Synergistic effects of hybrid n-doping on the thermoelectric performance and air-stability of water-processable single-walled carbon nanotubes.

Organic thermoelectrics (TEs) based on carbon nanotubes (CNTs) have attracted much attention with their inherent advantages, such as, earth-abundant elements, broad electronic tunability, and excellent mechanical compliance. However, the inferior TE performance and doping stability of n-type CNTs to those of p-type CNTs have been bottlenecks to establish CNT-based next-generation TEs. Herein, we report a hybrid n-doping method that improves the n-type TE performance and long-term air-stability of water-processable single-walled CNT (SWCNT) and carboxymethyl cellulose (CMC) composite. The hybrid n-doping process with polyethyleneimine (PEI) n-dopant contains primary addition and secondary immersion doping, which causes a simultaneous increase in electrical conductivity and Seebeck coefficient through efficient n-doping and surface energy filtering effect, respectively. Furthermore, the hybrid-doped films exhibit superior long-term stability by inhibiting the oxidation of SWCNT/CMC at nanoscale, which allows to ensure the initial power factor even after storing in ambient for a month. Finally, we successfully demonstrated hybrid-doped SWCNT/CMC-based TEGs with long-term stable output characteristics. This work can offer insights to develop efficient and air-stable n-type organic TE materials and devices.

Response of Foldable Protein Conformations to Non-physiological Perturbations: Interplay of Thermal Factors and Confinement.

Technological advances frequently interface biomolecules with nanomaterials at non-physiological conditions, necessitating response characterization of key processes. Similar encounters are expected in cellular contexts. We report in silico investigations of the response of diverse protein conformational states to lowering of temperature and imposition of spatial constraints. Conformational states are represented by folded form of the Albumin binding domain (ABD) protein, its compact denatured form, and structurally disordered nascent folding elements. Data from extensive simulations are evaluated to elicit structural, thermodynamic and dynamic responses of the states and their associated environment. Analyses reveal alterations to folding propensity with reduced thermal energy and confinement, with signatures of trend reversal in highly disordered states. Across temperatures, confinement has restrictive effects on volume and energetic fluctuations, leading to narrowing of differences in isothermal compressibility (κ) and heat capacities (Cp). While excess (over ideal gas) entropy of the hydration layer marks dependence on the conformational state at bulk, confinement triggers erasure of differences. These observations are largely consistent with timescales of protein-water hydrogen bonding dynamics. The results implicate multi-factorial associations within a simple bio-nano complex. We expect the current study to motivate investigations of more biologically relevant interfaces towards mechanistic understanding and potential applications.

Highly Conductive Ink Based on Self-Aligned Single-Walled Carbon Nanotubes through Inter-Fiber Sliding in Cellulose Fibril Networks.

Carbon nanotubes (CNTs), owing to their superior electrical and mechanical properties, are a promising alternative to nonmetallic electrically conducting materials. In practice, cellulose as a low-cost sustainable matrix has been used to prepare the aqueous dispersion of cellulose-CNT (C-CNT) nanocomposites. However, the compatibility with conventional solution-processing and structural rearrangement for improving conductivity has yet to be determined. Herein, a straightforward route to prepare a conductive composite material from single-walled CNTs (SWCNTs) and natural pulp is reported. High-power shaking realizes the self-alignment of individual SWCNTs in a cellulose matrix, resulting from the structural change in molecular orientations owing to countless collisions of zirconia beads in the aqueous mixture. The structural analysis of the dried C-CNT films confirms that the entanglement and dispersion of C-CNT nanowires determine the mechanical and electrical properties. Moreover, the rheological behavior of C-CNT inks explains their coating and printing characteristics. By controlling shaking time, the electrical conductivity of the C-CNT films with only 9 wt.% of SWCNTs from 0.9 to 102.4 S cm-1 are adjusted. the optimized C-CNT ink is highly compatible with the conventional coating and printing processes on diverse substrates, thus finding potential applications in eco-friendly, highly flexible, and stretchable electrodes is also demonstrated.

Beyond Mechanical Protection: The Electron-Shielding Effect of SWCNT for the Stabilized SiO Interface.

The single-walled carbon nanotube (SWCNT) commonly serves as a conductive additive for SiO-based anode materials due to the excellent conductivity and mechanical properties. However, the potential action mechanisms for the SWCNT beyond conductivity and mechanical features have rarely been studied. Herein, an interfacial electron-shielding effect and preferential adsorption to the electrolyte components for the SWCNT are revealed through a series of advanced characterizations and density functional theory (DFT) simulations. It can be determined that SWCNT networks could restrict the transmission of the electron from SiO interface to electrolyte with the reduced decomposition, because of the typical axial conductivity of the SWCNT. Moreover, the SWCNT shows stronger adsorption energy for LiPF6 and ethylene carbonate (EC) molecules, rather than nonselectivity of traditional carbon additives, facilitating the generation of inorganic-rich and denser solid electrolyte interface (SEI) film. As a result, benefiting from the electron-shielding effect, preferential adsorption, and mechanical protection, the SWCNT endows the SiO@C anode with a higher average Coulombic efficiency (CE) value of 99.4% over 100 cycles and a long cycling stability.

Systematic Selection of High-Affinity ssDNA Sequences to Carbon Nanotubes.

Single-walled carbon nanotubes (SWCNTs) have gained significant interest for their potential in biomedicine and nanoelectronics. The functionalization of SWCNTs with single-stranded DNA (ssDNA) enables the precise control of SWCNT alignment and the development of optical and electronic biosensors. This study addresses the current gaps in the field by employing high-throughput systematic selection, enriching high-affinity ssDNA sequences from a vast random library. Specific base compositions and patterns are identified that govern the binding affinity between ssDNA and SWCNTs. Molecular dynamics simulations validate the stability of ssDNA conformations on SWCNTs and reveal the pivotal role of hydrogen bonds in this interaction. Additionally, it is demonstrated that machine learning could accurately distinguish high-affinity ssDNA sequences, providing an accessible model on a dedicated webpage (http://service.k-medai.com/ssdna4cnt). These findings open new avenues for high-affinity ssDNA-SWCNT constructs for stable and sensitive molecular detection across diverse scientific disciplines.

Single-walled carbon nanotube-protein complex: A strategy to improve the immune response to protein in mice.

Vaccines represent an effective tool for controlling disease infection. As a key component of vaccines, many types of adjuvants have been developed and used today. This study is designed to investigate the efficacy of single-walled carbon nanotubes (SWCNTs) as a new adjuvant. The results showed that SWCNT could adsorb the antigen by intermolecular action, and the adsorption rate was significantly higher after dispersion of the SWCNTs in a sonic bath. The titer of specific antibody of mice in the SWCNTs group was higher than that of the mice in the antigen control group, confirming the adjuvant efficacy of SWCNTs. During immunisation, the specific antibody was detected earlier in the mice of the SWCNTs group, especially when the amount of antigen was reduced. And it was proved that the titer of antibodies was higher after subcutaneous and intraperitoneal injection compared to intramuscular injection. Most importantly, the mice immunised with SWCNTs showed almost the same level of immunity as the mice in the FCA (Freund's complete adjuvant) group, indicating that the SWCNTs were an effective adjuvant. In addition, the mice in the SWCNT group maintained antibody levels for 90 days after the last booster vaccination and showed a good state of health during the observed period. We also found that the SWCNTs were able to induce macrophages activation and enhance antigen uptake by mouse peritoneal macrophages.

High-sensitivity and energy-efficient chloride ion sensors based on flexible printed carbon nanotube thin-film transistors for wearable electronics.

The advent of flexible single-walled carbon nanotube thin-film transistors (SWCNT-TFTs) has transformed electronics, providing significant benefits like low operating voltage, reduced power consumption, cost-effectiveness, and improved signal amplification. This study focuses on leveraging these attributes to develop a novel flexible high-sensitivity and energy-efficient chloride ion sensors based on printed flexible SWCNT-TFTs utilizing polymers-sorted semiconducting SWCNTs (sc-SWCNTs) as the active layers and ion liquids-poly(4-vinylphenol as dielectric layers along with the evaporated deposition of aluminum electrodes and printed silver electrodes as the gate and source-drain electrodes, respectively. The sensors exhibit several operational advantages, including low voltage requirements (≤1 V), rapid response speed (5.32 s), significant signal amplification (Up to 702.6 %), low power consumption (0.31 µJ at 1 mmol chloride ion), good repeatability, high sensitivity for both low and high concentrations of chloride ion (up to 100 mmol/L) and excellent mechanical flexibility (No obvious changes after bending for 10,000 times with a 5 mm radius). The detection mechanism of chloride ions was analyzed using X-ray Photoelectron Spectroscopy (XPS). It was found that chloride ions react with silver nanoparticles (AgNPs) to form silver chloride (AgCl) on printed electrodes, impeding carrier transport and reducing the currents in SWCNT TFTs. Importantly, our sensors' compatibility with smart devices allows for real-time monitoring of chloride ion levels in human sweat, offering significant potential for daily health monitoring.

Large-Area Flexible Carbon Nanofilms with Synergistically Enhanced Transmittance and Conductivity Prepared by Reorganizing Single-Walled Carbon Nanotube Networks.

Large-area flexible transparent conductive films (TCFs) are highly desired for future electronic devices. Nanocarbon TCFs are one of the most promising candidates, but some of their properties are mutually restricted. Here, a novel carbon nanotube network reorganization (CNNR) strategy, that is, the facet-driven CNNR (FD-CNNR) technique, is presented to overcome this intractable contradiction. The FD-CNNR technique introduces an interaction between single-walled carbon nanotube (SWNT) and Cu─-O. Based on the unique FD-CNNR mechanism, large-area flexible reorganized carbon nanofilms (RNC-TCFs) are designed and fabricated with A3-size and even meter-length, including reorganized SWNT (RSWNT) films and graphene and RSWNT (G-RSWNT) hybrid films. Synergistic improvement in strength, transmittance, and conductivity of flexible RNC-TCFs is achieved. The G-RSWNT TCF shows sheet resistance as low as 69 Ω sq-1 at 86% transmittance, FOM value of 35, and Young's modulus of ≈45 MPa. The high strength enables RNC-TCFs to be freestanding on water and easily transferred to any target substrate without contamination. A4-size flexible smart window is fabricated, which manifests controllable dimming and fog removal. The FD-CNNR technique can be extended to large-area or even large-scale fabrication of TCFs and can provide new insights into the design of TCFs and other functional films.

Evaluating the Efficiency of Boron Nitride Coating in Single-Walled Carbon-Nanotube-Based 1D Heterostructure Films by Optical Spectroscopy.

Single-walled carbon nanotube (SWCNT) films exhibit exceptional optical and electrical properties, making them highly promising for scalable integrated devices. Previously, we employed SWCNT films as templates for the chemical vapor deposition (CVD) synthesis of one-dimensional heterostructure films where boron nitride nanotubes (BNNTs) and molybdenum disulfide nanotubes (MoS2NTs) were coaxially nested over the SWCNT networks. In this work, we have further refined the synthesis method to achieve precise control over the BNNT coating in SWCNT@BNNT heterostructure films. The resulting structure of the SWCNT@BNNT films was thoroughly characterized using a combination of electron microscopy, UV-vis-NIR spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and Raman spectroscopy. Specifically, we investigated the pressure effect induced by BNNT wrapping on the SWCNTs in the SWCNT@BNNT heterostructure film and demonstrated that the shifts of the SWCNT's G and 2D (G') modes in Raman spectra can be used as a probe of the efficiency of BNNT coating. In addition, we studied the impact of vacuum annealing on the removal of the initial doping in SWCNTs, arising from exposure to ambient atmosphere, and examined the effect of MoO3 doping in SWCNT films by using UV-vis-NIR spectroscopy and Raman spectroscopy. We show that through correlation analysis of the G and 2D (G') modes in Raman spectra, it is possible to discern distinct types of doping effects as well as the influence of applied pressure on the SWCNTs within SWCNT@BNNT heterostructure films. This work contributes to a deeper understanding of the strain and doping effect in both SWCNTs and SWCNT@BNNTs, thereby providing valuable insights for future applications of carbon-nanotube-based one-dimensional heterostructures.

Ultraconformable Capacitive Strain Sensor Utilizing Network Structure of Single-Walled Carbon Nanotubes for Wireless Body Sensing.

Capture and real-time recording of precise body movements using strain sensors provide personal information for healthcare monitoring and management. To acquire this information, a sensor that conforms to curved irregular surfaces, including biological tissue, is desired to record complex body movements while acting like a second skin to avoid interference with the movements. In this study, we developed a thin-film-type capacitive strain sensor that is flexible and stretchable on the surface of a living body. We fabricated conductive polymeric ultrathin films ("nanosheets") comprising polystyrene-block-polybutadiene (SB) elastomers and single-walled carbon nanotubes (SWCNTs) (i.e., SWCNT-SB nanosheets) via gravure coating; the SWCNT-SB-coated nanosheets were used as the flexible electrode in a capacitive strain sensor. The dielectric (DE) layer was then prepared using the silicone elastomer Ecoflex 00-30 because its Young's modulus is comparable to that of the epidermis. The normalized capacitance changes (ΔC/C0) in the sensor increased with increasing tensile strain over a range from 0-100%, indicating that the proposed sensor can measure the strain of biological movements, including those of skin and blood vessels. To improve sensor conformability further, the effect of sensor thickness on the gauge factor (GF) was investigated using thinner DE layers by focusing on their flexural rigidity. As a result, the GF increased from 0.64 to 1.13 as the DE layer thickness decreased from 260 to 40 µm. Finally, we evaluated the fabricated sensor's signal stability and mechanical durability, including during wireless sensing when applied to human skin and a vascular model. The ΔC/C0 values varied in response to the bending motion of a finger, dilation of a blood vessel, and the swallowing movement of the throat. These results indicate that our capacitive strain sensor is conformable and functional on biological tissue to enable monitoring of dynamic biological movements (e.g., pulse rate and arterial dilation) without wearer discomfort.

Nitric Oxide Detection Using a Corona Phase Molecular Recognition Site on Chiral Single-Walled Carbon Nanotubes.

Semiconducting single-walled carbon nanotubes (s-SWCNT) are structures that fluoresce in the near-infrared region. By coating SWCNT surfaces with polymeric materials such as single-chain DNA, changes in fluorescence emission occur in the presence of reagents. In this way, polymer-coated SWCNT structures allow them to be used as optical sensors for single molecule detection. Especially today, the inadequacy of the methods used in the detection of cellular molecules makes the early diagnosis of diseases such as cancer difficult at the single-molecule level. In this study, the detection of nitric oxide (NO) signals, which are a marker of cancer, was carried out at the single-molecule level. In this context, a sensor structure was formed by coating the 7,6-chiral s-SWCNT surface with ssDNA with different oligonucleotide lengths (AT). The sensor structure was characterized by using UV-vis spectroscopy and Raman spectroscopy microscopy. After formation of the sensor structure, a selectivity library was created using various molecules. As a result of the coating of the SWCNT (7,6) surface with DNA corona phase formation, Raman peaks at 195 and 276 cm-1 were observed to shift to the right. Additionally, the selectivity library results showed that the (AT)30 sequence can be used in NO detection. As a result of the studies using SWCNT (7.6)- (AT)30, the limit of detection (LOD) and limit of determination (LOQ) values of the sensor against NO were found to be 1.24 and 4.13 µM, respectively.

Single-Walled Carbon Nanotube-Guided Topical Skin Delivery of Tyrosinase to Prevent Photoinduced Damage.

When the skin is exposed to ultraviolet radiation (UV), it leads to the degradation of the extracellular matrix (ECM) and results in inflammation. Subsequently, melanocytes are triggered to induce tyrosinase-mediated melanin synthesis, protecting the skin. Here, we introduce a proactive approach to protect the skin from photodamage via the topical delivery of Streptomyces avermitilis-derived tyrosinase (SaTy) using single-walled carbon nanotube (SWNT). Utilizing a reverse electrodialysis (RED) battery, we facilitated the delivery of SaTy-SWNT complexes up to depths of approximately 300 µm, as analyzed by using confocal Raman microscopy. When applied to ex vivo porcine skin and in vivo albino mouse skin, SaTy-SWNT synthesized melanin, resulting in 4-fold greater UV/vis absorption at 475 nm than in mice without SaTy-SWNT. The synthesized melanin efficiently absorbed UV light and alleviated skin inflammation. In addition, the densification of dermal collagen, achieved through SaTy-mediated cross-linking, reduced photoinduced wrinkles by 66.3% in the affected area. Our findings suggest that SWNT-mediated topical protein delivery holds promise in tissue engineering applications.

An Aqueous Process for Preparing Flexible Transparent Electrodes Using Non-Oxidized Graphene/Single-Walled Carbon Nanotube Hybrid Solution.

In this study, we prepared flexible and transparent hybrid electrodes based on an aqueous solution of non-oxidized graphene and single-walled carbon nanotubes. We used a simple halogen intercalation method to obtain high-quality graphene flakes without a redox process and prepared hybrid films using aqueous solutions of graphene, single-walled carbon nanotubes, and sodium dodecyl sulfate surfactant. The hybrid films showed excellent electrode properties, such as an optical transmittance of ≥90%, a sheet resistance of ~3.5 kΩ/sq., a flexibility of up to ε = 3.6% ((R) = 1.4 mm), and a high mechanical stability, even after 103 bending cycles at ε = 2.0% ((R) = 2.5 mm). Using the hybrid electrodes, thin-film transistors (TFTs) were fabricated, which exhibited an electron mobility of ~6.7 cm2 V-1 s-1, a current on-off ratio of ~1.04 × 107, and a subthreshold voltage of ~0.122 V/decade. These electrical properties are comparable with those of TFTs fabricated using Al electrodes. This suggests the possibility of customizing flexible transparent electrodes within a carbon nanomaterial system.

Formulation and characterization of cisplatin-loaded hydroxyl functionalized single-walled carbon nanotubes for targeting gastric cancer stem cells.

Chemotherapy is the most commonly used therapeutic method for treating many malignancies including gastric cancer. Due to their non-specific and non-targeted drug delivery, it causes resistance leading to cancer progression, relapse, and metastasis of cancer. To overcome this problem we carried out a study aimed to develop a new cisplatin (Cisp) loaded hydroxyl functionalized single-walled carbon nanotube (OH-SWCNT) nanocarrier system to selectively eliminate gastric cancer stem cells. To our understanding, this is the first study of the non-covalent interaction of cisplatin loaded on the surface of hydroxyl-functionalized single-walled carbon nanotubes by ultrasonication. The physical and morphological characterization was carried out by UV-Vis, FTIR spectroscopy, and TEM. A sustained and controlled release of cisp from OH-SWCNT at all three pHs 3.5, 5.5, and 7.4 was observed. Gastric cancer stem cells were isolated from primary cells and were identified by using CD133+ and CD44+ specific markers. Cisplatin-loaded OH-SWCNT nanocarrier was capable of limiting the self-renewal capacity of both CD133+ and CD44+ populations and also decreasing the number of tumorspheres in gastric CSCs. The cell viability percent of AGS cells was 20% at 250 µg/ml concentration. The IC50 value was less than 50% mol/L at both 200 µg/ml and 250 µg/ml of cisplatin-loaded OH-SWCNT. Our findings suggest that cisplatin-loaded OH-SWCNT nanocarrier complexes could target gastric CSCs and also could provide a potential strategy for selectively targeting and efficiently eliminating gastric CSCs. This could be a promising approach to prevent gastric cancer recurrence and metastasis and also improve gastric cancer therapy.

Screening Enzymatic Degradation of Polyester Polyurethane with Fluorescent Single-walled Carbon Nanotube and Polymer Nanoparticle Conjugates.

Enzymatic biodegradation is a promising method to reclaim plastic materials. However, to date, a high-throughput method for screening potential enzyme candidates for biodegradation is still lacking. Here, we propose a single-walled carbon nanotube (SWCNT) fluorescence sensor for screening the enzymatic degradation of polyester polyurethane nanoparticles. Through wrapping the SWCNT with cationic chitosan, an electrostatic bond is formed between the SWCNT and Impranil, a widely applied model substrate of polyester polyurethane. As Impranil is being degraded by the enzymes, a characteristic quenching at a short reaction time followed by a brightening at a longer reaction time in the fluorescence signal is observed. The time-dependent fluorescence response is compared with turbidity measurement, and we conclude that the brightening in fluorescence results from the binding of the degradation product with the SWCNT. The proposed SWCNT sensor design has the potential to screen enzyme candidates for selective degradation of other plastic particles.

A Flexible and Transparent PtNP/SWCNT/PET Electrochemical Sensor for Nonenzymatic Detection of Hydrogen Peroxide Released from Living Cells with Real-Time Monitoring Capability.

We developed a transparent and flexible electrochemical sensor using a platform based on a network of single-walled carbon nanotubes (SWCNTs) for the non-enzymatic detection of hydrogen peroxide (H2O2) released from living cells. We decorated the SWCNT network on a poly(ethylene terephthalate) (PET) substrate with platinum nanoparticles (PtNPs) using a potentiodynamic method. The PtNP/SWCNT/PET sensor synergized the advantages of a flexible PET substrate, a conducting SWCNT network, and a catalytic PtNP and demonstrated good biocompatibility and flexibility, enabling cell adhesion. The PtNP/SWCNT/PET-based sensor demonstrated enhanced electrocatalytic activity towards H2O2, as well as excellent selectivity, stability, and reproducibility. The sensor exhibited a wide dynamic range of 500 nM to 1 M, with a low detection limit of 228 nM. Furthermore, the PtNP/SWCNT/PET sensor remained operationally stable, even after bending at various angles (15°, 30°, 60°, and 90°), with no noticeable loss of current signal. These outstanding characteristics enabled the PtNP/SWCNT/PET sensor to be practically applied for the direct culture of HeLa cells and the real-time monitoring of H2O2 release by the HeLa cells under drug stimulation.

Single-Walled Carbon Nanotube/Copper Core-Shell Fibers with a High Specific Electrical Conductivity.

Carbon nanotube (CNT)/Cu core-shell fibers are a promising material for lightweight conductors due to their higher conductivity than pure CNT fibers and lower density than traditional Cu wires. However, the electrical properties of the hybrid fiber have been unsatisfactory, mainly because of the weak CNT-Cu interfacial interaction. Here we report the fabrication of a single-walled CNT (SWCNT)/Cu core-shell fiber that outperforms commercial Cu wires in terms of specific electrical conductivity and current carrying capacity. A dense and uniform Cu shell was coated on the surface of wet-spun SWCNT fibers using a combination of magnetron sputtering and electrochemical deposition. Our SWCNT/Cu core-shell fibers had an ultrahigh specific electrical conductivity of (1.01 ± 0.04) × 104 S m2 kg-1, 56% higher than Cu. Experimental and simulation results show that oxygen-containing functional groups on the surface of a wet-spun SWCNT fiber interact with the sputtered Cu atoms to produce strong bonding. Our hybrid fiber preserved its integrity and conductivity well after more than 5000 bending cycles. Furthermore, the current carrying capacity of the coaxial fiber reached 3.14 × 105 A cm-2, three times that of commercial Cu wires.

Electrochemical assembly of single-walled carbon nanotube/polypyrrole/tellurium/lead telluride multi-layer nanocomposite films for room-temperature flexible thermoelectric application.

With the complexity and diversification of thermoelectric (TE) application scenarios, it becomes increasingly difficult for single-component thermoelectric materials to satisfy practical demands. Therefore, recent researches have largely focused on the development of the multi-component nanocomposites, which are probably a good solution for the TE application of some materials that are not eligible when used alone. In this work, a seires of single-walled carbon nanotube (SWCNT)/polypyrrole (PPy)/tellurium (Te)/lead telluride (PbTe) multi-layer flexible composite films were fabricated via the successive electrodeposition of the flexible PPy layer with a low thermal conductivity, the ultra-thin Te induction layer, and the brittle PbTe layer with a large Seebeck coefficient over the pre-fabricated SWCNT membrane electrode with a high electrical conductivity. Through the complementary advantages between different components and the multiple synergies of the interface engineering, the SWCNT/PPy/Te/PbTe composites harvested the excellent TE performance with a maximum power factor (PF) of 929.8 ± 35.4 µW m-1 K-2 at room temperature, outperforming those of most of the electrochemically-prepared organic/inorganic TE composites reported previously. This work evidenced that the electrochemical multi-layer assembly is a feasible tactic for constructing special thermoelectric materials to meet customized requirements, which could also be applied to other material platforms.

Broadband Full-Spectrum Raman Excitation Mapping Reveals Intricate Optoelectronic-Vibrational Resonance Structure of Chirality-Pure Single-Walled Carbon Nanotubes.

The Raman excitation spectra of chirality-pure (6,5), (7,5), and (8,3) single-walled carbon nanotubes (SWCNTs) are explored for homogeneous solid film samples over broad excitation energy and scattering energy ranges using a rapid and relatively simple full spectrum Raman excitation mapping technique. Identification of variation in scattering intensity with sample type and phonon energy related to different vibrational bands is clearly realized. Excitation profiles are found to vary strongly for different phonon modes. Some modes' Raman excitation profiles are extracted, with the G band profile compared to earlier work. Other modes, such as the M and iTOLA modes, have quite sharp resonance profiles and strong resonances. Conventional fixed wavelength Raman spectroscopy can miss these effects on the scattering intensities entirely due to the significant intensity changes observed for small variations in excitation wavelength. Peak intensities for phonon modes traceable to a pristine carbon lattice forming a SWCNT sidewall were greater for high-crystallinity materials. In the case of highly defective SWCNTs, the scattering intensities of the G band and the defect-related D band are demonstrated to be affected both in absolute intensities and in relative ratio, with the ratio that would be measured by single wavelength Raman scattering dependent on the excitation wavelength due to differences in the resonance energy profiles of the two bands. Lastly it is shown that the approach of this contribution yields a clear path toward increasing the rigor and quantification of resonance Raman scattering intensity measurements through tractable corrections of excitation and emission side variations in efficiency with excitation wavelength.

(n, m) Distribution of Single-Walled Carbon Nanotubes Grown from a Non-Magnetic Palladium Catalyst.

Non-magnetic metal nanoparticles have been previously applied for the growth of single-walled carbon nanotubes (SWNTs). However, the activation mechanisms of non-magnetic metal catalysts and chirality distribution of synthesized SWNTs remain unclear. In this work, the activation mechanisms of non-magnetic metal palladium (Pd) particles supported by the magnesia carrier and thermodynamic stabilities of nucleated SWNTs with different (n, m) are evaluated by theoretical simulations. The electronic metal-support interaction between Pd and magnesia upshifts the d-band center of Pd, which promotes the chemisorption and dissociation of carbon precursor molecules on the Pd surface, making the activation of magnesia-supported non-magnetic Pd catalysts for SWNT growth possible. To verify the theoretical results, a porous magnesia supported Pd catalyst is developed for the bulk synthesis of SWNTs by chemical vapor deposition. The chirality distribution of Pd-grown SWNTs is understood by operating both Pd-SWNT interfacial formation energy and SWNT growth kinetics. This work not only helps to gain new insights into the activation of catalysts for growing SWNTs, but also extends the use of non-magnetic metal catalysts for bulk synthesis of SWNTs.