Single-walled Carbon Nanotubes Hybrid Research Articles

Reversible Redox Activity by Ion-pH Dually Modulated Duplex Formation of i-Motif DNA with Complementary G-DNA.

The unique biological features of supramolecular DNA have led to an increasing interest in biomedical applications such as biosensors. We have developed an i-motif and G-rich DNA conjugated single-walled carbon nanotube hybrid materials, which shows reversible conformational switching upon external stimuli such as pH (5 and 8) and presence of ions (Li+ and K+). We observed reversible electrochemical redox activity upon external stimuli in a quick and robust manner. Given the ease and the robustness of this method, we believe that pH- and ion-driven reversible DNA structure transformations will be utilized for future applications for developing novel biosensors.

The Comparison of Optical Properties of Acridine Orange when Interact with Hybrids of Single-Walled Carbon Nanotubes and Single-Stranded DNA or DoubleStranded DNA

The optical properties (visible-ultraviolet emission and fluorescence) of acridine orange (AO) were compared and investigated to try to discuss the AO adsorption mechanisms when AO interacted with four aqueous dispersions, for example, single-stranded DNA (ssDNA), double-stranded DNA (dsDNA), hybrids of ssDNA and single-walled carbon nanotubes (SWNT-ssDNA), and hybrids of dsDNA and single-walled carbon nanotubes (SWNT-dsDNA). Molecule structure deformation and energy transfer maybe existed when AO attached to DNA chains or emerged into SWNT/DNA suspensions. DsDNA seemingly brought about an obvious structure deformation to AO; delocalized π-bond of AO/SWNT perhaps produce a little absorbance red-shift effect to AO, because of lower electronic transition energy for π-electron or n-electron; the energy transferred from DNA to AO, or from AO to SWNT. Most of AO molecules “prioritized” DNA chains, rather than SWNT surface; although AO molecules adsorbed to DNA chain and SWNT surface at the same time.

High Durability and Waterproofing rGO/SWCNT-Fabric-Based Multifunctional Sensors for Human-Motion Detection.

Wearable strain-pressure sensors for detecting electrical signals generated by human activities are being widely investigated because of their diverse potential applications, from observing human motion to health monitoring. In this study, we fabricated reduced graphene oxide (rGO)/single-wall carbon nanotube (SWCNT) hybrid fabric-based strain-pressure sensors using a simple solution process. The structural and chemical properties of the rGO/SWCNT fabrics were characterized using scanning electron microscopy (SEM), Raman, and X-ray photoelectron spectroscopy (XPS). Complex networks containing rGO and SWCNTs were homogeneously formed on the cotton fabric. The sensing performance of the devices was evaluated by measuring the effects of bending strain and pressure. When the CNT content was increased, the change in relative resistance decreased, while durability was significantly improved. The rGO/SWCNT (0.04 wt %) fabric sensor showed particularly high mechanical stability and flexibility during 100 000 bending tests at the extremely small bending radius of 3.5 mm (11.6% bending strain). Moreover, the rGO/SWCNT fabric device exhibited excellent water resistant properties after 10 washing tests due to its hydrophobic nature. Finally, we demonstrated a fabric-sensor-based motion glove and confirmed its practical applicability.

Switching the optical and electrical properties of carbon nanotube hybrid films using a photoresponsive dispersant as a dopant.

The light-induced switching of the optical and electrical properties of single-walled carbon nanotubes (SWCNTs) was demonstrated following hybridisation with an azobenzene-based photoresponsive dispersant in solid film. The resultant SWCNT/photoresponsive dispersant hybrid film showed switching of absorbance in the near-infrared region by the irradiation of UV and visible lights, which was caused by the change of the doping ability of the dispersant to SWCNT. In addition, the switching of the electrical properties of the SWCNT hybrid film was also observed.

Energetic Basis of Single-Wall Carbon Nanotube Enantiomer Recognition by Single-Stranded DNA

Hybrids of single-stranded DNA and single-walled carbon nanotubes (SWCNTs) have proven to be very successful in separating various chiralities and, recently, enantiomers of carbon nanotubes using aqueous two-phase separation. This technique sorts objects based on small differences in hydration energy, which is related to corresponding small differences in structure. Separation by handedness requires that a given ssDNA sequence adopt different structures on the two SWCNT enantiomers. Here we study the physical basis of such selectivity using a coarse-grained model to compute the energetics of ssDNA wrapped around an SWCNT. Our model suggests that difference by handedness of the SWCNT requires spontaneous twist of the ssDNA backbone. We also show that differences depend sensitively on the choice of DNA sequence.

Polypyrimidine/SWCNTS composite comprising Pt nanoparticles: Possible electrocatalyst for fuel cell

The poly(9,9-dioctyl fluorine-alt-2-amino-4,6-pyrimidine) (oligomer) is used as an effective dispersant for single walled carbon nanotubes (SWCNTs) and generates stable SWCNTs hybrid after elimination of the excess polymer. The covered polymers immobilized Pt nanoparticles onto the surface of single-walled carbon nanotubes (SWCNTs) by coordination between Pt and polymer and the amount of the loaded Pt on the hybrid was calculated to be 38.5 wt %. The average diameter of the Pt nanoparticles on the SWCNTs were about ∼4–5 nm and have a moderate electrochemically active surface area of 40.5 m2/g. These studies strongly imply the possible application of novel pyrimidine/carbon materials as catalyst supports in the electrodes of fuel cells.

Carbon Nanoparticle Hybrid Aerogels: 3D Double-Interconnected Network Porous Microstructure, Thermoelectric, and Solvent-Removal Functions.

We report reduced graphene oxide (rGO)/single-walled carbon nanotube (SWCNT) hybrid aerogels with enhanced thermoelectric (TE) performance and removal of organic solvents by designing 3D double-interconnected network porous microstructures. A convenient, cost-effective, and scalable preparation procedure is proposed compared with conventional high-temperature pyrolysis and supercritical drying techniques. The obtained hybrid aerogels are systematically characterized by apparent density, scanning electron microscopy, X-ray photoemission spectroscopy, Raman spectroscopy, and porosity. An enhanced TE performance of ZT ≈ ∼8.03 × 10-3 has been achieved due to the 3D double-interconnected network porous microstructure, the energy-filtering effect, and the phonon scattering at the abundant interfaces and joints. In addition, upon a large axial compression deformation, a high degree of retention of the Seebeck coefficient and a simultaneously significant enhancement of the electrical conductivity are observed. Finally, the hybrid aerogels display high capability for the removal of diverse organic solvents and good recyclability. These findings open a new avenue for exploiting aerogels with multifunctions and widening the applications of TE materials by judicious microstructure design.

A novel high energy hybrid Li-ion capacitor with a three-dimensional hierarchical ternary nanostructure of hydrogen-treated TiO2 nanoparticles/conductive polymer/carbon nanotubes anode and an activated carbon cathode

Lithium ion capacitors (LICs) are considered to be high-performance energy storage devices that have stimulated intense attention to bridge the gap between lithium ion battery and supercapacitor. Currently, the major challenge for LICs has been to improve the energy density without sacrificing the high rate of power output performance. Herein, we designed a three-dimensional (3D) hierarchical porous nanostructure of hydrogen-treated TiO2 nanoparticles wrapped conducting polymer polypyrrole (PPy) framework with single-walled carbon nanotubes (SWCNTs) hybrid (denoted as, H-TiO2/PPy/SWCNTs) anode material for LICs through a conventional and green approach. Such a unique network can offer continuous electron transport and reduce the diffusion length of lithium ions. A greatly lithium storage specific capacity is achieved with reversible discharge capacity ∼213 mA h g−1 (based on the mass of TiO2) over 50 cycles (@ 0.1 A g−1), which is almostly three times compared with raw TiO2 (a commercial TiO2 nanoparticles powder). In addition, coupled with commercial activated carbon (AC) cathode, the fully assembled H-TiO2/PPy/SWCNTs//AC LICs delivers a maximum energy and power densities of 31.3 Wh kg−1 and 4 kW kg−1, a reasonably good cycling stability (∼77.8% retention after 3000 cycles) within the voltage range of 1.0–3.0 V.

Observation of Adsorption Process of Single Stranded DNA to Single-Walled Carbon Nanotubes Surfaces by Fluorescence Quenching

Single walled carbon nanotubes (SWNTs) are one of the promising nanomaterials for various applications in nanotechnology. In biomedical fields, hybrids of DNA and SWNT (DNA-SWNT hybrids) are expected to be attractive nanodevices for drug delivery and DNA sensors. For preparing DNA-SWNT hybrids, mixture of SWNT and DNA solutions are prepared via sonication. Although DNA-SWNT hybridization techniques have been established, the diverse sonication conditions in every paper may affect structures of DNA-SWNT hybrids. Here we report a method of monitoring adsorption process of DNA to SWNT surfaces using fluorescent labeled single-stranded DNA (Fluor-ssDNA). It is known that fluorescent emission of fluorescent dyes is quenched when the dye is adsorbed on SWNT surfaces. Using this unique quenching phenomenon, we evaluated adsorption process of Fluor-ssDNA on SWNT surfaces. In the experiments, 0.25 mg of SWNT powder, 50 uL of Fluor-ssDNA solution (1.0 mg/mL in tris (hydroxymethyl aminomethane buffer solution, 200mM, pH 7.5)), and 450 uL of the buffer were mixed, and then sonicated under three different sonication conditions as follows: probe type with amplitude 60% of 130 W (P60), probe type with amplitude 20% of 130 W (P20), and bath type with 80 W (B80). In order to monitor the adsorption process, samples were characterized by fluorescent spectroscopy and atomic force microscopy. In the case of P60, fluorescent intensity of Fluor-ssDNA decreased 98% within 2 min. This suggests that most of Fluor-ssDNA rapidly adsorbed on SWNT surfaces. However, AFM images demonstrated that it took more time to form mono-dispersed DNA-SWNT hybrids. In the case of P20 and B80, 30 min was needed for 98% quenching. In addition, reproducibility of the B80 data was much higher than that of P20. This is an advantage of bath type sonicator.

Non-covalent anchoring of oligonucleotides on single-walled carbon nanotubes via short bioreducible linker

This paper describes a simple approach to obtain hybrids of single-walled carbon nanotubes with therapeutically relevant oligonucleotides that are able to be released upon glutathione treatment at physiological concentrations.

Study of electronic interactions and photo-induced electron transfer dynamics in a metalloconjugated polymer–single-walled carbon nanotube hybrid by ultrafast transient absorption spectroscopy

The present study demonstrated the selective dispersion of SWCNTs by the metalloconjugated polymer, and the evidence of electron injection from the sensitizers to SWCNTs.

Conformational analysis of 1,3-dioxane in nanotubes

Computer simulation of conformational transformations of 1,3-dioxane molecule within model single-walled carbon nanotubes (hybrid DFT-method PBE/3ζ) showed that the nanosystem considerably affects the conformational equilibrium and the nature of the main minimum on PES, first of all, because of its diameter. The decrease in the latter led to unusual shift of the conformational equilibrium of 1,3-dioxane to the side of 2,5-twist-form.

Removal of excess polymer from a suspension containing hybrids of thermoresponsive polymer and carbon nanotubes using aggregation phenomenon

Hybrids of organic molecules and single-walled carbon nanotubes (SWNTs) are attractive candidates for nanobiodevices. The removal of organic molecules after dispersing the SWNTs in organic media is a significant step in the preparation of these hybrid suspensions. We investigated the aggregation phenomenon in hybrids of poly(N-isopropylacrylamide) (PNIPAAm) and SWNTs. Our results indicate that the hybrids efficiently precipitated when a buffer or salt solution was added to the suspension at 25 °C. 4 mM tris(hydroxymethyl)aminomethane hydrochloride (Tris–HCl) buffer was sufficient to precipitate the hybrids. Then, by repeated centrifugations and replacements of solvents, excess PNIPAAm molecules were efficiently removed from the suspension. Results of UV–vis spectroscopy and atomic force microscopy (AFM) suggest that the PNIPAAm–SWNT hybrids retained their hybridized structures even after the treatment process. However, the aggregation phenomenon was not observed at 4 °C.

Selective dispersion of single-walled carbon nanotubes by binaphthyl-based conjugated polymers: Integrated experimental and simulation approach

Hybrids of π-conjugated polymers and single-walled carbon nanotubes (SWNTs) are an intriguing class of materials owing to their interesting electric and optoelectronic properties. Herein, we synthesized three types of 1,1′-binaphthyl-incorporated conjugated polymers with thiophene bridges. It was found that the molecular structure of the π-conjugated polymers affected the selective dispersion of individual SWNT species: the hexyl-substituted PBHT preferred (8,7) SWNT while polymers with no alkyl groups on the thiophenes (PBT and PB2T) preferred (8,6) species. Molecular dynamics (MD) simulations also revealed that the polymers were able to wrap around SWNTs and showed selective interactions with the SWNT species.

Atomic Force Microscopy of DNA-wrapped Single-walled Carbon Nanotubes in Aqueous Solution

We evaluated hybrids of DNA and single-walled carbon nanotubes (SWNTs) in aqueous solution and in air using atomic force microscopy (AFM). Although intensive AFM observations of these hybrids were previously carried out for samples in air, this is the first report on AFM observations of these hybrids in solution. As expected, diameters of DNA-SWNT hybrids dramatically increased in tris(hydroxymethyl)aminomethane-ethylenediaminetetraacetic acid (TE) buffer solution. The data suggest that DNA molecules maintain their structures even on the SWNT surfaces. Furthermore, we simultaneously observed single DNA-SWNT hybrids using three different AFM modes in air and in the TE buffer solution. Height value of the hybrids was largest in the solution, and lowest for the mode that repulsive force is expected in air. For the bare SWNT molecules, height differences among the three AFM modes were much lower than those of the DNA-SWNT hybrids. DNA molecules adsorbed on SWNT surfaces flexibly changed their morphology as well as DNA molecules on flat surfaces such as mica. This is hopeful results for biological applications of DNA-SWNT hybrids. In addition, our results revealed the importance of the single-molecule approach to evaluate DNA structures on SWNT surfaces.

Platinum nanoparticles-single-walled carbon nanotubes hybrid based chemiresistive sensor array for myoglobin detection

We examined the potential of platinum nanoparticles (PtNP) modified single-walled carbon nanotube (SWNT) hybrid chemiresistive sensor for detection of antigen myoglobin (Mb) in phosphate buffer saline. Protein antibody, Ab-Mb, was covalently immobilized through site specific binding on PtNP attached over SWNT. A concentration-dependent change in the source–drain current of the hybrid device was observed in the range of 0.1–1000 ng ml−1. The hybrid device response fitted well with the Hill–Langmuir equation with a maximum response of 111.14% and low dissociation constant value (Kd = 19.98 ng ml−1), indicating high protein antigen binding affinity at hybrid nanostructure.

Thermodynamics for the Formation of Double-Stranded DNA-Single-Walled Carbon Nanotube Hybrids.

For the first time, the thermodynamics are described for the formation of double-stranded DNA (ds-DNA)-single-walled carbon nanotube (SWNT) hybrids. This treatment is applied to the exchange reaction of sodium cholate (SC) molecules on SWNTs and the ds-DNAs d(A)20 -d(T)20 and nuclear factor (NF)-κB decoy. UV/Vis/near-IR spectroscopy with temperature variations was used for analyzing the exchange reaction on the SWNTs with four different chiralities: (n,m)=(8,3), (6,5), (7,5), and (8,6). Single-stranded DNAs (ss-DNAs), including d(A)20 and d(T)20, are also used for comparison. The d(A)20-d(T)20 shows a drastic change in its thermodynamic parameters around the melting temperature (Tm ) of the DNA oligomer. No such Tm dependency was measured, owing to high Tm in the NF-κB decoy DNA and no Tm in the ss-DNA.

Optimal conditions for decorating outer surface of single-walled carbon nanotubes with RecA proteins

In this study, we estimated the optimal reaction conditions for decorating the outer surface of single-walled carbon nanotubes (SWNTs) with RecA proteins by comparison with hybrids of RecA and single-stranded DNA (ssDNA). To react SWNTs with RecA proteins, we first prepared ssDNA–SWNT hybrids. The heights of the ssDNA–SWNT hybrids increased as the amount of RecA used in the reaction increased, as determined from atomic force microscopy images. We further confirmed the increasing adsorption of RecA proteins onto ssDNA on SWNT surfaces by agarose gel electrophoresis. These results suggest that the combination of RecA proteins and ssDNA–SWNT hybrids forms RecA–ssDNA–SWNT hybrids. We also successfully controlled the amount of RecA adsorbed on the ssDNA–SWNT hybrids. Our results thus indicate the optimized reaction conditions for decorating the outer surface of SWNTs with RecA proteins, which is the key to the development of novel biosensors and nanomaterial-based bioelectronics.

Physisorption of DNA molecules on chemically modified single-walled carbon nanotubes with and without sonication.

We investigated the physisorption phenomenon of single-stranded DNA (ssDNA) molecules onto two types of commercially available chemically functionalized single-walled carbon nanotubes (SWNTs) by atomic force microscopy (AFM) and agarose gel electrophoresis. We found that DNA molecules can adsorb on the water-soluble SWNT surfaces without sonication, although sonication treatment has been used for hybridization of DNA and SWNTs in many previous studies. Using our method, damage of DNA molecules by sonication can be avoided. On the other hand, the amount of DNA molecules adsorbed on SWNT surfaces increased when the samples were sonicated. This fact suggests that the sonication is effective not only at debundling of SWNTs, but also at assisting DNA adsorption. Furthermore, DNA adsorption was affected by the types of functionalized SWNTs. In the case of SWNTs functionalized with polyethylene glycol (PEG-SWNT), physisorption of ssDNA molecules was confirmed only by agarose-gel electrophoresis. In contrast, amino-terminated SWNTs (NH2-SWNTs) showed a change in the height distribution profile based on AFM observations. These results suggest that DNA molecules tended to adsorb to NH2-SWNT surfaces, although DNA molecules can also adsorb on PEG-SWNT surfaces. Our results revealed fundamental information for developing nanobiodevices using hybrids of DNA and SWNTs.

Protein Adsorption on Hybrids of Thermoresponsive Polymers and Single-Walled Carbon Nanotubes

Poly(N-isopropylacrylamide) (PNIPAAm) is one of the most popular thermoresponsive polymers. Adsorption of RecA proteins onto hybrids of PNIPAAm and single-walled carbon nanotubes (SWNTs) was observed in the presence and absence of DNA molecules. Although RecA molecules were adsorbed efficiently onto the hybrid surfaces at 37°C, even in the absence of DNA molecules, the adsorption of RecA was inhibited at 4°C. These results suggest that the thermoresponsive functions of PNIPAAm were effective, even on the SWNT surfaces, which supports the possibility of developing nanobiodevices using PNIPAAm-SWNT hybrids. However, although RecA is a DNA binding protein, there was no significant difference in the adsorption of RecA onto PNIPAAm-SWNT surfaces with and without DNA molecules. This study provides fundamental information for potential biological applications of PNIPAAm-SWNT hybrids.