Individual Dissolution of Single-Walled Carbon Nanotubes in Aqueous Solutions of Steroid or Sugar Compounds and Their Raman and Near-IR Spectral Properties

Effect of Thermal Oxidation of Carbon Nanotubes during Wet Spinning into Fibers Using Sodium Cholate Surfactant in Aqueous Dispersion

Surfactant-based wet spinning is a promising route toward the eco-friendly production of carbon nanotube fibers (CNTFs). However, currently, the properties of surfactant-based wet-spun CNTFs lag behind those produced by other methods, indicating the need for further understanding and research. Here, we explored the surface characteristics of carbon nanotubes (CNTs) that are advantageous for the properties of CNTFs produced by wet spinning, using sodium cholate as a surfactant. Our finding indicates that appropriate thermal oxidation of CNTs enhances the fiber properties, while excessive oxidation undermines them. This implies that the bonding mechanism between CNTs and sodium cholate involves hydrophobic interaction and π-π interaction. Therefore, it is crucial to preserve a clean surface of CNTs in wet spinning using sodium cholate. We believe our research will contribute to the advancement of surfactant-based wet spinning of CNTFs.

Sonochemical Synthesis and Ion Transport Properties of Surfactant-Stabilized Carbon Nanotube Porins

Carbon nanotube porins (CNTPs), short segments of carbon nanotubes stabilized by a lipid coating, are a promising example of artificial membrane channels that mimic a number of key behaviors of biological ion channels. While the lipid-assisted synthesis of CNTPs may facilitate their subsequent incorporation into lipid bilayers, it limits the applicability of these pores in other self-assembled membrane materials and also precludes the use of large-scale purified CNT feedstocks. Here we demonstrate that CNTPs can be synthesized by sonochemical cutting of long CNT feedstocks in the presence of different surfactants, producing CNTS with transport properties identical with those obtained by the lipid-assisted procedure. Our results open up a wide variety of synthetic routes for CNTP production.

Signatures of Chemical Dopants in Simulated Resonance Raman Spectroscopy of Carbon Nanotubes

Single-walled carbon nanotubes (SWCNTs) with organic sp2 or sp3 hybridization defects allow the robust tunability of many optoelectronic properties in these topologically interesting quasi-one-dimensional materials. Recent resonant Raman experiments have illuminated new features in the intermediate-frequency region upon functionalization that change with the degree of functionalization as well as with interactions between defect sites. In this Letter, we report ab initio simulated near-resonant Raman spectroscopy results for pristine and chemically functionalized SWCNT models and find new features concomitant with experimental observations. We are able to assign the character of these features by varying the frequency of the external Raman laser frequency near the defect-induced E11* optical transition using a perturbative treatment of the electronic structure of the system. The obtained insights establish relationships between the nanotube atomistic structure and Raman spectra facilitating further exploration of SWCNTs with tunable optical properties tuned by chemical functionalization.

Recent Advances in Structure Separation of Single-Wall Carbon Nanotubes and Their Application in Optics, Electronics, and Optoelectronics

Structural control of single-wall carbon nanotubes (SWCNTs) with uniform properties is critical not only for their property modulation and functional design but also for applications in electronics, optics, and optoelectronics. To achieve this goal, various separation techniques have been developed in the past 20 years through which separation of high-purity semiconducting/metallic SWCNTs, single-chirality species, and even their enantiomers have been achieved. This progress has promoted the property modulation of SWCNTs and the development of SWCNT-based optoelectronic devices. Here, the recent advances in the structure separation of SWCNTs are reviewed, from metallic/semiconducting SWCNTs, to single-chirality species, and to enantiomers by several typical separation techniques and the application of the corresponding sorted SWCNTs. Based on the separation procedure, efficiency, and scalability, as well as, the separable SWCNT species, purity, and quantity, the advantages and disadvantages of various separation techniques are compared. Combined with the requirements of SWCNT application, the challenges, prospects, and development direction of structure separation are further discussed.

Influence of Ionomer and Cyanuric Acid on Antistatic, Mechanical, Thermal, and Rheological Properties of Extruded Carbon Nanotube (CNT)/Polyoxymethylene (POM) Nanocomposites

The electrical properties of carbon-based filler-embedded polymer nanocomposites are essential for various applications such as antistatic and electromagnetic interference (EMI) applications. In this study, the impact of additives (i.e., ethylene-co-acid-co-sodium acid copolymer-based ionomer and cyanuric acid) on the antistatic, mechanical, thermal, and rheological properties of extruded multiwalled carbon nanotube (MWCNT)/polyoxymethylene (POM) nanocomposites were systematically investigated. The effects of each additive and the combination of additives were examined. Despite a slight reduction in mechanical properties, the incorporation of ionomer (coating on CNTs) and/or cyanuric acid (π-π interaction between CNTs and cyanuric acid) into the POM/CNT nanocomposites improved the CNT dispersity in the POM matrix, thereby enhancing electrical properties such as the electrical conductivity (and surface resistance) and electrical conductivity monodispersity. The optimum composition for the highest electrical properties was determined to be POM/1.5 wt% CNT/3.0 wt% ionomer/0.5 wt% cyanuric acid. The nanocomposites with tunable electrical properties are sought after, especially for antistatic and EMI applications such as electronic device-fixing jigs.

Nanophotonic biosensors harnessing van der Waals materials

Low-dimensional van der Waals (vdW) materials can harness tightly confined polaritonic waves to deliver unique advantages for nanophotonic biosensing. The reduced dimensionality of vdW materials, as in the case of two-dimensional graphene, can greatly enhance plasmonic field confinement, boosting sensitivity and efficiency compared to conventional nanophotonic devices that rely on surface plasmon resonance in metallic films. Furthermore, the reduction of dielectric screening in vdW materials enables electrostatic tunability of different polariton modes, including plasmons, excitons, and phonons. One-dimensional vdW materials, particularly single-walled carbon nanotubes, possess unique form factors with confined excitons to enable single-molecule detection as well as in vivo biosensing. We discuss basic sensing principles based on vdW materials, followed by technological challenges such as surface chemistry, integration, and toxicity. Finally, we highlight progress in harnessing vdW materials to demonstrate new sensing functionalities that are difficult to perform with conventional metal/dielectric sensors.

This review presents an overview of scenarios where van der Waals (vdW) materials provide unique advantages for nanophotonic biosensing applications. The authors discuss basic sensing principles based on vdW materials, advantages of the reduced dimensionality as well as technological challenges.

Recent Advances in Carbon Nanotubes for Nervous Tissue Regeneration

Regenerative medicine has taken advantage of several nanomaterials for reparation of diseased or damaged tissues in the nervous system involved in memory, cognition, and movement. Electrical, thermal, mechanical, and biocompatibility aspects of carbon-based nanomaterials (nanotubes, graphene, fullerenes, and their derivatives) make them suitable candidates to drive nerve tissue repair and stimulation. This review article focuses on key recent advances on the use of carbon nanotube- (CNT-) based technologies on nerve tissue engineering, outlining how neurons interact with CNT interfaces for promoting neuronal differentiation, growth and network reconstruction. CNTs still represent strong candidates for use in therapies of neurodegenerative pathologies and spinal cord injuries.

Multifunctional Heterogeneous Carbon Nanotube Nanocomposites Assembled by DNA-Binding Peptide Anchors

Although carbon nanotubes (CNTs) are remarkable materials with many exceptional characteristics, their poor chemical functionality limits their potential applications. Herein, a strategy is proposed for functionalizing CNTs, which can be achieved with any functional group (FG) without degrading their intrinsic structure by using a deoxyribonucleic acid (DNA)-binding peptide (DBP) anchor. By employing a DBP tagged with a certain FG, such as thiol, biotin, and carboxyl acid, it is possible to introduce any FG with a controlled density on DNA-wrapped CNTs. Additionally, different types of FGs can be introduced on CNTs simultaneously, using DBPs tagged with different FGs. This method can be used to prepare CNT nanocomposites containing different types of nanoparticles (NPs), such as Au NPs, magnetic NPs, and quantum dots. The CNT nanocomposites decorated with these NPs can be used as reusable catalase-like nanocomposites with exceptional catalytic activities, owing to the synergistic effects of all the components. Additionally, the unique DBP-DNA interaction allows the on-demand detachment of the NPs attached to the CNT surface; further, it facilitates a CNT chirality-specific NP attachment and separation using the sequence-specific programmable characteristics of oligonucleotides. The proposed method provides a novel chemistry platform for constructing new functional CNTs suitable for diverse applications.

Vial sonication and ultrasonic immersion probe sonication to generate stable dispersions of multiwall carbon nanotubes for physico-chemical characterization and biological testing

Nanotechnology is considered to be a key enabling technology and in recent years there has been much growth in the use of nanostructured materials in industrial applications and in consumer products. It is, therefore, important that prior to being commercialized in consumer products, engineered nanomaterials are subjected to a thorough physico-chemical characterization as part of broader risk assessment to evaluate their possible effects on human health and the environment. The proper dispersion of nanomaterials sourced as powders becomes a first crucial step in the characterization process. This paper focuses on the dispersion of multiwall carbon nanotubes - often hydrophobic and tangled - since it may be challenging to re-disperse them effectively in aqueous media prior to characterization. A comparison has been made of non-contact vial sonication and immersion probe sonication using tannic acid as a dispersant. Transmission electron microscopy and UV-Vis spectroscopy were the techniques used to evaluate the dispersions. We used High Content Imaging and Colony Forming Efficiency to perform in vitro cytotoxicity studies on Human Alveolar Epithelial cells. It was found that both sonication treatments produce equivalent stable dispersions. No cytotoxic effects from MWCNTs were observed although some toxicity was observed and attributed to excess of the tannic acid dispersant.

Surfactant-driven Amphoteric Doping of Carbon Nanotubes

Aqueous surfactant dispersion is the most typical starting step to functionalize materials consisting of carbon nanotubes, but the effects of surfactants on the electronic properties are still unclear. Here we report how the functional groups of surfactants affect the electronic properties of carbon nanotube films. Using spectroscopic and thermoelectric characterization, we demonstrate that anionic and non-ionic surfactants contribute to the formation of p-type and n-type carbon nanotubes, respectively. Additionally, p-type doping with oxygen adsorption is found to compete with surfactants' doping. These findings are useful for designing the srarting carbon nanotube materials exhibiting desirable electronic properties.

Cholate Adsorption Behavior at Carbon Electrode Interface and Its Promotional Effect in Laccase Direct Bioelectrocatalysis

Fast electron transfer between laccase (Lac) and single-walled carbon nanotubes (SWCNTs) can be achieved at a cholate-modified SWCNT interface. Furthermore, the catalytic reduction of O2 starts at a high potential, close to the equilibrium redox potential of the O2/H2O couple. A sodium cholate (SC)-modified electrode interface provides suitable conditions for Lac direct bioelectrocatalysis. In the present study, the SC promotional effect in Lac direct bioelectrocatalysis was investigated using various types of electrode materials. The fully hydrophilic surface of indium tin oxide and an Au electrode surface did not show a SC promotional effect, because SC did not bind to these surfaces. A carbon surface with a large number of defects was unsuitable for SC binding because of hydrophilic functional groups at the defect sites. Carbon surfaces with few defects, for example, basal-plane highly oriented pyrolytic graphite (HOPG), gave a SC promotional effect.

Scanning Techniques for Nanobioconjugates of Carbon Nanotubes

Nanobioconjugates using carbon nanotubes (CNTs) are attractive and promising hybrid materials. Various biological applications using the CNT nanobioconjugates, for example, drug delivery systems and nanobiosensors, have been proposed by many authors. Scanning techniques such as scanning electron microscopy (SEM) and scanning probe microscopy (SPM) have advantages to characterize the CNT nanobioconjugates under various conditions, for example, isolated conjugates, conjugates in thin films, and conjugates in living cells. In this review article, almost 300 papers are categorized based on types of CNT applications, and various scanning data are introduced to illuminate merits of scanning techniques.

Reversible dispersion and precipitation of single-walled carbon nanotubes using a pH-responsive rigid surfactant

Sonication is not required to re-disperse the precipitated SWNTs in a pH-responsive SWNTs dispersion using a rigid surfactant.

Micro-Raman spectroscopy as an enabling tool for long-term intracellular studies of nanomaterials at nanomolar concentration levels

Imaging of individual SWCNTs inside neural stem cells has been demonstrated using confocal scanning Raman microscopy. Hyperspectral Raman imaging allowed detection of nanomaterials applied to the cell in ultra-low doses in long-term studies.

Specific Molecular Interaction and Recognition at Single-Walled Carbon Nanotube Surfaces

Carbon nanotubes (CNTs) are carbon clusters (polymers) with huge molecular weight and have been the central material in the field of nanomaterials science and nanotechnology because of their remarkable electronic, thermal, mechanical, optical, and electrical properties. In this review article, we first focus on the formation of self-assembled CNT superstructures and spontaneous conductive CNT-honeycomb structure formation from CNT/long-chain ammonium lipids by simple solvent casting. We also summarized our recent studies on specific molecular interactions and recognition at single-walled carbon nanotube surfaces and CNT chirality recognition using specific polymers. For such studies, the key issue is to develop a methodology to solubilize/disperse them in solvent because as-synthesized CNTs form tightly bundled structures as a result of their strong van der Waals interactions and are insoluble in many solvents. For the analysis of molecules and CNT surfaces, the introduction of thermodynamic treatment and an HPLC method using CNT-coated silica as a stationary phase was powerful.

Photoluminescent carbon nanotubes interrogate the permeability of multicellular tumor spheroids

Nanomaterials have been extensively investigated for cancer drug delivery and imaging applications. Nanoparticles that show promise in two-dimensional cell culture systems often fail in more complex environments, possibly due to the lack of penetration in dense, three-dimensional structures. Multicellular tumor spheroids are an emerging model system to investigate interactions of nanoparticles with 3D in vitro cell culture environments. Using the intrinsic near-infrared emission of semiconducting carbon nanotubes to optically reconstruct their localization within a three-dimensional volume, we resolved the relative permeability of two different multicellular tumor spheroids. Nanotube photoluminescence revealed that nanotubes rapidly internalized into MCF-7 breast cancer cell-derived spheroids, whereas they exhibited little penetration into spheroids derived from SK-136, a cell line that we developed from murine liver cancer. Characterization of the spheroids by electron microscopy and immunohistochemistry revealed large differences in the extracellular matrix and interstitial spacing, which correlated directly with nanotube penetration. This platform portends a new approach to characterize the permeability of living multicellular environments.

Non-covalent polymer wrapping of carbon nanotubes and the role of wrapped polymers as functional dispersants

Carbon nanotubes (CNTs) have been recognized as a promising material in a wide range of applications from biotechnology to energy-related devices. However, the poor solubility in aqueous and organic solvents hindered the applications of CNTs. As studies have progressed, the methodology for CNT dispersion was established. In this methodology, the key issue is to covalently or non-covalently functionalize the surfaces of the CNTs with a dispersant. Among the various types of dispersions, polymer wrapping through non-covalent interactions is attractive in terms of the stability and homogeneity of the functionalization. Recently, by taking advantage of their stability, the wrapped-polymers have been utilized to support and/or reinforce the unique functionality of the CNTs, leading to the development of high-performance devices. In this review, various polymer wrapping approaches, together with the applications of the polymer-wrapped CNTs, are summarized.

Characterization of carbon nanotube dispersions in solutions of bile salts and derivatives containing aromatic substituents

Bile salts (BS) are known to solubilize high weight fractions of carbon nanotubes (CNTs) in aqueous solutions. Here, the efficiency of derivatives of bile salts (BSDs) containing aromatic substituents in dispersing single-wall CNTs (SWCNTs) has been investigated in order to check whether the presence of aromatic residues, because of their affinity toward carbon nanotube surfaces, determines improvements of the BS dispersion efficiency (DE). Electric arc and CoMoCAT SWCNTs were analyzed. The results, reported for the two surfactant concentrations of 0.06 and 1.0 wt %, show that the DE of BSDs depends on the position, orientation, and structure of the introduced aromatic residues. In the case of the CoMoCAT SWCNTs, at low surfactant concentration a DE improvement is observed in BSDs where the aromatic residue is linked either to carbon 3, located on the rigid four-ring system, or to the side chain. For the latter, this improvement is also enhanced in double-charge derivatives and kept at high surfactant concentration. It was also observed that at low concentrations of surfactant, the DE values of BSs and BSDs are usually larger than those of the more conventional detergent sodium dodecylsulfate.

Fuel cell electrocatalyst using polybenzimidazole-modified carbon nanotubes as support materials

Toward the next generation fuel cell systems, the development of a novel electrocatalyst for the polymer electrolyte fuel cell (PEFC) is crucial to overcome the drawbacks of the present electrocatalyst. As a conductive supporting material for the catalyst, carbon nanotubes (CNTs) have emerged as a promising candidate, and many attempts have been carried out to introduce CNT, in place of carbon black. On the other hand, as a polymer electrolyte, polybenzimidazoles (PBIs) have been recognized as a powerful candidate due to the high proton conductivity above 100 °C under non-humid conditions. In 2008, we found that these two materials have a strong physical interaction and form a stable hybrid material, in which the PBIs uniformly wrap the surfaces of the CNTs. Furthermore, PBIs serve as effective binding sites for the formation of platinum (Pt) nanoparticles to fabricate a ternary composite (CNT/PBIs/Pt). In this review article, we summarize the fundamental properties of the CNT/PBIs/Pt and discuss their potential as a new electrocatalyst for the PEFC in comparison with the conventional ones. Furthermore, potential applications of CNT/PBIs including use of the materials for oxygen reduction catalysts and reinforcement of PBI films are summarized.

Spectroscopic analysis of two distinct equilibrium states for the exchange reaction of sodium cholate and oligo-DNA on single-walled carbon nanotubes

Understanding the quantitative analysis of the transition adsorption structures of molecules on single-walled carbon nanotubes (SWNTs) is of importance from the point of view of both fundamental science and applications of nanotubes. Absorption spectroscopy reveals that two different equilibrium states are existent for the exchange reaction of sodium cholate (SC) and oligo-DNA (single-stranded 20-mer cytosine) on SWNTs. This is derived from the transitions of the adsorption structures of different chirality-types of SWNTs and SC/DNA at certain SC concentrations below the critical micelle concentration of SC.

Carbon Nanotubes: A Review on Structure and Their Interaction with Proteins

Carbon nanotubes (CNTs) are allotropes of carbon with a nanostructure that can have a length-to-diameter ratio greater than 1,000,000. Techniques have been developed to produce nanotubes in sizeable quantities, including arc discharge, laser ablation, and chemical vapor deposition. Developments in the past few years have illustrated the potentially revolutionizing impact of nanomaterials, especially in biomedical imaging, drug delivery, biosensing, and the design of functional nanocomposites. Methods to effectively interface proteins with nanomaterials for realizing these applications continue to evolve. The high surface-to-volume ratio offered by nanoparticles resulted in the concentration of the immobilized entity being considerably higher than that afforded by other materials. There has also been an increasing interest in understanding the influence of nanomaterials on the structure and function of proteins. Various immobilization methods have been developed, and in particular, specific attachment of enzymes on carbon nanotubes has been an important focus of attention. With the growing attention paid to cascade enzymatic reaction, it is possible that multienzyme coimmobilization would be one of the next goals in the future. In this paper, we focus on advances in methodology for enzyme immobilization on carbon nanotubes.

Thermodynamics on soluble carbon nanotubes: how do DNA molecules replace surfactants on carbon nanotubes?

Here we represent thermodynamics on soluble carbon nanotubes that enables deep understanding the interactions between single-walled carbon nanotubes (SWNTs) and molecules. We selected sodium cholate and single-stranded cytosine oligo-DNAs (dCn (n = 4, 5, 6, 7, 8, 10, 15, and 20)), both of which are typical SWNT solubilizers, and successfully determined thermodynamic properties (ΔG, ΔH and ΔS values) for the exchange reactions of sodium cholate on four different chiralities of SWNTs ((n,m) = (6,5), (7,5), (10,2), and (8,6)) for the DNAs. Typical results contain i) the dC5 exhibited an exothermic exchange, whereas the dC6, 8, 10, 15, and 20 materials exhibited endothermic exchanges, and ii) the energetics of the dC4 and dC7 exchanges depended on the associated chiral indices and could be endothermic or exothermic. The presented method is general and is applicable to any molecule that interacts with nanotubes. The study opens a way for science of carbon nanotube thermodynamics.

Noncovalent porphyrin-functionalized single-walled carbon nanotubes: solubilization and spectral behaviors

We describe the solubilization/dispersion of as-produced and purified single-walled carbon nanotubes (raw-SWNTs and p-SWNTs) with protoporphyrin IX derivatives and tetraphenylporphyrin iron(III) chloride, the spectral behavior of the octaalkylporphyrins-solubilized shortened-SWNTs (s-SWNTs), and the electrochemistry of a p-SWNTs/FePP cast film on a glassy carbon electrode. Transmission electron and atomic force microscopies, as well as UV-visible-near IR spectroscopy, revealed that the protoporphyrin IX derivatives individually dissolved the p-SWNTs in polar solvents under mild conditions of sonication using a bath-type sonicator, followed by centrifugation at 1000 g. The raw-SWNTs were more easily dissolved than the p-SWNTs with protoporphyrin IX zinc(II) ( ZnPP ), whereas the amount of the solubilized/dispersed p-SWNTs did not depend on the concentration of the solubilizer and sonication time. The absorption and fluorescence spectral measurements of the octaalkylporphyrins in dimethylformamide containing 1 vol% tetrahydrofuran with various amounts of the s-SWNTs showed that the absorption maxima of the octaalkylporphyrins decreased with an increase in the concentration of the s-SWNTs without wavelength shift and the fluorescence of the porphyrins was quenched by the addition of the s-SWNTs. These spectral behaviors are direct evidence for the interaction between the nanotube sidewall and the porphyrins in the solutions. The cyclic voltammograms of the p-SWNTs/hemin ( FePP ) and free hemin ( FePP ) suggest that the nanotubes act as a conduction passage for electrons between hemin ( FePP ) and the glassy carbon electrode.

Enhanced cell uptake via non-covalent decollation of a single-walled carbon nanotube-DNA hybrid with polyethylene glycol-grafted poly(l-lysine) labeled with an Alexa-dye and its efficient uptake in a cancer cell

The use of single-walled carbon nanotubes (SWNTs) for biomedical applications is a promising approach due to their unique outer optical stimuli response properties, such as a photothermal response triggered by near-IR laser irradiation. The challenging task in order to realize such applications is to render the SWNTs biocompatible. For this purpose, the stable and homogeneous functionalization of the SWNTs with a molecule carrying a biocompatible group is very important. Here, we describe the design and synthesis of a polyanionic SWNT/DNA hybrid combined with a cationic poly(l-lysine) grafted by polyethylene glycol (PLL-g-PEG) to provide a supramolecular SWNT assembly. A titration experiment revealed that the assembly undergoes an approximately 1 : 1 reaction of the SWNT/DNA with PLL-g-PEG. We also found that SWNT/DNA is coated with PLL-g-PEG very homogeneously that avoids the non-specific binding of proteins on the SWNT surface. The experiment using the obtained supramolecular hybrid was carried out in vitro and a dramatic enhancement in the cell uptake efficiency compared to that of the SWNT/DNA hybrid without PLL-g-PEG was found.

The potential of perylene bisimide derivatives for the solubilization of carbon nanotubes and graphene

Carbon nanotubes and graphene are outstanding materials of the 21st century with a broad spectrum of applications. However, major challenges are faced such as the intrinsically low solubility of both sp2 carbon allotropes. To overcome this hurdle the potential of noncovalent functionalization is summarized with a special focus on the establishment of the perylene bisimide unit as aromatic anchor to the graphitic surface. Rational surfactant design is unmasked as the key to solubilization of the carbon allotropes, while at the same time tailoring their surface properties, or even electronic properties in a fully reversible fashion.

Base and acid treatment of SWCNT-RNA transparent conductive films

RNA was used to exfoliate single-walled carbon nanotubes (SWCNTs) in aqueous solution, and the ratio of it was optimized to obtain the best dispersion state. The obtained homogeneous SWCNT solution with small bundle size was used to prepare flexible transparent conductive films by filtration method. Sodium hydroxide treatment combining short-time acid treatment was used to remove the RNA molecules. After treatment, the sheet resistance of the films decreased significantly, while the change on the transmittance was negligible. Besides, the polyethylene terephthalate substrate would not turn brittle through this treatment process. Flexible films with outstanding performance (190 Omega/sq, 85%) and good stability were obtained after treatment. X-ray photoelectron spectroscopy and scanning electron microscope were used to analyze the role of base and acid treatment in detail.

Noncovalent functionalization of single-walled carbon nanotubes

Single-walled carbon nanotubes (SWNTs) have attracted much attention on account of their potential to be transformed into new materials that can be employed to address a wide range of applications. The insolubility of the SWNTs in most solvents and the difficulties of handling these highly intractable carbon nanostructures, however, are restricting their real-life applications at the present time. To improve upon the properties of the SWNTs, low-cost and industrially feasible approaches to their modifications are constantly being sought by chemists and materials scientists. Together, they have shown that noncovalent functionalization of the SWNTs can do much to preserve the desired properties of the SWNTs while remarkably improving their solubilities. This Account describes recent advances in the design, synthesis, and characterization of SWNT hybrids and evaluates applications of these new hybrid materials based on noncovalently functionalized SWNTs. Their solubilization enables the characterization of these hybrids as well as the investigation of the properties of the SWNTs using solution-based techniques. Cognizant of the structural properties of the functional molecules on the SWNTs, we present some of the recent work carried out by ourselves and others under the umbrella of the following three subtopics: (i) aromatic small-molecule-based noncovalent functionalization, (ii) biomacromolecule-based noncovalent functionalization, and (iii) polymer-based noncovalent functionalization. Several examples for the applications of noncovalently functionalized SWNT hybrids in the fabrication of field-effect transistor (FET) devices, chemical sensors, molecular switch tunnel junctions (MSTJs), and photovoltaic devices are highlighted and discussed. The blossoming of new methods for the noncovalent functionalization of the SWNTs promises a new generation of SWNT hybrid-based integrated multifunctional sensors and devices, an outcome which is essential for the development of carbon nanotube chemistry that interfaces with physics, materials, biology, and medical science.