Multi-walled Carbon Nanotube Bundles Research Articles

Analytical Study of Bundled MWCNT and Edged MLGNR Interconnects: Impact on Propagation Delay and Area

This research letter presents an accurate and efficient model for rough-edged multi-layered graphene nanoribbon (MLGNR) and multi-walled carbon nanotube (MWCNT) bundled interconnects. To address the impact of delay and area, an analytical finite-difference time-domain and real-time simulation based approach are considered. In order to obtain the propagation delay, an equivalent single conductor (ESC) model is accurately presented by simplifying a multi-conductor transmission line (MTL) of bundled MWCNT and MLGNR interconnects. The proposed equivalent ESC model is in good agreement to the MTL with an average deviation of 4.6% only. In order to validate the proposed model, the equivalent resistance, inductance, and capacitance values are compared with standard experimental results. It is observed that the model expression possesses a good agreement with experimental data with an average error of below 9.93%. Using the ESC-based driver-interconnect-load setup, an approximate number of MWCNTs in a densely packed bundle is obtained for a rough-edged MLGNR at 22 nm technology to obtain an equivalent delay. In order to acquire the equivalent propagation delay, a fewer number of MWCNTs in a bundle can provide similar performance as of MLGNR for below 200 μm interconnect length. Furthermore, the number of MWCNTs significantly increases for longer interconnects. Therefore, on an average, an edged MLGNR requires 97.98% lesser area compared to the bundled MWCNT for global interconnects. Hence, a rough-edged MLGNR can be treated as a most desired interconnect material as compared to MWCNT bundle for the future interconnect technology.

Fullerene-to-MWCNT Structural Evolution Synthesized by Arc Discharge Plasma

The growth of multi-walled carbon nanotubes (MWCNTs) has been extensively studied using electron microscopy. The ex situ structural behavior was examined to investigate the growth of the MWCNTs under different environments and pressures using electron microscopy. The arc discharge plasma technique was applied to synthesize the MWCNTs by evaporating carbon through the arc plasma between two cylindrical graphite rods, with a background pressure of 10−2 to 102 mbar, inside a vacuum chamber under different ambient environments. The results showed that long MWCNT structures were successfully grown. We suggest that the mechanism involves: (i) fullerene formation; (ii) the elongation of fullerenes; and (iii) the growth of MWCNTs. Agglomeration with other structures then forms MWCNT bundles. We note that the pressure and environment in the vacuum chamber can affect the structure of the MWCNTs.

Surfactant assisted synthesis of Pt-Pd/MWCNT and evaluation as cathode catalyst for proton exchange membrane fuel cell

This study evaluates the role of two types of surfactants, the anionic sodium dodecyl sulfate (SDS) and cationic cetyltrimethylammonium bromide (CTAB) on the synthesis and properties of multi-walled carbon nanotube (MWCNT) supported bi-metallic Pt-Pd (atomic ratio 1:1) nanoparticles (NPs) and assess their performance as cathode catalyst in proton exchange membrane fuel cell (PEMFC). Pt-Pd/CNT catalysts are prepared through microwave assisted, polyol route in presence of SDS (Pt-Pd/CNT-S) or CTAB (Pt-Pd/CNT-C) and their performance is compared with Pt-Pd/CNT prepared in an identical way without any surfactant. The study shows the prominent influence of the type of surfactant in disaggregation of MWCNT bundles and the dispersion of Pt-Pd NPs on MWCNT support, which in turn controls their catalytic activity for oxygen reduction reaction. In-situ electrochemical characterization studies show improvement in the catalytic activity of Pt-Pd/CNT-S compared to Pt-Pd/CNT-C and Pt-Pd/CNT, demonstrating SDS as an efficient disperser for MWCNT. High fuel cell performance achieved with Pt-Pd/CNT-S having less Pt content (∼12 wt %) than the commonly employed pure Pt or Pt/C (20 wt %) catalysts demonstrates that it is a potential cathode catalyst for PEMFC that can help its wider commercialization.

Bandwidth expanding technology for dynamic crosstalk aware single-walled and multi-walled carbon nanotube bundle interconnects

In view of scarce bandwidth resources, an inductive peaking technology is used to expand 3-dB bandwidth of the coupled single-walled and multi-walled carbon nanotube bundle interconnects, which take the dynamic crosstalk into account. Based on decoupling technique and ABCD parameter matrix approach, the transfer function of the decoupled victim line at global level of 14 nm technology node is derived to analyze and compare the bandwidth performance under different length, diameter, temperature and load resistance conditions. It is obvious that 3-dB bandwidth can be effectively expanded by adding peaking inductance to the load irrespective of phase-mode. However, the bandwidth will remain nearly unchanged once the adding inductance reaches a certain extent. Furthermore, the overshoot and undershoot in the step response will be caused with the further increase of the peaking inductance. On the other hand, it is shown that the value of 3-dB bandwidth at out-of-phase mode is much smaller than that at in-phase mode under the same condition.

Evaluation of new cholinium-amino acids based room temperature ionic liquids (RTILs) as immobilization matrix for electrochemical biosensor development: Proof-of-concept with Trametes Versicolor laccase

In this work, we present new cholinium-amino acids room temperature ionic liquids (ChAARTILs) that can be used as an efficient immobilization matrix for electrochemical biosensor development. The ideal immobilization strategy should be able to ensure the highest enzyme loading and a tight enzymatic immobilization, preserving its native structure and biological activity. In this regard, ChAARTILs present different side chains on the amino acids giving rise to van der Waals, π-π stacking and hydrogen bonding interactions. All these interactions can affect the nanomaterial organization onto the electrode surface. To this aim, we have evaluated the main electrochemical parameters, namely electroactive area (AEA) and the heterogeneous electron transfer rate constant (k0), showing how both cations and anions of room temperature ionic liquids (RTILs) can independently affect multi-walled carbon nanotubes (MWCNTs) organization. In particular, [Ch][Phe] showed the best performance in terms of AEA (3.432 cm2) and k0 (4.71·10−3 cm s−1) with a homogeneous distribution of MWCNTs bundles onto the electrodes and a faster electron transfer rate.Finally, the modified electrode (MWCNTs-[Ch][Phe]) has been tested with a model enzyme, namely Trametes versicolor laccase (Tvl), in order to evaluate the possibility to use ChAARTILs as immobilization matrix, preventing enzymatic denaturation phenomena which would affect the biosensor performance in terms of sensitivity, linear range, and stability.

Advances in Solid Acid Fuel Cells

Intermediate temperature fuel cells, operating between 150-300 °C offer several advantages over traditional low temperature systems including faster kinetics, increased tolerance to catalyst poisons such as CO, and better fuel flexibility. Fuel cells based on the inorganic proton conductor CsH2PO4 (CDP)1 have the potential to be efficient devices for intermediate-temperature (230-260 °C) distributed generation applications2. Realizing this potential is contingent on the development of next-generation electrodes with significantly higher activity and lower precious metal content than the state of the art. Current SAFC electrodes are based on a porous framework of the CDP electrolyte functionalized with an interconnected film of platinum nanoparticles that serves as both the ORR catalyst and the electronic conductor3. The activity of these electrodes scales with the surface area of the electrolyte in the electrode2, but the requirement of a percolating Pt network also unfavorably scales the precious metal content of these high surface area electrodes. We have addressed this problem by developing a new electrode concept based on a multi-step, multiphase infiltration strategy. The CDP electrolyte is first infiltrated in the liquid phase into chemically-treated multi-walled carbon nanotube (MWNT) bundles, followed by vapor-phase Pt deposition on the nanocomposite structure. In addition to exerting a structural templating influence on the solid electrolyte, the role of electronic conduction is assumed by the MWNTs, allowing for much greater tri-phase boundary densities to be obtained at lower Pt content. We further examined the effect of electrode thickness and have observed that the majority of the electrochemical activity is within the first micron of the catalyst layer. Cathodes formed from these nanocomposite materials can exceed the activity of the state-of-the-art cathode (2.8 mgPt/cm2) at a fraction of the Pt content (0.18 mgPt/cm2). Pt utilization is increased at lower Pt loadings, with Pt mass-specific activity greater than 3 A/mgPt at 0.5 V. Cells based on this architecture are stable for greater than 300 hours at 0.6 V and 250 °C. In this presentation we will highlight our progress over the last few years and comment on efforts to commercialize this technology. A critical review of the unique features of the electrode architecture will be presented along with some commentary on recent observations that suggest that single atom Pt catalysts exist on the nanocomposite electrode that may play a role in the enhanced Pt activity. Acknowledgements This work is supported by ARPA-E under Cooperative Agreement Number DE-AR0000499. References 1 S.M. Haile, C.R.I. Chisholm, K. Sasaki, D.A. Boysen, and T. Uda, Faraday Discuss. 134, 17 (2007). 2 C. R. I. Chisholm, D. A. Boysen, A. B. Papandrew, S. K. Zecevic, S. Cha, K. A. Sasaki, Á. Varga, K. P. Giapis, and S.M. Haile, Electrochem. Soc. Interface 18, 53–59 (2009). 3 A. B. Papandrew, C. R.I. Chisholm, R. A. Elgammal, M. M. Özer, and S. K. Zecevic, Chem. Mater. 23, 1659–1667 (2011). Figure 1

On the Impacts of Process and Temperature Variations on the Crosstalk Effects in MWCNT Bundle Nanointerconnects in Ternary Logic

Multiple-valued logic systems have been considered as a solution for the challenges of the nanoscale binary very large scale integration chips. However, the main concerns about these systems are the noise impacts, especially in the presence of process and temperature variations. In this study, the impacts of process and temperature variations on the crosstalk effects in multiwall carbon nanotube (MWCNT) bundle interconnects in ternary systems are investigated. The deviation in the worst-case crosstalk delay, noise, and the power introduced by the process variations are investigated using comprehensive Monte Carlo simulations. Also, analyses are conducted for the global level interconnects at 22 nm technology node for repeated MWCNT bundle interconnects. The results indicate that the average deviations in the worst-case crosstalk delay and crosstalk noise area in the presence of all sources of process variations in the repeated MWCNT bundle interconnects are about 14%. In addition, the maximum variations in the lumped resistance, distributed resistance, kinetic inductance, electrostatic capacitance, coupling capacitance and quantum capacitance of the MWCNT bundle interconnects in ternary systems in the presence of all sources of process variations are 4.6%, 14%, 7.2%, 8.2%, 5.1%, and 5.6%, respectively. According to the results, higher temperature increases the resistance of the MWCNT bundle interconnects and thereby the crosstalk delay and crosstalk noise area mainly due to the reduction of the mean free path of the MWCNTs in a bundle.

Tuning vertical alignment and field emission properties of multi-walled carbon nanotube bundles

We report the growth of vertically aligned carbon nanotube bundles on Si substrate by thermal chemical vapor deposition technique. Vertical alignment was achieved without any carrier gas or lithography-assisted deposition. Growth has been carried out at 850 °C for different quantities of solution of xylene and ferrocene ranging from 2.25 to 3.00 ml in steps of 0.25 ml at a fixed concentration of 0.02 gm (ferrocene) per ml. To understand the growth mechanism, deposition was carried out for different concentrations of the solution by changing only the ferrocene quantity, ranging from 0.01 to 0.03 gm/ml. A tunable vertical alignment of multi-walled carbon nanotubes (CNTs) has been achieved by this process and examined by scanning and transmission electron microscopic techniques. Micro-crystalline structural analysis has been done using Raman spectroscopy. A systematic variation in field emission (FE) current density has been observed. The highest FE current density is seen for the film grown with 0.02 gm/ml concentration, which is attributed to the better alignment of CNTs, less structural disorder and less entanglement of CNTs on the surface. The alignment of CNTs has been qualitatively understood on the basis of self-assembled catalytic particles.

A phenomenological study of a Sn–Ag–Al composite solder reinforced with Mg–MWCNT: Improved electrical conductivity and thermo-physical performance

A Sn–Ag–Al composite solder alloy reinforced with Mg–multi-walled carbon nanotubes (MWCNT) was prepared using a powder metallurgy (P/M) method. The electrical resistivity of the Sn–Ag–Al–Mg–MWCNT composite solder alloy decreased to 21.91×10−6Ω·cm when the Sn–Ag–Al conventional solder alloy (36.15×10−6Ω·cm) was reinforced with 2.87wt% Mg and 0.60wt% MWCNT (3.47wt% Mg–MWCNT). The reinforcement by the Mg–MWCNT also provided relatively lower density (6.53g/cm3) to the composite solder alloy compared to the conventional solder alloy (7.34g/cm3). The onset melting temperature of the quinary solder alloy was 204.2°C, which was 10.0°C lower than that of the ternary solder alloy at 214.2°C. The wettability of the composite solder powders after reflow on the quartz substrate was increased due to the improved solder fluidity aided by the MWCNT bundle. The improved electrical and thermo-physical performance was induced by a combination of interactions driven by ionic and covalent bonds between the Mg atoms and the MWCNT, and by intermetallic compound formation between the Mg atoms and the other solder constituents.

Temperature-Dependent Modeling and Crosstalk Analysis in Mixed Carbon Nanotube Bundle Interconnects

The temperature-dependent circuit modeling and performance analysis in terms of crosstalk in capacitively coupled mixed carbon nanotube bundle (MCB) interconnects, at the far end of the victim line, have been analyzed with four different structures of MCBs (MCB-1, MCB-2, MCB-3 and MCB-4) constituted under case 1 and case 2 at the 22-nm technology node. The impact of tunneling and intershell coupling between adjacent shells on temperature-dependent equivalent circuit parameters of a multi-walled carbon nanotube bundle are also critically analyzed and employed for different MCB structures under case 1. A similar analysis is performed for copper interconnects and comparisons are made between results obtained through these analyses over temperatures ranging from 300 K to 500 K. The simulation program with integrated circuit emphasis simulation results reveals that, compared with all MCB structures under case 1 and case 2, with rise in temperature from 300 K to 500 K, crosstalk-induced noise voltage levels at the far end of the victim line are found to be significantly large in copper. It is also observed that due to the dominance of larger temperature-dependent resistance and ground capacitance in case 1, the MCB-2 is of lower crosstalk-induced noise voltage levels than other structures of MCBs. On the other hand, the MCB-1 has smaller time duration of victim output. Results further reveal that, compared with case 2 of MCB, with rise in temperatures, the victim line gets less prone to crosstalk-induced noise in MCB interconnects constituted under case 1, due to tunneling effects and intershell coupling between adjacent shells. Based on these comparative results, a promising MCB structure (MCB-2) has been proposed among other structures under the consideration of tunneling effects and intershell coupling (case 1).

Effect of coating mild steel with CNTs on its mechanical properties and corrosion behaviour in acidic medium

The study investigated the mechanical properties and corrosion behaviour of mild steel coated with carbon nanotubes at different coating conditions. Multi-walled carbon nanotubes (MWCNTs) were synthesized via the conventional chemical vapour deposition reaction using bimetallic Fe–Ni catalyst supported on kaolin, with acetylene gas as a carbon source. The HRSEM/HRTEM analysis of the purified carbon materials revealed significant reduction in the diameters of the purified MWCNT bundles from 50 nm to 2 nm and was attributed to the ultrasonication assisted dispersion with surfactant (gum arabic) employed in purification process. The network of the dispersed MWCNTs was coated onto the surfaces of mild steel samples, and as the coating temperature and holding time increased, the coating thickness reduced. The mechanical properties (tensile strength, yield strength, hardness value) of the coated steel samples increased with increase in coating temperature and holding time. Comparing the different coating conditions, coated mild steels at the temperature of 950 °C for 90 min holding time exhibited high hardness, yield strength and tensile strength values compared to others. The corrosion current and corrosion rate of the coated mild steel samples decreased with increase in holding time and coating temperature. The lowest corrosion rate was observed on sample coated at 950 °C for 90 min.

Development of Aspect Ratio Control Technique for Multi-wall Carbon Nanotube Bundle Shape for High Sensitivity Strain Sensor

Development of Aspect Ratio Control Technique for Multi-wall Carbon Nanotube Bundle Shape for High Sensitivity Strain Sensor

Impact of tunneling conductance on the performance of multi walled carbon nanotubes as VLSI interconnects for nano-scaled technology nodes

Multi walled carbon nanotube (MWCNT) has received most of the attention for their unique characteristics as a possible alternative for copper as a VLSI interconnects for future integrated circuits. Multiple equivalent single-conductor circuit (ESC) models are reported in the literature for analysis of MWCNT as an interconnect, however most of them have neglected the impact of intershell tunneling conductance on the performance of MWCNT as interconnect. In this paper, a model is proposed for deriving equivalent impedance parameters by including tunneling conductance in order to study the impact of intershell tunneling conductance on the performance of MWCNT interconnect in terms of delay. Based on the derived equivalent impedance parameters, existing ESC model is modified. Further, the analytical and simulated results obtained from proposed model are compared with the results of existing models. It is revealed from the comparative analysis that the tunneling conductance has considerable impact on the impedance parameters and the propagation delay of an MWCNT bundle interconnect at variable interconnects length for nano-scaled technology nodes i.e. 32, 22 and 16 nm.

Low-loss shielded through-silicon vias filled with multi-walled carbon nanotube bundle

In this paper, the multi-walled carbon nanotube bundle (MWCNTB) based shielded through-silicon via (S-TSV) is proposed and the compact expression for the equivalent conductivity of MWCNTB (σMWCNTB) is deduced to calculate the resistance of MWCNTB based S-TSV (MS-TSV). Then, the electrical characteristics including the S parameters, attenuation constant and time delay are investigated. The results indicate that |S21| of MS-TSV increases with the increase of the outermost diameter of MWCNT and decrease of the thickness of the shielding layer. Compared with the copper filled S-TSV (CuS-TSV), the MS-TSV has a larger |S21|, smaller attenuation and shorter time delay. Finally, the impact of the geometrical parameters on the conductivity of MS-TSV is analyzed. Also, the minimum packing density of MWCNTB satisfying σMWCNTB≥σCu has been deduced. The results show that the outermost diameter of MWCNT has the most significant impact on the conductivity of MS-TSV, and thicker MWCNT is helpful to increase the conductivity of MS-TSV, decrease the packing density of MWCNTB and reduce manufacturing difficulty.

From nano to giant? Designing carbon nanotubes for rubber reinforcement and their applications for high performance tires

Carbon nanotubes (CNTs) attract considerable scientific and engineering interest because of their excellent mechanical, electrical and thermal properties. Today, when manufacturers use CNTs, purification, chemical modifications and dispersion techniques are usually applied rendering them cost-effective in large-scale applications. Our research shows that multi-wall CNTs bundles (MWCNTBs) with the same alignment, orientation and high surface defects for each CNT can be directly incorporated into the elastomer matrix through melt compounding. A uniform dispersion of CNTs and strong interfacial interactions between elastomers and CNTs due to the silane-coupling agent can be simultaneously produced. The resulting elastomer/MWCNTBs nanocomposites demonstrate excellent mechanical properties, high thermal conductivity and low volume resistivity. Note that this nanocomposite is achieved using common compounding equipment that is easy to industrialize. Through further scale-up, we confirmed that this elastomer/MWCNTBs nanocomposite has the most optimized comprehensive performance with practical applications for fuel-savings and engineering tires. These advantages include fuel efficiency, anti-static electricity and long-time fatigue resistance. In light of the large number of tires used worldwide, this work is promising for future large-scale industrial applications of CNTs.

Effective disentangling method of bundled multi-walled carbon nanotubes into individual multi-walled carbon nanotubes by magnetic-field induction

Abstract A simple method that uses magnetic field induction for the disentanglement of bundled multiwall carbon nanotubes (MWCNTs) that are massively aggregated in a single and intact form was investigated. MWCNTs exposed to a 1 Tesla (T) field periodically switched on and off were separated into individual MWCNTs using 4,4′-azobis(4-cyanovaleric acid) as a radical initiator with iron oxide nanoparticles. The study results show that, in accordance with the dissipation working principle, MWCNT bundles under 40 nN achieved complete disentanglement within a few hours, and these results were theoretically verified by an Opera 3D simulation. We anticipate that single CNTs obtained using our method will have applications in several CNT research areas ranging from electronic devices to biocomputers.

Comprehensive Model for High-Speed Current-Mode Signaling in Next Generation MWCNT Bundle Interconnect Using FDTD Technique

The performance of current-mode signaling (CMS) scheme in carbon nanomaterial based multiwall carbon nanotube (MWCNT) bundle on-chip interconnect using finite-difference time-domain (FDTD) technique is investigated in the present paper. A very comprehensive model that analyzes both the traditional copper and the next-generation MWCNT bundle interconnects is presented. Further, this model is applicable for both the conventional voltage-mode signaling (VMS) and the delay-efficient CMS schemes. The number of MWCNT shells in a bundle interconnect is varied, and it is analyzed that MWCNTs with larger number of shells have better performance than both MWCNTs consisting of lesser number of shells and the copper interconnects. It is analyzed that CMS scheme has superior performance than VMS scheme in terms of smaller propagation delay and reduced crosstalk-induced delay. Various analyses have been performed for 32-nm technology node and are validated using SPICE simulations. The results obtained from the proposed FDTD based model and SPICE are found to be in close agreement, and the maximum error is within 3%.

Multi-walled carbon nanotubes/TiO2 thin layer for photocatalytic degradation of organic pollutant under visible light irradiation

This paper is based on preparation of MWCNT/TiO2 photoactive thin layer deposited on glass substrate using the sol–gel dip-coating technique. The thin layer consists of TiO2 coupled with different amount of per-noncovalent functionalized multi-walled carbon nanotubes (MWCNTs). The optimum MWCNTs/TiO2 weight ratio in the thin film was found to be 1.75 % under the experimental conditions investigated. The MWCNT/TiO2 film was characterized by a range of analytical techniques including: scanning electron microscopy, atomic force microscopy, X-ray diffraction, photoluminescence spectra, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and UV–Vis spectroscopy. The photoactivity of the prepared films, under visible light irradiation, was evaluated by decoloration of methyl orange (MO). Complete decoloration of MO was observed only in 2 h under visible light irradiation. Furthermore, we used chemical oxygen demand (COD) method to determine the degradation efficiency of the MWCNT/TiO2 thin layer. 42 % reduction in COD value of treated MO solution shows substantial degradation of MO by photoactive film. According to the results of MO removal experiment, the excellent activity of the photoactive film can be attributed to the strong interaction between TiO2 particles and MWCNT bundles and the high electron acceptability of CNTs network.

Infiltrated CsH2PO4-Carbon Nanotube Composites for High Performance Solid Acid Fuel Cathodes with Low Pt Loading

Fuel cells based on the inorganic proton conductor CsH2PO4 (CDP)1 have the potential to be efficient devices for intermediate-temperature (230-260 °C) distributed generation applications2. Realizing this potential is contingent on the development of next-generation electrodes with significantly higher activity and lower precious metal content than the state of the art. Current SAFC electrodes are based on a porous framework of the CDP electrolyte functionalized with an interconnected film of platinum nanoparticles that serves as both the ORR catalyst and the electronic conductor3. The activity of these electrodes scales with the surface area of the electrolyte in the electrode2, but the requirement of a percolating Pt network also unfavorably scales the precious metal content of these high surface area electrodes. We have addressed this problem by developing a new electrode concept based on a multi-step, multiphase infiltration strategy. The CDP electrolyte is first infiltrated in the liquid phase into chemically-treated multi-walled carbon nanotube (MWNT) bundles, followed by vapor-phase Pt deposition on the nanocomposite structure. In addition to exerting a structural templating influence on the solid electrolyte, the role of electronic conduction is assumed by the MWNTs, allowing for much greater tri-phase boundary densities to be obtained at lower Pt content. Cathodes formed from these nanocomposite materials can exceed the activity of the state-of-the-art cathode (2.8 mgPt/cm2) at a fraction of the Pt content (0.7 mgPt/cm2) (see Figure 1a). Pt utilization is increased at lower Pt loadings, with Pt mass-specific activity greater than 1 A/mgPt at 0.5 V possible at 0.35 mgPt/cm2 (Figure 1b). Cells based on this architecture are stable for greater than 150 hours at 0.6 V and 250 °C. Acknowledgments This work is supported by ARPA-E via cooperative agreement DE-AR0000499. References 1 S.M. Haile, C.R.I. Chisholm, K. Sasaki, D.A. Boysen, and T. Uda, Faraday Discuss. 134, 17 (2007). 2 C. R. I. Chisholm, D. A. Boysen, A. B. Papandrew, S. K. Zecevic, S. Cha, K. A. Sasaki, Á. Varga, K. P. Giapis, and S.M. Haile, Electrochem. Soc. Interface 18, 53–59 (2009). 3 A. B. Papandrew, C. R.I. Chisholm, R. A. Elgammal, M. M. Özer, and S. K. Zecevic, Chem. Mater. 23, 1659–1667 (2011). Figure 1

Intercalation-assisted longitudinal unzipping of carbon nanotubes for green and scalable synthesis of graphene nanoribbons.

We have demonstrated an effective intercalation of multi-walled carbon nanotubes (MWCNTs) for the green and scalable synthesis of graphene nanoribbons (GNRs) using an intercalation-assisted longitudinal unzipping of MWCNTs. The key step is to introduce an intercalation treatment of raw MWCNTs with KNO3 and H2SO4, making it promising to decrease the strong van der Waals attractions in the MWCNTs bundles and between the coaxial graphene walls of CNTs. Systematic micro Raman, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) characterizations suggest that potassium, nitrate, and sulfate ions play an important role in the CNT intertube and intratube intercalations during the pretreatment. Detailed scanning electron microscopy (SEM), transmission electron microscopy, XRD, and micro Raman characterizations indicate that the developed methodology possesses the ability to synthesis GNRs effectively with an improved CNT concentration in H2SO4 of 10 mg/ml at 70 °C, which is amenable to industrial-scale production because of the decreased amount of strong acid. Our work provides a scientific understanding how to enhance the GNR formation by accelerating the CNT longitudinal unzipping via suitable molecular intercalation.