Aligned Carbon Nanotubes Research Articles

ALD/MLD coating of patterned vertically aligned carbon nanotube micropillars with Fe-NH2TP hybrids.

The creation of nanoscale organic-inorganic hybrid coatings with uniform architecture and high surface area, while maintaining their structural and morphological integrity, remains a significant challenge in the field. In this study, we present a novel solution, by utilizing Atomic/Molecular Layer Deposition (ALD/MLD) to coat patterned vertically aligned carbon nanotube micropillars with a conformal amorphous layer of Fe-NH2TP, which is a trivalent iron complex complexed with 2-amino terephthalate. The effectiveness of the coating is verified through multiple analytical techniques, including high-resolution transmission electron microscopy, scanning transmission electron microscopy, grazing incidence X-ray diffraction, and Fourier transform infrared spectroscopy. The Fe-NH2TP hybrid film exhibits hydrophobic properties, as confirmed by water contact angle measurements. Our findings contribute to advancing the understanding of how to grow high-quality one-dimensional materials using ALD/MLD and hold promise for future research in this area.

Enhanced field emission stability of vertically aligned carbon nanotubes through anchoring for X-ray imaging applications

We reported the anchored carbon nanotube emitters shows enhanced field emission stability.

Rapidly Modulated Wide‐Spectrum Infrared Source Made of Super Aligned Carbon Nanotube Film for Greenhouse Gas Monitoring (Adv. Funct. Mater. 4/2023)

Rapidly Modulated Wide‐Spectrum Infrared Source Made of Super Aligned Carbon Nanotube Film for Greenhouse Gas Monitoring (Adv. Funct. Mater. 4/2023)

Effect of the state of catalytic nanoparticles on the growth of vertically aligned carbon nanotubes

Effect of the state of catalytic nanoparticles on the growth of vertically aligned carbon nanotubes

Soft landing of polyatomic anions onto three-dimensional semiconductive and conductive substrates.

Soft landing of well-characterized polyoxometalate anions, PW12O40 3- (WPOM) and PMo12O40 3- (MoPOM), was carried out to explore the distribution of anions in the semiconducting 10 and 6 μm-long vertically aligned TiO2 nanotubes as well as 300 μm-long conductive vertically aligned carbon nanotubes (VACNTs). The distribution of soft-landed anions on the surfaces and their penetration into the nanotubes were studied using energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). We observe that soft landed anions generate microaggregates on the TiO2 nanotubes and only reside in the top 1.5 μm of the nanotube height. Meanwhile, soft landed anions are uniformly distributed on top of VACNTs and penetrate into the top 40 μm of the sample. We propose that both the aggregation and limited penetration of POM anions into TiO2 nanotubes is attributed to the lower conductivity of this substrate as compared to VACNTs. This study provides first insights into the controlled modification of three dimensional (3D) semiconductive and conductive interfaces using soft landing of mass-selected polyatomic ions, which is of interest to the rational design of 3D interfaces for electronics and energy applications.

Correction: Enhanced field emission stability of vertically aligned carbon nanotubes through anchoring for X-ray imaging applications

Correction for ‘Enhanced field emission stability of vertically aligned carbon nanotubes through anchoring for X-ray imaging applications’ by Xinchuan Liu et al., J. Mater. Chem. C, 2023, 11, 2505–2513, https://doi.org/10.1039/d2tc04363g.

Multifunctional microneedle patches with aligned carbon nanotube sheet basement for promoting wound healing

Wound healing has become a health concern and economic burden worldwide for its high incidence and complexity. Attempts to improve wound treatment tend to develop biomedical patches with delicate structure design and functionality. In this paper, we present novel multifunctional microneedle patches with aligned carbon nanotube (CNT) sheet basement for promoting wound healing. Because of the outstanding biocompatibility, biodegradability and non-immunogenicity, hyaluronic acid (HA) is utilized to construct the CNT-integrated microneedle patch with vascular endothelial growth factor (VEGF) encapsulation. It was found that the aligned CNT layer basement could not only impart the composite microneedle patch with orientation morphology, but also endow the patch with controllable release performance, due to its photo-thermal or electro-thermal conversion capacity. Based on these features, we have demonstrated that the highly ordered microstructure of CNT could effectively induce the orientation of fibroblasts; while VEGF release could facilitate tubular formation of endothelial cells. Thus, the aligned CNT and VEGF-loaded multifunctional patch is beneficial to the wound repair process in a typical animal experiment. These results indicate that the proposed microneedle patch is potentially promising for regeneration medicine.

Structural Integrity Assessment of Aligned and Non-aligned Single Walled Carbon Nanotubes in Epoxy Resin

Carbon nanotubes have gained popularity due its unique electrical and thermal properties and high strength, widely finding it application in medical and electrical field. In the presented study the single walled carbon nanotubes (SWCNT) are assumed to be aligned using a DC electric field, taking into account transportation phenomena like the rotation of tube and its polarization to form chain like structure. Authors have examined and compared the structural properties under tensile loading of aligned and non-aligned single walled carbon nanotubes SWCNT in epoxy matrix using finite element analysis. COMSOL Multiphysics has been used to model the specimens and investigate its properties. The result lays out trends and relation between various parameters and the strength of the epoxy based SWCNT composite. The study draws out result on how changes in parameters of epoxy based SWCNT composite changes its physical properties.

Chromium (VI) reduction by two-chamber bioelectrochemical system with electrically conductive wall

Hexavalent chromium (Cr(VI)) poses a threat to public health and the environment owing to its high toxicity. Various microbial Cr(VI) reduction methods have been proposed to treat contaminated water; however, they are not effective at high concentrations of Cr(VI), which inhibit microbial growth and viability. To overcome the limitations of conventional microbial methods, we set up a novel bioelectrochemical reactor in which microbial cells were separated from Cr(VI) by an electroconductive barrier consisting of a vertically aligned carbon nanotube (VACNT) composite to remove toxic heavy metal ions. This study demonstrated that chromium compounds could be biologically and sustainably treated with the VACNT composite without growth inhibition, using electron transfer from an electron shuttle secreted by Pseudomonas aeruginosa, even at the microbial inhibitory concentration of Cr(VI). The content of Cr(VI) was measured using the diphenylcarbazide method, and Cr(III), the reduction product, was identified using X-ray photoelectron spectroscopy. Pyocyanin, a phenazine secreted by P. aeruginosa, was identified as an electron mediator in Cr(VI) reduction, using aeration and phz mutant assay. The bioelectrochemical reactor used in this study exhibited a Cr(VI) removal rate of 99.6% at 100 mg/L, which is the highest reduction rate achieved using P. aeruginosa. The microbial Cr(VI) reduction system developed in this study allows microbial Cr(VI) reduction to overcome the hurdles of biological treatment of toxic materials and has advanced the understanding of microbial electron transfer.

Continuous intercalation compound fibers of bromine wires and aligned CNTs for high-performance conductors

This work presents macroscopic fibers of aligned double-walled carbon nanotubes (DWCNTs) intercalated with long-range ordered bromine, with a stoichiometry close to C17Br. Tribromide ions lie inside interstitial sites between hexagonally-packed DWCNTs and extend parallel to their axis as ordered supramolecular “wires”. First-principles simulations confirm this structure and a transfer of 0.13 electrons per Br atom. The structure of nested bundles of CNTs with a homogeneous distribution of bromine species in the interstitial sites of the superlattice is directly imaged by cross-sectional HRTEM, showing full intercalation of highly dense and aligned fibers. The presence of Br2 and Br3– is confirmed by Raman spectroscopy, and their supramolecular organization is resolved by 2D wide-angle X-ray scattering. Intercalation increases room-temperature longitudinal electrical conductivity by a factor of 8.4. Through low-temperature transport measurements in the longitudinal and transverse directions, we show that the intercalate reduces the tunneling-dominated resistance associated with transport between adjacent CNTs, rather than exclusively acting as a dopant that increases conductance of individual CNTs. By preserving the separation between CNTs, the exceptional mechanical properties of the CNT fiber host are retained. The combined tensile strength above 2.46 GPa and conductivity of 10.68 MS/m makes intercalated CNT fibers attractive lightweight conductors with combined properties superior to metals and graphite intercalation compounds.

Trion confinement in monolayer MoSe2 by carbon nanotube local gating

We have successfully confined trions into a one-dimensional restricted space of a MoSe2 device with carbon nanotube (CNT) gate electrodes. The dry transfer process, including deterministic dry transfer of aligned CNTs, has led to an hBN-encapsulated MoSe2 device with CNT back gate electrodes. In contrast to a location without CNT gate electrodes, applying voltage via CNT gate electrodes significantly alters PL spectra at a location with CNT gate electrodes. PL imaging has revealed that image contrast from trions is linear along the CNT electrode underneath, consistent with 1D confinement of trions in response to the CNT local gating. The confinement width obtained from the PL image is 5.5 × 102 nm, consistent with nanoscale 1D confined trions with the diffraction limit broadening. This work has demonstrated electrical control of excitonic states at the nanoscale, leading to novel optoelectronic properties and exciton devices in the future.

Single Zinc Atom Aggregates: Synergetic Interaction to Boost Fast Polysulfide Conversion in Lithium-Sulfur Batteries.

Single-atom catalysts (SACs) pave new possibilities to improve the utilization efficiency of sulfur electrodes arising from polysulfide shuttle effects and sluggish kinetics due to their excellent applicability in atomic-scale reaction mechanisms and structure-activity relationships. Herein, nitrogen (N)-anchored SACs on the highly ordered N-doped carbon nanotube arrays are reported as the sulfur host for fast redox conversion in lithium-sulfur (Li-S) batteries. The cube structure of the aligned carbon nanotubes can promote the rapid mass transfer under high sulfur loadings, and abundant single-atom active sites further accelerate the conversion of lithium polysulfides (LiPSs). The synergistic enhancement effect induced by adjacent single atoms with interatomic distances <1nm further accelerates the rapid multi-step reaction of sulfur at high sulfur loadings. As a result, the obtained Li-S batteries exhibit outstanding cycle stability with a high areal capacity of 5.6mAhcm-2 after 100 cycles under a high sulfur loading of 7.2mgcm-2 (electrolyte to sulfur ratio is ≈3.7mLg-1 ). Even assembled into a pouch cell, it still delivers a high capacity of 953.4mAhg-1 after 100 cycles at 0.1C, contributing to the development of the practically viable Li-S batteries.

Nanostructuring Strategies for Silicon‐based Anodes in Lithium‐ion Batteries: Tuning Areal Silicon Loading, SEI Formation/Irreversible Capacity Loss, Rate Capability Retention and Electrode Durability

AbstractSilicon is one of the most promising anode materials for lithium‐ion batteries. Silicon endures volume changes upon cycling, which leads to subsequent pulverization and capacity fading. These drawbacks lead to a poor lifespan and hamper the commercialization of silicon anodes. In this work, a hybrid nanostructured anode based on silicon nanoparticles (SiNPs) anchored on vertically aligned carbon nanotubes (VACNTs) with defined spacing to accommodate volumetric changes is synthesized on commercial macroscopic current collector. Achieving electrodes with good stability and excellent electrochemical properties remain a challenge. Therefore, we herein tune the active silicon areal loading either through the modulation of the SiNPs volume by changing the silicon deposition time at a fixed VACNTs carpet length or through the variation of the VACNT length at a fixed SiNPs volume. The low areal loading of SiNPs improves capacity stability during cycling but triggers large irreversible capacity losses due to the formation of the solid electrolyte interphase (SEI) layer. By contrast, higher areal loading electrode reduces the quantity of the SEI formed, but negatively impacts the capacity stability of the electrode during the subsequent cycles. A higher gravimetric capacity and higher areal loading mass of silicon is achieved via an increase of VACNTs carpet length without compromising cycling stability. This hybrid nanostructured electrode shows an excellent stability with reversible capacity of 1330 mAh g−1 after 2000 cycles.

Electrical anisotropy controlled heating of acrylonitrile butadiene styrene 3D printed parts

This study proposes a simple method to produce three-dimensional (3D) manufacts with multiscale configurations and controlled electrical resistivity. 3D printed artefacts, based on acrylonitrile butadiene styrene and carbon nanotubes (CNTs), are obtained by fused filament fabrication. Highly orientated conductive pathways are achieved in the sample by selecting appropriate printing parameters. Scanning electron microscopy and tunnelling atomic force microscopy confirm that the conductive traces are essentially composed of aligned CNTs. The printing process determines an increase in the electrical conductivity from 6.88 × 10-2 (spooled filament) to 11.9 S/m (printed filament). The orientation of the spatial domains from the macro- to nanoscale is responsible for a decrease in the electrical resistance from 7782 (90° raster angle sample) tο 478 Ω (0° raster angle sample). Appropriate selection of the configuration and dimensions of electrical contacts confers the ability to selectively heat the part when subjected to an electric source. Temperature differences up to 55 °C were obtained in samples printed with a double-angle raster combination by changing the applied voltage from 20 to 40 V. This strategy can be used to fabricate electronic devices, thermistors capable of converting electrical energy to thermal energy, heat exchangers, and shielding for electromagnetic interference in a single step.

Patterning of Silicon Substrate with Self-Assembled Monolayers Using Vertically Aligned Carbon Nanotube Electron Sources.

We introduce a novel patterning technique based on e-beam lithography using vertically aligned carbon nanotube (VACNT) emitters with self-assembled monolayers (SAMs). A 20 μm line width of silicon wafer patterning was successfully demonstrated using octadecyl trichlorosilane (OTS) as a photoresist. To investigate surface modification by the irradiated electrons from the emitters, both contact angle measurement and energy dispersive X-ray (EDX) analysis were conducted. The patterning mechanism of the electron beam irradiated on OTS-coated substrate by our cold cathode electron beam (C-beam) was demonstrated by the analyzed results. The effect of current density and exposure time on the OTS patterning was studied and optimized for the Si wafer patterning in terms of the electronic properties of the VACNTs. The authors expect the new technique to contribute to the diverse applications to microelectromechanical (MEMS) technologies owing to the advantages of facile operation and precise dose control capability based on field electron emission current from the VACNT emitter arrays.

Aligned carbon nanotube composite belts stitching of laminated composites for enhanced fracture toughness and enriched functionalities

AbstractRealizing the full potential of advanced fiber reinforced polymeric composites has been impeded by their weak interlaminar performance. Herein, a whole‐through‐thickness stitching strategy was proposed to address this key challenge by using ultrathin, high performance aligned carbon nanotube (CNT) composite belts as stitching sutures. During the fabrication of aligned CNT composite belts, the as‐made CNT belts that consist of randomly orientated CNTs were firstly stretched before resin infiltration. It has been found that the tensile strength and modulus of aligned CNT composite belts reached 1126.9 MPa and 56.2 GPa, with an improvement of 227.9% and 726.5% than those of unstretched composite belts, respectively. After stitching, the Mode I interlaminar fracture toughness and through‐thickness electrical conductivity of carbon fiber reinforced laminated composites was enhanced by 138.7% and 426.7%, respectively, which was mainly due to the bridging effect of strong and conducting CNT belts. In addition, the interlaminar crack propagations can be in situ monitored by tracking the resistance variation of the stitched laminates under loading. Thus, this stitching strategy provides an effective approach to not only enhance the structural performance of fiber reinforced polymeric composites, but also enrich their functionalities.

Beam Trajectory Analysis of Vertically Aligned Carbon Nanotube Emitters with a Microchannel Plate

Vertically aligned carbon nanotubes (CNTs) are essential to studying high current density, low dispersion, and high brightness. Vertically aligned 14 × 14 CNT emitters are fabricated as an island by sputter coating, photolithography, and the plasma-enhanced chemical vapor deposition process. Scanning electron microscopy is used to analyze the morphology structures with an average height of 40 µm. The field emission microscopy image is captured on the microchannel plate (MCP). The role of the microchannel plate is to determine how the high-density electron beam spot is measured under the variation of voltage and exposure time. The MCP enhances the field emission current near the threshold voltage and protects the CNT from irreversible damage during the vacuum arc. The high-density electron beam spot is measured with an FWHM of 2.71 mm under the variation of the applied voltage and the exposure time, respectively, which corresponds to the real beam spot. This configuration produces the beam trajectory with low dispersion under the proper field emission, which could be applicable to high-resolution multi-beam electron microscopy and high-resolution X-ray imaging technology.

Hydromechanical Impact on an Array of Horizontally Aligned Carbon Nanotubes

Hydromechanical Impact on an Array of Horizontally Aligned Carbon Nanotubes

Microporous vertically aligned CNT nanocomposites with tunable properties for use in flexible heat sinks

Effective thermal management of electronic systems depends on the heat transfer efficiency or the heat dissipation capability, and the thermal conductivity of heat sink components, which has a critical impact on the performance of the devices. The rapidly growing field of microelectronics creates an enormous need for next-generation flexible, lightweight heat sinks. In this work, flexible, microporous nanocomposites are fabricated utilizing a unique yet easily tunable processing method, targeting heat-sink applications. The highly porous and low-density nanohybrid structures were fabricated in a unique processing technique using conformally pyrolytic carbon (PyC) coated vertically aligned carbon nanotube (VACNT) arrays and polydimethylsiloxane (PDMS) infiltration. Simply by varying the concentration of the PDMS in the VACNT structure, the microporosity can be tuned from 50% to 93%, and at the same time, the density of the structure varies from 0.11 g/cm 3 to 0.51 g/cm 3 . The through-thickness thermal conductivity of the VACNT – PDMS nanocomposites did not vary substantially with increasing PDMS concentration, and the highest performance samples exhibited 14.1 W/mK thermal conductivity. The highly flexible nanocomposite structure also showed excellent mechanical resiliency and exhibited complete recovery from 80% compressive strain. The final heat-sink structure with fins was fabricated by a controlled laser etching technique. Analysis of the flexible VACNT array heat sink showed a significant ∼27% reduction in thermal resistance with an air velocity of 1.5 m/s, and about ∼40% improvement in the output performance of a thermoelectric generator (TEG) on which it was mounted. The high thermal conductivity of VACNTs and the large surface area provided by the microporous structure, as well as the laser-etched fins all together contributed to better thermal management performance.

Effect of the chemical vapor deposition process on the aspect ratio of vertically aligned carbon nanotubes (VACNTs)

Effect of the chemical vapor deposition process on the aspect ratio of vertically aligned carbon nanotubes (VACNTs)