Self-assembled Nanotubes Research Articles

Investigation and optimization of polarization properties of self-assembled carbon nanotube films

Super-aligned carbon nanotubes (CNTs) film has strong anisotropy to light propagation. In order to better integrate the self-assembled CNTs into microelectromechanical system (MEMS) for polarization applications, some inherent impacts on polarization properties of CNT film were investigated. We described the polarization effects of the film thickness variation in detail, giving an optimum thickness range which is around 700–800 nm. The amorphous carbon content of CNT film was reduced by oxidation process where the transmittance increased by almost 4 folds. The alignment of CNT arrangement was optimized from 0.41 (Chebyshev orientation parameter) to 0.54 by manipulating the C2H4 flow rate from 54 to 80 sccm. More specifically, a sample possessing a degree of polarization up to 99% and transmittance over 45% was obtained through proper regulations. The validated optimization makes the aligned CNT films more feasible and valuable for the integration of the CNT polarimeters with MEMS technology.

Cryo-EM of Helical Polymers.

While the application of cryogenic electron microscopy (cryo-EM) to helical polymers in biology has a long history, due to the huge number of helical macromolecular assemblies in viruses, bacteria, archaea, and eukaryotes, the use of cryo-EM to study synthetic soft matter noncovalent polymers has been much more limited. This has mainly been due to the lack of familiarity with cryo-EM in the materials science and chemistry communities, in contrast to the fact that cryo-EM was developed as a biological technique. Nevertheless, the relatively few structures of self-assembled peptide nanotubes and ribbons solved at near-atomic resolution by cryo-EM have demonstrated that cryo-EM should be the method of choice for a structural analysis of synthetic helical filaments. In addition, cryo-EM has also demonstrated that the self-assembly of soft matter polymers has enormous potential for polymorphism, something that may be obscured by techniques such as scattering and spectroscopy. These cryo-EM structures have revealed how far we currently are from being able to predict the structure of these polymers due to their chaotic self-assembly behavior.

Effect of different deposition techniques of PCDTBT:PC71BM composite on the performance of capacitive-type humidity sensors

The performance and hence pragmatic use of organic humidity sensors requires various factors to be addressed outside of progress in high-performance organic-based sensing materials. While important, evaluation of fabrication techniques also requires attention to optimise performance. Herein we report the effect of different application techniques on the humidity sensing performance of poly[N-90-heptadecanyl-2,7-carbazole-alt-5,5-(40,70-di-2-thienyl-20,10,30-benzothiadiazole)] (PCDTBT) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) organic composites. Spin-coating, immersion and drop-casting techniques have been applied to prepare sensors. Field-emission scanning electronic microscopy (FESEM) analysis of the prepared films revealed different types of self-assembled nanorods and nanotubes to be formed. The morphological and self-assembled differences could be attributed to various crystallisation processes as a result of different deposition techniques. Capacitive responses of all three sensors have been studied as a function of relative humidity at room temperature. PCDTBT:PC71BM composites prepared through the immersion technique showed superior sensing performance including higher sensitivity (62.34 pF/%RH) than sensors prepared through the spin coating (0.2 pF/%RH) and drop-casting (7.5 pF/%RH) techniques. The superior sensing performance of the sensor prepared through the immersion technique can be ascribed to both the nanotube and porous morphology exhibited.

A dimethyl methylphonate sensor based on HFIPPH modified SWCNTs

In order to meet the requirements of ultra-fast real-time monitoring of sarin simulator with high sensitivity and selectivity, it is of great significance to develop high performance dimethyl methylphonate (DMMP) sensor. Herein, we proposed a DMMP sensor based on p-hexafluoroisopropanol phenyl (HFIPPH) modified self-assembled single-walled carbon nanotubes (SWCNTs) with field effect transistor (FET) structure. The self-assembly method provides a 4 nanometres thick and micron sized SWCNT channel, with high selectivity to DMMP. The proposed SWCNTs-HFIPPH based sensor exhibits remarkably higher response to DMMP than bare SWCNT based gas sensor within only few seconds. The gas sensing response of SWCNTs-HFIPPH based sensor for 1 ppm DMMP is 18.2%, and the response time is about 10 s. What’s more, the gas sensor we proposed here shows excellent selectivity and reproducibility, and the limitation of detection is as low as ppb level. The proposed method lays the foundation for miniaturization and integration of DMMP sensors, expecting to develop detection system for practical sarin sensing application.

Self-assembled cellulose nanofiber-carbon nanotube nanocomposite films with anisotropic conductivity.

In this study, a nanocellulose-based material showing anisotopic conductivity is introduced. The material has up to 1000 times higher conductivity along the dry-line boundary direction than along the radial direction. In addition to the material itself, the method to produce the material is novel and is based on the alignment of cationic cellulose nanofibers (c-CNFs) along the dry-line boundary of an evaporating droplet composed of c-CNFs in two forms and conductive multi-walled carbon nanotubes (MWCNTs). On the one hand, c-CNFs are used as a dispersant of MWCNTs, and on the other hand they are used as an additional suspension element to create the desired anisotropy. When the suspended c-CNF is left out, and the nanocomposite film is manufactured using the high energy sonicated c-CNF/MWCNT dispersion only, conductive anisotropy is not present but evenly conducting nanocomposite films are obtained. Therefore, we suggest that suspending additional c-CNFs in the c-CNF/MWCNT dispersion results in nanocomposite films with anisotropic conductivity. This is a new way to obtain nanocomposite films with substantial anisotropic conductivity.

Achiral copper clusters helically confined in self-assembled chiral nanotubes emitting circularly polarized phosphorescence

Achiral Cu5− cluster coassembled with a chiral amphiphile to afford helical nanotubes, where the Cu5− cluster was confined within the nanotubes, forming helical arrangement with emerged chiroptical activities (CD and CPP), with a large gabs up to 0.018.

Fano resonance line shapes in the Raman spectra of tubulin and microtubules reveal quantum effects

Microtubules are self-assembling biological nanotubes made of the protein tubulin that are essential for cell motility, cell architecture, cell division, and intracellular trafficking. They demonstrate unique mechanical properties of high resilience and stiffness due to their quasi-crystalline helical structure. It has been theorized that this hollow molecular nanostructure may function like a quantum wire where optical transitions can take place, and photoinduced changes in microtubule architecture may be mediated via changes in disulfide or peptide bonds or stimulated by photoexcitation of tryptophan, tyrosine, or phenylalanine groups, resulting in subtle protein structural changes owing to alterations in aromatic flexibility. Here, we measured the Raman spectra of a microtubule and its constituent protein tubulin both in dry powdered form and in aqueous solution to determine if molecular bond vibrations show potential Fano resonances, which are indicative of quantum coupling between discrete phonon vibrational states and continuous excitonic many-body spectra. The key findings of this work are that we observed the Raman spectra of tubulin and microtubules and found line shapes characteristic of Fano resonances attributed to aromatic amino acids and disulfide bonds.

A Novel Biological Nano Confinement Inhibits Cancer Metastasis

Cancer is a complex genetic disease hallmarked with a strong competitive capacity in energy and utilization of substances compared to normal cells, which is partially due to the ability to adjust their metabolism in response to environmental changes. During the lifespan of cancer cells, either during carcinogenesis, progress, or metastasis, massive energy and other substances are essential prerequisites, however, the underlying mechanisms are controversial and still remain unclear. Understanding how cancer cells seize much of the energy and other substances than normal cells is of utmost importance for next-generation cancer therapy, along with the finding of novel drug target and drug design. Recent reports about ‘mitochondrial hijack’ of cancer cells through selfassembled protein nanotubes connected with normal cells and ‘graded messengers pool’ in cytoplasm have evoked a great interest. Considering the widely discussed ‘nanodomain’ in physical and chemical areas, we proposed the concept of biological nano confinement (BNC), by which we may rationally elucidate the priorities of solid tumors on utilization of energy and substances at hypoxia, and less nutrition supplying environments both extraand intra-cellular. The ultimate objective was to address the confusion that CAR-T therapies are effective for hematological cancers but less effective for solid tumors and also to reveal the fact that chimeric antigens receptor-T (CAR-T) adjuvant therapy with chemotherapy has synergetic enhancement effects. In turn, developing novel inhibitors to depolymerize biological nanoconfinement is urgently needed.

Antioxidant Activity of SEO Decorated Self-Assembled Nanotubes of 3,5-Bis-Trifluromethyl Benzylamine Derivative of Phenylalanine Electrochemical Activity and its Dft Studies

Antioxidant Activity of SEO Decorated Self-Assembled Nanotubes of 3,5-Bis-Trifluromethyl Benzylamine Derivative of Phenylalanine Electrochemical Activity and its Dft Studies

Supramolecular assemblies of histidine-containing peptides with switchable hydrolase and peroxidase activities through Cu(II) binding and co-assembling.

Modulating enzyme activities or functionalities is one of the primary features of biological systems, which is, however, a great challenge for artificial enzyme systems. In this work, we designed and synthesized a series of self-assembling peptides from histidine and other amino acids (Asp, Ser, Lys or Arg), which exist in the active site of natural enzymes. These peptides could undergo a conformational transition from random coils to β-sheet structures under physiological conditions and formed self-assembled nanotubes with obvious hydrolase activities. After incorporation of transition metal ions such as Cu2+, these peptides could coordinate with Cu2+ ions, switch molecular conformations, and self-assemble into hybrid nanomaterials with altered morphologies and peroxidase-like activities. This work illustrates a facile approach for constructing artificial enzymes from self-assembling peptides with histidine residues whose catalytic functions could be modulated by incorporation of Cu2+ ions.

A novel self-enhancement NCNDs-BPEI-Ru nanocomposite with highly efficient electrochemiluminescence as signal probe for ultrasensitive detection of MTB

Herein, a novel self-enhanced Ru(Ⅱ)-based nanocomposite (NCNDs-BPEI-Ru), synthesized by covalently connecting nitrogen-doped carbon nanodots (NCNDs) and tris (4,4′-dicarboxylicacid-2,2′-bipyridyl) ruthenium (II) dichloride (Ru(dcbpy)3Cl2) through branched polyethyleneimine (BPEI), could be used as an electrochemiluminescence (ECL) signal probe for ultrasensitive detection of mycobacterium tuberculosis (MTB) DNA fragment. Without any extraneous coreactants, NCNDs-BPEI-Ru could generate an ultra-strong initial ECL signal on the glassy carbon electrode (GCE) (signal-on) due to the coreaction from BPEI and NCNDs to Ru(dcbpy)3Cl2. Then, self-assembled DNA nanotubes embedding methylene blue molecules (MB-DNANTs) were modified on the nanocomposite to effectively quench the ECL intensity of NCNDs-BPEI-Ru owing to the quenching effect of MB for Ru(dcbpy)3Cl2 (signal-off). Finally, the 3D DNA nanomachine, formed by a DNA-functionalized magnetic beads (DNA-MBs) could transform trace target MTB into massive output DNA, and the MB-DNANTs could be disintegrated to get ECL signal recovery (signal-on) due to hybridization of output DNA and the S2 in DNANTs. Therefore, the proposed biosensor exhibited predominant performance for the detection of MTB DNA fragment with a low detection limit of 1.4 aM, which showed great application value in the detection of biomarkers in clinical diagnosis.

Gold Carbide: A Predicted Nanotube Candidate from First Principle.

In the present work, density functional theory (DFT) calculations were applied to confirm that the gold carbide previously experimentally synthesized was AuC film. A crucial finding is that these kinds of AuC films are self-folded on the graphite substrate, leading to the formation of a semi-nanotube structure, which significantly diminishes the error between the experimental and simulated lattice constant. The unique characteristic, the spontaneous archlike reconstruction, makes AuC a possible candidate for self-assembled nanotubes. The band structure indicated, in the designed AuC nanotube, a narrow gap semiconductor with a bandgap of 0.14 eV. Both AIMD (at 300 and 450 K) results and phonon spectra showed a rather high stability for the AuC nanotube because a strong chemical bond formed between the Au–5d and C–2p states. The AuC nanotube could become a novel functional material.

Tubular Assembly Formation Induced by Leucine Alignment along the Hydrophobic Helix of Amphiphilic Polypeptides.

The introduction of α-helical structure with a specific helix–helix interaction into an amphipathic molecule enables the determination of the molecular packing in the assembly and the morphological control of peptide assemblies. We previously reported that the amphiphilic polypeptide SL12 with a polysarcosine (PSar) hydrophilic chain and hydrophobic α-helix (l-Leu-Aib)6 involving the LxxxLxxxL sequence, which induces homo-dimerization due to the concave–convex interaction, formed a nanotube with a uniform 80 nm diameter. In this study, we investigated the importance of the LxxxLxxxL sequence for tube formation by comparing amphiphilic polypeptide SL4A4L4 with hydrophobic α-helix (l-Leu-Aib)2-(l-Ala-Aib)2-(l-Leu-Aib)2 and SL12. SL4A4L4 formed spherical vesicles and micelles. The effect of the LxxxLxxxL sequence elongation on tube formation was demonstrated by studying assemblies of PSar-b-(l-Ala-Aib)-(l-Leu-Aib)6-(l-Ala-Aib) (SA2L12A2) and PSar-b-(l-Leu-Aib)8 (SL16). SA2L12A2 formed nanotubes with a uniform 123 nm diameter, while SL16 assembled into vesicles. These results showed that LxxxLxxxL is a necessary and sufficient sequence for the self-assembly of nanotubes. Furthermore, we fabricated a double-layer nanotube by combining two kinds of nanotubes with 80 and 120 nm diameters—SL12 and SA2L12A2. When SA2L12A2 self-assembled in SL12 nanotube dispersion, SA2L12A2 initially formed a rolled sheet, the sheet then wrapped the SL12 nanotube, and a double-layer nanotube was obtained.

Synthesis and Applications of Functional Nanomaterials

The unique physical and chemical properties and variable application potential of nanomaterials are continuously devoted to stimulating scientists’ studying enthusiasm. Extremely fine grains bring quantities excellent properties such as low density, low elastic modulus, high resistance and low thermal conductivity to nanomaterials, which has extensive use in the photoelectric field, environment, bioengineering and other fields. The research progress of graphene quantum dots, transparent reflective coatings and self-assembled nanotubes are mainly demonstrated. This paper shows the role of graphene quantum dots in solar cells, summarizes the synthesis methods of self-assembled nanotubes and their applications in bioengineering, and describes the development of transparent thermal reflective coatings for energy-saving glass attributed to providing relevant reference and basis for the development and research of nanomaterials.

Lithium-Conducting Self-Assembled Organic Nanotubes.

Supramolecular polymers are compelling platforms for the design of stimuli-responsive materials with emergent functions. Here, we report the assembly of an amphiphilic nanotube for Li-ion conduction that exhibits high ionic conductivity, mechanical integrity, electrochemical stability, and solution processability. Imine condensation of a pyridine-containing diamine with a triethylene glycol functionalized isophthalaldehyde yields pore-functionalized macrocycles. Atomic force microscopy, scanning electron microscopy, and in solvo X-ray diffraction reveal that macrocycle protonation during their mild synthesis drives assembly into high-aspect ratio (>103) nanotubes with three interior triethylene glycol groups. Electrochemical impedance spectroscopy demonstrates that lithiated nanotubes are efficient Li+ conductors, with an activation energy of 0.42 eV and a peak room temperature conductivity of 3.91 ± 0.38 × 10-5 S cm-1. 7Li NMR and Raman spectroscopy show that lithiation occurs exclusively within the nanotube interior and implicates the glycol groups in facilitating efficient Li+ transduction. Linear sweep voltammetry and galvanostatic lithium plating-stripping tests reveal that this nanotube-based electrolyte is stable over a wide potential range and supports long-term cyclability. These findings demonstrate how the coupling of synthetic design and supramolecular structural control can yield high-performance ionic transporters that are amenable to device-relevant fabrication, as well as the technological potential of chemically designed self-assembled nanotubes.

Hydration-dependent band gap tunability of self-assembled phenylalanyl tryptophan nanotubes

Bioinspired peptide nanotubes have emerged as a brand new category of organic semiconductors employed in many nanotechnological applications. Trapped solvent, long-range ordering, and configurational versatility play important roles in the control and tuning of the electronic properties of these nanotubes. Here, the density-functional theory-based tight-binding approach is employed to study the impact of building block separation, caused by confined water molecules, on the geometry and electronic structure of phenylalanyl tryptophan nanotubes (PTNTs). The amount of water in the PTNT walls changes considerably the distance between the building blocks. This structural modification causes a modulation of the PTNT bandgap and changes its nature from indirect to direct. An effective control of the structure and electronic properties of these one-dimensional PTNTs can pave the way for potential applications in bioelectronic and medical devices.

Modeling of Self-Assembled Peptide Nanotubes and Determination of Their Chirality Sign Based on Dipole Moment Calculations.

The chirality quantification is of great importance in structural biology, where the differences in proteins twisting can provide essentially different physiological effects. However, this aspect of the chirality is still poorly studied for helix-like supramolecular structures. In this work, a method for chirality quantification based on the calculation of scalar triple products of dipole moments is suggested. As a model structure, self-assembled nanotubes of diphenylalanine (FF) made of L- and D-enantiomers were considered. The dipole moments of FF molecules were calculated using semi-empirical quantum-chemical method PM3 and the Amber force field method. The obtained results do not depend on the used simulation and calculation method, and show that the D-FF nanotubes are twisted tighter than L-FF. Moreover, the type of chirality of the helix-like nanotube is opposite to that of the initial individual molecule that is in line with the chirality alternation rule general for different levels of hierarchical organization of molecular systems. The proposed method can be applied to study other helix-like supramolecular structures.

Polyoxymethylene/Carbon Nanotube Self-Assembly Networks with Improved Electrical Conductivity for Engineering Functional Structural Materials

Polyoxymethylene/Carbon Nanotube Self-Assembly Networks with Improved Electrical Conductivity for Engineering Functional Structural Materials

Delivery of a Cancer-Testis Antigen-Derived Peptide Using Conformationally Restricted Dipeptide-Based Self-Assembled Nanotubes.

Use of tumor-associated antigens for cancer immunotherapy is limited due to their poor in vivo stability and low cellular uptake. Delivery of antigenic peptides using synthetic polymer-based nanostructures has been actively pursued but with limited success. Peptide-based nanostructures hold much promise as delivery vehicles due to their easy design and synthesis and inherent biocompatibility. Here, we report self-assembly of a dipeptide containing a non-natural amino acid, α,β-dehydrophenylalanine (ΔF), into nanotubes, which efficiently entrapped a MAGE-3-derived peptide (M3). M3 entrapped in F-ΔF nanotubes was more stable to a nonspecific protease treatment and both F-ΔF and F-ΔF-M3 showed no cellular toxicity for four cancerous and noncancerous cell lines used. F-ΔF-M3 showed significantly higher cellular uptake in RAW 267.4 macrophage cells compared to M3 alone and also induced in vitro maturation of dendritic cells (DCs). Immunization of mice with F-ΔF-M3 selected a higher number of IFN-γ secreting CD8+ T cells and CD4+ T compared to M3 alone. On day 21, a tumor growth inhibition ratio (TGI, %) of 41% was observed in a murine melanoma model. These results indicate that F-ΔF nanotubes are highly biocompatible, efficiently delivered M3 to generate cytotoxic T lymphocytes responses, and able to protect M3 from degradation under in vivo conditions. The F-ΔF dipeptide-based nanotubes may be considered as a good platform for further development as delivery agents.

A self-assembled montmorillonite-carbon nanotube hybrid nanoreinforcement for poly-l-lactic acid bone scaffold

The high tendency of montmorillonite (MMT) or carbon nanotube (CNT) agglomeration makes their uniform dispersion as reinforcements in biopolymer a great challenge. Herein, CNT was acidified to produce carboxylic groups and then grafted with aminopropyltriethoxysilane (KH550) followed by reacting with glacial acetic acid, which introduced ammonium salt onto the surface of CNT. The ammonium salt-grafted CNT could intercalate into the interlayers of MMT through cation exchange reaction between the alkylammonium cations and the sodium cations of MMT to form a self-assembled MMT-CNT hybrid nanostructure. In this nanostructure, tubular CNT sandwiched between the interlayer of MMT reduced the stacking of MMT, whereas the lamellar MMT acted as steric hindrance to block the entanglement of CNT, thus improving the dispersion of each other via a synergistic effect. As a result, the incorporation of MMT-CNT hybrid into poly-l-lactic acid scaffold enhanced the mechanical properties, including tensile strength and modulus increased by 113.04% and 111.46%, respectively, and compressive strength and modulus increased by 58.20% and 63.27%, respectively. In addition, the scaffold exhibited improved hydrophilicity and degradability, and favorable affinity for cell adhesion, growth and proliferation.