Single-walled Carbon Nanotube Bundles Research Articles

Intrinsic Temperature Dependence of Raman-Active Modes in Individual Isolated Single- and Double-Walled Carbon Nanotubes.

The intrinsic temperature dependence of Raman-active modes in carbon nanotubes (CNTs), particularly the radial breathing mode (RBM), has been a topic of a long-standing controversy. In this study, we prepared suspended individual CNTs to investigate how their Raman spectra depend on temperature and to understand the effects of environmental conditions on this dependency. We analyzed the intrinsic temperature dependence of the main Raman-active modes, including the RBM, the moiré-activated R feature, and the G-band in double-walled carbon nanotubes (DWCNT) and single-walled carbon nanotubes (SWCNTs) after complete desorption of air. The inner tube of the DWCNT, like the desorbed SWCNTs, was free from environmental influences, resulting in minimal temperature-induced RBM frequency shifts. We show that the larger RBM shift of SWCNTs upon initial heating is not intrinsic but is due to air desorption. The R feature, attributed to moiré-activated phonon scattering and nondispersive in nature, demonstrated a quasi-linear temperature dependence, akin to the G-band but with a lower temperature coefficient. The G-band, which was largely unaffected by environmental conditions, exhibited a consistent temperature coefficient across SWCNTs, DWCNTs, and small SWCNT bundles.

Direct Tracking of SnO2-Li+ Reactions in Confined Carbon Nanospace

SnO2 has a high theoretical capacity of 1492 mAh/g-SnO2 by (1) a conversion reaction and (2) an alloying-dealloying reaction, described as follows: SnO2 + 4 Li+ + 4 e- ⇌ Sn + 2 Li2O (1) Sn + 4.4 Li+ + 4.4 e- ⇌ Li4.4Sn (2)However, the fact of the matter is that the SnO2 electrode hardly exhibits such high capacity due to poor reversibility of lithiation and delithiation reactions. The irreversibility is largely a result of an aggregation of Sn metal particles in Li2O matrix through the lithiation and delithiation reactions.[1] The coarsening of Sn in Li2O matrix reduces the interface area for the reverse conversion reaction and leads large void in the Li2O matrix at the delithiation process.[2] The prevention of Sn coarsening is critical for improving the reversibility of the conversion reaction. The nanosizing of SnO2 and the confinement of reaction spaces were especially effective to improve the reversibility of the conversion reaction.[3] However, the effects on the phase change of SnO2 in sub-nanometer space have not been clarified. It is important to understand the mechanisms that provide high reversibility to maximize the performance of rechargeable batteries. In this study, we present the lithiation and delithiation reactivity and structural changes of SnO2 confined in sub-nanometer space using the inside space of single-walled carbon nanotubes (SWCNT). The SnO2-loaded SWCNT composite (SnO2@CNTs) was obtained by rinsing with water after introducing SnCl2 vapor into the SWCNT.[4] Charge-discharge characteristics of SnO2@CNTs were evaluated in the coin-type cells using Li metal counter and 1 M LiFP6 in EC-DMC electrolyte. The structural changes in the SnO2@CNTs during charge-discharge were evaluated using ex situ and in situ scanning transmission electron microscope (STEM) observations. In situ STEM observations were performed using a probe-type in situ TEM holder; a metal Li foil with an oxidized surface was used as the counter electrode, and SnO2@CNTs were used as the working electrode. The counter and working electrodes were contacted in the TEM column, and in situ TEM observations were conducted during the charging and discharging processes of the SnO2@CNTs. Structural characterization showed that SnO2 nanocrystals were loaded within the inner space of the SWCNTs. A small amount of SnO2 particles was loaded onto the SWCNT bundle surfaces. The ex situ STEM observations clearly show that reversible lithiation and delithiation of the SnO2 electrode were achieved in the carbon nanospaces. In contrast, the SnO2 particles on the outer surface of the SWCNTs changed to large Sn particles after the initial delithiation process, indicating that the reverse conversion reaction of SnO2 particles on the surface of SWCNTs is irreversible. To investigate the dynamics of the reversible SnO2 and Li-ion reactions in the SWCNTs, in situ STEM observations were performed. SnO2 particles in the carbon nanospace expanded into the carbon pores during the lithiation process. The LixSn and Li2O phases produced in the conversion reaction had domains of approximately 1 nm. Aggregation of Sn and LixSn particles did not occur as in the bulk material, and the aggregation of Sn particles was less likely to occur in the carbon nanospace. In the delithiation process, the LixSn and Li2O phases were converted back to SnO2 particles. The results of our study showed the morphological reversibility of SnO2 electrode was achieved by the nano-confinement against SnO2 in sub-nm space and leaded the reversibility of lithiation and delithiation reactions.[5][1] S. Nam, S. Kim, S. Wi, H. Choi, S. Byun, S.-M. Choi, S.-I. Yoo, K. T. Lee, B. Park, J. Power Sources 2012, 211, 154-160.[2] R. Hu, H. Zhang, Z. Lu, J. Liu, M. Zeng, L. Yang, B. Yuan, M. Zhu, Nano Energy 2018, 45, 255-265.[3] J. Han, D. Kong, W. Lv, D.-M. Tang, D. Han, C. Zhang, D. Liu, Z. Xiao, X. Zhang, J. Xiao, X. He, F.-C. Hsia, C. Zhang, Y. Tao, D. Golberg, F. Kang, L. Zhi, Q.-H. Yang, Nat. Commun. 2018, 9, 402.[4] S. Oro, K. Urita, I. Moriguchi, Chem. Commun. 2014, 50, 7143-7146.[5] H. Notohara, K. Urita, I. Moriguchi, ACS Applied Materials & Interfaces 2023, 15, 30600-30605.

Enhanced mechanical and electrical properties of single-walled carbon nanotube fibers via electric field-assisted wet spinning

Researchers have been working on creating fibers from single-walled carbon nanotubes (SWCNTs) that have optimal properties at the molecular level. However, the prepared SWCNT fibers have showed much lower properties than the ones predicted by theory because the interactions between SWCNTs and SWCNT bundles were not strong enough due to the poor alignment of SWCNTs in the fibers. In this study we improved the mechanical and electrical properties of the SWCNT fibers by using an electric field during the wet spinning process. The electric field, which was applied to the top of the syringe plunger and the tip of the spinneret, oriented the SWCNTs in the chlorosulfonic acid dope solution in a nozzle system, and made them more compact. The SWCNT fibers produced through our process exhibited a significant improvement in their properties. Specifically, we observed a 117.5 % increase in tensile strength and a 140.5 % increase in electrical conductivity. Importantly, these enhancements were achieved without the need for any additional post-treatments. This clearly demonstrates the effectiveness of our current wet spinning method.

Enhanced Thermoelectric Properties of Stable n-Type Ferrocene Derivatives-Doped Polyethylenimine/Single-Walled Carbon Nanotube Composite Films.

Preparing stable n-type flexible single-walled carbon nanotube (SWCNT)-based thermoelectric films with high thermoelectric (TE) performance is desirable for self-powering wearable electronics but remains a challenge. Here, the interface regulation and thermoelectric enhancement mechanism of ferrocene derivatives on polyethylenimine/single-walled carbon nanotube (PEI/SWCNT) composite films have been explored by doping ferrocene derivatives (f-Fc-OH) into PEI/SWCNT films. The results show that the introduction of f-Fc-OH leads to the formation of "thorn" structures on the surfaces of SWCNT bundles via hydrophilic and hydrophobic interactions, the generated energy-filtering effect improves the thermoelectric properties of the PEI/SWCNT film, and the f-Fc-OH-doped PEI/SWCNT (f-Fc-OH/PEI/SWCNT) achieves the highest room-temperature power factor of 182.22 ± 8.60 μW m-1 K-2 with a Seebeck coefficient of -64.28 ± 0.96 μV K-1 and the corresponding ZT value of 4.69 × 10-3. The Seebeck coefficient retention ratio of the f-Fc-OH/PEI/SWCNT nearly remained 68% after being exposed to air for 3672 h, while the PEI/SWCNT film changed from n-type to p-type after being exposed to air for about 432 h. In addition, the temperature-dependent thermoelectric properties show that the f-Fc-OH/PEI/SWCNT achieves a high power factor of 334.57 μW m-1 K-2 at 353 K. Finally, a flexible TE module consisting of seven pairs of p-n junctions is assembled using the optimum composite film, which produces an open-circuit voltage of 42 mV and a maximum output power of 4.32 μW at a temperature gradient of 60 K. Therefore, this work provides guidance for preparing stable n-type SWCNT-based composite films with enhanced thermoelectric properties, which have potential applications in flexible generators and wearable electronic devices.

Investigation of Optical Interconnects for nano-scale VLSI applications

The relentless trend toward miniaturization has brought interconnects to the brink of communication bottlenecks, operating at or near their ampacity (current carrying capacity) limits. This degradation in performance necessitates novel technologies with increased ampacity. This study explores optical interconnect (OI) as a potential future technology, offering high-bandwidth communication and low latency. This study models and simulates OI, integrating recent optical device advancements with modest modulator and detector capacitance (50 fF). Performance metrics including signal delay, power dissipation, and power-delay-product (PDP) are compared across copper (Cu) and single-wall carbon nanotube bundle (SWCNT-B) interconnects at 22 nm and 14 nm technology nodes. Results consistently show OI, with an active voltage current feedback (AVCF) based regulated gain cascode (RGC) transimpedance amplifier (TIA) receiver, outperforms Cu and SWCNT-B interconnects at global lengths and beyond. For instance, at 1000 μm and 22 nm, OI exhibits 88.47 % and 62.15 % delay improvements over Cu and SWCNT-B, respectively. This trend persists at 14 nm, with OI showing 93.68 % and 84.29 % delay improvements, respectively. Additionally, OI surpasses Cu and SWCNT-B in power efficiency beyond a critical length. As interconnects extend to global scales and beyond, the differences in delay, power, and PDP between OI and electrical interconnect increases, highlighting OI's advantages for future VLSI IC applications.

SWCNT fibers decorated with Au nanoparticles as voltammetric sensors for arsenic (III) determination

We developed a new method to produce fiber electrodes from single-walled carbon nanotube (SWCNT) films, which can be employed as a novel sensing platform for electrochemical investigations and analysis. By assembling SWCNT bundles in the form of a strong free-standing fiber with almost entire surface accessible to an analyte, we are able to avoid the interference of substrate and improve detection efficiency. We examined the influence of physical, chemical and electrochemical pretreatments of the new electrode SWCNT material on its properties. Transmission and scanning electron microscopy, Raman spectroscopy and cyclic voltammetry were used to characterize the SWCNT fibers. The modification of the SWCNT fiber electrode with gold nanoparticles provides the necessary analytical characteristics including high repeatability and sensitivity and low detection limit (1.3 – 2.1 μg L-1) for arsenic determination by anodic stripping voltammetry. Arsenic detection parameters such as deposition potential, deposition time and scan rate were optimized. Linear responses were found in concentration ranges from 3 to 210 μg L-1 and 7 to 125 μg L-1 for gold modified SWCNT fiber sensors (the SWCNTs were synthesized using CO or ethanol as precursors) at a relatively low deposition time of 60 s. The developed Au-SWCNT sensors allow rapid As determination in real samples and exhibit high durability and long service life.

(Invited) Collective Radial Breathing Modes in Homogeneous Nanotube Bundles

Carbon nanotubes (CNTs) exist in many atomic structures typically grow as mixtures of of many chiralities with a vast variety of properties. Identical CNTs that are arranged into two-dimensional hexagonal lattices, their vibrational properties have been predicted to change with additional low-frequency modes appearing in the Raman spectrum. [1] Up to now, the experimental study of collective vibrations has been limited by a lack of pure homogeneous chirality bundles. We overcome this challenge by employing a self-coil mechanism of a very long CNT that loop into itself during the growth process resulting in a tightly packed hexagonal stack [2]. This lattice is perfectly homogeneous in terms of diameter, chiral twist, and even handedness of the tube. By characterizing and comparing the physical properties of the coil with respect to its tails, the bundling effects are clearly visible. We report on two breathing-like modes for quasi-infinite bundles, compared to the single radial breathing mode characteristic for isolated tubes. The exciton-phonon coupling in these modes is probed with resonant Raman spectroscopy, revealing the same resonance energy for both breathing-like peaks. Additionally, we study the dependence of vibrational coupling on the tube diameter by analysing different tube’s diameter coils and other bundling geometries. Our experimental findings align well with previously reported theoretical studies, demonstrating a 1/d scaling for all modes, as well as confirming the relative shift of the modes dependent on intertube interaction. These vibrations provide insight into the role of intertube lattice dynamics in two-dimensional THz-range phononic crystals.[1] Popov, V. N.; Henrard, L. Evidence for the existence of two breathinglike phonon modes in infinite bundles of single-walled carbon nanotubes. Phys. Rev. B 2001, 63, 233407[2] Nakar, D.; Gordeev, G.; Machado, L. D.; Popovitz-Biro, R.; Rechav, K.; Oliveira, E. F.; Kusch, P.; Jorio, A.; Galvao, D. S.; Reich, S.; others Few-wall Carbon Nanotube Coils. Nano Letters 2019, 20, 953–962.

Epitaxial growth of highly atomically ordered Pt-Fe nanoparticles from carbon nanotube bundles as durable oxygen reduction electrocatalysts

Intermetallic Pt-based nanoparticles have displayed excellent activity for the oxygen reduction reaction (ORR) in fuel cells. However, it remains a great challenge to synthesize highly atomically ordered Pt-based nanoparticle catalysts because the formation of an atomically ordered structure usually requires high-temperature annealing accompanied by grain sintering. Here we report the direct epitaxial growth of well-aligned, highly atomically ordered Pt3Fe and PtFe nanoparticles (<5 nm) on single-walled carbon nanotube (SWCNT) bundles films. The long-range periodically symmetric van der Waals (vdW) interactions between SWCNT bundles and Pt-Fe nanoparticles play an important role in promoting not only the alignment ordering of inter-nanoparticles but also the atomic ordering of intra-nanoparticles. The ordered Pt3Fe/SWCNT catalyst showed enhanced ORR catalytic performance of 2.3-fold higher mass activity and 3.1-fold higher specific activity than commercial Pt/C. Moreover, the formation of an interlocked interface and strong vdW interaction endow the Pt-Fe/SWCNT catalysts with extreme long-term stability in potential cycling and excellent anti-thermal sintering ability.

Ultrathin skin-conformable electrodes with high water vapor permeability and stretchability characteristics composed of single-walled carbon nanotube networks assembled on elastomeric films

Herein, we report on conductive ultrathin films (nanosheets) with the characteristics of stretchability and water vapor permeability for skin-conformable bioelectrodes. The films are fabricated by combining conductive fibrous networks of single-wall carbon nanotubes (SWCNTs) and poly(styrene-b-butadiene-b-styrene) (SBS) nanosheets (i.e., SWCNT-SBS nanosheets). An increase in the number of SWCNT coatings increases both the thicknesses and densities of the SWCNT bundles. The SBS nanosheets coated with three layers of SWCNTs (i.e., SWCNT 3rd-SBS nanosheets) show comparable sheet resistance to the SBS nanosheets coated with poly(3,4-ethylenedioxithiophene) doped with poly(4-styrenesulfonate acid) (PEDOT:PSS) containing 5 wt.% butylene glycol (i.e., PEDOT:PSS/BG5-SBS nanosheets). In addition, the SWCNT 3rd-SBS nanosheets exhibit significantly reduced elastic moduli and increased elongations at break compared to the PEDOT:PSS/BG5-SBS nanosheets. Furthermore, the calculated water vapor transmission ratio of the 210-nm-thick SBS nanosheets (268,172 g m−2 (2 h)−1) is greater than that of the filter paper (6345 g m−2 (2 h)−1). The SWCNT 3rd-SBS nanosheets attached to model skin show high tolerances to bending and artificial sweat at different pH values (i.e., the electrical resistance changes ~1.1 times). Finally, the SWCNT 3rd-SBS nanosheet is applied to detect the surface electromyogram from the forearm of a subject. This nanosheet displays a signal-to-noise ratio similar to that of the PEDOT:PSS/BG5-SBS nanosheet.

Evaluating SWCNT assembly properties from the temperature dependence of electrical resistivity

We developed a theoretical model to describe the electrical resistivity in films and fibers made of single-walled carbon nanotubes (SWCNTs). The proposed model considers the formation of randomly oriented bundles of metallic and semiconducting nanotubes and takes into account the influence of temperature, while separating contributions of SWCNTs and their junctions to the total resistivity. To verify the model, we applied a powerful experimental tool – measurements of the temperature dependence of electrical resistivity of the investigated macroscopic SWCNT assemblies (pristine and doped SWCNT fibers). This allowed us to estimate various parameters of the material, such as the average length of SWCNT bundles, the acoustic phonon scattering length, and the bundle contact resistance, which are difficult to evaluate experimentally for entangled SWCNTs. The study highlights the importance of understanding the relationship between structural characteristics and electrical properties in SWCNT assemblies. The findings provide insights into optimizing the conductivity of these materials and offer a quick estimation method of the SWCNT network properties based on varying temperature measurements for future fiber and film-based applications.

Effect of bundling on phonon transport in single-walled carbon nanotubes

Thermally conductive bulk materials composed of single-walled carbon nanotubes (SWCNTs), such as fibers and mats, are characterized by a complex network formed by entangled SWCNTs. The fundamental unit of this network is a bundle, in which SWCNTs are assembled through weak van der Waals interactions. Although the thermal conductivity of a bundle is conventionally described as the sum of the heat conduction in the constituent SWCNTs, recent experiments have demonstrated that bundling may reduce the high thermal conductivity of SWCNTs, which is counterintuitive considering the weak interactions between SWCNTs in a bundle. Herein, by performing spectral phonon transport analysis for bundles of SWCNTs with radii of approximately 3.4 Å, we explore the effect of the bundle size and chiral configuration on phonon transport in bundles. Results show that although the heat conduction properties of individual SWCNTs are maintained for bundles with a length of less than 1 μm around room temperature in both the ballistic and quasi-ballistic regimes, intertube interactions between constituent SWCNTs coupled with their structural low dimensionality may yield additional thermal resistance. In particular, the thermal conductivity of a bundle decreases when low-frequency phonons influenced by intertube interactions substantially contribute to the overall heat conduction, namely, either at low temperatures or for long bundles. Although the observed additional thermal resistance cannot fully explain the experimental results of reduced thermal conductivity, our findings on the effect of bundling can advance the understanding of thermal transport in bundles and the thermal management of SWCNT bulk materials.

Self-supporting oxygen vacancy-rich α-MnO2 nanowire/few-layer graphite/SWNT bundle composite film for high-performance flexible aqueous zinc-ion battery cathode

The increasing demand for flexible and wearable electronic devices has led to widespread interest in flexible electrochemical energy storage devices. However, the transformation of the battery structure from conventional to flexible presents a great challenge to the battery design. Herein, we developed a facile method for the preparation of a self-supporting composite film consisting of oxygen-vacancy rich MnO2 nanowires (NWs), few-layer graphite nanosheets (FLGs), and single-walled carbon nanotube (SWNT) bundles as the cathode of flexible zinc-ion batteries. This ternary interwoven interconnection 3D structure enhances the electrochemical performance of the battery and realizes fast charge transfer; oxygen vacancies in the MnO2 NWs caused by heat treatment (300 °C in Ar) allow for rapid intercalation and diffusion of Zn2+. The interwoven FLGs and SWNT bundles improve the electrical conductivity, and the robust interactions between the two carbon nanomaterials and the MnO2 NWs effectively make the composite film with excellent mechanical properties. This self-supporting flexible electrode exhibits a high specific capacity of 374 mAh/g at 0.4 A/g, maintains a Coulombic efficiency of ∼ 100 % after 1600 cycles at 2 A/g, and has a high energy density of 651.5 Wh kg−1 at 65.2 W kg−1. Moreover, the flexible zinc ion batteries assembled with the electrode demonstrate good mechanical properties and a high reversible specific capacity of 343 mAh/g after 75 bending cycles. Based on these findings, we believe that this composite film holds great promise as a cathode material in flexible energy storage applications.

Thermal Conductance between &lt;6 nm Single-Walled Carbon Nanotube Bundle and Si Substrate

Thermal Conductance between &lt;6 nm Single-Walled Carbon Nanotube Bundle and Si Substrate

Электрохимические сенсоры на основе сеток из однослойных углеродных нанотрубок для вольтамперометрического определения аскорбиновой кислоты

Modern highly sensitive and selective sensors are able to determine biologically active substances, which makes this direction one of the most popular areas of analytical chemistry. The study featured the electrochemical properties of new fiber materials based on single-wall carbon nanotubes with prospects of using them in the voltammetry of ascorbic acid. &#x0D; The authors developed a new technology to synthesize films from disordered single-wall carbon nanotubes by chemical vapor deposition. Fibers were produced from a solvent by wet-pulling of single-wall carbon nanotubes networks. Thin films of randomly oriented single-wall carbon nanotube bundles were deposited downstream of a floating aerosol CVD reactor, which included a high temperature furnace with a quartz tube. The synthesis of the single-wall carbon nanotube samples was performed at 825°C. Ethanol served as carbon source while ferrocene was used as catalyst precursor. The single-wall carbon nanotubes were collected on a nitrocellulose filter in the form of films with transmittances of 10% in the middle of the visible wavelength (550 nm). The method was optimized to involve air annealing at 300–320°C and a treatment with strong inorganic acids, i.e., HCl, HNO3 + H2SO4. The voltammetric curves recording included background electrolyte, scan rate, and preconditioning. These parameters were selected experimentally to obtain the maximal sensor response to ascorbic acid content. The anodic peak of ascorbic acid in the phosphate buffer electrolyte (pH 6.86) was observed at a potential of +0.2 V. The current and peak area of ascorbic acid oxidation depended neither on the time nor on the conditioning potential of the sensor. The linear dependences of these parameters on the concentration of ascorbic acid stayed within 50–500 μmol/L (8.8–90 mg/L) at a scan rate of 0.1 mV/s. The single-wall carbon nanotube microsensor had a length of 0.5 cm and an average width of 400 μm. Its sensitivity was two times as high as that of a disk glassy carbon electrode with a diameter of 5 mm. &#x0D; The experimental sensors proved effective in determining ascorbic acid in food products, pharmaceuticals, and biological fluids.

Effect of the reinforcement phase on the electrical and mechanical properties of Cu–SWCNTs nanocomposites

In this research a pre-treatment of single-walled carbon nanotubes (SWCNTs) was performed to obtain Cu–SWCNTs composites by powder metallurgy technique. The SWCNTs were subjected to a chemical functionalization in acidic medium followed by a copper coating to improve their incorporation into the metal matrix. The results revealed a considerable inclusion of carboxyl, carbonyl and hydroxyl groups in the nanotubes, maintaining their structural integrity which was demonstrated by characterization using X-ray photoelectronic spectroscopy (XPS), scanning electron microscopy (SEM) and Raman spectroscopy techniques. The electroless process used allowed a complete reduction of copper sulfate to a metallic copper obtaining a suitable and homogeneous carbon nanotubes incorporation into the copper matrix. Microhardness measurements of the Cu–0.01 % SWCNT composite presented an improvement of 13 % compared with pure copper. Furthermore, this composite showed the best tribological properties obtaining a wear rate of 2.1 × 10−4 mm3/Nm, 18 % better than Cu, which was associated with the improved dispersion of the SWCNTs bundles into the matrix, and with a lower amount of surface defects. The maximum electrical conductivity obtained was 96 % IACS in the samples with the least amount of reinforcement phase which confirms their homogeneity into the copper matrix.

Dynamic Performance of Hybrid Infrared Modulator Based on Single‐Walled Carbon Nanotubes and Ionic Liquid Enabling Fast Response

Herein, a new type of infrared film using single‐walled carbon nanotubes (SWNTs) is developed. The optimal sonication settings to produce SWNTs with the highest possible absorption of infrared light are discovered. A hybrid infrared modulator that combines SWNTs with ionic liquids, with a very fast response time is also developed. By carefully controlling the size of the SWNT bundles and the pore size of the filter membrane used to deposit the SWNTs, a response time of a few hundred microseconds (635 μs) at the half‐power point is achieved, which is the optical 3‐dB point. This technology has the potential to be used in a variety of innovative applications, such as smart windows and military camouflage, due to its excellent infrared optical properties.

Scattering-induced circuit modelling and performance analysis of coupled hybrid Interconnections: Sub-threshold performance evaluation

This paper presents the scattering induced circuit modelling and performance analysis in terms of crosstalk and frequency stability in the newly proposed hybrid interconnects operating in the sub-threshold domain. The electrical performances of hybrid copper carbon-nanotube (HCNT), hybrid copper graphene nanoribbon (HGNR) and hybrid Copper carbon (H Carbon) interconnects are examined and compared with that of copper (Cu), single walled carbon nanotube bundles (SWCNTs) and lithium doped multilayer graphene nanoribbon (MLGNR) interconnects in terms of dynamic and functional crosstalk results by employing the transmission line (TL) analytical model for sub-threshold applications. The impact of the grain-size on the resistivity of Cu and the various scatterings induced mean free path (MFP) on the overall resistance has been analysed in the modelling of HGNR interconnects. The comprehensive analysis of the crosstalk induced delay (dynamic crosstalk), the positive peaks and the time-duration (functional crosstalk) ensures the efficacy of hybrid interconnects, especially H Carbon interconnects in the designing of on-chip interconnects. It has also been observed from the frequency response that the maximum 3-dB bandwidth is obtained in the case of H Carbon hybrid interconnects (approx. 6.7586 × 1010 Hz) at 300 K temperature values. Further, the bandwidth values tend to decrease with the rise in temperature values.

Structural transition of single-walled carbon nanotube (6, 6) bundles under lateral shocks

Dynamic response of single-walled carbon nanotube (SWCNT) (6,6) bundles under planar shock are investigated using molecular dynamics (MD) simulations. The Hugoniot data indicate that the shock velocity (up) in the range of 0–12 km/s can generate a wide range of shock waves (0–24 km/s), and high pressure up 0–500 GPa. The SWCNT bundles undergo a radial deformation at ∼5 GPa (up=1 km/s). As pressure reaches ∼38 GPa (up=3 km/s), the bundles are activated and transform into a diamond-graphite structure, and a diamond-like mixture at ∼90 GPa (up=5 km/s) is formed, which is partly reversible upon release to atmospheric pressure. Finally, it completely liquefied into an amorphous carbon structure at pressure over 150 GPa (up=6 km/s). Meanwhile, the density functional theory calculations show that structural transition processes of SWCNT (6,6) bundles under lateral compression agree well with the MD simulations. This study provides atomistic insights into the structural transition of SWCNT bundles under shock compressions.

Phase transitions of carbon nanotube bundles under non-proportional triaxial compressions

Lateral compressions of (n, n) and (n, 0) single-walled carbon nanotube (SWCNT) bundles are simulated by density functional theory. Feasible transition pathways are verified by the body-centered tetragonal C4 (bct-C4) phase from the (4, 4) bundle and the carbon-centered orthorhombic C8 (Cco-C8) phase from (6, 6) and (8, 8) bundles. Three new phases, the sp3-hybridized phases Cco-C16 from the (4, 0) bundle and Cco-C32 from the (8, 0) bundle, the hexagonal phase Hex-C24 composed of sp2- and sp3-hybridized carbons from the (6, 0) bundle, under non-proportional triaxial loading are predicted. Measured hardness values for Cco-C16/C32 exceed 40 GPa, indicating super-hardness. Electronic band structures of Cco-C16/C32 exhibit a 3.64 eV bandgap, while Hex-C24 exhibits metallic carbon properties. Our results provide the potential phase transition pathways of SWCNT bundles under non-proportional compression.

(Invited) Engineering Single Wall Carbon Nanotubes for Sub-Cellular Drug Delivery

Single wall carbon nanotubes (SWCNTs) have been rigorously studied and engineered for a myriad of applications including drug delivery due to their unique, desirable properties. Since SWCNTs bundle in aqueous media and the bundling substantially diminishes their desirable properties along with inducing cytotoxicity, strategies to disperse individually SWCNTs with therapeutic molecules and biologic excipients have been heavily investigated. However, a handful of studies has been performed to understand the interactions between therapeutic molecules and excipients with SWCNT interface as well as the mechanism of intracellular release for therapeutic effects. Additionally, little attention has been paid to how cell type and cell metabolic activity level influence internalization of SWCNTs with different lengths. In this talk, I will discuss cell type, cell metabolic activity, and SWCNT length dependent cellular processing of SWCNTs dispersed with diverse biocompatible dispersing agents. Our results demonstrate that proper choice of dispersing agent can allow for interaction with F-actin, accumulation in the endoplasmic reticulum for eventual expulsion, or accumulation in cell nucleus. Further, macrophages with relatively high cell metabolic activity level compared to other cell types such as fibroblasts have shown to internalize significantly higher amount of SWCNTs per cell. The total mass of SWCNTs internalized per cell increases with a decrease in SWCNT length. Lastly, I will discuss our recent effort to create a ternary complex of SWCNTs, drug, and protein for intracellular delivery and release of model drugs. To overcome the limitation of the existing methods being only plausible for model drugs that are soluble in aqueous solutions, we developed a facile schema to assemble stepwise various combinations of therapeutic molecules and excipients on SWCNTs in different solvents using a preformed SWCNT network. These ternary complexes allow dialing in delivery of therapeutic molecules and excipients to achieve desired cell viability reduction. These findings allow for the development of new SWCNT-based biological applications as they establish important parameters of biomolecule adsorption on SWCNTs, SWCNT internalization and subcellular processing, which are crucial for applications ranging from drug delivery to cell type-specific modulation.