High-resolution Electron Microscopy Analysis Research Articles

High Spatial and Energy Resolution Analytical Scanning Transmission Electron Microscopy for Quantum Materials

High Spatial and Energy Resolution Analytical Scanning Transmission Electron Microscopy for Quantum Materials

Enhanced generation of intraluminal vesicles in neuronal late endosomes in the brain of a Down syndrome mouse model with endosomal dysfunction

Down syndrome (DS) is a human genetic disease caused by trisomy of chromosome 21 and characterized by early developmental brain abnormalities. Dysfunctional endosomal pathway in neurons is an early event of DS and Alzheimer's disease. Recently, we have demonstrated that exosome secretion is upregulated in human DS postmortem brains, in the brain of the trisomic mouse model Ts[Rb(12.1716 )]2Cje (Ts2) and by DS fibroblasts as compared with disomic controls. High levels of the tetraspanin CD63, a regulator of exosome biogenesis, were observed in DS brains. Partially blocking exosome secretion by DS fibroblasts exacerbated a pre-existing early endosomal pathology. We thus hypothesized that enhanced CD63 expression induces generation of intraluminal vesicles (ILVs) in late endosomes/multivesicular bodies (MVBs), increasing exosome release as an endogenous mechanism to mitigate endosomal abnormalities in DS. Herein, we show a high-resolution electron microscopy analysis of MVBs in neurons of the frontal cortex of 12-month-old Ts2 mice and littermate diploid controls. Our quantitative analysis revealed that Ts2 MVBs are larger, more abundant, and contain a higher number of ILVs per neuron compared to controls. These findings were further corroborated biochemically by Western blot analysis of purified endosomal fractions showing higher levels of ILVs proteins in the same fractions containing endosomal markers in the brain of Ts2 mice compared to controls. These data suggest that upregulation of ILVs production may be a key homeostatic mechanism to alleviate endosomal dysregulation via the endosomal-exosomal pathway.

Structural and optical properties of synthesized poly(methyl methacrylate) (PMMA) and lanthanide $$\upbeta $$-diketonate complexes incorporated electrospun PMMA nanofibres for optical devices

Fabrication of electrospun nanofibres is the glittering area of research because of their flexible characteristics and numerous applications in almost all walks of life and technology. Poly(methyl methacrylate) (PMMA) is one of the significant and interested synthetic polymers in the recent research because of their characteristic properties like higher environmental stability, resistance to attack by moulds and enzymes, commercial availability, easiness to handle, etc. In the present study, pristine PMMA nanofibres with diameters of 60–150 nm with 109 nm as the most distributed one are prepared by an electrospinning method using a binary solvent mixture. An enhancement in the intensity of visible photoluminescence emission is observed in PMMA nanofibres embedded with samarium and neodymium $$\upbeta $$ -diketonate complexes. The morphological incorporation of samarium and neodymium $$\upbeta $$ -diketonate complexes in PMMA nanofibres and material composition of the samples are examined by high resolution electron microscopy analyses. The amorphous nature and molecular bonding of pure PMMA nanofibres and incorporated fibre complexes are elucidated through structural and molecular analyses. The supreme optical absorptions and reemissions of samarium and neodymium $$\upbeta $$ -diketonate complexes embedded in the pure PMMA fibre sample in the visible region indicate not only their application in lighting or display devices, but also as active materials in organic light emitting diodes for new era curved/rolled display devices. Ultrafine poly(methyl methacrylate) (PMMA) nanofibres and those incorporated with the prepared lanthanide complexes are also prepared by an electrospinning method. An enhancement in the intensity of visible photoluminescence emission is observed in PMMA nanofibres embedded with samarium and neodymium $$\upbeta $$ -diketonate complexes. The supreme optical absorptions and reemissions of samarium and neodymium $$\upbeta $$ -diketonate complexes embedded in the pure PMMA fibre sample in the visible region indicate not only their application in lighting or display devices but also as active materials in organic light emitting diodes for new era curved/rolled display devices.

APC/C: current understanding and future perspectives.

The separation of sister chromatids at anaphase, which is regulated by an E3 ubiquitin ligase called the anaphase-promoting complex/cyclosome (APC/C), is arguably the most important irrevocable event during the cell cycle. The APC/C and cyclin-dependent kinase 1 (Cdk1) are just two of the many significant cell cycle regulators and exert control through ubiquitylation and phosphorylation, respectively. The temporal and spatial regulation of the APC/C is achieved by multiple mechanisms, including phosphorylation, interaction with the structurally related co-activators Cdc20 and Cdh1, loading of distinct E2 ubiquitin-conjugating enzymes, binding with inhibitors and differential affinities for various substrates. Since the discovery of APC/C 25 years ago, intensive studies have uncovered many aspects of APC/C regulation, but we are still far from a full understanding of this important cellular machinery. Recent high-resolution cryogenic electron microscopy analysis and reconstitution of the APC/C have greatly advanced our understanding of molecular mechanisms underpinning the enzymatic properties of APC/C. In this review, we will examine the historical background and current understanding of APC/C regulation.

One-Step Fabrication of GeSn Branched Nanowires

We report for the first time the self-catalyzed, single-step growth of branched GeSn nanostructures by a vapor–liquid–solid mechanism. These typical GeSn nanostructures consist of ⟨111⟩-oriented, Sn-rich (∼8 atom %) GeSn “branches” grown epitaxially on GeSn “trunks”, with a Sn content of ∼4 atom %. The trunks were seeded from Au0.80Ag0.20 nanoparticles followed by the catalytic growth of secondary branches (diameter ∼ 50 nm) from the excess of Sn on the sidewalls of the trunks, as determined by high-resolution electron microscopy and energy-dispersive X-ray analysis. The nanowires, with ⟨111⟩-directed GeSn branches oriented at ∼70° to the trunks, have no apparent defects or change in crystal structure at the trunk–branch interface; structural quality is retained at the interface with epitaxial crystallographic relation. The electrochemical performance of these highly ordered GeSn nanostructures was explored as a potential anode material for Li-ion batteries, due to their high surface-to-volume ratio and increased charge carrier pathways. The unique structure of the branched nanowires led to high specific capacities comparable to, or greater than, those of conventional Ge nanowire anode materials and Ge1–xSnx nanocrystals.

The effects of intergranular carbides on the grain boundary oxidation and cracking in a cold-worked Alloy 600

Intergranular oxidation occurred in a cold-worked Alloy 600 after exposure to pressurized water reactor primary water. Micromechanical testing was conducted to study the process of intergranular cracking under the external loading. High-resolution analytical electron microscopy was conducted to characterize the microstructure and chemistry of the oxidized grain boundaries before and after the micromechanical testing. The matrix around the intergranular carbides was preferentially oxidized and Cr in the intergranular carbides diffused out to facilitate the formation of Cr-rich oxide. Cracks preferentially propagated along the oxide-matrix interfaces during the micromechanical tests. Intergranular carbides are assumed to increase cracking resistance after cold-working.

High-Resolution SEM and EDX Characterization of Deposits Formed by CH₄+Ar DBD Plasma Processing in a Packed Bed Reactor.

The deposits formed during the DBD plasma conversion of CH4 were characterized by high-resolution scanning electron microscopy (HRSEM) and energy dispersive X-ray elemental analysis (EDX) for both cases of a non-packed reactor and a packed reactor. For the non-packed plasma reactor, a layer of deposits was formed on the dielectric surface. HRSEM images in combination with EDX and CHN elemental analysis of this layer revealed that the deposits are made of a polymer-like layer with a high content of hydrogen (60 at%), possessing an amorphous structure. For the packed reactor, γ-alumina, Pd/γ-alumina, BaTiO3, silica-SBA-15, MgO/Al2O3, and α-alumina were used as the packing materials inside the DBD discharges. Carbon-rich agglomerates were formed on the γ-alumina after exposure to plasma. The EDX mapping furthermore indicated the carbon-rich areas in the structure. In contrast, the formation of agglomerates was not observed for Pd-loaded γ-alumina. This was ascribed to the presence of Pd, which enhances the hydrogenation of deposit precursors, and leads to a significantly lower amount of deposits. It was further found that the structure of all other plasma-processed materials, including MgO/Al2O3, silica-SBA-15, BaTiO3, and α-alumina, undergoes morphological changes. These alterations appeared in the forms of the generation of new pores (voids) in the structure, as well as the moderation of the surface roughness towards a smoother surface after the plasma treatment.

Synthesis and characterisation of bis(2 methyl-8-hydroxyquinoline) zinc nanoparticles for organic light emitting diode applications

ABSTRACTIn this paper, bis(2 methyl-8-hydroxyquinoline) zinc (Zn(mq)2) nanoparticles were synthesised at room temperature by a simple chemical precipitation method. The Zn(mq)2 nanoparticles were characterised by powder X-ray diffraction (PXRD) analysis to confirm the crystalline nature of the Zn(mq)2 nanoparticles. The morphology and the elemental composition of Zn (mq)2 nanoparticles were analysed by high-resolution scanning electron microscopy (HR-SEM) and energy dispersive X-ray analysis (EDAX). The functional groups of the compound were studied with the help of Fourier transform infrared spectroscopy (FTIR) and FT Raman spectroscopy. Further, Zn (mq)2 nanoparticles were characterised by C-13 NMR spectroscopy, mass spectroscopy and CHN analysis. The thermal stability of the particles was studied using TG-DSC curve. The optical properties of the particles were studied by means of UV–Visible spectroscopy. The luminescence property of the synthesised particles was observed from the photoluminescence spectrum to confirm the possible application in organic light emitting diode.

Graphene Oxide Decorated Nanometal-Poly(Anilino-Dodecylbenzene Sulfonic Acid) for Application in High Performance Supercapacitors.

Graphene oxide (GO) decorated with silver (Ag), copper (Cu) or platinum (Pt) nanoparticles that are anchored on dodecylbenzene sulfonic acid (DBSA)-doped polyaniline (PANI) were prepared by a simple one-step method and applied as novel materials for high performance supercapacitors. High-resolution transmission electron microscopy (HRTEM) and high-resolution scanning electron microscopy (HRSEM) analyses revealed that a metal-decorated polymer matrix is embedded within the GO sheet. This caused the M/DBSA–PANI (M = Ag, Cu or Pt) particles to adsorb on the surface of the GO sheets, appearing as aggregated dark regions in the HRSEM images. The Fourier transform infrared (FTIR) spectroscopy studies revealed that GO was successfully produced and decorated with Ag, Cu or Pt nanoparticles anchored on DBSA–PANI. This was confirmed by the appearance of the GO signature epoxy C–O vibration band at 1040 cm−1 (which decreased upon the introduction of metal nanoparticle) and the PANI characteristic N–H stretching vibration band at 3144 cm−1 present only in the GO/M/DBSA–PANI systems. The composites were tested for their suitability as supercapacitor materials; and specific capacitance values of 206.4, 192.8 and 227.2 F·g−1 were determined for GO/Ag/DBSA–PANI, GO/Cu/DBSA–PANI and GO/Pt/DBSA–PANI, respectively. The GO/Pt/DBSA–PANI electrode exhibited the best specific capacitance value of the three electrodes and also had twice the specific capacitance value reported for Graphene/MnO2//ACN (113.5 F·g−1). This makes GO/Pt/DBSA–PANI a very promising organic supercapacitor material.

Greener synthesis of ZnO and Ag-ZnO nanoparticles using Silybum marianum for diverse biomedical applications.

To investigate the physical and biological properties of Silybum marianum inspired ZnO nanoparticles (NPs), Ag-ZnO heterostructures. Experiment: Nanoparticles were characterized using ultraviolet-visible and infrared spectroscopy, x-ray diffraction, high resolution electron microscopy, ζpotential and thermo-gravimetric analysis etc. Results: Ag-ZnO-NPs indicated slightly higher antimicrobial potential then ZnO-NPs. Good antileishmanial (IC50=246μg/ml for Ag-ZnO; 341μg/ml for ZnO) and antioxidant potential while moderate enzyme inhibition is reported. 2, 2-Diphenyl 1-picrylhydrazyl radical scavenging of Ag-ZnO was higher relative to ZnO-NPs. Nanocosmaceutical formulation of nanoparticles indicated stable antimicrobial performance. Biosynthesized nanoparticles indicated interesting biological properties and should be subjected to further research to establish their pharmacological relevance.

Triaxially uniform high-quality AlxGa(1−x)N (x ∼ 50%) nanowires on template free sapphire substrate

We have demonstrated the growth of high-quality AlxGa(1−x)N (x ∼ 50%) nanowires (NWs) for the first time on the sapphire substrate without using GaN NWs as the template, by plasma-assisted molecular beam epitaxy. Our newly developed process elucidates that depending on the substrate temperature and V/III ratio an AlGaN network is formed on sapphire substrate prior to the NWs growth. We find that the ledges of this kinked shaped network act as nucleation sites for the NW growth. The present observations suggest that availability of nucleation sites and higher substrate temperature during growth are the key parameters for the growth of homogeneous AlGaN NWs on the sapphire substrates. Energy dispersive x-ray spectroscopy, high-resolution transmission electron microscopy, Raman spectroscopy, x-ray diffraction, photoluminescence spectroscopy, and scanning electron microscopy analysis show that AlGaN NWs exhibit near-atomic scale compositional uniformity along the length as well as across the diameter.

Effects of an alloying element on a c-component loop formation and precipitate resolution in Zr alloys during ion irradiation

ABSTRACT It is important to clarify the mechanisms of the dislocation loop formation, dissolution of precipitates to understand the degradation behavior of the fuel cladding tubes in light water reactors (LWR) under neutron irradiation. In this study, 3.2 MeV Ni ion irradiation was carried out at 400°C on Zircaloy-2 and two types of model alloys with and without Fe (Zr-1.5Sn-0.3Fe and Zr-1.5Sn). To understand the effects of hydrogen, 60 and 300 ppm pre-injected Zircaloy-2 samples were also irradiated. The microstructure was observed with a conventional transmission electron microscopy. Additionally, the dissolution of precipitates and the enrichment of the alloying element due to irradiation were analyzed using a spherical aberration (Cs)-corrected high-resolution analytical electron microscope. After ion irradiation at 400°C, the dissolution of Fe-enriched precipitates and the c-component dislocation loops were observed in the region of peak ion damage. Observations by STEM-EDS showed that Fe atoms were enriched in the c-component dislocation loops. On the contrary, the c-component dislocation loops were detected in Fe-containing alloys (Zircaloy-2 and Zr-1.5Sn-0.3Fe alloy) but were not in the Zr-1.5Sn alloy. These results indicate that the dissolution of Fe-enriched precipitates and the enhanced formation of c-component dislocation loops are essential for the degradation of LWR fuel cladding under irradiation.

Synthesis of Anisotropic Tin Monosulphide Nanoparticles Using Sn-Thiourea as a Single Molecular Precursor.

We report the synthesis of high quality tin sulphide nanoparticles from tetrathiourea tin(II) chloride complex as a single molecular precursor. Thiourea ligand was used in the preparation of the complex due to its low toxicity and thermal stability. The reaction conditions were changed (reaction time, reaction temperature and nature of surfactant) to obtain high quality SnS nanoparticles that varied in morphology and size. The metal to sulphur ratio (Sn:S::1:1) and purity were confirmed using energy dispersive X-ray analysis (EDX). Spherical and rod shapes were obtained with an average particle size of 92.79 nm, estimated from transmission electron microscopy (TEM) images. Highresolution electron microscopy and X-ray diffraction (XRD) analysis show that the as-synthesized SnS nanoparticles had a pure orthorhombic crystal phase, with lattice spacing of 3.27 and 0.32 nm, which were assigned to the (111) and (021) reflection planes. A strong quantum effect was evident from the far blue shifted optical direct and indirect band gaps of 1.77 and 1.52 eV, respectively.

Effect of an Fe(II)-modified trivalent chromium conversion process on Cr(VI) formation during coating of AA 2024 alloy

A trivalent chromium conversion coating formed in an Fe(II)-containing solution on AA2024 alloy has been investigated by high resolution analytical electron microscopy, ion beam analysis, Raman spectroscopy and electrochemical tests. It is shown that preferential oxidation of Fe(II) species by H2O2 at cathodic sites on the alloy surface suppresses the oxidation of Cr(III) species, hence reducing the Cr(VI) content of the coating. The addition of Fe(II) species has only minor influences on the general composition of the coating, the kinetics of coating growth and the corrosion protection of the alloy.

CHARGE TRANSPORT FEATURES IN THE COMPOSITE ANODES OF SOLID OXIDE FUEL CELLS: MICROSTRUCTURAL AND IN-SITU RAMAN SPECTROSCOPY ANALYSES

In this work, we carry out the high-resolution electron microscopy of microstructure of grains boundaries of anion and electronic conductors in composite Ni/YSZ anodes before and after study of the current–voltage characteristics of model SOFCs. We propose a mechanism of 2-stage reaction of hydrogen oxidation occurring in the vicinity of triplephase boundary of Ni/YSZ SOFC anodes. On the first stage, metallic nickel is oxidized to nickel oxide by oxygen anion coming from the solid electrolyte membrane. On the second one, hydrogen reduces nickel oxide to metallic nickel, and water is formed. Decrease of the Ni grains size in the vicinity of contact with anion conductor grains is shown to be the result of NiO nano-grains appearance and their consequent reduction to metallic Ni during SOFC operation. High-resolution electron microscopy analysis demonstrates the significant changes in microstructure of grains boundaries of anion and electronic conductors in composite Ni/YSZ anodes after application of load current to SOFC. Nano-sized NiO grains appear in near-boundary regions of Ni grains after current tests. Orientation alignment between YSZ and nano-sized NiO lattices is unambiguous evidence of epitaxial growth of nickel oxide at YSZ surface as on a substrate that is possible only as a result of oxygen anion transport from anion conductor YSZ to the metal surface during current passage through the solid oxide fuel cell. We study the chemical transformations in the electrochemical reaction zone in SOFC composite electrodes depending on the current density passing the SOFC by new “in-situ” Raman spectroscopy technique. Increase of the current passing is shown to lead to growth in the intensity of Raman peak connected with symmetric oscillations of CeO 2 group. We connect this result with the change of the cerium cations charge state from Ce 3+ to Ce 4+ and consider this to be direct proof of the charge transfer in composite anode via oxygen anion transfer.

Effect of Mercapto-Terminated Silane Treatment on Rheological and Mechanical Properties of Rice Bran Carbon-Reinforced Nitrile Butadiene Rubber Composites

This paper aims at correlating the silane treatment of rice bran carbon (RBC) in nitrile butadiene rubber (NBR) matrix with the rheological properties of RBC/NBR composites. The surface morphology and structure of RBC were characterized by X-ray diffraction, thermogravimetric analysis, high-resolution scanning electron microscopy (HR-SEM), Raman spectroscopy, and adsorption analysis. The RBC/NBR polymer-matrix composites were fabricated by using the latex compounding technique, based on the superior hydrophilic characteristics of RBC. The silane treatment process was conducted by in situ interfacial modification technique. The dispersion of RBC and the interfacial morphologies between the RBC and NBR matrix were confirmed by HR-SEM. The bonding mechanism was analyzed in detail by mechanical and dynamic rheological determinations. At the same filler concentration, the (3-mercaptopropyl) trimethoxysilane (MPTMS) treated composites exhibited stronger mechanical properties and higher storage modulus than original RBC/NBR composite, as the interfacial interaction via MPTMS connected RBC and NBR molecules was stronger than the interaction in RBC/NBR composites connected by hydrogen bonds and weaker π-π stacking.

Investigation of instability of M23C6 particles in F82H steel under electron and ion irradiation conditions

In order to clarify the instability of M23C6 in F82H steel under irradiation, both electron irradiation using a high voltage electron microscope (HVEM) and ion irradiation using an ion accelerator were performed. For the electron irradiation, in-situ observation under 2 MV electron irradiation and ex-situ high resolution electron microscopic (HREM) analysis were utilized to evaluate the response of M23C6 against irradiation. The temperature dependence of the irradiation induced instability of the carbide was first confirmed: 293 K < T < 573 K, by observation of lowering in contrast at the periphery of carbides, 698 K < T < 773 K, fragmentation at the interface between carbides and matrix, and at 773 K, formation and coarsening of new particles near the periphery of M23C6. HREM analysis showed the loss of the lattice fringe contrast at the pre-existing M23C6 precipitates at temperatures ranging from 473 to 773 K, indicating severe loss of crystallinity due to dissolution of the constituent atoms though irradiation-enhanced diffusion under the vacancy diffusion by the focused electron beam irradiation. For the ion irradiation, 10.5 MeV-Fe3+ ion was applied to bombard the F82H steel at 673 K to achieve the displacement damage of ≈20 dpa at the depth of 1.0 μm from surface. Cross-section TEM specimens were prepared by a focused ion beam technique. The shrinkage of carbide particles was observed especially near the irradiation surface. Besides, the lattice fringes at the periphery of carbide were observed in the irradiated M23C6 by the HREM analysis, which is different from that observed in the electron irradiation. It was clarified that the instability of M23C6 is dependent on the irradiation conditions, indicating that the flow rate of vacancy type defects might be the key factor to cause the dissolution of constituent atoms of carbide particles into matrix under irradiation.

Cosmogenic Substances in the Zhamanshin Crater

Using high-resolution analytical electron microscopy, heterogeneous fragments of cosmogenic substances, such as nickelphosphide Ni3P and the unnamed intermetallide ZnAl2, are detected for the first time for a large meteorite crater, the Zhamanshin circular structure. Due to the impossibility of simultaneous finding these phases in the same meteorite, an assumption is made on the cometary nature of the impactor of the Zhamanshin crater.

Reliable Multistate Data Storage with Low Power Consumption by Selective Oxidation of Pyramid-Structured Resistive Memory.

Multilevel data storage using resistive random access memory (RRAM) has attracted significant attention for addressing the challenges associated with the rapid advances in information technologies. However, it is still difficult to secure reliable multilevel resistive switching of RRAM due to the stochastic and multiple formation of conductive filaments (CFs). Herein, we demonstrate that a single CF, derived from selective oxidation by a structured Cu active electrode, can solve the reliability issue. High-quality pyramidal Cu electrodes with a sharp tip are prepared via the template-stripping method. Morphology-dependent surface energy facilitates the oxidation of Cu atoms at the tip rather than in other regions, and the tip-enhanced electric fields can accelerate the transport of the generated Cu ions. As a result, CF growth occurs mainly at the tip of the pyramidal electrode, which is confirmed by high-resolution electron microscopy and elemental analysis. The RRAM exhibits highly uniform and low forming voltages (the average forming voltage and its standard deviation for 20 pyramid-based RRAMs are 0.645 and 0.072 V, respectively). Moreover, all multilevel resistance states for the RRAMs are clearly distinguished and show narrow distributions within 1 order of magnitude, leading to reliable cell-to-cell performance for MLC operation.

Polyimide derived laser-induced graphene as adsorbent for cationic and anionic dyes

Laser-induced graphene (LIG) is fabricated on polyimide films directly by irradiation with a CO2 laser. This reagent-free method to synthesize graphene in a single step is applicable for many uses including water treatment technology. Here we demonstrated that LIG is an effective adsorbent for water treatment and observed removal of methylene blue (MB) and methyl orange (MO) from aqueous solutions. LIG powder was obtained by sonication of LIG that was scraped from polyimide films. Raman and X-ray diffraction analysis confirmed the graphene component in the material, while high-resolution scanning electron microscopy and atomic-force microscopy analysis indicated the presence of multilayered graphene sheets. LIG powder showed significant removal of MB and MO dyes from the aqueous solutions where hydrophobicity played an important role, but especially a high adsorption of the MB dye was seen. Adsorption of MB and MO on LIG followed a pseudo-second-order kinetic model and the maximum adsorption capacity (Freundlich) was 926 mg g−1 and 132 mg g−1, respectively. The adsorption process was fast and exothermic, which involved both π-π interaction and electrostatic forces as observed using Raman spectroscopy. The expedient solvent-free fabrication of LIG that is generated on surfaces might be an advantageous graphene-based adsorbent for water remediation.