Surface Of Single-walled Carbon Nanotubes Research Articles

Block Copolymers as Dispersants for Single-Walled Carbon Nanotubes: Modes of Surface Attachment and Role of Block Polydispersity.

When using amphiphilic polymers to exfoliate and disperse carbon nanotubes in water, the balance between the hydrophobic and hydrophilic moieties is critical and nontrivial. Here, we investigate the mode of surface attachment of a triblock copolymer, Pluronics F127, composed of a central hydrophobic polypropylene oxide block flanked by hydrophilic polyethylene oxide blocks, onto single-walled carbon nanotubes (SWNTs). Crucially, we analyze the composition in dispersant of both the as-obtained dispersion (the supernatant) and the precipitate-containing undispersed materials. For this, we combine the carefully obtained data from 1H NMR peak intensities and self-diffusion and thermogravimetric analysis. The molecular motions behind the observed NMR features are clarified. We find that the hydrophobic blocks attach to the dispersed SWNT surface and remain significantly immobilized leading to 1H NMR signal loss. On the other hand, the hydrophilic blocks remain highly mobile and thus readily detectable by NMR. The dispersant is shown to possess significant block polydispersity that has a large effect on dispersibility. Polymers with large hydrophobic blocks adsorb on the surface of the carbonaceous particles that precipitate, indicating that although a larger hydrophobic block is good for enhancing adsorption, it may be less effective in dispersing the tubes. A model is also proposed that consistently explains our observations in SWNT dispersions and some contradicting findings obtained previously in carbon nanohorn dispersions. Overall, our findings help elucidating the molecular picture of the dispersion process for SWNTs and are of interest when looking for more effective (i.e., well-balanced) polymeric dispersants.

Synthesis of polyethyleneimines protonated by 1-pyrenesulfonic acid and their usability for solublization of single-walled carbon nanotube

Reaction of 1-pyrenesulfonic acid (Pyr-SO3H) with branched polyethyleneimine (PEI) in molar ratios of 1:1, 1:2, 1:3, and 1:4 produced PEIs with sulfopyrenyl pendant groups, denoted as Pyr-PEI(1:1), Pyr-PEI(1:2), Pyr-PEI(1:3), and Pyr-PEI(1:4), respectively; the degrees of protonation depended on the feed ratios of Pyr-SO3H/PEI. Treatment of single-walled carbon nanotube (SWNT) with Pyr-PEIs caused adhering of the pyrenyl group on the SWNT surface and produced soluble composites, SWNT-Pyr-PEIs. UV–vis and photoluminescence (PL) measurements indicated that the absorbance and PL intensity corresponding to SWNT in SWNT-Pyr-PEIs increased with increasing the content of the PEI unit in the composites. The electrical conductivities of SWNT-Pyr-PEIs were higher than that of pristine SWNT owing to n-doping, based on electron migration from the PEI unit to the SWNT.

Restriction Enzyme Analysis of Double-Stranded DNA on Pristine Single-Walled Carbon Nanotubes.

Nanoprobes such as single-walled carbon nanotubes (SWCNTs) are capable of label-free detection that benefits from intrinsic and photostable near-infrared fluorescence. Despite the growing number of SWCNT-based applications, uncertainty surrounding the nature of double-stranded DNA (dsDNA) immobilization on pristine SWCNTs has limited their use as optical sensors for probing DNA-protein interactions. To address this limitation, we study enzyme activity on unmodified dsDNA strands immobilized on pristine SWCNTs. Restriction enzyme activity on various dsDNA sequences was used to verify the retention of the dsDNA's native conformation on the nanotube surface and to quantitatively compare the degree of dsDNA accessibility. We report a 2.8-fold enhancement in initial enzyme activity in the presence of surfactants. Förster resonance electron transfer (FRET) analysis attributes this enhancement to increased dsDNA displacement from the SWCNT surface. Furthermore, the accessibility of native dsDNA was found to vary with DNA configuration and the spacing between the restriction site and the nanotube surface, with a minimum spacing of four base pairs (bp) from the anchoring site needed to preserve enzyme activity. Molecular dynamics (MD) simulations verify that the anchored dsDNA remains within the vicinity of the SWCNT, revealing an unprecedented bimodal displacement of the bp nearest to SWCNT surface. Together, these findings illustrate the successful immobilization of native dsDNA on pristine SWCNTs, offering a new near-infrared platform for exploring vital DNA processes.

Dispersing Carbon Nanotubes in Water with Amphiphiles: Dispersant Adsorption, Kinetics, and Bundle Size Distribution as Defining Factors

Debundling and dispersing single-walled carbon nanotubes (SWNTs) is essential for applications, but the process is not well understood. In this work, aqueous SWNT dispersions were produced by sonicating pristine SWNT powder in the presence of an amphiphilic triblock copolymer (Pluronic F127) as dispersant. Upon centrifugation, one obtains a supernatant with suspended individual tubes and thin bundles and a precipitate with large bundles (and impurities). In the supernatant, that constitutes the final dispersion, we determined the dispersed SWNT concentration by thermogravimetric analysis (TGA) and UV–vis spectroscopy, and the dispersant concentration by 1H NMR. The fraction of dispersant adsorbed at the SWNT surface was obtained by 1H diffusion NMR. Sigmoidal dispersion curves recording the concentration of dispersed SWNTs as a function of supernatant dispersant concentration were obtained at different SWNT loadings and sonication times. As SWNT bundles are debundled into smaller and smaller ones, the ess...

Improved solubility and efficient optical limiting for methacrylate-co-porphyrins covalently functionalized single walled carbon nanotube nanohybrids

To improve the dispersibility of single walled carbon nanotube (SWCNT) in common organic solvents and adjust its photoelectronic performance, two methacrylate-co-porphyrins covalently functionalized SWCNT nanohybrids (SWCNT-TPP 1 and SWCNT-TPP 2) were prepared by radical polymerization. This attachment of porphyrins onto the surface of SWCNT significantly improves their solubility and dispersion stability of the SWCNT-based materials in organic solvents. The electronic interactions between porphyrins and SWCNT were investigated by the UV–vis, fluorescence and Raman spectroscopic methods. Z-scan measurements suggested that both nanohybrids exhibited increased nonlinear absorption and optical limiting performances compared to the separate SWCNT and porphyrins, which can be ascribed to the synergetic effects originating from the charge transfer effect between the two counterparts. The best optical limiting performance is observed for SWCNT-TPP 1 due to more effective charge transfer effect in comparison with those of other samples. These results suggest that the radical polymerization is a useful approach towards the rational design of solution-processible yet stable optical limiting materials, and this concept may be readily extended to other directional optoelectronic properties.

Noncovalent Pyrene-Polyethylene Glycol Coatings of Carbon Nanotubes Achieve in Vitro Biocompatibility.

Single-walled carbon nanotubes (SWNTs) have become increasingly exploited in biological applications, such as imaging and drug delivery. The application of SWNTs in biological settings requires the surface chemistry to remain through the low solubility in aqueous media. In this research, a facile approach for the preparation of a polyethylene glycol (PEG)-coated SWNT-based nanocarrier was reported. We focused on the effect of PEG chain length and SWNT size on the cytotoxicity of PEG-coated SWNTs as a superior drug delivery nanovector. First, all-atom molecular dynamics (MD) simulations were employed to explore the stability and behavior of SWNT/pyrene-PEG (SWNT/Pyr-PEG) structures at a molecular level that is not attainable with experiments. The MD studies revealed that (i) π-π stacking interactions between the pyrene bearing PEG molecules and SWNTs are maintained in bulky situations, regardless of PEG molecular weight or SWNT size; (ii) pyrene molecules diffuse over the SWNT surface without detaching; and (iii) both short and long dynamic Pyr-PEG chains have the capability of effectively coating the SWNT surface. In light of the simulations, noncovalent (π-π stacking) assemblies of SWNT/Pyr-PEG with different molecular weights of PEG ( Mw = 2000, 5000, and 12000) were successfully fabricated and characterized. For longer PEG chains, more effective coating of SWNTs was obtained, resulting in more biocompatible SWNT/Pyr-PEG nanomaterials. The number of SWNTs coated by Pyr-PEG was highly dependent on the length of pyrene bearing PEG polymers. Moreover, the short SWNTs showed a higher amount of PEG coating with respect to the long SWNTs. Cell viability results demonstrated a dose-dependent cytotoxicity of coated SWNTs. Short SWNTs coated with longer PEG chains have low cytotoxicity to be used in in vivo studies.

Chiral Selective Chemical Reaction of Flavin-Derivative-Wrapped Semiconducting Single-Walled Carbon Nanotubes Based on a Specific Recognition

Abstract A specific chiral selective chemical reaction on flavin-wrapped single-walled carbon nanotubes (SWNTs) is recognized based on a unique assembled structure formation of the flavin when using a chlorinated solvent such as chloroform; namely, the self-assembled flavin onto the SWNT surface protected (8,6)SWNTs from the chlorine radical reaction.

A Fluorescent Carbon Nanotube Sensor Detects the Metastatic Prostate Cancer Biomarker uPA.

Therapeutic outcomes in patients with prostate cancer are hindered by the inability to discern indolent versus aggressive disease. To address this problem, we developed a quantitative fluorescent nanosensor for the cancer biomarker urokinase plasminogen activator (uPA). We used the unique fluorescent characteristics of single-walled carbon nanotubes (SWCNT) to engineer an optical sensor that responds to uPA via optical bandgap modulation in complex protein environments. The sensing characteristics of this construct were modulated by passivation of the hydrophobic SWCNT surface with bovine serum albumin (BSA). The sensor enabled quantitative detection of known uPA concentrations in human blood products. These experiments potentiate future use of this technology as a rapid, point-of-care sensor for biomarker measurements in patient fluid samples. We expect that further work will develop a method to discern aggressive vs indolentprostate cancer and reduceovertreatment of this disease.

Near-Infrared Fluorescence Modulation of Refolded DNA Aptamer-Functionalized Single-Walled Carbon Nanotubes for Optical Sensing

Selective modulation of near-infrared (NIR) fluorescence of single-walled carbon nanotubes (SWNTs) is important for their applications as NIR optical sensors and devices. Here, we study the target-molecule-mediated NIR fluorescence modulation of refolded DNA aptamer-functionalized SWNTs, using platelet-derived growth factor (PDGF) and a PDGF-binding aptamer as a model system. The aptamer–SWNT complexes use SWNT as nanoscale NIR optical emitters and DNA aptamers as molecular recognition elements. The binding of target molecules, PDGFs in this study, to PDGF-binding aptamers on the surface of SWNTs induces a conformation change of the aptamers, which modulates the NIR fluorescence of SWNT emitters. This study suggests that PDGF-binding aptamers noncovalently assembled on the SWNT surface can undergo a temperature- and divalent-ion-induced conformational change into a folded structure through multiple stages, which renders aptamer-functionalized SWNTs optically responsive to target molecules. In addition, ou...

Metal ion effect on the supramolecular structures of metalloporphyrins on single-walled carbon nanotube surface

In this study, supramolecular structures of metalloporphyrin derivatives, i.e., Zn, Co, and Ni on a single-walled carbon nanotube (SWNT) surface have been investigated using microscopic and spectroscopic measurements as well as density functional theory calculations, to identify the effect of metalation on the supramolecular structures of porphyrins on a curved carbon surface (SWNT). By changing the central metal incorporated inside the porphyrin ring, different supramolecular structures can be observed on the SWNT surface using scanning tunneling microscopy, which displays the effect of different metal centers on the supramolecular structure. Although predicting or understanding supramolecular structures on the SWNT surfaces is still a big challenge, this study will serve as a helpful key point for further understanding, building new supramolecular architectures on SWNT surfaces and designing novel molecular architectonics of porphyrin/SWNTs-based devices.

Ordered Nanostructures of Carbon Nanotube–Polymer Composites from Lyotropic Liquid Crystal Templating

AbstractA series of polymer nanocomposites containing single‐walled carbon nanotubes (SWNTs) are prepared from polymerizable quaternary ammonium surfactants using photo‐polymerization and investigated by means of polarized optical microscopy, small‐angle X‐ray scattering, and rheological measurements. The surfactant monomers with various alkyl chains of nonpolar tails form lyotropic liquid crystalline (LLC) mesophases in aqueous medium with hexagonal packing of cylindrical micelles. The physical adsorption of nonpolar tails of surfactants on the surface of SWNTs results in de‐bundled nanotubes. The LLC phase diagram is investigated as functions of alkyl chain length, concentration, temperature, and SWNTs. As such, addition of SWNTs does not change the hexagonal mesophases but enhances the order–disorder transition temperatures and alters the rheological behaviors. After photo‐polymerization, the microstructures of hexagonal packing are changed while addition of SWNTs does not disrupt the resulting microstructures. The polymerized composites are consistent with both lamellar and gyroid nanostructures and a possible model is proposed to interpret the observed phenomenon. Under the shear flow, the defect‐free monodomain structures are obtained in the LLC phase and subsequently locked in the solid film after polymerization.

Control of Electron Flow Direction in Photoexcited Cycloplatinated Complex Containing Conjugated Polymer-Single-Walled Carbon Nanotube Hybrids.

Conjugated polymers incorporated with cycloplatinated complexes (P1-Pt and P2-Pt) were used as dispersants for single-walled carbon nanotubes (SWCNTs). Significant changes in the UV-vis absorption spectra were observed after the formation of the polymer/SWCNT hybrids. Molecular dynamics (MD) simulations revealed the presence of a strong interaction between the cycloplatinated complex moieties and the SWCNT surface. The photoinduced electron transfer processes in these hybrids were strongly dependent on the type of the comonomer unit. Upon photoexcitation, the excited P1-Pt donates electrons to the SWCNT, while P2-Pt accepts electrons from the photoexcited SWCNT. These observations were supported by results from Raman and femtosecond time-resolved transient absorption spectroscopy experiments. The strong electronic interaction between the Pt complexes and the SWCNT gives rise to a new hybrid system that has a controllable photoinduced electron transfer flow, which are important in regulating the charge transport processes in SWCNT-based optoelectronic devices.

A high precision method for length-based separation of carbon nanotubes using bio-conjugation, SDS-PAGE and silver staining.

Parametric separation of carbon nanotubes, especially based on their length is a challenge for a number of nano-tech researchers. We demonstrate a method to combine bio-conjugation, SDS-PAGE, and silver staining in order to separate carbon nanotubes on the basis of length. Egg-white lysozyme, conjugated covalently onto the single-walled carbon nanotubes surfaces using carbodiimide method. The proposed conjugation of a biomolecule onto the carbon nanotubes surfaces is a novel idea and a significant step forward for creating an indicator for length-based carbon nanotubes separation. The conjugation step was followed by SDS-PAGE and the nanotube fragments were precisely visualized using silver staining. This high precision, inexpensive, rapid and simple separation method obviates the need for centrifugation, additional chemical analyses, and expensive spectroscopic techniques such as Raman spectroscopy to visualize carbon nanotube bands. In this method, we measured the length of nanotubes using different image analysis techniques which is based on a simplified hydrodynamic model. The method has high precision and resolution and is effective in separating the nanotubes by length which would be a valuable quality control tool for the manufacture of carbon nanotubes of specific lengths in bulk quantities. To this end, we were also able to measure the carbon nanotubes of different length, produced from different sonication time intervals.

Synthesis of Single-Walled Carbon Nanotubes Coated with Thiol-Reactive Gel via Emulsion Polymerization.

Single-walled carbon nanotubes (SWNTs) have unique near-infrared absorption and photoemission properties that are attractive for in vivo biological applications such as photothermal cancer treatment and bioimaging. Therefore, a smart functionalization strategy for SWNTs to create biocompatible surfaces and introduce various ligands to target active cancer cells without losing the unique optical properties of the SWNTs is strongly desired. This paper reports the design and synthesis of a SWNT/gel hybrid containing maleimide groups, which react with various thiol compounds through Michael addition reactions. In this hybrid, the method called carbon nanotube micelle polymerization was used to noncovalently modify the surface of SWNTs with a cross-linked polymer gel layer. This method can form an extremely stable gel layer on SWNTs; such stability is essential for in vivo biological applications. The monomer used to form the gel layer contained a maleimide group, which was protected with furan in endo-form. The resulting hybrid was treated in water to induce deprotection via a retro-Diels-Alder reaction and then functionalized with thiol compounds through Michael addition. The functionalization of the hybrid was explored using a thiol-containing fluorescent dye as a model thiol, and the formation of the SWNT-dye conjugate was confirmed by energy transfer from the dye to SWNTs. Our strategy offers a promising SWNT-based platform for biological functionalization for cancer targeting, imaging, and treatment.

Theoretical Investigation of Single-Molecule Sensing Using Nanotube-Enhanced Circular Dichroism.

First-principles calculations have been used to investigate the potential use of circular dichroism (CD) spectroscopy in single-molecule sensing. Using a real-space implementation of time-dependent density functional theory (TDDFT), several systems involving single-walled carbon nanotubes (SWCNT) and small molecules have been studied to evaluate their CD response. Large induced CD (ICD) effects, differing for each test molecule, were observed in all SWCNT-molecule complexes. As the SWCNT used in this study shows no intrinsic CD response, the ICD spectra are the result of interaction with the small molecules. This finding is general and independent of the (a)chiral nature of the adsorbed molecule. Our results indicate that it is possible to design a system that uses SWCNT for detection of molecules using the change in CD spectrum of the system induced by adsorption of the molecule onto the SWCNT surface.

Hybrid Materials Based on Poly-3-amine-7-methylamine-2-methylphenazine and Magnetite Nanoparticles Immobilized on Single-Walled Carbon Nanotubes.

Polymer-metal-carbon hybrid nanomaterials based on thermostable electroactive poly-3-amine-7-methylamine-2-methylphenazine (PAMMP), single walled carbon nanotubes (SWCNT), and magnetite (Fe3O4) nanoparticles were synthesized for the first time. Hybrid Fe3O4/SWCNT/PAMMP nanomaterial synthesis was carried out via in situ chemical oxidative polymerization of 3-amine-7-methylamine-2-methylphenazine hydrochloride in the presence of metal-carbon Fe3O4/SWCNT nanocomposites. Fe3O4/SWCNT nanocomposites were obtained by the immobilization of magnetite nanoparticles on the SWCNT surface in the course of Fe3O4 nanoparticles synthesis in alkaline medium. The developed nanocomposite materials were characterized by FTIR spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission (FE-SEM) scanning electron microscopy, atomic absorption spectrometry (AAS), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and magnetometry. The chemical structure and phase composition, magnetic and electrical properties, and thermal stability of the obtained multifunctional nanomaterials, depending on synthesis conditions, were investigated.

Encapsulation of single-walled carbon nanotubes with asymmetric pyrenyl-gemini surfactants

Whereas the encapsulation technology of surfactants coating on the surface of single-walled carbon nanotubes (SWCNTs) attracts much attention, the mechanisms of asymmetric surfactants interacting with the SWCNTs and their molecular structures are rarely reported. Herein, we report a molecular dynamics (MD) simulation study on the investigation of surfactant adsorption and induced colloidal stability onto different SWCNTs. The surfactant-based encapsulation system, originating from the complementary π-π stacking, is validated through two-dimensional number density maps. We find that the asymmetric pyrenyl-gemini surfactants (APGSs) form double-layer assembled architecture films on nanotube surface. The inner layers of the films are packed with the pyrenyl groups of APGSs, which interact with SWCNTs via π-π stacking, while the outer layers composed of alkyl chains of APGSs coat at the nanotube surface through van der Waals interactions. In addition, we observe a configurational transformation of APGSs on the SWCNT surface from the folding configuration to unfolding patterns, when increasing the nanotube radius or the surface coverage of APGSs. Our study provides helpful insights into the encapsulation mechanism of APGSs on the SWCNT surface and the design of highly selective dispersants for SWCNTs.

Control of Integrin Affinity by Confining RGD Peptides on Fluorescent Carbon Nanotubes.

Integrins are transmembrane receptors that mediate cell-adhesion, signaling cascades and platelet-mediated blood clotting. Most integrins bind to the common short peptide Arg-Gly-Asp (RGD). The conformational freedom of the RGD motif determines how strong and to which integrins it binds. Here, we present a novel approach to tune binding constants by confining RGD peptide motifs via noncovalent adsorption of single-stranded DNA (ssDNA) anchors onto single-walled carbon nanotubes (SWCNTs). Semiconducting SWCNTs display fluorescence in the near-infrared (nIR) region and are versatile fluorescent building blocks for imaging and biosensing. The basic idea of this approach is that the DNA adsorbed on the SWCNT surface determines the conformational freedom of the RGD motif and affects binding affinities. The RGD motif was conjugated to different ssDNA sequences in both linear ssDNA-RGD and bridged ssDNA-RGD-ssDNA geometries. Molecular dynamics (MD) simulations show that the RGD motif in all the synthesized systems is mostly exposed to solvent and thus available for binding, but its flexibility depends on the exact geometry. The affinity for the human platelet integrin αIIbβ3 could be modulated up to 15-fold by changing the ssDNA sequence. IC50 values varied from 309 nM for (C)20-RGD/SWCNT hybrids to 29 nM for (GT)15-RGD/SWCNT hybrids. When immobilized onto surface adhesion of epithelial cells increased 6-fold for (GT)15-RGD/SWCNTs. (GT)15-RGD/SWCNTs also increased the number of adhering human platelets by a factor of 4.8. Additionally, αIIbβ3 integrins on human platelets were labeled in the nIR by incubating them with these ssDNA-peptide/SWCNT hybrids. In summary, we show that ssDNA-peptide hybrid structures noncovalently adsorb onto SWCNTs and serve as recognition units for cell surface receptors such as integrins. The DNA sequence affects the overall RGD affinity, which is a versatile and straightforward approach to tune binding affinities. In combination with the nIR fluorescence properties of SWCNTs, these new hybrid materials promise many applications in integrin targeting and bioimaging.

Advances in surface-coated single-walled carbon nanotubes as near-infrared photoluminescence emitters for single-particle tracking applications in biological environments

Single-particle tracking (SPT) represents a powerful tool for revealing the single-molecule dynamics in a number of biological processes in live cells and biological tissue. Single-walled carbon nanotubes (SWCNTs) are promising photoluminescence emitters for SPT applications in various biological environments due to their characteristic large-aspect-ratio structures along with their bright and stable near-infrared (NIR) photoluminescence, which are invaluable for long-term video-rate imaging and tracking applications at the single-molecule level with high signal-to-noise ratios (SNRs). Recent advances in applying SWCNTs as NIR photoluminescence emitters have highlighted the understanding of brain tissue organization at the nanometer scale. In the first section, this review article summarizes the latest advances in different surface coatings commonly used for encapsulating SWCNT surfaces via molecular self-assembly in order to obtain surface-coated nanotubes with low cytotoxicity and minimal nonspecific interactions with live cells while maintaining their emission of bright photoluminescence to enable long-term photoluminescent imaging and tracking at the single-nanotube level in biological environments. The second section offers a comparison of different excitation strategies of (6,5) SWCNTs to determine the best excitation wavelength for efficient video-rate imaging and tracking of individual nanotubes in live brain tissue for up to tens of minutes without inducing unacceptable phototoxicity or temperature increases. Finally, this review showcases that, by utilizing the photoluminescence tracking of single nanotubes combined with super-resolution single-molecule localization microscopy technologies, it is practical to elucidate the ultrafine nanometer-scale organization of the brain extracellular space (ECS) and probe the local rheological properties of young rat brain with a subdiffraction optical resolution down to 50 nm at a subwavelength accuracy of ~40 nm. The findings primarily indicate the great diversity of the brain ECS and the inhomogeneous properties of the local viscosity in live brain tissue. Overall, because of their advantages of low cytotoxicity, bright photoluminescence, high SNRs (~25), and deep tissue penetration (~100 μm) for long-term video-rate imaging and tracking at the single-nanotube level under 845 nm excitation (K-momentum exciton–phonon sideband, KSB), phospholipid-polyethylene glycol-coated SWCNTs hold great potential as NIR photoluminescence emitters for single-particle tracking in biological environments, as exemplified here in live brain tissue, and may find extended applications in elucidating the fundamental roles of the brain ECS in various biological processes, such as sleep, memory, aging, brain tumor progression, and neurodegenerative disease development.

Influence of Carbon Nanotube Chirality on Sodium Cholate Adsorption in Aqueous Suspensions

Established chirality separation techniques for single-wall carbon nanotubes (SWNTs) in aqueous suspensions make use of chirality specific adsorption behavior of surfactants on these nano-carbon surfaces. Here, we investigate the adsorption of sodium cholate on SWNTs of different chirality with diameters ranging from 0.7 to 1 nm. Titration studies are performed at different temperatures by measuring photoluminescence emission energies of the diluted SWNT suspensions. The high sensitivity of the exciton to its environment allows to detect small changes in arrangement and concentration of surfactants on the SWNT surface, as recently shown for the (6,5) chirality by Bergler et al. [1]. Here we report on substrate-induced cooperative adsorption regimes for sodium cholate on five different SWNT chiralities. The critical micelle concentrations of the cholate-SWNT micelles exhibit a linear increase with SWNT diameter, while the thermodynamic stability of the cholate-SWNT micelles decreases. These diameter and temperature dependences may play a key role in the separation of SWNT chiralities by density gradient ultracentrifugation and aqueous two phase extraction and thus may help not only to understand the microscopic sorting mechanisms but also to improve empirical preparation protocols. [1] Bergler et al., Langmuir 2016, 32, 9598-9603, DOI: 10.1021/acs.langmuir.6b02759