Large Mechanical Strength Research Articles

In silico stress-strain measurements on self-assembled protein lattices.

Due to their large mechanical strength and potential for functionalization, beta-solenoid proteins show promise as building blocks in biomaterials applications such as two- and three-dimensional scaffolds. We have designed simulation models of two-dimensional square and honeycomb protein lattices by covalently linking a beta-solenoid protein, the spruce budworm antifreeze protein (SBAFP), to symmetric protein multimers. Periodic boundary conditions applied to the simulation cell allow for the simulation of an infinite lattice. We use molecular dynamics to strain the lattice by deforming the simulation cell and measuring the resulting stress tensor. We evaluate the linear portion of stress-strain curves to extract the corresponding bulk and shear elastic moduli. When strained at a rate of 0.3 nm ps-1, the lattices yield a bulk modulus of approximately 3 GPa. This large elastic modulus demonstrates that 2-dimensional structures designed from beta-solenoid proteins can be expected to retain the exceptional material strength of their building blocks.

Atomic mechanical properties of structure and diffusion in the MoO3 anode materials during lithiation

In order to realize MoO3 as an anode material in lithium ion batteries, it is important to understand the atomic level mechanisms of MoO3 structures evolution during lithiation. A first-principle method is employed to evaluate the volumetric deformation, electronic structure, and Young’s modulus during lithiation based on density function theory. The electrochemical insertion of Li ions into MoO3 anode materials prompts a volumetric deformation along the perpendicular direction. Moreover, we analyzed the projected density of states during lithiation for MoO3. The band gap will vanish at high enough Li concentration, the electron will dope into Mo atoms by Li interaction. In addition, the migration energy barriers of lithium ions along the z-direction are the lowest among other pathways, while a large deformation caused by lithiation remained in the MoO3 materials. In particular, the Young’s modulus of the MoO3 anode materials increased during lithiation, but the large mechanical strength can sustain this. Those results may reveal the mechanism of structural transition from the MoO3 to Li2MoO3 and provide some valuable mechanical understanding of LixMoO3 materials in lithium ion batteries.

Dual-surface flexible THz Fano metasensor

Sensing technologies based on terahertz waves have immense potential due to their non-destructive, transparent, and fingerprint spectral response of several materials that are opaque to other parts of the electromagnetic spectrum. Terahertz metasensors reported so far merely exploit the fringing electric field on the top of the subwavelength resonators. Here, we experimentally demonstrate an ultrathin flexible terahertz metamaterial sensor on a low refractive index substrate which enables sensing of analytes from the top and bottom surfaces of the metamaterial, opening up avenues for dual-surface sensing of analytes with fringing resonant fields on both front and rear sides of a metasurface. Since most of the real-world objects have 3D curvatures, the reported flexible metasensor with large mechanical strength and stability in free space would be an ideal platform for ultrasensitive sensing of dielectrics, chemicals, and biomolecules of extremely low concentrations with dual non-planar surfaces.

Three-dimensional graphene monolith-based composite: superiority in properties and applications

ABSTRACTWith the development of graphene research, the three-dimensional graphene monolith (3DGM), which can be prepared by the chemical vapour deposition method (CVD-3DGM) and the self-assembly of reduced graphene oxide nanosheets (RGO-3DGM), has drawn increasing attention because of its properties and application prospects that are better than those of two-dimensional graphene nanosheets. By utilising its excellent electrical property, large BET area and favourable mechanical strength, some research findings on the 3DGM-assisted thermal interface materials, conductive polymers and films, dye-sensitised solar cells and supercapacitors have been reported. In this perspective, we review recent progress in the synthesis and application of 3DGM-based composites and devices. In particular, the advantages of the CVD-3DGM are highlighted after comparing the reports, and the specific reasons are analysed and discussed. Finally, the probable directions of development, research focus and corresponding challenges for the preparation and application of the CVD-3DGM in the future are proposed.

Modelling Effective Charge Density in Graphene-Based DNA Sensor

Due to its unique properties, including high conductivity, large surface area and significant mechanical strength, graphene has attracted a great deal of attention among researchers in physics, biology, nanoelectronics and nanotechnology fields, especially over the past few years. A fundamental understanding of the DNA-hybridization detection mechanism and technical prediction and optimization of many graphene-based DNA sensors requires extensive modeling and simulation of devices. Although there have been numerous experimental studies in this field, the lack of analytical models is felt deeply. In this work, to start with modelling, a liquid field effect transistor-based structure is employed as a platform, and graphene charge density variation based on the Poisson-Boltzman equations are studied under the impact induced by the adsorption of different values of DNA concentration on its surface. The effect of DNA molecules concentration and surface charge density of ssDNA and dsDNA before and after hybridization are considered in the calculation of the analytical model. The obtained current-voltage characteristics of the proposed model are compared with available experimental data existing, and a good agreement is found. For all the concentrations considered in this work, the proposed model can track experimental curves documented by other authors, with acceptable accuracy.

Syntheses of carboxymethylcellulose/graphene nanocomposite superabsorbent hydrogels with improved gel properties using electron beam radiation

Nanocomposite superabsorbent hydrogels (NCSHs) were prepared via electron beam radiation-assisted polymerization using carboxymethylcellulose (CMC) and carbon materials as a superabsorbent polymer and additive inorganic nanomaterial, respectively. Carbon materials such as graphite oxide (GO), reduced graphene oxide (rGO), and activated carbon (AC) were used as additives. The chemical structure and morphology of the prepared NCSHs and pure superabsorbent hydrogels (SHs) were characterized using Fourier transform infrared spectroscopy and optical microscopy. In the prepared NCSHs, the carbon components were dispersed well in the CMC polymer matrix. The mechanical strength and gel fraction of the prepared materials were measured, and the swelling kinetics were evaluated using distilled water, urea solution, and physiological saline water. The prepared NCSHs using GO and rGO exhibited larger gel fraction and mechanical strength than the corresponding non-composite SHs. Electron beam radiation was more effective than solution polymerization in the syntheses of SHs and NCSHs with large gel fraction and high mechanical strength. The NCSHs prepared by electron beam radiation exhibited comparable swelling capabilities to those prepared by solution polymerization. Open image in new window

Strong and fast-recovery organic/inorganic hybrid AuNPs-supramolecular gels based on loofah-like 3D networks.

Super strong and fast-recovery organic/inorganic hybrid gold nanoparticle (AuNPs)-supramolecular gels based on a three-dimensional loofah-like nanoscale network self-assembled by polyhedral oligomeric silsesquioxane (POSS) core supramolecular gelators are reported for the first time. Two series of POSS core organic/inorganic hybrid gelators, POSS-BOC-l-Homophenylalanine (POSS-Hpy) and POSS-Boc-Cys(Bzl)-OH (POSS-Cys), with two types of peripherals having different abilities for driving the self-assembly of AuNPs in gels were designed and synthesized, both of which self-assembled into three-dimensional loofah-like nanoscale gel networks producing hybrid physical gels with fast-recovery behaviors. The mechanical properties of the resultant hybrid gels were dramatically increased by as much as 100 times in the system of sulfur containing POSS-Cys gelators without destroying the fast-recovery behaviors, with the addition of AuNPs, which had direct interaction with AuNPs to give S-Au non-covalent driving force to lead AuNPs self-assemble onto the 3D loofah-like network nanofibres in the supramolecular hybrid gel system. However, in the POSS-Hpy gelator system without sulfur, no strong interaction with AuNPs existed and the POSS-Hpy nanocomposites showed no clear changes in morphology, thermal stability or rheological properties, confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), tube-inversion and rotational rheometer measurements. This indicated that the organic/inorganic hybrid gelator POSS-Cys could be applied to the formation of soft materials in which AuNPs were self-assembled and closely arranged into three-dimensional nanoscale networks. This hybrid material has great potential for applications in self-recovery, nano- and micron-scale electronic devices, because it has both a large mechanical strength and a fast-recovery capability.

2D nanostructures for water purification: graphene and beyond.

Owing to their atomically thin structure, large surface area and mechanical strength, 2D nanoporous materials are considered to be suitable alternatives for existing desalination and water purification membrane materials. Recent progress in the development of nanoporous graphene based materials has generated enormous potential for water purification technologies. Progress in the development of nanoporous graphene and graphene oxide (GO) membranes, the mechanism of graphene molecular sieve action, structural design, hydrophilic nature, mechanical strength and antifouling properties and the principal challenges associated with nanopore generation are discussed in detail. Subsequently, the recent applications and performance of newly developed 2D materials such as 2D boron nitride (BN) nanosheets, graphyne, molybdenum disulfide (MoS2), tungsten chalcogenides (WS2) and titanium carbide (Ti3C2Tx) are highlighted. In addition, the challenges affecting 2D nanostructures for water purification are highlighted and their applications in the water purification industry are discussed. Though only a few 2D materials have been explored so far for water treatment applications, this emerging field of research is set to attract a great deal of attention in the near future.

Electron Transfer Kinetics on Mono- and Multi-Layer Graphene

Since the first isolation of graphene monolayer via mechanical exfoliation in 2004, many other production methods have emerged in the following years. These methods include chemical vapour deposition, liquid phase graphite exfoliation, graphite oxide reduction and epitaxial growth, each having its pros and cons. The unique properties of graphene, such as high electron mobility, large specific surface area, mechanical strength and high transparency, ignited an enormous research interest to explore the electrochemical properties of graphene sheets, with potential uses in many immediate applications such as energy storage, solar cell technology and corrosion protection. Understanding how the electron transfer kinetics of a redox reaction between the graphene surface and a molecule compares to graphite or other carbon based materials is crucial to future use of graphene as a ‘supreme’ electrode material.1 Herein, the electrochemical response of mono-layer and multi-layer graphene electrodes, prepared using both chemical vapour deposition and mechanical exfoliation, is presented. Experiments were carried out using a microinjector, micromanipulator and optical microscopy, enabling precise deposition of size-controlled droplets on the flake surface.1 The insulating substrates used for flake preparation include inorganic materials and organic polymers. Graphene/graphite flakes were characterised using optical microscopy, Raman spectroscopy and atomic force microscopy.The electron transfer rate at the basal planes, edge planes and boundaries between graphene flakes was determined using voltammetric techniques. The redox couple, number of graphene layers, presence of defects and nature of the substrate are all shown to have a significant effect on the electrochemical activity.2-3 Furthermore, the stability of the droplets on the surface depends on various factors, such as the solvent choice, electrolyte content, number of graphene layers, underlying substrate and method of flake preparation.1. Valota, A. T.; Toth, P. S.; Kim, Y. J.; Hong, B. H.; Kinloch, I. A.; Novoselov, K. S.; Hill, E. W.; Dryfe, R. A. W., Electrochimica Acta, 2013, 110, 9-15.2. Valota, A. T.; Kinloch, I. A.; Novoselov, K. S.; Casiraghi, C.; Eckmann, A.; Hill, E. W.; Dryfe, R. A. W., ACS Nano, 2011, 5 (11), 8809-8815.3. P. S. Toth; A. Valota; M. Velicky; I. Kinloch; K. Novoselov; E. W. Hill; R. A. W. Dryfe, Chemical Science, 2013, DOI:10.1039/C3SC52026A.

A facile approach to fabricate flexible all-solid-state supercapacitors based on MnFe2O4/graphene hybrids

A critical challenge for the construction of flexible electrochemical capacitors is the preparation of flexible electrodes with large specific capacitance and robust mechanical strength. Here, we demonstrate a facile approach to make high performance and flexible electrodes by dropping MnFe2O4/graphene hybrid inks onto flexible graphite sheets (as current collectors and substrates) and drying under an infrared lamp. MnFe2O4/graphene hybrid inks are synthesized by immobilizing the MnFe2O4 microspheres on the graphene nanosheets via a simple solvothermal route. Electrochemical studies show that MnFe2O4/graphene exhibits a high capacitance of 300 F g−1 at a current density of 0.3 A g−1. In addition, the excellent electrochemical performance of a supercapacitor consisting of a sandwich structure of two pieces of MnFe2O4/graphene hybrids modified electrodes separated by polyvinyl alcohol (PVA)-H2SO4 gel electrolyte is further explored. Our studies reveal that the flexible supercapacitor device with 227 μm thickness can achieve a maximum specific capacitance of 120 F g−1 at a current density of 0.1 A g−1 and excellent cycle performance retaining 105% capacitance after 5000 cycles. This research may offer a method for the fabrication of lightweight, stable, flexible and high performance energy storage devices.

Mechanical and microstructural dissimilarities in alkali-activation for six Class F Korean fly ashes

This study presents the preliminary investigation for the microstructural characteristics of the alkali-activated fly ashes, synthesized using six different Korean Class F fly ashes, to address the large mechanical strength differences between the activated ashes using compressive strength testing, XRF, XRD, and SEM/EDS (YAG BSE, SE and elemental mapping). The results show that although the original fly ashes are not much different in XRD and XRF data, the reaction products after activation were dissimilar between the activated ashes. Particularly, the activated sample containing Al-rich chabazite produced much higher compressive strength than the other samples with zeolite A–Na. The SEM/EDS results exhibit that the activated fly ashes tended to have the higher compressive strengths as the reaction products possessed the lower Si/Al ratios down to one.

Modification of carbon nanotubes by CuO-doped NiO nanocomposite for use as an anode material for lithium-ion batteries

Abstract CuO-doped NiO (CuNiO) with porous hexagonal morphology is fabricated via a modified in-situ co-precipitation method and its nanocomposite is prepared with carbon nanotubes (CNTs). The electrochemical properties of CuNiO/CNT nanocomposite are investigated by cyclic voltammetry (CV), galvanostatic charge–discharge tests and electrochemical impedance spectroscopy (EIS). Since Cu can both act as conductor and a catalyst, the CuNiO/CNT nanocomposite exhibits higher initial coulombic efficiency (82.7% of the 2nd cycle) and better capacity retention (78.6% on 50th cycle) than bare CuNiO (78.9% of the 2nd cycle), CuO/CNT (76.8% of the 2nd cycle) and NiO/CNT (77.7% of the 2nd cycle) at the current density of 100 mA /g. This high capacity and good cycling ability is attributed to the partial substitution of Cu+2 for Ni+2, resulting in an increase of holes concentration, and therefore improved p-type conductivity along with an intimate interaction with CNTs providing large surface area, excellent conduction, mechanical strength and chemical stability.

Superplastically Foaming Method for Reliable Porous Ceramics

Porous ceramics incorporates pores to improve several properties including thermal insulation, maintaining inherent ceramic properties such as corrosion resistance and large mechanical strength. Conventional porous ceramics is usually fabricated through an insufficient sintering, leading to degraded strength and durability. Contrary to this, we have innovated superplastically foaming method to make ceramic foam only in the solid state. In this method, the previously inserted foam agent evaporates after the full densification of matrix at around the sintering temperature. Closed pores expand utilizing the superplastic deformation driven by the evolved gas pressure. Based on this concept we fabricated 8mol% yttria stabirized zirconia based porous ceramics and examined the properties concerning the high temperature structural material with thermal insulation.

Graphite oxide/polyurea and graphene/polyurea nanocomposites: A comparative investigation on properties reinforcements and mechanism

Abstract Graphite oxide (GO) and graphene were incorporated into polyurea (PUA) via in situ polymerization and the properties reinforcements of the nanocomposites and the mechanism were compared and investigated through evaluating molecular weights, dispersion and interface interactions. As for the mechanical behaviors, 0.2 wt.% of graphene in the nanocomposites achieved the maximum increase in the tensile strength (80%). However, the tensile properties of PUA/GO nanocomposites decreased with the increase of GO contents. The GPC, TEM, FTIR and the immersion experiments indicate that the molecular weights of polyurea, dispersion of GO and the hydrogen bonds between the GO and PUA matrix are the three decisive factors for the deduced mechanical strength of PUA/GO nanocomposites. In contrast, due to the homogeneous dispersion and large mechanical strength of the graphene sheets, polyurea/graphene nanocomposites exhibited improved tensile strength, hardness and glass transition temperature. Moreover, it was found that the carbonyl, epoxy and hydroxyl groups in the graphite oxide influence the molecular weights and weakened the hydrogen bonds among polyurea molecules and those resulted in the deduced mechanical properties of polyurea.

Functionalized halloysite nanotube-based carrier for intracellular delivery of antisense oligonucleotides

Halloysites are cheap, abundantly available, and natural with high mechanical strength and biocompatibility. In this paper, a novel halloysite nanotube [HNT]-based gene delivery system was explored for loading and intracellular delivery of antisense oligodeoxynucleotides [ASODNs], in which functionalized HNTs [f-HNTs] were used as carriers and ASODNs as a therapeutic gene for targeting survivin. HNTs were firstly surface-modified with γ-aminopropyltriethoxysilane in order to facilitate further biofunctionalization. The f-HNTs and the assembled f-HNT-ASODN complexes were characterized by transmission electron microscopy [TEM], dynamic light scattering, UV-visible spectroscopy, and fluorescence spectrophotometry. The intracellular uptake and delivery efficiency of the complexes were effectively investigated by TEM, confocal microscopy, and flow cytometry. In vitro cytotoxicity studies of the complexes using MTT assay exhibited a significant enhancement in the cytotoxic capability. The results exhibited that f-HNT complexes could efficiently improve intracellular delivery and enhance antitumor activity of ASODNs by the nanotube carrier and could be used as novel promising vectors for gene therapy applications, which is attributed to their advantages over structures and features including a unique tubular structure, large aspect ratio, natural availability, rich functionality, good biocompatibility, and high mechanical strength.

Synthesis of Foam-Shaped Nanoporous Zeolite Material: A Simple Template-Based Method

Nanoporous zeolite foam is an interesting crystalline material with an open-cell microcellular structure, similar to polyurethane foam (PUF). The aluminosilicate structure of this material has a large surface area, extended porosity, and mechanical strength. Owing to these properties, this material is suitable for industrial applications such as large-scale gas separation and catalysis. As the applications of this material are significant, the underlying concepts for the design and synthesis may be used in an upper-level undergraduate laboratory in inorganic synthesis or material chemistry courses. This type of experiment can increase student understanding and integrate a variety of chemical concepts, such as targeted synthesis, characterization, and adsorption theory of gases. This laboratory experiment involves the synthesis and characterization of ZSM-5 type of zeolite foam that is synthesized from inexpensive materials and characterized by bulk density and porous volume measurements. This course would acquaint students with general characterization methods that are not normally encountered in a typical material or inorganic chemistry laboratory.

Graphene anchored with mesoporous NiO nanoplates as anode material for lithium-ion batteries

Graphene is an excellent substrate to load nanomaterials for energy applications due to its large surface area, excellent conductivity, mechanical strength, and chemical stability. In this study, thermal exfoliated functionalized graphene sheets with good conductivity and high BET surface area are anchored with mesoporous NiO nanoplates by in situ chemical synthesis approach. Electrochemical characterization shows that functionalized graphene sheets–NiO sample exhibits a high capacity of about 700 mAh/g at a discharge current density of 100 mA/g and a good cycling ability. The high capacity and good cycling ability of functionalized graphene sheets –NiO material were attributed to the intimate interaction between the graphene sheets and NiO nanoplates. The graphene sheets not only enhance the conductivity of NiO nanoplates but also improve the structure stability of NiO nanoplates. Furthermore, the mesoporous structure of NiO nanoplates is available to the transfer of electrolyte. Such functionalized graphene sheets–NiO nanocomposite could be a promising candidate material for a high-capacity, low cost, and nontoxic anode for lithium-ion batteries.

Superplastically foaming method to make closed pores inclusive porous ceramics

Porous ceramics incorporates pores to improve several properties including thermal insulation maintaining inherenet ceramic properties such as corrosion resistance and large mechanical strength. Conventional porous ceramics is usually fabricated through an insufficient sintering. Since the sintering accompanies the exclusion of pores, it must be terminated at the early stage to maintain the high porosity, leading to degraded strength and durability. Contrary to this, we have innovated superplastically foaming method to make ceramic foams only in the solid state. In this method, the previously inserted foam agent evaporates after the full densification of matrix at around the sintering temperature. Closed pores expand utilizing the superplastic deformation driven by the evolved gas pressure. The typical features of this superplastically foaming method are listed as follows, 1. The pores are introduced after sintering the solid polycrystal. 2. Only closed pores are introduced, improving the insulation of gas and sound in addition to heat. 3. The pore walls are fully densified expecting a large mechanical strength. 4. Compared with the melt foaming method, this method is practical because the fabrication temperature is far below the melting point and it does not need molds. 5. The size and the location pores can be controlled by the amount and position of the foam agent.

Surface Modification of Slide-Ring Gel by Strip-line Microwave Micro Atmospheric Plasma

A third class of polymer gel, termed a (topological) gel, which is based on mobile cross-linker with a figure-of-eight structured dimer of cyclodextrin has been attracting numerous attentions; because of its remarkable physical properties such as large extensibility and mechanical strength. In this study, we applied atmospheric microplasma, based on microwave strip-line technology, to surface functionalization of a slide-ring gel to improve the surface hydrophilicity. When the gel surface was modified with microplasma in ambient air, the contact angle drastically changed into nearly 0° from the original angle of 46°. The x-ray photoelectron spectroscopy (XPS) after the treatment indicated 3.3 at.% atomic oxygen increase and 3.4 at.% atomic carbon decrease, respectively. These results suggest that the slide-ring gel surface is highly sensitive to the atmospheric microplasma and is functionalized promptly/effectively for biomimetic applications with less thermal damages even in ambient air.

Micromachined Hydrogel Stamper for Soft Printing of Biomolecules with Adjustable Feature Dimensions

We report on the development of a hydrogel stamper with built-in reservoirs for soft-printing of biomolecules with adjustable feature dimensions. The stamper consists of potassium hydroxide (KOH)-etched silicon cavities onto which biomolecule-soaked low cross-linked density hydrogel with large pores and low mechanical strength is loaded. Application of weight to the top surface allows for a controllable protrusion of hydrogel from the opposite nozzles. Such protrusion combined with a suitable spacer between the stamper and a substrate provides a means for printing features with dimensions depending on the applied weight. Utilizing the above method, we successfully stamped bovine serum albumin conjugated with fluorescein isothiocyanate (BSA-FITC) model proteins on hydrophilic silicon substrates with a feature dimension ratio of 20:1 using a single stamper.