Confinement In Carbon Nanotubes Research Articles

Perylene diimide growth on both sides of carbon nanotubes for remarkably boosted photocatalytic degradation of diclofenac

Perylene diimide and its derivatives are promising photocatalysts for clean and efficient production, but their practical application in the field of photocatalysis is still limited by the rapid photogenerated charge recombination. In this work, the confined photocatalysts were synthesized by using a gas-phase self-assembly method and comparing the morphology and photocatalytic properties of different photocatalysts after the confinement of carbon nanotubes. The confinement effect of carbon nanotubes acts to stabilize perylene diimide. Electrostatic interaction formed by a wide range of dispersion forces is dominant in the process of stabilization. Benefitting from the three-dimensional electron transfer pathway formed by the conjugation of perylene diimide with a large number of π electrons to the carbon nanotubes plane, the confined photocatalyst shows the pseudo-first-order kinetic constant k of 1.106 h−1 for the photocatalytic degradation of diclofenac under light, which is 6.11 times higher than that of perylene diimide. The electron transfer created an internal electric field at the interface from carbon nanotubes to perylene diimide, which greatly accelerated the separation of photogenerated electron-hole pairs and improved the photocatalytic activity. This study further expands the applicability of perylene diimide in the field of photocatalysis and provides a new approach for water environment treatment.

Nanoscale confinement in carbon nanotubes encapsulated zero-valent iron for phenolics degradation by heterogeneous Fenton: Spatial effect and structure–activity relationship

• Confinement effect was significant for 3–7 nm carbon nanotubes (CNTs) cavity encapsulated Fe. • The better reusability of Fe 0 @CNTs (3)-(7) was exhibited for five runs compared with other CNTs. • The active enhancement attributed to electron transfer and interaction between Fe and CNTs. • The confinement role reached 2.13-folds of homogeneous role for phenol removal by Fe 0 @CNTs (5). • Fe 0 @CNTs ( x ) with positive charges was conductive to adsorb the negatively charged phenols. In heterogeneous Fenton, nanostructured iron catalysts with confinement effect greatly improve the effectiveness for organic pollutants removal, however, this effect dependence on the space of substrate remains unclear and thereby limit the application of confined catalysis. Herein, Fe particles encapsulated in carbon nanotubes with inner diameter of 3–30 nm (Fe 0 @CNTs ( x )) were prepared and tested as catalysts to degrade model pollutant of phenol and four phenolic compounds ( p -diphenol ( p -DP), p -aminophenol ( p -AP), p -nitrophenol ( p -NP) and p -chlorophenol ( p -CP)). With the increasing of CNTs inner diameter from 3 to 30 nm, the encapsulated Fe particles linearly increased from 2.68 to 14.75 nm. The confinement effect was significant in the range of 3–7 nm of CNTs cavity, especially at 5 nm, which was critical to decrease iron leaching and enrich hydroxyl radical generation for efficient pollutants removal by surface heterogeneous reaction (2.13-folds compared with the homogeneous Fenton). In addition, the Fe 0 @CNTs (3) - (7) with positive charges was conductive to adsorb the negatively charged phenols ( p -DP and p -AP) compared with non-spatial confinement of Fe-CNTs with negative charge. According to the experiment and DFT calculations, the quantitative structure–activity relationship about electron transfer was established, indicating that the electron from highest occupied molecular orbital (HOMO) of p -AP could migrate to lowest unoccupied molecular orbital (LUMO) of Fe 0 @CNTs and further to HOMO of Fe 0 @CNTs. The electron in HOMO of Fe 0 @CNTs could migrate into H 2 O 2 to generate · OH. This finding suggested a new paradigm to fulfill selective oxidation of the pollutants with electron-withdrawing group by suitable heterogeneous catalysts having significant confinement effect with more effective utilization of · OH in Fenton reaction.

Powder assembly & alloying to CNT/Al–Cu–Mg composites with trimodal grain structure and strength-ductility synergy

A novel strategy of powder assembly & alloying was used to achieve trimodal grain structure in carbon nanotubes (CNTs) reinforced aluminum matrix composites. The soft pure Al and hard 2024Al powders were firstly ball milled with CNTs for CNT/Al and CNT/2024Al flakes with different thicknesses, then were assembled with coarse-grained pure Al powders. Under the confinement of CNTs, these three building blocks evolved into ultrafine grains (UFG) smaller than 500 nm, fine grains (FG) between 500 nm and 2 μm and coarse grains (CG) about 9.8 μm, respectively, while the Al–Cu–Mg matrix achieved by the diffusion of Cu and Mg powders and elemental alloying with Al. Such a UFG-FG-CG trimodal grain structure contributed to superior strength-ductility synergy, as the 1.5 wt% CNT/Al–Cu–Mg composites exhibited tensile strength of 723 ± 6 MPa and elongation of 6.7 ± 0.6%. Therefore, powder assembly & alloying was proved an effective way to design and fabricate heterogeneous structured metal matrix nanocomposites.

A Polarization Boosted Strategy for the Modification of Transition Metal Dichalcogenides as Electrocatalysts for Water-Splitting.

The design and fabrication of transition metal dichalcogenides (TMDs) are of paramount significance for water-splitting process. However, the limited active sites and restricted conductivity prevent their further application. Herein, a polarization boosted strategy is put forward for the modification of TMDs to promote the absorption of the intermediates, leading to the improved catalytic performance. By the forced assembly of TMDs (WS2 as the example) and carbon nanotubes (CNTs) via spray-drying method, such frameworks can remarkably achieve low overpotentials and superior durability in alkaline media, which is superior to most of the TMDs-based catalysts. The two-electrode cell for water-splitting also exhibits perfect activity and stability. The enhanced catalytic performance of WS2 /CNTs composite is mainly owing to the strong polarized coupling between CNTs and WS2 nanosheets, which significantly promotes the charge redistribution on the interface of CNTs and WS2 . Density functional theory (DFT) calculations show that the CNTs enrich the electron content of WS2 , which favors electron transportation and accelerates the catalysis. Moreover, the size of WS2 is restricted caused by the confinement of CNTs, leading to the increased numbers of active sites, further improving the catalysis. This work opens a feasible route to achieve the optimized assembling of TMDs and CNTs for efficient water-splitting process.

Hydration of a small protein under carbon nanotube confinement: Adsorbed substates induce selective separation of the dynamical response

The co-involvement of biological molecules and nanomaterials has increasingly come to the fore in modern-day applications. While the "bio-nano" (BN) interface presents physico-chemical characteristics that are manifestly different from those observed in isotropic bulk conditions, the underlying molecular reasons remain little understood; this is especially true of anomalies in interfacial hydration. In this paper, we leverage atomistic simulations to study differential adsorption characteristics of a small protein on the inner (concave) surface of a single-walled carbon nanotube whose diameter exceeds dimensions conducive to single-file water movement. Our findings indicate that the extent of adsorption is decided by the degree of foldedness of the protein conformational substate. Importantly, we find that partially folded substates, but not the natively folded one, induce reorganization of the protein hydration layer into an inner layer water closer to the nanotube axis and an outer layer water in the interstitial space near the nanotube walls. Further analyses reveal sharp dynamical differences between water molecules in the two layers as observed in the onset of increased heterogeneity in rotational relaxation and the enhanced deviation from Fickian behavior. The vibrational density of states reveals that the dynamical distinctions are correlated with differences in crucial bands in the power spectra. The current results set the stage for further systematic studies of various BN interfaces vis-à-vis control of hydration properties.

A nuclear spin and spatial symmetry-adapted full quantum method for light particles inside carbon nanotubes: clusters of 3He, 4He, and para-H2.

We present a new nuclear spin and spatial symmetry-adapted full quantum method for light fermionic and bosonic particles under cylindrical carbon nanotube confinement. The goal is to address Fermi-Dirac and Bose-Einstein nuclear spin statistics on an equal footing and to deliver excited states with a similar accuracy to that of the ground state, implementing ab initio-derived potential models as well. The method is applied to clusters of up to four (three) 4He atoms and para-H2 molecules (3He atoms) inside a single-walled (1 nm diameter) carbon nanotube. Due to spin symmetry effects, the bound states energy landscape as a function of the angular momentum around the tube axis becomes much more complex and rich as the number of 3He atoms increase compared to the spinless 4He and para-H2 counterparts. Four bosonic 4He and para-H2 particles form pyramidal-like structures which are more compact as the particle mass and the strength of the inter-particle interaction increases. They feature stabilization of the collective rotational motion as bosonic quantum rings bearing persistent rotational motion and superfluid flow. Our results are brought together with two key experimental findings from the group of Jan-Peter Toennies: (1) the congestion of spectral profiles in doped 3He droplets as opposed to the case of 4He droplets (S. Gebenev, J. P. Toennies and A. F. Vilesov, Science, 1998, 279, 2083); (2) the onset of microscopic superfluidity in small doped clusters of para-H2 molecules (S. Grebenev, B. G. Sartakov, J. P. Toennies and A. F. Vilesov, Science, 2000, 289, 1532), but at the reduced dimensionality offered by the confinement inside carbon nanotubes.

Formation of one-dimensional quantum crystals of molecular deuterium inside carbon nanotubes

Crystallization under stringent cylindrical confinement leads to novel quasi-one-dimensional materials. Substances with strong cohesive interactions can eventually preserve the symmetries of their bulk phase compatible with the restricted geometry, while those with weak cohesive interactions develop qualitatively different structures. Frozen molecular deuterium (D2), a solid with a strong quantum character, is structurally held by weak dispersive forces. Here, the formation of one-dimensional D2 crystals under carbon nanotube confinement is reported. In contradiction with its weak cohesive interactions, their structures, scrutinized using neutron scattering, correspond to definite cylindrical sections of the hexagonal close-packed bulk crystal. The results are rationalized on the grounds of numerical calculations, which point towards nuclear quantum delocalization as the physical mechanism responsible for the stabilization of such outstanding structures.

Superior activity of Pd nanoparticles confined in carbon nanotubes for hydrogen production from formic acid decomposition at ambient temperature

Designing highly efficient and low-cost catalysts is essential toward realizing the practical application of hydrogen generation by formic acid decomposition (FAD) under ambient conditions. Herein, we report the synthesis of a hybrid material of Pd nanoparticles encapsulated within carbon nanotubes (CNTs) (Pd-CNTs-in). Transmission electron microscopy images show that most Pd nanoparticles (mean diameter 4.2 ± 0.8 nm) are located inside the nanotubes. Temperature-programmed reduction studies of H2 reveal that the average reduction temperature of the Pd(II) species adsorbed on the interior wall of the CNTs is 12 °C lower than those adsorbed on the outer walls of the CNT. Moreover, the as-prepared Pd-CNTs-in catalysts show extremely high FAD activity and durability at ambient temperature. The turn over frequency (TOF) value is as high as 1135 h−1 for the initial 10 min and does not decay significantly during the consecutive 3-time recycling studies. X-Ray photoelectron spectroscopy (XPS), surface-enhanced infrared spectroscopy (SEIRAS), and gas chromatography (GC) studies indicate that CNT confinement induced electronic structure modulation of Pd could be the major reason for the enhancement of FAD catalysis on the Pd-CNTs-in surface. This work could provide promising strategies for the fabrication of cost-effective and high-active Pd-based catalysts for formic acid dehydrogenation.

Enhanced thermal conductivity and electrical insulation properties of polymer composites via constructing Pglass/CNTs confined hybrid fillers

The preparation of thermal conductive and electrical insulating polymer composites has gained extensive interest due to their important applications. The morphological control of functional fillers is thought as an effective approach to achieve this. Herein, a novel method involves the confinement of carbon nanotubes (CNTs) in phosphate glass (Pglass) domains is presented. Due to the large interfacial tension between Pglass and polymer matrix, strong confinement of CNTs can be achieved while CNTs is incorporated into Pglass. Thus, the formation of CNTs conductive networks in polymer matrix can be prohibited in ternary polymer/Pglass/CNTs composites. Comparing with similar composites having high density polyethylene (HDPE) to realize confinement on CNTs, much higher thermal conductivity and much lower electrical conductivity are observed in polymer composites based on polypropylene (PP) containing boron nitride (BN). It is thought that the use of Pglass can provide an effective method for the preparation of thermally conductive and electrically insulating polymer composites.

Strong process-structure interaction in stoveable poly(urethane-urea) aligned carbon nanotube nanocomposites

The exceptional static and dynamic physical properties of poly(urethane-urea) (PUU) elastomers make them prime candidates for impulsive loading structural applications, such as blast protection coatings. Since the theoretical physical properties of carbon nanotubes (CNTs) are among the best for any currently known material, a number of previous studies explored the use of CNTs as nanoscale fillers to enhance the properties of PUU nanocomposites. However, due to the challenges inherent in dispersing CNTs in a PUU matrix and the resulting random orientation of the CNTs, these previous works observed marginal improvements in physical properties, and were unable to establish clear structure-property relations. Here, we report the synthesis of aligned-CNT (A-CNT) reinforced PUU polymer nanocomposites (A-PNCs) by infusing A-CNT forests with a stoveable PUU, and establish process-structure-property relations that quantify the contribution of CNT confinement on the PUU mechanical response. This stoveable process was achieved using blocked isocyanate which prevented polymerization until the blocks were removed with heat. PUUs of two distinct compositions were explored: one with 40 wt% hard-segment content (PUU211) and the other with 66 wt% hard-segment content (PUU541). Thermogravimetric analysis indicates that A-CNTs enhance the thermal stability of the hard-segment phase in PUU A-PNCs at 340 °C by up to 45% over the baseline PUUs. Atomic force microscopy reveals that the elongated nanophase hard-segment formations along the CNT axis observed only in the nanocomposites were of similar characteristic size to the average inter-A-CNT spacing (∼70 nm), indicating a strong influence of A-CNTs on the size and orientation of hard-segment nanophases, as corroborated via small angle X-ray scattering. Nanoindentation testing reveals that PUU A-PNCs possess significant elastic anisotropy, and exhibit enhanced longitudinal effective indentation moduli of ∼460 MPa (>3 × that of the PUU211 baseline) and ∼1350 MPa (∼1.5 × that of the PUU541 baseline) for PUU211 and PUU541 nanocomposites, respectively. This difference in magnitude of CNT reinforcement efficacy indicates that CNT confinement leads to significant hard-segment re-organization in the PUU211 A-PNCs, whereas the interconnected network of hard-segments in the PUU541 is affected by CNT templating to a lesser extent. Dynamic nanoindentation testing results are consistent with these interpretations, where longitudinally-loaded PUU211 A-PNCs are found to exhibit a >3 × enhancement in storage modulus at 1 Hz of ∼730 MPa, whereas the longitudinally-loaded PUU541 A-PNCs exhibit a slightly enhanced storage modulus enhancement at 1 Hz of 2190 MPa (∼1.5 × that of the PUU541 baseline). Reinforcement of PUUs with A-CNTs is a promising way to tune the physical properties of the PNCs; higher A-CNT packing densities, where the inter-CNT spacing could approach the nanophase characteristic diameter, could further enhance the PUU performance in ballistic protection applications.

Dispersion corrected interaction of polar and nonpolar fluids confined within carbon nanotubes: Density functional theoretical analysis using Grimme's D3 scheme

AbstractThe structural and flow characteristics of fluids within carbon nanotube (CNT) is dictated by the interaction of fluid molecules within the nanocavity of CNT. Therefore, in the present study, dispersion corrected density functional theory has been used to investigate the structure and interaction of polar and nonpolar molecules within CNT. The present study shows that there is profound effect on the interaction due to dispersion. The interaction energy of the confined water was found to be reduced with increasing distance of the water molecule from the wall of the CNT. The water is preferentially adsorbed over methane due to stronger interaction with CNT over methane. Further, water is preferentially adsorbed over methanol molecule when interaction is calculated without dispersion but after inclusion of dispersion interaction, the calculated results show that the methanol–CNT interaction is stronger than that of water molecule and hence preferentially adsorbed within the CNT as revealed from MD simulation. The present calculation reveals that that the effect of CNT confinement on the IR spectra of the single file water is quite considerable compared to the IR spectra of tetrahedral bulk water cluster. Therefore, the present results might be useful for the separation of polar molecule from nonpolar molecule during fabrication of CNT‐based filter and purification system.

Modeling the Self-Assembly of Bolaamphiphiles under Nanoconfinement by Coarse-Grained Molecular Dynamics.

Novel and complex nanostructures of amphiphiles assemblies facilitate realizing of many practical applications in nanotechnologies. Under different physical conditions, amphiphiles can form various morphologies. In this article, the self-assembly of bolaamphiphiles was investigated under the cylindrical confinement of carbon nanotubes by coarse-grained molecular dynamics simulation. We found that bolaamphiphiles inside a carbon nanotube with a relatively large diameter tended to self-assemble into curved cylindrical micelles, and further some of these micelles can form double helix structures which were not observed in bulk solutions. We develop an effective method to characterize different morphologies. Our analysis results showed that the formation of double helix and other amorphous morphologies of micelles in carbon nanotubes is not induced by the conformational variation of bolaamphiphiles. Moreover, through examining the potential energies of different structures, we infer that it is entropy which leads micelles to bend even to form double stranded helix structures. In addition, we analyzed the sizes of micelles and find the scission and recombination of micelles during the double helix formation process. This work indicates that the confinement of carbon nanotube is an available method to produce complex nanostructures and provides some new insights of the self-assembly of bolaamphiphiles.

Mesoscale evolution of non-graphitizing pyrolytic carbon in aligned carbon nanotube carbon matrix nanocomposites

Polymer-derived pyrolytic carbons (PyCs) are highly desirable building blocks for high-strength low-density ceramic meta-materials, and reinforcement with nanofibers is of interest to address brittleness and tailor multi-functional properties. The properties of carbon nanotubes (CNTs) make them leading candidates for nanocomposite reinforcement, but how CNT confinement influences the structural evolution of the PyC matrix is unknown. Here, the influence of aligned CNT proximity interactions on nano- and mesoscale structural evolution of phenol-formaldehyde-derived PyCs is established as a function of pyrolysis temperature ( $$T_{\mathrm {p}}$$ ) using X-ray diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy. Aligned CNT PyC matrix nanocomposites are found to evolve faster at the mesoscale by plateauing in crystallite size at $$T_{\mathrm {p}}$$ $$\sim$$ 800 $$^{\circ }\hbox {C}$$ , which is more than $$200\,\,^{\circ }\hbox {C}$$ below that of unconfined PyCs. Since the aligned CNTs used here exhibit $$\sim$$ 80 nm average separations and $$\sim$$ 8 nm diameters, confinement effects are surprisingly not found to influence PyC structure on the atomic-scale at $$T_{\mathrm {p}}$$ $$\le $$ 1400 $$^{\circ }\hbox {C}$$ . Since CNT confinement could lead to anisotropic crystallite growth in PyCs synthesized below $$\sim$$ 1000 $$^{\circ }\hbox {C}$$ , and recent modeling indicates that more slender crystallites increase PyC hardness, these results inform fabrication of PyC-based meta-materials with unrivaled specific mechanical properties.

Controlling activation barrier by carbon nanotubes as nano-chemical reactors.

The oxidative addition of primary amine on a monocyclic phospholane was studied in confined conditions. This one-step chemical reaction has been investigated using the DFT technique to elucidate the role of confinement in carbon nanotubes on the reaction. Calculations were carried out by a progressive increase of the nanotube diameters from 10Å to 15Å in order to highlight the dependence of the reactivity on the nanotube diameter. First, single point investigations were dedicated to the study of reactants, transition states, and products placed in the different nanotubes while keeping their optimized structure as free compounds. Second, all studied compounds were relaxed inside nanotubes and their geometries were fully optimized. Within these approaches, we proved that the activation barrier could be controlled depending on the confinement, generating a well-controlled catalysis process.

Size-dependence of carbon nanotube confinement in catalysis.

An increasing number of studies have demonstrated that confinement within carbon nanotubes (CNTs) provides an effective approach for the modulation of catalysis. It was generally predicted that confinement became stronger with a decreasing diameter of CNTs. However, our present study here overturns the previous expectation: the influence on catalysis is not monotonic. Instead, it exhibits a volcano relationship with CNT diameter. Taking Pt catalyzing O2 conversion and Re catalyzing N2 conversion as probes using density functional theory, we show that only within tubes with an i.d. of ∼1 nm can the activity of metal clusters be enhanced to its maximum. Furthermore, confinement only enhances the catalytic activity of metals with strong intrinsic binding with reactants, whereas it is suppressed for those with weak binding. These findings shed further light on the fundamental effects of confinement on catalysis, and could guide more rational design of confined catalysts.

On-surface synthesis of graphene nanoribbons with zigzag edge topology.

Graphene-based nanostructures exhibit electronic properties that are not present in extended graphene. For example, quantum confinement in carbon nanotubes and armchair graphene nanoribbons leads to the opening of substantial electronic bandgaps that are directly linked to their structural boundary conditions. Nanostructures with zigzag edges are expected to host spin-polarized electronic edge states and can thus serve as key elements for graphene-based spintronics. The edge states of zigzag graphene nanoribbons (ZGNRs) are predicted to couple ferromagnetically along the edge and antiferromagnetically between the edges, but direct observation of spin-polarized edge states for zigzag edge topologies--including ZGNRs--has not yet been achieved owing to the limited precision of current top-down approaches. Here we describe the bottom-up synthesis of ZGNRs through surface-assisted polymerization and cyclodehydrogenation of specifically designed precursor monomers to yield atomically precise zigzag edges. Using scanning tunnelling spectroscopy we show the existence of edge-localized states with large energy splittings. We expect that the availability of ZGNRs will enable the characterization of their predicted spin-related properties, such as spin confinement and filtering, and will ultimately add the spin degree of freedom to graphene-based circuitry.

Enhancement of the hydrogenation activity of a Pd-tridecilamine (TDA) complex by confinement in carbon nanotubes

An active hydrogenation Pd complex has been immobilised by impregnation on CNTs submitted to several treatments that lead to important differences in their surface chemistry and in the proportion of tubes with both ends open. Most of the hybrid catalysts are more active than the complex in homogeneous phase, but the support properties have an important impact in the catalytic activity. In general, the more developed the surface chemistry, the lower the activity. However, when CNTs are open at both ends, the Pd complex can enter the tubular cavity and an important enhancement of the catalytic activity due to a confinement effect is observed.

Ultimate osmosis engineered by the pore geometry and functionalization of carbon nanostructures.

Osmosis is the key process in establishing versatile functions of cellular systems and enabling clean-water harvesting technologies. Membranes with single-atom thickness not only hold great promises in approaching the ultimate limit of these functions, but also offer an ideal test-bed to explore the underlying physical mechanisms. In this work, we explore diffusive and osmotic transport of water and ions through carbon nanotube and porous graphene based membranes by performing molecular dynamics simulations. Our comparative study shows that the cylindrical confinement in carbon nanotubes offers much higher salt rejection at similar permeability in osmosis compared to porous graphene. Moreover, chemical functionalization of the pores modulates the membrane performance by its steric and electrostatic nature, especially at small-size pores due to the fact that the optimal transport is achieved by ordered water transport near pore edges. These findings lay the ground for the ultimate design of forward osmosis membranes with optimized performance trade-off, given the capability of nano-engineering nanostructures by their geometry and chemistry.

Thermodynamics of fluid conduction through hydrophobic channel of carbon nanotubes: the exciting force for filling of nanotubes with polar and nonpolar fluids.

Thermodynamic properties of the fluid in the hydrophobic pores of nanotubes are known to be different not only from the bulk phase but also from other conventional confinements. Here, we use a recently developed theoretical scheme of "two phase thermodynamic (2PT)" model to understand the driving forces inclined to spontaneous filling of carbon nanotubes (CNTs) with polar (water) and nonpolar (methane) fluids. The CNT confinement is found to be energetically favorable for both water and methane, leading to their spontaneous filling inside CNT(6,6). For both the systems, the free energy of transfer from bulk to CNT confinement is favored by the increased entropy (TΔS), i.e., increased translational entropy and increased rotational entropy, which were found to be sufficiently high to conquer the unfavorable increase in enthalpy (ΔE) when they are transferred inside CNT. To the best of our knowledge, this is the first time when it has been established that the increase in translational entropy during confinement in CNT(6,6) is not unique to water-like H bonding fluid but is also observed in case of nonpolar fluids such as methane. The thermodynamic results are explained in terms of density, structural rigidity, and transport of fluid molecules inside CNT. The faster diffusion of methane over water in bulk phase is found to be reversed during the confinement in CNT(6,6). Studies reveal that though hydrogen bonding plays an important role in transport of water through CNT, but it is not the solitary driving factor, as the nonpolar fluids, which do not have any hydrogen bond formation capacity can go inside CNT and also can flow through it. The associated driving force for filling and transport of water and methane is enhanced translational and rotational entropies, which are attributed mainly by the strong correlation between confined fluid molecules and availability of more free space for rotation of molecule, i.e., lower density of fluid inside CNT due to their single file-like arrangement. To the best of our information, this is perhaps the first study of nonpolar fluid within CNT using 2PT method. Furthermore, the fast flow of polar fluid (water) over nonpolar fluid (methane) has been captured for the first time using molecular dynamic simulations.

A Carbon Nanotube Confinement Strategy to Implement Homogeneous Asymmetric Catalysis in the Solid Phase

A readily recyclable asymmetric catalyst has been developed based on the self-assembly of a homogeneous catalyst in a fibrous network of multiwalled carbon nanotubes (MWNTs). Dimerization of an amide-based chiral ligand with a suitable spacer allows for the efficient formation of a heterogeneous catalyst by self-assembly on addition of Er(OiPr)3. The self-assembly proceeds in the MWNT fibrous network and small clusters of assembled catalyst are confined in the MWNTs, producing an easily handled solid-phase catalyst. The resulting MWNT-confined catalyst exhibits a good catalytic performance in a catalytic asymmetric Mannich-type reaction, which can be conducted in a repeated batch system and in a continuous-flow platform.