposites: LiCl as Supramolecular Structure-Directing Agent. Biomacromolecules, 12 (11),[4086][4087][4088][4089][4090][4091][4092][4093][4094] ABSTRACT: This work relies on the CNT dispersion in either solution or a polymer matrix through the formation of a three component supramolecular system composed of PEO-b-PLLA diblock copolymer, carbon nanotubes (CNTs) and lithium chloride. According to a one-pot procedure in solution, the "self-assembly" concept has demonstrated its efficiency using suspension tests of CNTs.Characterizations of the supramolecular system by photon correlation spectroscopy, raman spectroscopy and molecular dynamics simulations highlight the charge transfer interaction from the CNTs towards the PEO-b-PLLA/LiCl complex. Finally, this concept was successfully extended in bulk (absence of solvent) via melt-processing techniques by dispersing these complexes in a poly(L-Lactide) (PLA) matrix. Electrical conductivity measurements and transmission electron microscopy attested for the remarkable dispersion of CNTs, leading to high-performance PLA-based materials.KEYWORDS: carbon nanotubes, polylactide, poly(ethylene oxide), supramolecular interactions, reactive extrusion, nanocomposites, molecular dynamics simulations Intr oductionOver the last two decades, carbon nanotubes (CNTs) have attracted a special attention to design new nanocomposites due to a unique combination of mechanical, thermal, structural and electrical properties. [1][2][3] In the field of biotechnology, CNTs-based biomaterials have also proved quite versatile with applications as diverse as prosthesis, biomolecular recognition and drug delivery systems. 4 Nonetheless, strong intermolecular π-π interactions between the nanotube walls and their high aspect ratio lead to a bundle-like arrangement, which represents a major drawback for their processability and application. 5 Different strategies aiming at the dispersion of the CNTs in solution or in a polymer matrix have thus been developed. Most of them lie in the non-covalent and covalent functionalizations of CNT surface. 6 However, the supramolecular approach is emerging as a very appealing pathway since it takes advantage of the preservation of the unsaturated conjugated structure. [7][8] This is also supported by a wide range of non-covalent interactions, performed in a reliable and cost-effective manner. For instance, these 3 non-covalently coated CNTs maintain their intrinsic features, namely a robust mechanical behavior, a high electronic conductivity, and their potential biosensing properties.Poly(ethylene oxide) (PEO) belongs to the class of polyethers, exhibiting good solubility in water and organic solvents. As far as their applications are concerned, PEO-containing compounds are used as excipients or as carriers in different biological materials, foods and cosmetics. Moreover, these polymers can develop a specific behavior under varied stimuli such as temperature and salt conce...

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Chemistry of Single-Walled Carbon Nanotubes

Cited by 1,462 publications

References 127 publications

Photophysics of Individual Single-Walled Carbon Nanotubes

Photophysics of Individual Single-Walled Carbon Nanotubes

Field-Effect Transistors Assembled from Functionalized Carbon Nanotubes

Poly(ethylene oxide)-b-poly(l-lactide) Diblock Copolymer/Carbon Nanotube-Based Nanocomposites: LiCl as Supramolecular Structure-Directing Agent

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