Nanometer-scale Size Research Articles

Alloying reactions in nanostructured multilayers during intense deformation

Abstract Under intense deformation of metallic multilayer samples, a nanometer-scale layer thickness and grain size develops during repeated cold-rolling. Along with the evolution of the highly refined microstructure, a nanoscale interfacial alloying occurs that can result in an amorphization reaction. The deformation of multilayers exhibits driven system behavior during alloying. As the length scale of the layer thickness converges to the length scale of the mixing zone during rolling, amorphization develops in appreciable volumes. The results from selected experiments demonstrate that the relative specific interfacial area is the key microstructural metric to describe the deformation-driven alloying.

Advances in the Development of Phage-Based Probes for Detection of Bio-Species.

Bacteriophages, abbreviated as “phages”, have been developed as emerging nanoprobes for the detection of a wide variety of biological species, such as biomarker molecules and pathogens. Nanosized phages can display a certain length of exogenous peptides of arbitrary sequence or single-chain variable fragments (scFv) of antibodies that specifically bind to the targets of interest, such as animal cells, bacteria, viruses, and protein molecules. Metal nanoparticles generally have unique plasmon resonance effects. Metal nanoparticles such as gold, silver, and magnetism are widely used in the field of visual detection. A phage can be assembled with metal nanoparticles to form an organic–inorganic hybrid probe due to its nanometer-scale size and excellent modifiability. Due to the unique plasmon resonance effect of this composite probe, this technology can be used to visually detect objects of interest under a dark-field microscope. In summary, this review summarizes the recent advances in the development of phage-based probes for ultra-sensitive detection of various bio-species, outlining the advantages and limitations of detection technology of phage-based assays, and highlighting the commonly used editing technologies of phage genomes such as homologous recombination and clustered regularly interspaced palindromic repeats/CRISPR-associated proteins system (CRISPR-Cas). Finally, we discuss the possible scenarios for clinical application of phage-probe-based detection methods.

2-Methoxy-estradiol Loaded Alpha Lipoic Acid Nanoparticles Augment Cytotoxicity in MCF-7 Breast Cancer Cells.

The therapeutic effectiveness of anticancer drugs with a selective target for the nucleus of cancer cells may be improved by experimental approaches. In this regard, the formulation of anticancer drugs is considered one of the best ways to improve their effectiveness in targeting cancerous tissues. To enhance the anticancer activity of 2-methoxy-estradiol (2 ME) for breast cancer, 2-methoxyestradiol loaded alpha lipoic acid nanoparticles have been formulated. The prepared formula was observed to be spherical with a nanometer-scale and low PDI size (.234). The entrapment efficiency of the 2ME-ALA NPs was 87.32 ± 2.21% with > 85% release of 2 ME within 24 h. There was a 1.2-fold increase in apoptosis and a 3.46-fold increase in necrosis of the MCF-7 cells when incubated with 2ME-ALA NPs when compared to control cells. This increased apoptosis was also associated with increased ROS and increased p53 expression in 2ME-ALA NPs treated cells compared to the raw-2 ME group. Evaluation of cell-cycle data showed a substantial arrest of the G2-M phase of the MCF-7 cells when incubated with 2ME-ALA NPs. At the same time, a dramatically increased number of pre-G1 cells showed the increased apoptotic potential of the 2 ME when administered via the proposed formulation. In the end, the differential upregulation of caspase-3, p53, and ROS in MCF-7 cells established the superiority of the 2ME-ALA-Ms approach in targeting breast cancer. In summary, these results demonstrate that 2ME-ALA NPs are an efficient delivery tool for controlling the growth of breast cancer cells.

The effect of ultrasmall grain sizes on the thermal conductivity of nanocrystalline silicon thin films

Nanocrystallization has been an important approach for reducing thermal conductivity in thermoelectric materials due to limits on phonon mean-free path imposed by the characteristic structural size. We report on thermal conductivity as low as 0.3 Wm−1K−1 of nanocrystalline silicon thin films prepared by plasma-enhanced chemical-vapor deposition as grain size is reduced to 2.8 nm by controlling hydrogen dilution of silane gas during growth. A multilayered film composed by alternating growth conditions, with layer thicknesses of 3.6 nm, is measured to have a thermal conductivity 30% and 15% lower than its two constituents. Our quantitative analysis attributes the strong reduction of thermal conductivity with decreasing grain size to the magnifying effect of porosity which occurs concomitantly due to increased mass density fluctuations. Our results demonstrate that ultrasmall grain sizes, multilayering, and porosity, all at a similar nanometer-size scale, may be a promising way to engineer thermoelectric materials.

Cell Alignment Modulated by Surface Nano-Topography – Roles of Cell-Matrix and Cell-Cell Interactions

Cell alignment is critical in numerous areas, from tissue engineering to biohybrid robotics. Cell alignment is modulated through many features including surface topographies, mechanical cues from cell-matrix interactions, and cell-cell interactions. In this study, we present our approach to examine the role of surface topographies and cell-cell interactions with respect to cell alignment. We developed an approach to create wavy surface topographies at the nanometer size scale, which when integrated with cell culture affects cell alignment. Within a defined range of wavelengths and amplitudes of the surface topographies, cell alignment is dependent on culture confluency. This cell alignment’s dependence on confluency suggests that cell-cell interactions related to alignment may be correlated to cell-matrix interactions. Thus, we inhibited N-cadherin related cell-cell interactions through introduced anti-N-cadherin while culturing cells on our controlled surface topographies. We found that when using anti-N-cadherin, cells on patterned surfaces required greater confluency to achieve the same alignment to cell culture not in the presence of the antibody. Our results will be important in numerous areas including tissue repair, cell differentiation, and biohybrid systems.

Second-order correction of Klinkenberg equation and its experimental verification on gas shale with respect to anisotropic stress

Shale is an extremely tight and fine-grained sedimentary rock with nanometer-scale pore sizes. The internal nanopore structure gives rise to not merely the ultra-low permeability of shale, but also the significant slip flow (non-Darcy) phenomenon. This study involves a second-order correction of the traditional Klinkenberg equation and its experimental verification, in consideration of the effect of anisotropic stress, using cube-sized shale samples sourced from a typical Chinese sedimentary basin. The effects of two gas slippage factors, Klinkenberg-corrected permeability, and anisotropic stress were also discussed. The results showed an increasing trend of apparent permeability with decreasing pore pressure when the pressures are relatively low, due to the gas slippage effect. The second-order model results in a lower Klinkenberg-corrected permeability compared with that from the traditional Klinkenberg equation and yields a better match with the experimental data. Analysis of the experimental data showed that both the first-order slippage factor A and the second-order slippage factor B rose as stress anisotropy increased, and that A was more sensitive to stress anisotropy compared with B. Interestingly, both A and B first increased slightly and then dramatically as the permeability declined. It is recommended that when the shale permeability is below 10−3 mD, the second-order approach should be taken into consideration. Darcy's law starts to deviate when Kn > 0.01 and is invalid at high Knudsen numbers. The second-order approach alleviates the problem of permeability overestimation compared with the traditional Klinkenberg equation. When subjected to effective stress, shale pores become constricted and the degree of this constriction decreases gradually as the effective stress continues to increase.

Trilayer Interlinked Graphene Oxide Membrane for Wearable Hemodialyzer.

2D nanomaterials have long been considered for development of high permeability membranes. However, current processes have yet to yield a viable membrane for practical use due to the lack of scalability and substantial performance improvements over existing membranes. Herein, an ultrathin graphene oxide (GO) membrane with a permeability of 1562 mL h-1 mmHg-1 m-2, two orders of magnitude higher than the existing nanofiltration membranes, and a tight molecular weight cut-off is presented. To build such a membrane, a new process involving self-assembly and optimization of GO nanoplatelet physicochemical properties is developed. The process produces a highly organized mosaic of nanoplatelets enabling ultra-high permeability and selectivity. An adjustable molecular interlinker between the layers enables absolute nanometer-scale size cut-offs. These characteristics promise significant improvements to many nanoparticle and biological separation applications. In this work, the performance of the membrane in blood dialysis scenarios is evaluated. Urea and cytochrome-c sieving coefficients of 0.5 and 0.4 are achieved while retaining 99% of albumin. Hemolysis, complement activation, and coagulation studies exhibit a performance on par or superior to the existing dialysis membrane materials.

Atomic force microscopy imaging for nanoscale and microscale assessments of extracellular matrix in intervertebral disc and degeneration.

Degeneration of the intervertebral disc (IVD) is a condition that is often associated with debilitating back pain. There are no disease‐modifying treatments available to halt the progression of this ubiquitous disorder. This is partly due to a lack of understanding of extracellular matrix (ECM) changes that occur at the micro‐ and nanometer size scales as the disease progresses. Over the past decade, atomic force microscopy (AFM) has been utilized as a tool to investigate the impact of disease on nanoscale structure of ECM in bone, skin, tendon, and dentin. We have expanded this methodology to include the IVD and report the first quantitative analysis of ECM structure at submicron size scales in a murine model for progressive IVD degeneration. Collagen D‐spacing, a metric of nanoscale structure at the fibril level, was observed as a distribution of values with an overall average value of 62.5 ± 2.5 nm. In degenerative discs, the fibril D‐spacing distribution shifted towards higher values in both the annulus fibrosus and nucleus pulposus (NP) (P < .05). A novel microstructural feature, collagen toroids, defined by a topographical pit enclosed by fibril‐forming matrix was observed in the NP. With degeneration, these microstructures became more numerous and the morphology was altered from circular (aspect ratio 1.0 ± 0.1) to oval (aspect ratio 1.5 ± 0.4), P < .005. These analyses provide ECM structural details of the IVD at size scales that have historically been missing in studies of disc degeneration. Knowledge gained from these insights may aid the development of novel disease‐modifying therapeutics.

Tuning the ultralow β* optics at the KEK Accelerator Test Facility 2

For future linear colliders, a nanometer-scale beam size at the interaction point (IP) is one of the most challenging technical aspects. To explore the feasibility of a final focus system with a high chromaticity level, comparable to that of the Compact Linear Collider, the ultralow ${\ensuremath{\beta}}^{*}$ optics has been proposed and tuned at the KEK Accelerator Test Facility 2. In this paper, the recent experimental results are presented, which demonstrate the capability of achieving and stabilizing a vertical average beam size of 60 nm and below at the virtual IP. The observed vertical beam size is about 20 nm above the numerical predictions in the presence of static and dynamic imperfections. We interpret this discrepancy as beam size growth due to multipole fields, beam jitters and wakefield effects, and diagnostic errors.

(Invited) Novel Structured Carbon Materials Under High Pressure

Design and synthesis of new carbon materials have been attracting intensive attention due to their application in various fields. The study of carbon nano materials under high pressure provides us a very effective method to the creation of new carbon materials, especially superhard material which is hardly discovered at ambient condition because of the appearance of nanometer scale size effect and the novel high pressure behavior. Deeply understanding those unusual high pressure structures and physical phenomena also unveils new aspects of the intrinsic physics of nanomaterials. Fullerene, for example C60 is an important member and a representative zero-dimensional nano material in carbon family which has twice as much bulk modulus as diamond. It provides us an ideal carbon source to study novel phase and design new carbon materials induced by high pressure. In this presentation, several examples on high pressure induced novel structural phase transition in recently studied typical nano-confined fullerene will be outlined, including unique long range ordered crystal with amorphous nano clusters as building blocks (OACC) in solvated C60 and C70 crystals which brings new physical insight to understand order and disorder concept and new approach to design superhard carbon materials, a new carbon allotrope with a fully sp 3 bonded monoclinic structure (termed V carbon) from compressed C70 inside of single wall nanotubes (C70 peapod). These findings present a new strategy for constructing new carbon material with application of high pressure and nano-carbon material as building blocks.

Scaling behavior of low-temperature orthorhombic domains in the prototypical high-temperature superconductor La1.875Ba0.125CuO4

Translational/rotational symmetry breaking and recovery in condensed matter systems are closely related to exotic physical properties such as superconductivity (SC), magnetism, spin density waves (SDW) and charge density waves (CDW). The interplay between different order parameters is intricate and often subject to intense debate, as in the case of CDW order and superconductivity. In La1:875Ba0:125CuO4 (LBCO), the locations of CDW domains are found to be pinned on the nanometer size scale. Coherent X-ray diffraction techniques open routes to directly visualize the domain structures associated with these symmetry changes. We have pushed Bragg Coherent Diffractive Imaging (BCDI) into the cryogenic regime where most phase transitions in quantum materials reside. Utilizing BCDI, we image the structural evolution of LBCO microcrystal samples during the high-temperature-tetragonal (HTT) to low-temperature-orthorhombic (LTO) phase transition. Our results show the formation of LTO domains close to the transition temperature and how the domain size varies with temperature. The LTO domain size is shown to decrease with temperature and to be inversely proportional to the magnitude of the orthorhombic distortion. The number of domains follows the secondary order parameter (or orthorhombic strain) measurement with a critical exponent that is consistent with the 3D universality class.

Continuous growth phenomenon for direct synthesis of monodisperse water-soluble iron oxide nanoparticles with extraordinarily high relaxivity.

The direct synthesis of highly water-soluble nanoparticles has attracted intensive interest, but systematic size control has not been reported. Here, we developed a general method for synthesizing monodisperse water-soluble iron oxide nanoparticles with nanometer-scale size increments from 4 nm to 13 nm in a single reaction. Precise size control was achieved by continuous growth in an amphiphilic solvent, diethylene glycol (DEG), where the growth step was separated from the nucleation step by sequential addition of a reactant. There was only one reactant in the synthesis and no need for additional capping agents and reducing agents. This study reveals the "living growth" character of iron oxide nanoparticles synthesised in an amphiphilic solvent. The synthetic method shows high reproducibility. The as-prepared iron oxide nanoparticles are extremely water soluble without any surface modification. Surprisingly, the synthesized 9 nm iron oxide nanoparticles exhibit extremely high transversal and longitudinal relaxivities of 425 mM-1 s-1 and 32 mM-1 s-1 respectively, which is among the highest transversal relaxivity in the literature for sub-10 nm spherical nanoparticles. This study will not only shed light on the continuous growth phenomenon of iron oxide nanoparticles in an amphiphilic solvent, but could also stimulate the synthesis and application of iron oxide nanoparticles. The continuous growth method could be further extended to other materials for the controlled synthesis of water-soluble nanoparticles.

The atomic structure of a bulk metallic glass resolved by scanning tunneling microscopy and ab-initio molecular dynamics simulation

Scanning tunneling microscopy (STM) technique is widely used to study the electronic and structural properties of nano structures. Here we study the atomic structure of a Ni–Nb BMG by means of ultra high vacuum (UHV) STM in local areas of nanometer scale size, and report the direct atomic structure observation supported by ab initio molecular dynamics (MD) and density functional theory (DFT) simulations used to understand the observed structural and electronic features. It was possible to resolve the atomic surface structure of a bulk metallic glassy sample while MD simulation explained relatively large interatomic distances observed using STM.

Phenylboronic acid functionalized silica nanoparticles with enlarged ordered mesopores for efficient insulin loading and controlled release

Mesoporous silica particles have been extensively used to construct various drug delivery systems. An optimized design of pore size, surface functionalization and pore structure, is still needed for further application, especially for use as biomacromolecules carriers. Herein, one intelligent glucose-responsive insulin delivery system Insulin@ZnO-P@G-MSP was constructed based on mesoporous silica nanoparticles with large ordered mesopores (>5 nm) and small particle sizes (∼150 nm), combined with phenylboronic acids as glucose-responsive units and zinc oxide nanoparticles as the capping agents. The release characteristics of this system showed a positive correlation with the species and concentration of the saccharides and could be switched on and off by adjusting the glucose concentration. The stable release rate in the serum and good biocompatibility with liver cells illustrated the feasibility of this system in further biological applications. This work demonstrates an innovative approach to the development of a biomolecules delivery system by introducing mesoporous silica particles with large ordered mesopores and nanometer-scale particle sizes.

Orbital angular momentum from semiconductor high-order harmonics.

Light beams carrying orbital angular momentum (OAM) have led to stunning applications in various fields from quantum information to microscopy. We examine OAM from the recently observed high-harmonic generation (HHG) in semiconductor crystals. HHG from solids could be a valuable approach for integrated high-flux short-wavelength coherent light sources. First, we verify the transfer and conservation of the OAM in the strong-field regime of interaction from the generation laser to the harmonics. Secondly, we create OAM beams by etching a spiral zone structure directly at the surface of a zinc oxide crystal. Such diffractive optics act on the generated harmonics and produces focused optical vortices with sub-micrometric size.

Gd0.2Ce0.8O2 Diffusion Barrier Layer between (La0.58Sr0.4)(Co0.2Fe0.8)O3−δ Cathode and Y0.16Zr0.84O2 Electrolyte for Solid Oxide Fuel Cells: Effect of Barrier Layer Sintering Temperature on Microstructure

Combining high-performance (La0.58Sr0.4)(Co0.2Fe0.8)O3-δ (LSCF) cathodes with Y-doped ZrO2(YDZ) electrolytes in solid oxide fuel cells leads to the formation of SrZrO3 (SZO) as secondary phase with exceedingly low oxygen ion conductivity and poor catalytic capability. A promising prevention strategy is the insertion of Gd-doped CeO2 (GDC) as a reaction barrier. In this work, screen-printed GDC layers were sintered on YDZ substrates at temperatures varying from 1100 to 1400 °C. Subsequently, screen-printed LSCF was sintered on top at 1080 °C. The goal of this work was to understand microstructure formation during the two subsequent sintering processes by the analysis of nanometer-scale elemental distributions, crystal structures, and grain sizes of this extended cathode/electrolyte interface as a function of the GDC sintering temperature. Various representative regions on all samples were analyzed by transmission electron microscopy combined with energy dispersive X-ray spectroscopy with high spatial resol...

Preparation and application of novel bionanocomposite green membranes for gas separation

We report in this study the synthesis of thin-film bionanocomposite (BNC) membranes. In the presented study, at firstly, the synthesis and full characterization of new diamine and polyimide derived from amino acid (methionine) and benzimidazole fractions in the structure of pendant group are presented. Then, to improve the effect of surface modification, TiO2 was predisposed in ethanol via ultrasonic waves. Surface modification of TiO2 was conducted using 3-methacryloxypropyl-trimethoxysilane (MPS) under ultrasonic irradiation. The new BNC-containing chiral monomer (amino acid) is employed as a key monomer for the fabrication of a series of BNCs films with various TiO2 percentages under ultrasonic irradiation. The modified TiO2 presented good compatibility in PI matrix. The structures of the modified hybrid nanocomposites were identified with a FT-IR, whereas the size of the TiO2 in polyimides was characterized with a scanning electron microscope (SEM). SEM results indicated the formation and dispersion of nanometer scale size of inorganic domains inside the polyimide matrix due to the introduction of modified TiO2 and the interactions between organic and inorganic phases. The size of TiO2 particles in the modified system was about 25 nm. The transmission electron microscope analysis showing the well-dispersed nanosized titania NPs. Moreover, their thermal and mechanical properties exhibited a significant improvement. The studies on the optical properties of the hybrid films indicate redshift of the absorption band that increased with increased TiO2 content. The high TiO2, content in PI/TiO2, nanocomposite membranes resulted in the great enhancement of gas separation performance of the TiO2 polyimide nanocomposite materials compared with polyimide. When the TiO2, content in PI/TiO2, composite membranes was above 10 wt%, the permeability of the PI/TiO2 composite membranes was remarkably enhanced and the selectivity of PI/TiO2 composite membranes remained at a high level.

Anisotropic grain growth kinetics in nanocrystalline nickel

ABSTRACTIntriguing properties exhibited by nanocrystalline metals, including a high level of mechanical strength, arise from their nanometer-scale grain sizes. It is critical to determine the evolution of grain size of nanocrystalline materials at elevated temperature, as this process can drastically change the mechanical properties. In this work, a nanocrystalline Ni foil with grain size ∼ 25 nm was annealed in situ in an X-ray diffractometer. X-ray diffraction peaks were analysed to determine the grain growth kinetics. The grain growth exponents obtained were ∼ 2–4 depending upon the crystallographic direction, indicating the anisotropic nature of the grain growth kinetics.

Ramesh Shrestha, Sheng Shen and Maarten P. de Boer *

Because they can achieve a high degree of molecular chain alignment in comparison with their bulk counterparts, the mechanical and thermal properties of polymer nanofibers are of great interest. However, due to their nanometer-scale size, it is difficult to manipulate, grip, and test these fibers. Here, we demonstrate simple repeatable methods to transfer as-drawn fibers to micrometer-scale test platforms where their properties can be directly measured. Issues encountered and methods to minimize measurement artifacts are also discussed.

Fabrication and characterization of novel polyester thin‐film nanocomposite membranes achieved by functionalized SiO2 nanoparticles for gas separation

In this article, a new type of soluble polyester/silica (PE/SiO2) hybrid was prepared by the ultrasonic irradiation process. Surface modification of SiO2 was conducted using coupling agent γ‐glycidyloxypropyltrimethoxysilane (GOTMS) under ultrasonic irradiation. The structures of the modified hybrid nanocomposites were identified with a Fourier‐transform infrared spectroscopy (FT‐IR), whereas the size of the SiO2 in PE was characterized with a scanning electron microscope (SEM). SEM results indicated the formation and dispersion of nanometer scale size of inorganic domains inside the PE matrix due to the introduction of modified SiO2 and the interactions between organic and inorganic phases. The size of SiO2 particles in the modified system was about 25 nm. The transmission electron microscope (TEM) analysis showing the well‐dispersed nanosized titania nanoparticles (NPs). The densities and solubilities of the PE/SiO2 hybrids were also measured. Furthermore, thermal stability, residual solvent in the membrane film, and structural ruination of membranes were analyzed by thermal gravimetric analysis (TGA). Moreover, their mechanical properties were also characterized. It can be observed that the Young's moduli (E) of the hybrid films increase linearly with the silica content. The results obtained from gas permeation experiments showed that adding SiO2 to the PE membrane structure increased the permeability of the membranes. POLYM. ENG. SCI., 59:E237–E247, 2019. © 2018 Society of Plastics Engineers