Surface Of Single-walled Carbon Nanotubes Research Articles

The role of branched alkylthio side chain on dispersion and thermoelectric properties of regioregular polythiophene/carbon nanotubes nanocomposites

Herein, poly(3-alkylthiophene)s (P3ATs) and poly[(3-alkylthio)thiophene]s (P3ATTs) are respectively synthesized using poly(thiophene)s with linear/branched alkyl groups and branched alkylthio moieties with short/long side chain lengths for dispersing single-walled carbon nanotubes (SWCNTs), and the resulting composites are solution-processed for use as p-type thin film thermoelectric devices. With an additional sulfur atom on the side chain, a well-dispersed P3ATTs/SWCNTs nanocomposite is obtained by polymer-wrapping at the SWCNTs surfaces driven by S − π and π − π interactions between the alkylthio side chain substituents and π-conjugated backbones of the P3ATTs and SWCNTs, thereby contributing to greatly improved thermoelectric performance relative to the P3ATs/SWCNTs nanocomposite without the added sulfur. The poly[3-(2-hexyldecylthio)thiophene] (P3HDTT) nanocomposite with the longest alkylthio side chain exhibits the strongest interaction with the SWCNTs, yielding the highest power factor (PF) of 307.7 μW m−1 K−2. The ability of this spray-coated nanocomposite film to generate power is demonstrated with a prototype flexible thermoelectric generator (TEG) that produces 888.1 μW m−2. Thus, the introduction of debundled SWCNTs networks wrapped by P3ATTs with alkylthio side chains suggests a feasible strategy for the design of high-performance thermoelectric materials and opens up new opportunities for capturing waste heat in wearable electronics.

HRMAS-NMR and simulation study of the self-assembly of surfactants on carbon nanotubes.

Polyethoxylated surfactants, such as those of the Tween and Pluronic series, are commonly used to disperse carbon nanotubes (CNTs) and other nanoparticles. However, the current understanding of the nature of interactions between these surfactants and CNTs is limited. The nature of the interactions between surfactants (Tween-80 [T80] and Pluronic F68 [PF68]) and CNTs was investigated using high-resolution magic angle spinning nuclear magnetic resonance (HRMAS-NMR) and coarse-grained molecular dynamics (MD) simulations. HRMAS-NMR revealed that T80 molecules interact with single-walled CNTs (SWCNTs) and multi-walled CNTs (MWCNTs) via the oleyl chain, whereas PF68 molecules interact with the surface of SWCNTs and MWCNTs via the polypropylene oxide residues. The polyethylene oxide chains were oriented towards the external aqueous environment. The HRMAS-NMR results were supported by MD simulations, and the latter provided further insights into the nature of the interactions.

Robust method for uniform coating of carbon nanotubes with V2O5 for next-generation transparent electrodes and Li-ion batteries.

Composites comprising vanadium-pentoxide (V2O5) and single-walled carbon nanotubes (SWCNTs) are promising components for emerging applications in optoelectronics, solar cells, chemical and electrochemical sensors, etc. We propose a novel, simple, and facile approach for SWCNT covering with V2O5 by spin coating under ambient conditions. With the hydrolysis-polycondensation of the precursor (vanadyl triisopropoxide) directly on the surface of SWCNTs, the nm-thick layer of oxide is amorphous with a work function of 4.8 eV. The material recrystallizes after thermal treatment at 600 °C, achieving the work function of 5.8 eV. The key advantages of the method are that the obtained coating is uniform with a tunable thickness and does not require vacuuming or heating during processing. We demonstrate the groundbreaking results for two V2O5/SWCNT applications: transparent electrode and cathode for Li-ion batteries. As a transparent electrode, the composite shows stable sheet resistance of 160 Ω sq-1 at a 90% transmittance (550 nm) - the best performance reported for SWCNTs doped by metal oxides. As a cathode material, the obtained specific capacity (330 mA h g-1) is the highest among all the other V2O5/SWCNT cathodes reported so far. This approach opens new horizons for the creation of the next generation of metal oxide composites for various applications, including optoelectronics and electrochemistry.

MONKEYPOX DISEASE TREATMENT BY TECOVIRIMAT ADSORBED ONTO SINGLE-WALLED CARBON NANOTUBE THROUGH DRUG DELIVERY METHOD

In this work, it has been investigated the Monkeypox disease which occurs in both humans and animals by infection with a double-stranded DNA virus having the symptoms consisting of fever, fatigue, headache, and muscle pains like flu. Tecovirimat drug can be applied in prohibition of monkeypox virus through adsorbing onto surface of single-walled carbon nanotube (SWCNT) as the drug delivery method due to direct electron transfer principle which has been studied by density functional theory (DFT) methods.

Tuning humidity sensing properties via grafting fluorine and nitrogen-containing species on single-walled carbon nanotubes.

The effect of humidity on the electrical conductivity of single-walled carbon nanotube (SWCNT) films depends on both the conductivity of individual nanotubes and the electrical contacts between them. Here, we study these factors by comparing the sensor response of nanotubes with fluorine- and nitrogen-containing groups attached to the sidewalls. Experiments carried out in a wide range of relative humidity (RH) at room and elevated temperatures showed that the conductivity of non-functionalized SWCNTs and contacts between them decreases upon the adsorption of water molecules. Covalent fluorination reduces the conductivity of SWCNTs and significantly increases the sensitivity of the film to low concentrations of water vapor. The response at high RH decreases due to the large number of water molecules adsorbed on the conductive regions of the nanotubes. As a result of substitutional reactions of fluorinated SWCNTs with dimethylformamide and ethylenediamine, nitrogen-containing groups are added, the amount of which, however, is much less than the amount of fluorine. This modification of the SWCNTs improves intertube contacts in the film and increases the surface area for water adsorption. Our results show that an increase in the number of functional groups on the SWCNT surface enhances the sensitivity of the sensor to low water concentrations and worsens the response at high RH. SWCNTs modified with ethylenediamine have the highest sensitivity over the entire range of RH.

Drug delivery mechanism of doxorubicin and camptothecin on single-walled carbon nanotubes by DFT study

We used a density functional-based tight-binding method corrected with London-type dispersion to simulate the stable action model of doxorubicin and camptothecin on the surfaces of single-walled carbon nanotubes. In this study, we considered armchair (n, n) (n = 6–10) and zigzag (n, 0) (n = 10–14) carbon nanotubes of different sizes and lengths. The arrangements of the drug molecules doxorubicin and camptothecin on the surface of single-walled carbon nanotubes are discussed in detail, and the size, chirality and length of CNT, and the binding energies of the drug molecules in the stable configuration of the complex were analyzed. The structural properties of the models were further determined by analyzing the action distance between the carbon nanotube surface and representative atoms in the drug molecule. We also analyzed the molecular orbital properties of the stable complexes to further study the binding interactions. The Gibbs free energy of solvation was studied to measure the solubility of the drug delivery complex. By comparing the drug loading mechanism of doxorubicin and camptothecin, it is hoped that this work will provide a theoretical reference for the construction and study of the drug loading model for different types of drugs.

Dihydrolevoglycosenone as a novel bio-based nanofluid for thermal energy storage: Physiochemical and quantum chemical insights

Dihydrolevoglycosenone, commercially known as Cyrene, is a biodegradable solvent with a multitude of potential applications such as chemical reactions and heat transfer media. The current work reports a nanofluid comprising cyrene as a potential bio-organic thermal base media dispersed with Multi-walled carbon nanotube (MWCNT) nanoparticles. Two volume fractions (0.0016 and 0.0032) of nanoparticles were added to enhance the heat transfer capacity of the resulting nanofluid. Thereafter, thermophysical properties were reported in the temperature range of 30–85 °C for both base fluid and nanofluid. The measured values were then compared with a commercial heat transfer fluid, Paramtherm GLT, within the temperature range of 30–85 °C. Further, the stability of the nanofluid was investigated by a combination of visual observation, microscopic analysis, and zeta potential measurements. Thereafter, forced convection experiments were performed in a circular tube section under laminar conditions to measure the local heat transfer coefficient alongside temperature profiles. Results showed that the nanofluid possessing 0.0032 volume fraction of MWCNT-Cyrene nanofluid at NRe = 1881 gave the highest heat transfer coefficient. Density Functional Theory was also used to investigate the microstructure formed by Cyrene on the surface of Single-walled carbon nanotube (SWCNT). The orbital energy and influence of interaction energy on the van der Waals (vdW) interactions of Cyrene and ethylene glycol with SWCNT were examined and correlated with the dispersive forces within the fluid. The orbital energy revealed the fact that the HOMO-LUMO energy gap of the Cyrene/SWCNT was reduced due to the approach of Cyrene towards SWCNT surface, making it a stable nanofluid system. Reduced density gradient (RDG) analysis further demonstrated that weak vdW interactions were the primary driving force between solvent-SWCNT systems, primarily through X…π interactions.

Decoupling Individual Optical Nanosensor Responses Using a Spin-Coated Hydrogel Platform.

Significant advances have been made in fields such as nanotechnology and biomedicine using the unique properties of single-walled carbon nanotubes (SWCNTs). Specifically, SWCNTs are used as near-infrared fluorescence sensors in the solution phase to detect a wide array of biologically relevant analytes. However, solution-based sensing has several limitations, including limited sensitivity and poor spatial resolution. We have therefore devised a new spin-coated poly(ethylene glycol) diacrylate (PEG-DA) hydrogel platform to examine individual DNA-functionalized SWCNTs (DNA-SWCNTs) in their native aqueous state and have subsequently used this platform to investigate the temporal modulations of each SWCNT in response to a model analyte. A strong surfactant, sodium deoxycholate (SDC), was chosen as the model analyte as it rapidly exchanges with DNA oligonucleotides on the SWCNT surface, modulating several optical properties of the SWCNTs and demonstrating multiparameter analyte detection. Upon addition of SDC, we observed time-dependent spectral modulations in the emission center wavelengths and peak intensities of the individual SWCNTs, indicative of a DNA-to-surfactant exchange process. Interestingly, we found that the modulations in the peak intensities, as determined by kinetic data, were significantly delayed when compared to their center wavelength counterparts, suggesting a potential decoupling of the response of these two spectral features. We used a 1-D diffusion model to relate the local SDC concentration to the spectral response of each SWCNT and created dose-response curves. The peak intensity shifts at a higher SDC concentration than the center wavelength, indicating a potential change in the conformation of the surfactant molecules adsorbed to the SWCNT sidewall after the initial exchange process. This platform allows for a unique single-molecule analysis technique that is significantly more sensitive and modifiable than utilizing SWCNTs in the solution phase.

Polyethyleneimine-Starch Functionalization of Single-Walled Carbon Nanotubes for Carbon Dioxide Sensing at Room Temperature.

There is an ever-growing interest in the detection of carbon dioxide (CO2) due to health risks associated with CO2 emissions. Hence, there is a need for low-power and low-cost CO2 sensors for efficient monitoring and sensing of CO2 analyte molecules in the environment. This study reports on the synthesis of single-walled carbon nanotubes (SWCNTs) that are functionalized using polyethyleneimine and starch (PEI-starch) in order to fabricate a PEI-starch functionalized SWCNT sensor for reversible CO2 detection under ambient room conditions (T = 25 °C; RH = 53%). Field-emission scanning electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy are used to analyze the physiochemical properties of the as-synthesized gas sensor. Due to the large specific surface area of SWCNTs and the efficient CO2 capturing capabilities of the amine-rich PEI layer, the sensor possesses a high CO2 adsorption capacity. When exposed to varying CO2 concentrations between 50 and 500 ppm, the sensor response exhibits a linear relationship with an increase in analyte concentration, allowing it to operate reliably throughout a broad range of CO2 concentrations. The sensing mechanism of the PEI-starch-functionalized SWCNT sensor is based on the reversible acid-base equilibrium chemical reactions between amino groups of PEI and adsorbed CO2 molecules, which produce carbamates and bicarbonates. Due to the presence of hygroscopic starch that attracts more water molecules to the surface of SWCNTs, the adsorption capacity of CO2 gas molecules is enhanced. After multiple cycles of analyte exposure, the sensor recovers to its initial resistance level via a UV-assisted recovery approach. In addition, the sensor exhibits great stability and reliability in multiple analyte gas exposures as well as excellent selectivity to carbon dioxide over other interfering gases such as carbon monoxide, oxygen, and ammonia, thereby showing the potential to monitor CO2 levels in various infrastructure.

Theoretical study of the adsorption mechanism of ioversol contrast agent on the single-walled carbon nanotube surface

Ioversol, an organoiodine compound, has high iodine content and several hydrophilic groups. 1-N,3-N-bis(2,3-dihydroxypropyl)-5-[(2-hydroxyacetyl)-(2-hydroxyethyl)amino]-2,4,6-triiodobenzene-1,3-dicarboxamide (ioversol) and its derivatives are used in a wide variety of X-ray procedures, such as computed tomography scans, imaging of the kidneys, arteries and veins. DFT calculations at B3LYP level with LANL2DZ and DGDZVP basis sets were performed to determine electronic, structural and thermodynamic properties of the ioversol contrast agent in gas and water phases. In this study, we investigated the effect of Carbon Nanotube (CNT) and Si-doped CNT on the properties of ioversol, a contrast agent in gas phase and in water phase.

Hybrid Carbon Nanotubes/Gold Nanoparticles Composites for Trace Nitric Oxide Detection over a Wide Range of Humidity

Composites of functionalized single walled carbon nanotubes (SWCNTs) and gold nanoparticles (Au NPs) of ≈15 nm diameter were drop-cast on a printed circuit board (PCB) substrate equipped with interdigitated electrodes to make a hybrid thin film. Addition of Au NPs decorated the surface of SWCNTs networked films and acted as catalysts which resulted into an enhanced sensitivity and low ppb concentration detection limit. The compositions of the film were characterized by scanning electron microscope (SEM). SWCNTs clusters were loaded with various amount of Au NPs ranging from 1–10% (by weight) and their effect on Nitric oxide (NO) sensitivity was studied and optimized. Further, the optimized composite films were tested in both air and nitrogen environments and as well as over a wide relative humidity range (0–97%). Sensors were also tested for the selectivity by exposing to various gases such as nitrous oxide, ammonia, carbon monoxide, sulfur dioxide and acetone. Sensitivity to NO was found much higher than the other tested gases. The advantage of this sensor is that it is sensitive to NO at low ppb level (10 ppb) with estimated response time within 10 s and recovery time around 1 min, and has excellent reproducibility from sensor to sensor and works within the wide range of relative humidity (0–97%).

Differential near-infrared imaging of heterocysts using single-walled carbon nanotubes

The internalization of near-infrared (NIR) optical nanoprobes in photosynthetic microbes can be exploited for applications ranging from energy conversion to biomolecule delivery. However, the intrinsic, species-dependent properties of microbial cell walls, including their surface charge density, composition, thickness, and elasticity, can severely impact nanoprobe uptake and affect the cellular response. An examination of the interaction of the optical nanoprobe in various species and its impact on cell viability is, therefore, imperative for the development of new imaging technologies. Herein, we extend the technology recently developed for internalizing fluorescent single-walled carbon nanotubes (SWCNTs) in prokaryotes, specifically unicellular Synechocystis sp. PCC 6803, to a filamentous cyanobacterial strain, Nostoc punctiforme. Using a combination of NIR fluorescence, scanning electron microscopy (SEM), and Raman spectroscopy, we investigate uptake in vegetative cells as well as differentiated heterocysts. We demonstrate a strong dependence of long-term cell integrity, activity, and viability on SWCNT surface functionalization. We further show differential uptake of SWCNTs across a single filament, with positively charged functionalized SWCNTs preferentially localizing within the heterocysts of the filament. This cell dependency of the nanoparticle internalization motivates the use of SWCNTs as a NIR stain for monitoring cell differentiation.Graphical abstract

Stabilization of Carbon Nanotubes and Graphene by Tween-80: Mechanistic Insights from Spectroscopic and Simulation Studies.

Polyoxyethylene sorbitan monooleate is commonly used to obtain stable dispersions of nanoparticles (NPs) such as carbon nanotubes (CNTs) and graphene. However, the mechanism underlying dispersion is poorly understood. The present study aimed at investigating the mechanism of stabilization of carbon NPs (CNPs), namely, single-walled CNTs (SWCNTs), multi-walled CNTs (MWCNTs), and graphene, by Tween-80 using attenuated total internal reflection-Fourier transform infrared and nuclear magnetic resonance (NMR) spectroscopy. Molecular dynamics (MD) simulations were performed to identify, at the atomic scale, the significant interactions that underlie the adsorption and the stabilizing effect of Tween-80 on CNPs, in this way corroborating the spectroscopy results. Spectroscopic analysis revealed that the alkyl chain tether to SWCNT, MWCNT, and graphene surface, presumably through π-π interactions between the carbon-carbon double bond in the alkyl chain and the aromatic rings of CNPs. The hydrophilic polyethoxylate chains extend into the aqueous environment and stabilize the suspension by steric hindrance. MD simulations also showed that Tween-80 molecules interact with the CNP surface via the alkyl chain, thus corroborating spectroscopy results. MD simulations additionally revealed that Tween-80 aggregates on the CNP surface shifted from planar to micelle-like with increasing Tween-80 ratios, underscoring concentration-dependent changes in the nature of these interactions.

Rheological and Mechanical Properties of Thermoplastic Crystallizable Polyimide-Based Nanocomposites Filled with Carbon Nanotubes: Computer Simulations and Experiments.

Recently, a strong structural ordering of thermoplastic semi-crystalline polyimides near single-walled carbon nanotubes (SWCNTs) was found that can enhance their mechanical properties. In this study, a comparative analysis of the results of microsecond-scale all-atom computer simulations and experimental measurements of thermoplastic semi-crystalline polyimide R-BAPB synthesized on the basis of dianhydride R (1,3-bis-(3′,4-dicarboxyphenoxy) benzene) and diamine BAPB (4,4′-bis-(4″-aminophenoxy) biphenyl) near the SWCNTs on the rheological properties of nanocomposites was performed. We observe the viscosity increase in the SWCNT-filled R-BAPB in the melt state both in computer simulations and experiments. For the first time, it is proven by computer simulation that this viscosity change is related to the structural ordering of the R-BAPB in the vicinity of SWCNT but not to the formation of interchain linkage. Additionally, strong anisotropy of the rheological properties of the R-BAPB near the SWCNT surface was detected due to the polyimide chain orientation. The increase in the viscosity of the polymer in the viscous-flow state and an increase in the values of the mechanical characteristics (Young’s modulus and yield peak) of the SWCNT-R-BAPB nanocomposites in the glassy state are stronger in the directions along the ordering of polymer chains close to the carbon nanofiller surface. Thus, the new experimental data obtained on the R-BAPB-based nanocomposites filled with SWCNT, being extensively compared with simulation results, confirm the idea of the influence of macromolecular ordering near the carbon nanotube on the mechanical characteristics of the composite material.

(Invited) Theoretical Insight into New Strategies of Carbon Nanotube Functionalization

An intentional introduction of quantum defects to the single-walled carbon nanotube (SWCNT) surface leads to unique photoluminescence properties that may be useful for a wide range of optoelectronic, sensing, imaging and quantum communication applications. Quantum-chemical simulations help to rationalize spectroscopic observation and fine tune synthetic strategies. I will overview photosynthetic control of chemical binding configurations of quantum defects through the spin multiplicity of photoexcited intermediates. Here photoexcited aromatics react with SWCNT sidewalls to undergo a singlet-state pathway in the presence of dissolved oxygen, leading to ortho binding configurations of the aryl group on the nanotube. In contrast, the oxygen-free photoreaction activates previously inaccessible para configurations through a triplet-state mechanism. To understand the atomistic mechanism of these photo-activated reactions and their dependence on spin multiplicity, we have modeled the reaction with and without triplet quenching using density functional theory. Computed reaction pathways demonstrate selectivity and dependence of outcomes of the photo-activated reaction on the presence or absence of triplet quenching, corresponding to presence or absence of oxygen, respectively. Such spin-selective photochemistry diversifies SWCNT emission tunability by controlling the morphology of the emitting sites.

Photoluminescence Brightening of Single-Walled Carbon Nanotubes Using Graphene Quantum Dots

Single-walled carbon nanotubes (SWCNTs) emit near-infrared (NIR) photoluminescence (PL) that spans the tissue transparency window, allowing them to optically penetrate biological tissue for deep-tissue optical sensing. Such optical SWCNT sensors are often functionalized with single stranded DNA (ssDNA) to promote biocompatibility, responsivity, and selectivity. However, the low brightness of these ssDNA-wrapped sensors restricts the depth at which such sensors can be implanted in biological tissue. In this work, we overcome this limitation by demonstrating the PL enhancement of ssDNA-wrapped SWCNTs through the incorporation of biocompatible graphene quantum dots (GQDs). We compare the enhancement effects of two preparations of GQDs, pristine (PGQDs) and nitrogen-doped (NGQDs) graphene quantum dots. Both preparations of GQDs were shown to significantly increase the fluorescence emissions of ssDNA-SWCNTs to a comparable extent after 3 h of incubation. We further observed a diameter dependence of this enhancement, with the larger (8,6) SWCNT chirality demonstrating a 30-fold enhancement as compared to the 2-fold enhancement observed for the (6,5) SWCNT chirality. This PL enhancement was shown to vary with the exposed surface area of the SWCNTs, whereby SWCNT chiralities with wrappings that yield larger exposed SWCNT surfaces resulted in increased PL enhancement on conjugation with the GQDs.Despite the similarities in the final fluorescence enhancements, the NGQDs and PGQDs showed kinetic differences in their brightening effects. The NGQDs were able to achieve stabilized SWCNT fluorescence brightening 2 min after their addition, whereas the SWCNTs showed continued PL increases even 1 h after the addition of the PGQDs. Electrochemical analysis of the NGQDs confirms their behavior as reducing agents, which have been previously shown to enhance the rate of SWCNT brightening through the passivation of oxygen defect sites. The brightening effects of the NGQDs were further demonstrated in confocal single-molecule measurements, where we observed a 3-fold increase in the detection of individual SWCNTs on conjugation to the NGQDs compared to the unconjugated ssDNA-SWCNTs. The photoluminescence enhancements enabled by the GQDs thus provides a promising tool for engineering the brightness of NIR sensors for biomedical applications and enabling improved detection in deep-tissue sensing and imaging applications.

ZnO nanoparticles functionalized SWCNTs as highly sensitive SERS substrate for heavy metal ions detection

This report presents the most effective and novel approach to fabricate a three-dimensional (3D) Surface-Enhanced Raman Scattering (SERS) substrate for detection of heavy metal ions in the environment. Firstly, Single Wall Carbon Nanotubes (SWCNTs) are synthesized by Plasma Enhanced Chemical Vapor Deposition (PECVD) technique at low temperature. Then, the surface of SWCNTs is functionalized by Zinc Oxide nanoparticles (ZnO NPs) using thermal evaporation technique to achieve ZnO@SWCNTs nanocomposite film as a SERS substrate. The ZnO@SWCNTs with 3D nanostructure increases the coverage of plasmonic nanostructure. The effect of intertube and interparticle coupling generates the multitude ‘hot spots’ with a strong SERS effect. Different characterization techniques- Field Emission Scanning Electron Microscope (FESEM), X-Ray Diffraction (XRD), UV–Vis and Raman spectroscopy were performed. For detection of heavy metal ions, the Raman spectra are recorded for samples of different metal ions- Pb2+, Hg2+, Cd2+, Cu2+, and As2+. The proposed substrate demonstrates high sensitivity, selectivity and very low Limit of detection of the order of 0.225 nM with high stability and repeatability for Pb2+. Therefore, the proposed ZnO@SWCNTs nanocomposite SERS substrate can be used as a powerful tool for the detection of heavy metal ion- Pb2+ in aqueous solutions for a green environment.

Confined PdMo Ultrafine Nanowires in CNTs for Superior Oxygen Reduction Catalysis

AbstractOne‐dimensional (1D) ultrafine nanowires of different materials, especially noble metals, present an enticing prospect for catalyst applications due to their numerous active sites exposed. However, the controllable synthesis and stability issues hinder their practical applications. Herein, single‐walled carbon nanotubes (SWCNTs) are adopted as the template to synthesize and stabilize ultrafine nanowires of metals. Furthermore, the oxygen reduction reaction (ORR) is employed as an application demonstration. Impressively, the as prepared PdMo nanowires exhibit a half‐wave potential of 0.923 V and the mass activity is 35 times and 130 times higher than those of commercial Pt/C and Pd/C catalysts, respectively. Because of the protection, a superior ORR durability with 50 000 cycles can be achieved. Density functional theory (DFT) calculations reveal that the SWCNTs surface can be activated by the encapsulated PdMo NWs to achieve the exclusive adsorption of O2and the following reduction reaction. In addition, PdMo NWs@SWCNTs demonstrate excellent catalytic performance as the cathode of lithium‐oxygen batteries. The cell can reach a high discharge capacity of over 10 000 mAh g−1, better than most of the former reported catalytic electrodes. The tailored design PdMo NWs@SWCNTs show widespread applications in various energy storage & conversion fields.

Effect of curvature on the mono-methylation of carbon belt surfaces using density functional theory

The surface functionalization of single-walled carbon nanotubes (SWCNTs) by direct radical addition has received considerable attention. The introduction of substituents is useful for tuning the π-character, enhancing the substrate anchoring, and improving the solubility. In this study, we investigated the binding energies of mono-methylated carbon belts (short SWCNTs) using density functional theory to elucidate the effect of curvature. The binding energy decreased as the curvature κ decreased and was approximately 25 kcal mol−1 less for κ = 0.166 Å−1 than for κ = 0.364 Å−1. This is because a change in curvature significantly impacts the interaction energy between the CH3 moiety and the carbon belt portion but not the deformation energy of the system. These results suggest that curvature can control the grafting onto the SWCNT surface.

Diameter Dependent Melting and Softening of dsDNA Under Cylindrical Confinement

Carbon nanotubes (CNTs) are considered promising candidates for biomolecular confinement, including DNA encapsulation for gene delivery. Threshold values of diameters have been reported for double-stranded DNA (dsDNA) encapsulation inside CNTs. We have performed all-atom molecular dynamics (MD) simulations of dsDNAs confined inside single-walled CNTs (SWCNTs) at the physiologically relevant temperature of 300 K. We found that the dsDNA can be confined without being denatured only when the diameter of the SWCNT exceeds a threshold value. Below this threshold diameter, the dsDNA gets denatured and melts even at the temperature of 300 K. Our simulations using SWCNTs with chirality indices (20,20) to (30,30) at 300 K found the critical diameter to be 3.25 nm (corresponding to (24,24) chirality). Analyses of the hydrogen bonds (H-bonds), Van der Walls (VdW) energy, and other inter-base interactions show drastic reduction in the number of H-bonds, VdW energy, and electrostatic energies between the bases of dsDNA when it is confined in narrower SWCNTs (up to diameter of 3.12 nm). On the other hand, the higher interaction energy between the dsDNA and the SWCNT surface in narrower SWCNTs assists in the melting of the dsDNA. Electrostatic mapping and hydration status analyses show that the dsDNA is not adequately hydrated and the counter ion distribution is not uniform below the critical diameter of the SWCNT. As properly hydrated counter ions provide stability to the dsDNA, we infer that the inappropriate hydration of counter ions and their non-uniform distribution around the dsDNA cause the melting of the dsDNA inside SWCNTs of diameter below the critical value of 3.25 nm. For confined dsDNAs that do not get denatured, we computed their elastic properties. The persistence length of dsDNA was found to increase by a factor of about two and the torsional stiffness by a factor of 1.5 for confinement inside SWCNTs of diameters up to 3.79 nm, the stretch modulus also following nearly the same trend. Interestingly, for higher diameters of SWCNT, 3.79 nm and above, the dsDNA becomes more flexible, demonstrating that the mechanical properties of the dsDNA under cylindrical confinement depend non-monotonically on the confinement diameter.