Single-walled Carbon Nanotube Scaffold Research Articles

One-pot hydrothermal growth of indium oxide-CNT heterostructure via single walled carbon nanotube scaffolds and their application toward flexible NO2 gas sensors

Single walled carbon nanotubes (SWNTs) are recognized as a promising sensing material for flexible NO2 gas sensors, whereas poor recovery at room temperature is a significant barrier to practical application. This study reports a one-pot hydrothermal synthesis of an indium oxide/single-walled carbon nanotube heterostructure (h-In2O3/SWNT) for efficient recovery in gas sensors. This results in the stable formation of 2-dimensional electron gases and their favorable electron compensation in the channel layers. The h-In2O3/SWNT FET gas sensors (h-GS) exhibit a sensing resolution of 1 ppm, negligible degradation over 9 consecutive cycled exposures with a 2-day-interval, and a significant improvement in recovery within 10 min at room temperature. Surprisingly, even when the flexible h-GS is evaluated under repeated tensile strain of 0.88 %, electrical reliability and reproducibility of the h-GS is fully validated. Thus, with its demonstrated robust sensing properties and compensation scheme, the h-In2O3/SWNT is expected to be a promising candidate for use as a novel sensing layer in a wearable gas sensor, resolving one of the long-standing issues associated with gas sensor sluggish recovery and reliability for impact.

Three-Dimensional Monolithic Organic Battery Electrodes.

Design of freestanding electrodes incorporated with redox-active organic materials has been limited by the poor intrinsic electrical conductivity and lack of methodology driving the feasible integration of conductive substrate and the organic molecules. Single-walled carbon nanotube (SWCNT) aerogels, which possess continuous network structure and high surface area, offer a three-dimensional electrically conducting scaffold. Here, we fabricate monolithic organic electrodes by coating a nanometer-scale imide-based network (IBN) that possesses abundant redox-active sites on the 3D SWCNT scaffold. The substantially integrated 3D monolithic organic electrodes sustain high electrical conductance through a 3D electronic pathway in their compressed form (∼21 μm). A thin and controllable layer (<8 nm) of IBN organic materials has a strong adhesion onto the ultra-lightweight and conductive substrate and facilitates multielectron redox reactions to deliver a specific capacity of up to 1550 mA h g-1 (corresponding to the areal capacity of ∼2.8 mA h cm-2). The redox-active IBN in synergy with the 3D SWCNT scaffold can enable superior electrochemical performances compared to the previously reported organic-based electrode architectures and inorganic-based electrodes.

Insulin Detection Using a Corona Phase Molecular Recognition Site on Single-Walled Carbon Nanotubes.

Corona phase molecular recognition (CoPhMoRe) is a technique whereby an external, adsorbed phase around a colloidal nanoparticle is selected such that its molecular conformation or interaction recognizes a specific target analyte. In this work, we employ a high-throughput screening of a library of poly(ethylene glycol) (PEG)-conjugated lipids adsorbed onto near-infrared fluorescent single-walled carbon nanotubes to discover a corona phase selective for insulin. We find that a C16-PEG(2000 Da)-ceramide causes a 62% fluorescent intensity decrease of the (10,2) chirality nanotube in the presence of 20 μg/mL insulin. The insulin protein has no prior affinity toward the C16-PEG(2000 Da)-ceramide molecules in free solution, verified by isothermal titration calorimetry, and the interaction occurs only upon their adsorption onto the single-walled carbon nanotube scaffolds. Testing a panel of proteins originating from human blood as well as short 7 amino acid fragments of the insulin peptide rules out nonselective recognition mechanisms such as molecular weight, isoelectric point, and hydrophobicity-based detection. Interestingly, longer fragments of isolated α- and β-peptide chains of insulin are detected by the construct, albeit with lower affinity compared to that of the intact insulin protein, suggesting that the construct recognizes insulin in its native form and conformation. Finally, the insulin recognition and the quantification of its solution concentration were demonstrated both in buffer and in blood serum, showing that the CoPhMoRe construct works in this complex environment despite the presence of potential nonspecific adsorption. Our results further motivate the search for nonbiological synthetic recognition sites and open up a new path for continuous insulin monitoring in vivo with the hope of improving glycemic control in closed-loop artificial pancreas systems.

Enhancement of osteogenesis and stem cell differentiation by injectable nanocomposite and dynamic acoustic radiation force stimulation

Osteopenia affects mineral density, microstructure, and integrity of bone, leading to increased risk of fractures, as well as high rates of non-union, which affect patients’ quality of life. Current treatments are ineffective, requiring invasive surgeries and/or long-term drug therapy. The objective of this study was to develop a novel noninvasive biomimetic treatment for rapid regeneration to promote cell differentiation and osteogenesis. An injectable orthopedic implant was designed by developing a thermosensitive scaffold incorporating carbon nanotubes and chitosan-β glycerophosphate hydrogels. An innovative biophysical stimulation using dynamic ultrasound radiation force (ARF) was used to induce carbon nanotube resonance for regulating osteogenic differentiation of stem cells. An assay on activity of ALP, a biomarker of osteogenesis, and a fluorescence-based live/dead cell assay were conducted to determine the best treatment for inducing rapid cell formation. The single-walled carbon nanotube scaffold and 60 mW/cm2 ARF group was the best treatment, and enhanced ALP activity and stem cell differentiation by 430%. Cell viability was increased by 65% through the ARF treatment. This study developed a novel treatment for regulating cell proliferation using single-walled carbon nanotube nanocomposite implants and synergistic stimulation of stem cells with ultrasound. This rapid, noninvasive, cost-effective treatment may provide an innovative alternative for osteoporotic treatment and rapid fracture healing.

Superior separation performance of ultrathin gelatin films

Ultrathin gelatin films were prepared by filtering gelatin on a porous nanofibrous scaffold and cross-linked by glutaraldehyde. The gelatin thin films were obtained by using a copper hydroxide nanostrand scaffold after removal of the scaffold. At relative high pressure, the rejection properties of these gelatin films became worse due to mechanical fouling. However, the gelatin/carbon nanotube composite thin films prepared on a single-walled carbon nanotube scaffold could sustain a pressure up to 18 bars with more than 90% rejection for 2–3 nm molecules. The carbon nanotube layer dramatically increased the mechanical properties of the gelatin layer. The pressure dynamically controlled the network structure of the gelatin layer. The corresponding separation performances were investigated in detail. The gelatin films could be as thin as 62 nm. These gelatin films can separate 865 Dalton Direct Yellow 50 molecules at a rate of magnitude one to two orders higher than that of commercially available membranes with similar rejections.

Epoxy composite sheets with a large interfacial area from a high surface area-supplying single-walled carbon nanotube scaffold filler

Closed single-walled carbon nanotubes (SWCNTs) with the highest available specific surface area (>1000 m 2/g) were used to provide a very large interfacial area with the matrix to fabricate epoxy composite sheets. Through mechanical redirection of the vertically aligned SWCNTs, we created a laterally aligned “scaffold” sheet, into which epoxy resin was impregnated. The SWCNT scaffold was engineered in structure to meet two almost mutually exclusive demands, i.e. to have nanometer mesopores (∼2–50 nm) to facilitate homogeneous impregnation of the epoxy resin and to possess a cohesive mechanical strength to tolerate the compaction forces generated during impregnation. Through this approach, a SWCNT/epoxy composite sheet was realized where long and aligned SWCNTs were loaded at a high weight fraction (33%) with an intertube distance approaching the radius of gyration for polymers. The resultant composite showed a Young’s modulus of 15.0 GPa and a tensile strength of 104 MPa, thus achieving 5.4- and 2.1-fold reinforcement compared to the epoxy resin.

Single-Walled Carbon Nanotube Scaffolds for Dye-Sensitized Solar Cells

The influence of single-walled carbon nanotube (SWCNT) architectures for facilitating charge transport in mesoscopic semiconductor films has been probed using a TiO2/Ru(II) trisbipyridyl complex system. Both transient absorption and emission measurements indicate that the SWCNT network in the film has no noticeable influence on the charge injection process from the excited Ru(II) trisbipyridyl complex into TiO2 particles. However, it plays an important role in improving the charge separation, as the rate of back electron transfer between the oxidized sensitizer (Ru(III)) and the injected electrons becomes slower in the presence of the SWCNT scaffold. The beneficial aspect of charge collection by SWCNT has been further explored by carrying out photoelectrochemical measurements. The dye-sensitized solar cells constructed using this SWCNT scaffold show an improvement in the photocurrent generation. However, this improvement in photocurrent generation is neutralized by a lower photovoltage as the apparent Fermi level of the TiO2 and SWCNT composite becomes more positive than that of pristine TiO2.

Single-Walled Carbon Nanotube Scaffold for improving Charge Transport Efficiency in Nanostructured Titanium Dioxide Films

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Single-Walled Carbon Nanotube Scaffolds Promote Stem Cell Differentiation into Bone Forming Cells

AbstractThe use of carbon nanotubes for tissue engineering has become one of the most fascinating applications. The exquisite electronic and mechanical properties of carbon nanotubes may provide a three-dimensional (3D) microenvironment that closely mimics in vivo situation for facilitating the use of stem cells in the tissue regeneration. Therefore, it is important to know whether carbon nanotubes enhance the adhesion, proliferation, and differentiation of stem cells. Here, we hypothesized that the carbon nanotubes promote the differentiation of osteoblast progenitors into mature osteoblasts. To test this hypothesis, we quantified the differentiation of murine osteoblast progenitors, with and without pro-differentiating growth factor Bone Morphogenetic Protein-2 (BMP-2), cultured on the 3D scaffolds made by single-walled carbon nanotubes (SWNTs). Three types of SWNT samples, chitosan functionalized SWNTs, acid-oxidized SWNTs, and surfactant-free pristine SWNTs were used for the construction of these 3D microarchitectures. Osteoblast progenitors were harvested from calvariae from 3∼5-day-old mice, and cultured on the 3D scaffolds made by carbon nanotubes until ∼ 80% confluent. Then the cells were treated with BMP-2 (100 ng/ml) for 5 days. It was found that osteoblast progenitors cultured on the SWNTs dramatically increased the level of mature osteoblastic marker osteocalcin in either the absence or the presence of BMP-2, as compared to the cells cultured on the regulate tissue culture plastic plates. The results suggested that SWNTs highly promote osteoblast progenitor differentiation into mature osteoblasts. The finding indicates that SWNTs may provide an ideal scaffold for facilitating the differentiation of osteoblast progenitors in the repair of bone defects.