Surface Of Single-walled Carbon Nanotubes Research Articles

Chemi-Impeditive Sensing Platform Based on Single-Walled Carbon Nanotubes.

Chemical sensing methodology based on electrochemical impedance spectroscopy (EIS) targeting analytes in aqueous samples on functionalized single-walled carbon nanotube (SWCNT) is reported. The SWCNT in contact with electrolyte shows unique impedance spectra that cannot be analyzed with classical equivalent circuit models. Inspired by the charge transport property of mixed ionic-electronic conductors, we propose an equivalent circuit based on transmission line model (TLM), by which the impedance of the CNT-electrolyte system can be analyzed to track down all the equivalent circuit parameters. By combining multiple pieces of information, which are technically immeasurable with conventional chemiresistive or chemicapacitive techniques, several analyte species responding to the sensor can be differentiated from each other. We demonstrate the "chemi-impeditive" concept on chemically modified SWCNTs for detecting perfluoroalkyl substances (PFAS) in aqueous solutions. The EIS coupled with a fluorination chemistry on SWCNT surface provides unique changes in equivalent circuit components for each PFAS, i.e., changes in CNT and solution resistances, as well as interfacial CNT-solution capacitance, through which perfluorooctanesulfonic acid, perfluorooctanoic acid, hexafluoropropylene oxide dimer acid, and perfluorobutanesulfonic acid are detected in a discriminative manner. The new impedimetric method opens up new vistas in chemical sensing in that the EIS analysis provides an additional dimension of information beyond the single resistance or capacitance typically measured by many conventional types of sensors.

Impact of Surfactant to DNA Exchange on Carbon Nanotube Emission for Biosensing Applications

Synthesis methods of single walled carbon nanotubes (SWCNTs) result in mixtures of different chiralites. Chirality affects SWCNT diameter as well electronic and optical properties. For use in optical sensors, mono-chirality SWCNTs offer better signal compared to chirality mixtures. A common chirality separation method is aqueous two-phase extraction, where solutions of surfactants are used to partition SWCNTs based on chirality. The process results in a mono-chiral solution of SWCNTs wrapped in surfactant, however for sensing applications SWCNTs need to be exchanged from this surfactant wrapping to single stranded DNA wrapping. Concerns have been raised about residual surfactant remaining on the SWCNT surface after the exchange process and the effect this would have on the sensing capabilities of the SWCNT. To investigate this, we compared the emission spectra of covalently modified SWCNTs sonicated directly in DNA to that of SWCNTs exchanged from surfactant into DNA. We observed that emission from exchanged SWCNTs was red shifted compared to direct DNA sonicated SWCNTs, however exchanged SWCNTs had similar environmental responsivity to direct DNA sonicated SWCNTs.

Aqueous Two-Phase Extraction of Single-Chirality Carbon Nanotubes with Functionalized ssDNA for Biomarker-Specific Antibody Conjugation

Multiplexed detection of biomarkers for cancer and chronic inflammatory diseases is necessary to improve diagnostic sensitivity and specificity. Our prior studies and that of others has used near-infrared fluorescent single-walled carbon nanotubes (SWCNT) as sensor transducers because of their sensitivity to the local environment, photostability, and emission in the tissue-transparent window. That work engineered the SWCNT surface through non-covalent interactions with short ssDNA oligonucleotides containing a functional group to which a biomarker-specific antibody was conjugated. Further, previous work by other groups has demonstrated the ability to obtain single SWCNT chiralities using the aqueous two-phase extraction (ATPE) technique with non-functionalized ssDNA sequences. Here, we have incorporated primary amine-functionalized ssDNA sequences into the ATPE separation technique to obtain individual SWCNT chiralities with functionalized ssDNA. To those primary amine-functionalized ssDNA-SWCNT complexes, we conjugated antibodies against two inflammatory cytokines. We investigated the sensitivity and specificity of these individual SWCNT chirality sensors specific to two biomarkers together in buffer and serum, finding that each chirality responds specifically only to its cognate biomarker and not the other. This is the first demonstration of single-chirality, molecularly-specific multiplexed SWCNT sensors. It forms the basis of ongoing work to obtain additional chiral species with other functional groups, as well as to develop multiplexed cytokine sensors for in vivo diagnostics.

Orthogonal Determination of Competing Surfactant Adsorption onto Single-Wall Carbon Nanotubes During Aqueous Two-Polymer Phase Extraction via Fluorescence Spectroscopy and Analytical Ultracentrifugation.

A combination of analytical ultracentrifugation (AUC) and fluorescence spectroscopy are utilized to orthogonally probe compositions of adsorbed surfactant layers on the surface of (7,5) species single-wall carbon nanotubes (SWCNTs) under conditions known to achieve differential partitioning in aqueous two-phase extraction (ATPE) separations. Fluorescence emission intensity and AUC anhydrous particle density measurements independently probe and can discriminate between adsorbed surfactant layers on a (7,5) nanotube comprised of either of two common nanotube dispersants, the anionic surfactants sodium deoxycholate and sodium dodecyl sulfate. Measurements on dispersions containing mixtures of both surfactants indicate near total direct exchange of the dominant surfactant species adsorbed to the carbon nanotube at a critical concentration ratio consistent with the ratio leading to partitioning change in the ATPE separation. By conducting these orthogonal measurements in a complex environment reflective of an ATPE separation, including multiple surfactant and polymer solution components, the results provide direct evidence for the hypothesis that it is the nature of the adsorbed surfactant layer that primarily controls partitioning behavior in selective ATPE separations of SWCNTs.

Facile Doping of 2,2,2-Trifluoroethanol to Single-Walled Carbon Nanotubes Electrodes for Durable Perovskite Solar Cells

Perovskite solar cells with an indium tin oxide (ITO)/SnO2/CH3NH3PbI3/Spiro-OMeTAD/2,2,2-trifluoroethanol (TFE) doped single-walled carbon nanotube (SWCNT) structure were developed by dropping TFE onto SWCNTs, which replaced the metal back electrode, and a conversion efficiency of 14.1% was achieved. Traditionally, acidic doping of the back electrode, SWCNT, has been challenging due to the potential damage it may cause to the perovskite layer. However, TFE has facilitated easy doping of SWCNT as the back electrode. The sheet resistance of the SWCNTs decreased and their ionization potential shifted to deeper levels, resulting in improved hole transport properties with a lower barrier to carrier transport. Furthermore, the Seebeck coefficient (S) increased from 34.5 μV/K to 73.1 μV/K when TFE was dropped instead of EtOH, indicating an enhancement in the behavior of p-type charge carriers. It was observed that hydrophilic substances adhered less to the SWCNT surface, and the formation of PbI2 was suppressed. These effects resulted in higher conversion efficiency and improved solar cell performance. Furthermore, the decrease in conversion efficiency after 260 days was suppressed, showing improved durability. The study suggests that combining SWCNTs and TFEs improves solar cell performance and stability.

Sequence-Dependent Surface Coverage of ssDNA Coatings on Single-Wall Carbon Nanotubes.

A combination of experimental measurements and molecular dynamics (MD) simulations was used to investigate how the surfaces of single-wall carbon nanotubes (SWCNTs) are covered by adsorbed ssDNA oligos with different base compositions and lengths. By analyzing the UV absorption spectra of ssDNA-coated SWCNTs before and after coating displacement by a transparent surfactant, the mass ratios of adsorbed ssDNA to SWCNTs were determined for poly-T, poly-C, GT-containing, and AT-containing ssDNA oligos. Based on the measured mass ratios, it is estimated that an average of 20, 22, 26, or 32 carbon atoms are covered by one adsorbed thymine, cytosine, adenine, or guanine nucleotide, respectively. In addition, the UV spectra revealed electronic interactions of varying strengths between the nucleobase aromatic rings and the nanotube π-systems. Short poly-T DNA oligos show stronger π-π stacking interactions with SWCNT surfaces than do short poly-C DNA oligos, whereas both long poly-C and poly-T DNA oligos show strong interactions. These experiments were complemented by MD computations on simulated systems that were constrained to match the measured ssDNA/SWCNT mass ratios. The surface coverages computed from the MD results varied with oligo composition in a pattern that correlates higher measured yields of nanotube fluorescence with greater surface coverage.

Research on optimizing ultrasonic frequencies for efficient single-walled carbon nanotube dispersion in water using a focused ultrasonic system

Single-walled carbon nanotubes (SWCNTs) can be applied in a wide range of fields owing to their excellent mechanical rigidity, electrical conductivity, and thermal conductivity. However, their application is limited because of their strong van der Waals forces and poor dispersion owing to their hydrophobic properties. To address this problem, ultrasonic dispersion technology has been used in the industry. However, very few studies have investigated the surface damage or effectiveness of the surfactants of SWCNTs with a focus on the frequencies of specific ultrasonic equipment. In this study, the dispersibility of SWCNTs at frequencies of 270, 400, and 700 kHz was investigated using a new focused ultrasonic instrument. The dispersion stability of the samples was analyzed according to each frequency, and the SWCNT surface was studied in detail using field-emission transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The adsorption of the polymeric surfactant to the SWCNT was most observed at 270 kHz, and the dispersion stability after processing at this frequency was better than that of the other samples. Therefore, the frequency of the ultrasonic intensity has a direct effect on the surface modification of SWCNTs.

Probing iodide/iodonium salt interactions with single-walled carbon nanotubes for resilient electrochemical capacitor

Self-standing films from single-walled carbon nanotubes (SWCNTs) were successfully used as electrochemical capacitors’ (ECs) electrode material, which exhibited state-of-the-art characteristics. The surface of SWCNTs was modified by iodonium salt molecules that substantially and permanently improved their electrical conductivity. The addition of pyridinium iodine chloride salt (IPyCl) quadrupled the value of the electrical conductivity of the SWCNT film, which reached values as high as 1022 S cm−1. Subsequently, the electrochemical performance of the newly designed self-standing SWCNTs with deposited IPyCl in aqueous neutral 1 M Li2SO4 and redox-active 1 M KI electrolytes was thoroughly analysed. Because redox activity of iodine species was observed mainly on the positive electrode, activated carbon with a developed surface area was used as a negative electrode to balance the faradaic charge. Due to the notable stability of iodonium salt dopant (instead of labile halogen-containing compounds typically used for SWCNT doping), robust charge/discharge performance of EC was demonstrated (> 10 000 cycles) in Li2SO4 electrolyte. Moreover, a significant improvement of capacitor metrics (from 49 to 75 F g−1) was obtained when electrodes modified by previously unexplored iodonium salt were utilized in 1 M KI electrolyte. Extensive analysis of the obtained data led to the elucidation of the doping mechanism responsible for the aforementioned achievements. The novel SWCNT-based electrodes enhanced with iodonium salt are auspicious materials, which can be used to build EC systems of appreciable capacitance.

Spin coated ultrathin PEDOT:PSS/SWCNT film with high electronic conductivity

Conductive Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been extensively used as non-metallic electrodes. However, the relatively low electrical conductivity of pristine PEDOT:PSS film restricts its further application. Although doping high content conductive filler or increasing the film thickness are effective for enhancing the electrical property, the transparency is sacrificed, which limits the application of PEDOT:PSS films. In this study, preparing PEDOT:PSS composite film with highly conductive and transparent property was the primary purpose. To achieve this goal, single-walled carbon nanotubes (SWCNTs) and dimethyl sulfoxide (DMSO) was chosen to composite with PEDOT:PSS. The spin-coated SWCNT/PEDOT:PSS composite film exhibited excellent electrical conductivity and transparency. The electrical conductivity of composite film with desired transmittance property (78%) reached the highest value (1060.96 S cm−1) at the SWCNTs content was 6 wt%. Under the modification process applied in this work, the non-conductive PSS was partially removed by incorporated DMSO and SWCNTs. Then, the molecular chains of PEDOT stretched and adsorbed onto the surface of SWCNTs, forming a highly efficient three-dimensional conductive structure, which contributed to the enhancement of electrical conductivity and transparency. Additionally, the spin-coating process allowed for the reduction of film thickness, ensuring better transparency. This research contributed to expanding the further applications of PEDOT:PSS films in high-performance transparent film electrodes.

Poly-Thionine/ SWCNT Nanocomposite Coated Electrochemical Sensor for Determination of Vitamin C

Background: The electrochemical sensors convert biological or chemical information, such as analyte concentration or a biomolecular (biochemical receptor) interaction, into electrical signals. In this paper, we describe the development of a poly-thionine/ single-walled carbon nanotube (P-Th/SWCNT) composite for the electrochemical detection of ascorbic acid (vitamin C). Methods: To improve electrochemical performance, we attempted to electro-polymerize the thionine monomers, an essential chemical building block, directly on the surface of singlewalled carbon nanotubes (SWCNT). Results: Field Emission Scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS) results revealed that a complex structure of the P-Th/SWCNT was formed. The presence of carbon (C), oxygen (O), nitrogen (N), and sulfur (S) components was confirmed, which indicated the effective fusion of poly-thionine onto SWCNT. Moreover, the X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy confirmed the composite formation. Utilizing cyclic voltammetry, the composite's electrochemical behavior was examined. Conclusions: Excellent electrocatalytic activity towards the oxidation of ascorbic acid was shown by the P-Th/SWCNT composite. The as-prepared P-Th/SWCNT composite-modified sensor can detect ascorbic acid in food, medical, and pharmaceutical samples.

Ratiometric fluorescent sensing of pyrophosphate with sp³-functionalized single-walled carbon nanotubes

Inorganic pyrophosphate is a key molecule in many biological processes from DNA synthesis to cell metabolism. Here we introduce sp3-functionalized (6,5) single-walled carbon nanotubes (SWNTs) with red-shifted defect emission as near-infrared luminescent probes for the optical detection and quantification of inorganic pyrophosphate. The sensing scheme is based on the immobilization of Cu2+ ions on the SWNT surface promoted by coordination to covalently attached aryl alkyne groups and a triazole complex. The presence of Cu2+ ions on the SWNT surface causes fluorescence quenching via photoinduced electron transfer, which is reversed by copper-complexing analytes such as pyrophosphate. The differences in the fluorescence response of sp3-defect to pristine nanotube emission enables reproducible ratiometric measurements in a wide concentration window. Biocompatible, phospholipid-polyethylene glycol-coated SWNTs with such sp3 defects are employed for the detection of pyrophosphate in cell lysate and for monitoring the progress of DNA synthesis in a polymerase chain reaction. This robust ratiometric and near-infrared luminescent probe for pyrophosphate may serve as a starting point for the rational design of nanotube-based biosensors.

Ionic Strength-Mediated "DNA Corona Defects" for Efficient Arrangement of Single-Walled Carbon Nanotubes.

Single-stranded DNA oligonucleotides wrapping on the surface of single-walled carbon nanotubes (SWCNTs), described as DNA corona, are often used as a dispersing agent for SWCNTs. The uneven distribution of DNA corona along SWCNTs is related to the photoelectric properties and the surface activity of SWCNTs. An ionic strength-mediated "DNA corona defects" (DCDs) strategy is proposed to acquire an exposed surface of SWCNTs (accessible surface) as large as possible while maintaining good dispersibility via modulating the conformation of DNA corona. By adjusting the solution ionic strength, the DNA corona phase transitioned from an even-distributed and loose conformation to a locally compact conformation. The resulting enlarged exposed surface of SWCNTs is called DCDs, which provide active sites for molecular adsorption. This strategy is applied for the arrangement of SWCNTs on DNA origami. SWCNTs with ≈11nm DCD, providing enough space for the adsorption of "capture ssDNA" (≈7nm width required for 24-nt) extended from DNA origami structures are fabricated. The DCD strategy has potential applications in SWCNT-based optoelectronic devices.

Study of the electron-doping mechanism in single-walled carbon nanotubes using dimethylbenzimidazole.

Single-walled carbon nanotubes (SWCNTs) exhibit p-type properties in air, necessitating electron doping using n-dopants (e.g., reducing agents) for the development of SWCNT-based electronic devices. Dimethylbenzimidazole (DMBI-H) derivatives serve as effective electron dopants, not only for SWCNTs, but also for various organic semiconducting materials. However, the doping reaction is still a subject of debate. In this study, the electron-doping reactions of ortho-methoxy-substituted DMBI-H for SWCNTs were analyzed in protic and aprotic solvents in the presence and absence of dioxygen (O2). The presence of O2 was found to cause the reduction of O2 on the SWCNT surface in the protic solvent, resulting in the production of DMBI cations and water through proton-coupled electron transfer (PCET) from the n-doped SWCNT and ethanol. This work elucidates the mechanism behind the air-stability of n-type SWCNTs.

Preparation and properties of single-walled carbon nanotube/polyetherimide electromagnetic shielding film

In practical applications, flexibility, lightweight, and high performance are the characteristics that polymer-based electromagnetic shielding materials should have. At present, it is still a great challenge to prepare polymer-based electromagnetic shielding materials with excellent conductivity, electromagnetic shielding properties, and mechanical properties. Therefore, in this work, single-walled carbon nanotubes/polyetherimide composite films are prepared by electrostatic spinning and vacuum-assisted filtration through using single-walled carbon nanotubes and polyetherimide as raw materials. By regulating the surface density of single-walled carbon nanotubes, the conductivity of the composite film can be enhanced to 1866 S/cm. For the electromagnetic shielding performance, the total electromagnetic shielding effectiveness of single-walled carbon nanotubes/polyetherimide composite film in Ku band (12–18 GHz) is in a range of 75.78–81.83 dB, which is higher than that of pure single-walled carbon nanotube film (65.19–69.81 dB). This is attributed to the formation of interfaces between the polyetherimide fibers and the single-walled carbon nanotubes, with more interfaces consuming more electromagnetic wave energy for a given range of single-walled carbon nanotube surface densities. For the mechanical properties, the maximum tensile strength and elongation at the break of the single-walled carbon nanotube/polyetherimide film are 1.13 and 1.5 times higher than those of the single-walled carbon nanotube film, with the values of 28.52 MPa and 7.91%, respectively. As the surface density of single-walled carbon nanotubes increases, the interaction between single-walled carbon nanotubes as well as the interaction between polyetherimide fibers and single-walled carbon nanotubes at the interface plays a role in enhancing the mechanical properties of the composite films. The single-walled carbon nanotube/polyetherimide composite films, as an excellent polymer-based electromagnetic shielding composite material, can be used in fields such as the protection of precision electronic instruments and wearable electronic devices.

Mapping the Morphology of DNA on Carbon Nanotubes in Solution Using X-ray Scattering Interferometry.

Single-walled carbon nanotubes (SWCNTs) with adsorbed single-stranded DNA (ssDNA) are applied as sensors to investigate biological systems, with potential applications ranging from clinical diagnostics to agricultural biotechnology. Unique ssDNA sequences render SWCNTs selectively responsive to target analytes such as (GT)n-SWCNTs recognizing the neuromodulator, dopamine. It remains unclear how the ssDNA conformation on the SWCNT surface contributes to functionality, as observations have been limited to computational models or experiments under dehydrated conditions that differ substantially from the aqueous biological environments in which the nanosensors are applied. We demonstrate a direct mode of measuring in-solution ssDNA geometries on SWCNTs via X-ray scattering interferometry (XSI), which leverages the interference pattern produced by AuNP tags conjugated to ssDNA on the SWCNT surface. We employ XSI to quantify distinct surface-adsorbed morphologies for two (GT)n ssDNA oligomer lengths (n = 6, 15) that are used on SWCNTs in the context of dopamine sensing and measure the ssDNA conformational changes as a function of ionic strength and during dopamine interaction. We show that the shorter oligomer, (GT)6, adopts a more periodically ordered ring structure along the SWCNT axis (inter-ssDNA distance of 8.6 ± 0.3 nm), compared to the longer (GT)15 oligomer (most probable 5'-to-5' distance of 14.3 ± 1.1 nm). During molecular recognition, XSI reveals that dopamine elicits simultaneous axial elongation and radial constriction of adsorbed ssDNA on the SWCNT surface. Our approach using XSI to probe solution-phase morphologies of polymer-functionalized SWCNTs can be applied to yield insights into sensing mechanisms and inform future design strategies for nanoparticle-based sensors.

Size-Based Norfentanyl Detection with SWCNT@UiO-MOF Composites.

Single-walled carbon nanotube (SWCNT)@metal-organic framework (MOF) field-effect transistor (FET) sensors generate a signal through analytes restricting ion diffusion around the SWCNT surface. Four composites made up of SWCNTs and UiO-66, UiO-66-NH2, UiO-67, and UiO-67-CH3 were synthesized to explore the detection of norfentanyl (NF) using SWCNT@MOF FET sensors with different pore sizes. Liquid-gated FET devices of SWCNT@UiO-67 showed the highest sensing response toward NF, whereas SWCNT@UiO-66 and SWCNT@UiO-66-NH2 devices showed no sensitivity improvement compared to bare SWCNT. Comparing SWCNT@UiO-67 and SWCNT@UiO-67-CH3 indicated that the sensing response is modulated by not only the size-matching between NF and MOF channel but also NF diffusion within the MOF channel. Additionally, other drug metabolites, including norhydrocodone (NH), benzoylecgonine (BZ), and normorphine (NM) were tested with the SWCNT@UiO-67 sensor. The sensor was not responding toward NH and or BZ but a similar sensing result toward NM because NM has a similar size to NF. The SWCNT@MOF FET sensor can avoid interference from bigger molecules but sensor arrays with different pore sizes and chemistries are needed to improve the specificity.

Wireless Detection of Trace Ammonia: A Chronic Kidney Disease Biomarker.

Elevated levels of ammonia in breath can be linked to medical complications, such as chronic kidney disease (CKD), that disturb the urea balance in the body. However, early stage CKD is usually asymptomatic, and mass screening is hindered by high instrumentation and operation requirements and accessible and reliable detection methods for CKD biomarkers, such as trace ammonia in breath. Enabling methods would have significance in population screening for early stage CKD patients. We herein report a method to effectively immobilize transition metal selectors in close proximity to a single-walled carbon nanotube (SWCNT) surface using pentiptycene polymers containing metal-chelating backbone structures. The robust and modular nature of the pentiptycene metallopolymer/SWCNT complexes creates a platform that accelerates sensor discovery and optimization. Using these methods, we have identified sensitive, selective, and robust copper-based chemiresistive ammonia sensors that display low parts per billion detection limits. We have added these hybrid materials to the resonant radio frequency circuits of commercial near-field communication (NFC) tags to achieve robust wireless detection of ammonia at physiologically relevant levels. The integrated devices offer a noninvasive and cost-effective approach for early detection and monitoring of CKD.

(Invited) Directed Evolution and Machine Learning for Improved ssDNA-SWCNTs Sensor for Nitric Oxide Detection

Single-walled carbon nanotubes (SWCNTs) show great potential for biosensing applications due to their unique optical properties. SWCNTs emit fluorescence in the near-infrared (NIR) region that is stable, biotransparent, and highly sensitive to changes in their environment. The biocompatibility and the selectivity of their interactions can be engineered through SWCNT surface functionalization. One of the most common functionalization approaches is the non-covalent wrapping of SWCNTs with single-stranded DNA (ssDNA). Though the ssDNA sequences can be varied to control the optical response of these SWCNT sensors, the dependence of the optical response on the sequence is unknown and unpredictable. This lack of information on the relationship between the ssDNA sequence and sensor performance is a major bottleneck in engineering SWCNT-based optical sensors.In this work, we develop a guided approach to engineer optical ssDNA-SWCNT sensors. Using a combination of machine learning and directed evolution[1], we designed an optical sensor for nitric oxide (NO), a pro-inflammatory mediator that induces inflammation[2]. We demonstrate a 7-fold enhancement in sensor response compared to the state-of-the-art sensor based on the (AT)15 sequence[3]. This approach thus provides a powerful means of overcoming existing bottlenecks in SWCNT sensor design, ushering a new generation of near-infrared technologies for biomedical research and clinical diagnostics.

A DFT investigation of Osmium decorated single walled carbon nanotubes for hydrogen storage

The investigation for hydrogen storage in armchair single walled carbon nanotubes (SWCNTs) with decoration of osmium atom on the surface of tube has been done using ab-initio method utilizing Density Functional Theory (DFT). In the present work, single/dual osmium atoms decoration on the surface of SWCNTs (5,5) has been investigated regarding the effects on structural, electronic and thermodynamic properties. Frontier molecular orbital (FMO) i.e. HOMO and LUMO structures and electrostatic potential surfaces (ESP) of all geometrically optimized and stable species are studied. Investigations regarding metal-metal clustering are carried out by calculating diffusion barrier energy for osmium atoms and atomistic molecular dynamic simulations performed at 300°K temperature for 1ps. It is found that osmium decoration on SWCNTs enhances the hydrogen storage capacity via spillover mechanism. It is observed that the adsorption energy per hydrogen molecule in case of Pristine SWCNT is -0.001eV, which is increased with decoration of osmium atoms and finally found to be -0.575eV/H2 in case of single osmium decorated SWCNT (Os-CNT) and -0.681eV/H2 due to double osmium decoration on SWCNT (2Os-CNT). This study reveals gravimetric hydrogen storage capacity of 1.32 wt% and 2.53 wt% for Os-CNT and 2Os-CNT respectively at 298.15 K temperature and 10 atm pressure. Average Van't Hoff desorption temperature for osmium decorated SWCNTs are also calculated.

Acid-base engineered strategy of HKUST-1 dopants for high electrical conductivity of single-walled carbon nanotubes films

The improvement of electrical conductivity of carbon nanotubes is still a challenge via tuning the carrier concentration and mobility with organic or inorganic dopants due to low doping efficiency. In this paper, single-walled carbon nanotubes (SWCNTs) have been doped with Cu3(BTC)2·(H2O)3 (HKUST-1) as metal organic frameworks via simple mixing and vacuum filtration method. With fine acid or base post-treatment, the crystal structure of HKUST-1 was broken into fragments with more active sites and provided plenty of carriers injecting into SWCNTs. The electrical conductivity of SWCNTs/HKUST-1 films was increased by almost 2.5 times compared to pristine SWCNTs at room temperature. The defect tuning of dopants on SWCNTs surface is an effective carrier injection strategy, which provides a way to improve the electrical conductivity of SWCNTs.