Search Results (85)

Densely packed semiconducting carbon nanotube (CNT) arrays with well-controlled morphology are highly desirable for high-performance CNT-based electronics. Although dielectrophoresis (DEP) enables precise, efficient, and site-selective assembly, increasing array density often destabilizes process regulation and aggravates nanotube bundling because of the dynamic interplay among assembly conditions. Here, we introduce the effective deposition region (EDR) to reformulate DEP assembly into a framework that links DEP conditions and final arrays through an interpretable CNT deposition dynamic based on the effective DEP capture. Within this framework, experiments and modeling indicate a self-regulating, negative-feedback mechanism in which conductive CNT bridging reduces the gap voltage, contracts the EDR, and weakens sustained CNT-capture capability, thereby driving the assembly toward self-termination. By synergistically optimizing the applied voltage, electrode configuration, and CNT dispersion concentration to regulate EDR contraction, we obtained dense, bundle-suppressed CNT arrays with the number of nanotubes per unit width of approximately 140 tubes µm⁻¹. The formation of small bundles implies that further combination of EDR-regulated assembly with additional inter-tube interactions is required to realize dense, monolayer CNT arrays. This work provides a coherent mechanistic framework for understanding feedback-regulated DEP assembly and enables a practical approach for optimizing both densification and morphology control in CNT array assembly. Full article

Spatial confinement strongly affects matter by altering structural stability, relaxation times, and equilibrium properties. Interest in hydrogen storage within carbon nanotube bundles has grown because it addresses practical energy needs while revealing rich confined-fluid physics. Understanding how geometry and defects influence hydrogen structure and dynamics is essential to the development of effective storage materials. Here, we investigate how confinement in single-walled carbon nanotube (SWCNT) bundles with vacancies alters the spatial distribution and phase behavior of physisorbed hydrogen. At low temperature, hydrogen forms solid-like, cylindrical layered structures both inside and outside the tubes. Raising the temperature broadens these layers and produces a liquid-like arrangement within the confined regions. This confined solid-to-liquid crossover controls storage capacity and release behavior and can be tuned by temperature, confinement dimensions, and vacancy defects. Full article

Single-walled carbon nanotube (SWCNT) films are promising materials for thermoelectric power generation; however, the dependence of their transport properties on their thickness remains insufficiently understood. This study examined the relationship between the transport properties and the internal structure of SWCNT films with thicknesses ranging from 28 to 193 µm. The structural, mechanical, thermoelectric, and phonon transport properties exhibited a discontinuous dependence on the film thickness. Films up to 72 µm in thickness formed a uniform, dense network that maximized electrical conductivity, whereas films exceeding 97 µm exhibited a coarse and densely layered morphology. This coarse-dense structure increased the contact resistance between SWCNT bundle layers, leading to a reduction in electrical conductivity. Additionally, the increased number of layered interfaces increased phonon scattering, which decreased thermal conductivity and phonon mean free path. These findings provide insights into phonon transport in SWCNT films and have implications for SWCNT-based thermoelectric generator design and optimization. Full article

Tuning the electrical properties of biocompatible materials with minimal amounts of nanofiller presents a significant challenge in neuroimplant development. This study investigates the influence of single-walled carbon nanotube (SWCNT) agglomerate size on the electrical conductivity of a bioinspired biopolymer composite. The composites were fabricated via photolithography. We analyzed the effect of ultrasonic homogenization on the size distribution of SWCNT bundles. Our results demonstrate that the degree of nanotube dispersion is critical for determining electrical conductivity. The highest conductivity was achieved with an average bundle size of 95 µm and a defect level of no more than 0.143, as measured by the I_D/I_G+ band ratio using Raman spectroscopy. We attribute this to the formation of an interconnected percolation network within the biopolymer matrix. These findings demonstrate a viable approach for controlling the conductive properties of bioinspired composites. Full article

A sensitive and cost-effective voltammetric sensor using a carbon-containing electrode (CCE) with a renewable surface modified with multi-walled carbon nanotubes (MWCNTs) was developed for the determination of prednisolone in pharmaceuticals and blood serum. The morphological effects of the functionalization process on the MWCNTs were investigated by transmission electron microscopy (TEM). Analysis of the micrographs indicated that the functionalized nanotubes exhibited a higher density of surface defects and a reduced tendency to form bundles compared to their pristine counterparts. Energy dispersive spectrometry (EDS) confirmed that residual iron particles were removed from the MWCNTs during acid functionalization, demonstrating their intrinsic conductivity. The MWCNTs/CCE was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The electrochemical behavior of prednisolone in Britton–Robinson buffer at the MWCNTs/CCE was investigated by linear sweep cathodic voltammetry, while the quantitative determination was performed by differential pulse voltammetry (DPV). Under optimal conditions, the sensor exhibited a linear concentration range from 0.04 to 0.6 μM with a detection limit of 8 nM. The proposed method was successfully applied in the determination of prednisolone in pharmaceutical formulations and blood serum. Full article

A fully aqueous, N-methyl-2-pyrrolidone–free strategy for debundling single-walled carbon nanotubes (SWCNTs) is reported using the renewable dispersant Vanisperse^® LI. Dispersions at 2 mg mL⁻¹ were subjected to probe ultrasonication at 0.3 W mL⁻¹ and evaluated using oscillatory rheology. Complex viscosity (η*) exhibited a transient maximum (~75 min) consistent with the formation of a percolated fibrous network, followed by a decline as debundling progressed. An optimum dispersant coverage of ~1.5 mg m⁻² minimized η*, while overdosing likely induced multilayer adsorption and bridging seen by a rapid increase in η*. A two-stage centrifugation at 10,000× g yielded storage-stable suspensions of debundled SWCNTs without ultracentrifugation. SEM confirmed substantial debundling into thin fiber-like bundles. By formulating a dispersion with a dispersant that has a significantly lower cradle-to-gate carbon footprint than both fossil-based and bio-based alternatives such as CMC, this work presents a more sustainable approach to producing debundled SWCNT dispersions for advanced material applications. Full article

Single-walled carbon nanotube (SWCNT) inks were prepared by mixing SWCNTs with ethanol and varying the amplitude of ultrasonic dispersion. When the SWCNT inks were prepared by dispersion amplitudes at 60% (nominal value of 200 W), the SWCNT inks had low viscosity and a small variation of the particle size. The SWCNT films fabricated under this dispersion condition had well-distributed SWCNT bundles and exhibited the highest power factor. However, when the dispersion amplitude was excessive, the viscosity of the SWCNT ink increased due to the reduced contact between the SWCNTs owing to over-dispersion, and the crystallinity of the SWCNT films decreased, exhibiting a lower power factor. When the optimized SWCNT films at 60% were applied to heat-source-free water-floating SWCNT-TEGs, an output voltage of 2.0 mV could be generated under sunlight irradiation. These findings are useful for preparing various electronic devices with SWCNT films to improve the film quality using ultrasonic dispersion. Full article

With the rapid development of wearable electronics, traditional rigid thermal management materials face limitations in flexibility, conformability, and multi-physics adaptability. Low-dimensional carbon materials such as graphene and carbon nanotubes combine ultrahigh thermal conductivity with outstanding mechanical compliance, making them promising building blocks for flexible thermal regulation. This review summarizes recent advances in integrating these materials into textile architectures, mapping the evolution of this emerging field. Key topics include phonon-dominated heat transfer mechanisms, strategies for modulating interfacial thermal resistance, and dimensional effects across scales; beyond these intrinsic factors, hierarchical textile configurations further tailor macroscopic performance. We highlight how one-dimensional fiber bundles, two-dimensional woven fabrics, and three-dimensional porous networks construct multi-directional thermal pathways while enhancing porosity and stress tolerance. As for practical applications, the performance of carbon-based textiles in wearable systems, flexible electronic packaging, and thermal coatings is also critically assessed. Current obstacles—namely limited manufacturing scalability, interfacial mismatches, and thermal performance degradation under repeated deformation—are analyzed. To overcome these challenges, future studies should prioritize the co-design of structural and thermo-mechanical properties, the integration of multiple functionalities, and optimization guided by data-driven approaches. This review thus lays a solid foundation for advancing carbon-based smart textiles toward next-generation flexible thermal management technologies. Full article

This study aims to comprehensively evaluate the mechanical performance of dry-spun twisted carbon nanotube (CNT) yarns (CNTYs) subjected to uniaxial tensile load. To this end, in contrast to earlier approaches, the current research lies in an innovative approach to incorporating the orthotropic properties of all hierarchical structures of a CNTY structure. The proposed bottom-up model ranges from nanoscale bundles to mesoscale fibrillar and, finally, microscale CNTYs. The proposed methodology distinguishes itself by addressing the interplay of constituents across multiple scale levels to compute the transverse properties (orthotropic nature). By doing so, rigidity and mass equivalent principles are adopted to introduce a replacement of the model by converting the truss structure containing two-node beam elements representing (vdW) van der Waals forces in a nanoscale bundle and inclined narrower bundles in mesoscale fibrillar used in previous works to the equivalent shell model. Followed by the evaluation of mechanical properties of nanoscale bundles, they are translated to the mesoscale level to quantify its orthotropic properties and then are fed into the microscale CNTY model. The results indicate that the resultant CNT bundle and fibrillar exhibit much lower transverse elastic modulus compared to those in the axial direction reported in the prior literature. For the sake of validation of the proposed method, the reproduced overall stress–strain curve of CNTYs is compared to that attained experimentally, showing excellent correlation. The presented theoretical approach provides a valuable tool for enhancing the understanding and predictive capabilities related to the mechanical performances of CNTY structures. Full article

This current work provides a comprehensive Computational Fluid Dynamics (CFD) investigation of three-dimensional magnetohydrodynamic (MHD) mixed convection of carbon nanotube (CNT)-water nanofluid within a vented rectangular cavity featuring an internal vertical rod bundle with circular, square, and triangular cross-sections. The finite element method (FEM) was used to investigate the effects of key parameters, including the Richardson number (0.01 ≤ Ri ≤ 10), Hartmann number (0 ≤ Ha ≤ 100), and CNT nanoparticle concentration (0 ≤ ϕ ≤ 0.045), in relation to fluid flow and heat transfer performance. The CNT nanoparticle incorporation increases the nanofluid’s heat transfer capacity by up to 22%, with the highest average Nusselt number (Nu_av) achieved with circular rods at ϕ = 0.045, which corresponds to the higher convective heat transfer efficiency. The magnetic field further stabilizes the flow by reducing thermal convection irregularities, with a 15% improvement in temperature distribution uniformity when Ha = 100. The investigation’s outcomes reveal that due to their smoother geometries, the circular rods exhibit better thermal exchange rates compared to square and triangular rods. Moreover, a polynomial regression model is used to correlate the governing parameters and heat transfer rates, and it achieves a high R² of 0.964. These findings highlight the potential of CNT-water nanofluid and magnetic field applications for thermal management optimization in various engineering systems. Full article

Double-walled carbon nanotube-yttria-stabilized ZrO₂ nanocomposites are prepared by a mixing route followed by Spark Plasma Sintering. The double-walled carbon nanotubes (DWCNTs) have been previously subjected to a covalent functionalization. The nanocomposites present a high densification and show a homogenous dispersion of DWCNTs into a matrix about 100 nm in size. The DWCNTs are well distributed at the matrix grain boundaries but form larger bundles upon the increase in carbon content. The Vickers microhardness of the nanocomposites decreases regularly upon the increase in carbon content. Incorporation of carbon at contents higher than 2 wt.% results in significantly lower friction coefficients, both against alumina and steel balls, possibly because of the elastic deformation of the DWCNTs at the surface of the sample. Their presence also favors a reduction of the steel/ceramic contacts and reduces the wear of the steel ball at high loads. DWCNTs improve wear resistance and reduce friction without incurring any severe damage, contrary to multi-walled carbon nanotubes. Full article

One of the challenging issues that hinders the application of single-walled carbon nanotubes (SWCNTs) is the poor solubility and the inevitable formation of bundles. Efforts still need to be made towards solving the problem. Herein, we report a non-covalent strategy to disperse aggregated SWCNTs by aromatic cyclic Schiff bases assisted by ultrasonic techniques. The aromatic cyclic Schiff base (OMM) was synthesized via Schiff base reactions, and the molecular structure was determined by ATR-FT-IR, solid-state ¹³C-NMR, and HRMS. Although the yielded product showed poor solubility in aqueous solution and organic solvents, it could interact with and disperse the aggregated SWCNTs in dimethyl formamide (DMF) under the condition of ultrasound. UV-vis-NIR, FL, Raman spectra, AFM, and TEM, along with computer simulations, provide evidence for the interactions between OMM molecules and SWCNTs and the dispersion thereof. The semiconductive (7,5), (8,6), (12,1), and (9,7)-SWCNTs expressed a preference for dissolution. The capability of dispersion is contributed by π-π, C-H·π, and lone pair (lp)·π interactions between OMM and SWCNTs based on the simulated results. The present non-covalent strategy could provide inspiration for preparing organic cyclic compounds as dispersants for SWCNTs and then facilitate their further utilization. Full article

Single-walled carbon nanotube (SWCNT) thin films were synthesized by using a floating catalyst chemical vapor deposition (FCCVD) method with a low flow rate (200 sccm) of mixed gases (Ar and H₂). SWCNT thin films with different thicknesses can be prepared by controlling the collection time of the SWCNTs on membrane filters. Transmission electron microscopy (TEM) showed that the SWCNTs formed bundles and that they had an average diameter of 1.46 nm. The Raman spectra of the SWCNT films suggested that the synthesized SWCNTs were very well crystallized. Although the electrical properties of SWCNTs have been widely studied so far, the Hall effect of SWCNTs has not been fully studied to explore the electrical characteristics of SWCNT thin films. In this research, Hall effect measurements have been performed to investigate the important electrical characteristics of SWCNTs, such as their carrier mobility, carrier density, Hall coefficient, conductivity, and sheet resistance. The samples with transmittance between 95 and 43% showed a high carrier density of 10²¹–10²³ cm⁻³. The SWCNTs were also treated using Brønsted acids (HCl, HNO₃, H₂SO₄) to enhance their electrical properties. After the acid treatments, the samples maintained their p-type nature. The carrier mobility and conductivity increased, and the sheet resistance decreased for all treated samples. The highest mobility of 1.5 cm²/Vs was obtained with the sulfuric acid treatment at 80 °C, while the highest conductivity (30,720 S/m) and lowest sheet resistance (43 ohm/square) were achieved with the nitric acid treatment at room temperature. Different functional groups were identified in our synthesized SWCNTs before and after the acid treatments using Fourier-Transform Infrared Spectroscopy (FTIR). Full article

As power sources for Internet-of-Things sensors, thermoelectric generators must exhibit compactness, flexibility, and low manufacturing costs. Stretchable and flexible painted thermoelectric generators were fabricated on Japanese paper using inks with dispersed p- and n-type single-walled carbon nanotubes (SWCNTs). The p- and n-type SWCNT inks were dispersed using the anionic surfactant of sodium dodecylbenzene sulfonate and the cationic surfactant of dimethyldioctadecylammonium chloride, respectively. The bundle diameters of the p- and n-type SWCNT layers painted on Japanese paper differed significantly; however, the crystallinities of both types of layers were almost the same. The thermoelectric properties of both types of layers exhibited mostly the same values at 30 °C; however, the properties, particularly the electrical conductivity, of the n-type layer increased linearly, and of the p-type layer decreased as the temperature increased. The p- and n-type SWCNT inks were used to paint striped patterns on Japanese paper. By folding at the boundaries of the patterns, painted generators can shrink and expand, even on curved surfaces. The painted generator (length: 145 mm, height: 13 mm) exhibited an output voltage of 10.4 mV and a maximum power of 0.21 μW with a temperature difference of 64 K at 120 °C on the hot side. Full article

The electronic structure of carbon nanotube bundles (CNTBs) can be a tough task for the routine first-principle calculation. The difficulty comes from several issues including the atomic structure, the boundary condition, and above all the very large number of atoms that makes the calculation quite cumbersome. In this work, we estimated the band gap of the CNTBs based on the results from single-walled carbon nanotubes (SWCNTs) under different deformations. The effects of squeezing, stretching, and torsion on the bands of SWCNTs were investigated through first-principle calculations, from which the band gaps of bundles were analyzed because the effects of these deformations were qualitatively independent when the distortions were small. Specifically, the gaps of (4,4) and (8,0) CNTBs under a reasonable torsional strength were predicted, wherein we were able to see metal–semiconductor and semiconductor–metal transitions, respectively. Such reversible mechanical modification of the conductivity may be helpful to the future band-gap engineering in nanoscale circuits. Full article