Selected Area Electron Diffraction Images Research Articles

Biocompatible Fluorescent Graphene Oxide Quantum Dots for Imaging of Drosophila melanogaster.

Developing reliable biocompatible bioimaging agents is paramount for diagnosing critical diseases and disorders early through oral ingestion of fluorescent probes to image living organisms. Here, we prepared fluorescent, water-dispersed graphene oxide quantum dots via pyrolysis of a Glycyrrhiza glabra root in the water medium using a cost-effective and environmentally benign method to enable Drosophila melanogaster, an organism analogous to the human genome, to be imaged alive. The prepared graphene oxide quantum dots demonstrated a 2.6 nm diameter and 0.36 nm graphitic spacing with carboxylic acid, carbonyl, and hydroxyl functionalities. The selected area electron diffraction image analysis reveals a series of bright circular patterns that confirm the crystalline nature of the graphene oxide quantum dots. Raman and X-ray diffraction analyses also validate the crystallinity nature of prepared materials. The graphene oxide quantum dots exhibited blue fluorescence under ultraviolet-light irradiation with excitation-dependent emission properties from blue to red emission. The synthesized graphene oxide quantum dots consistently fluoresce in the larva-fed graphene oxide quantum dots without exhibiting toxicity. The current study evaluates the toxic effect of synthesized fluorescent graphene quantum dots by examining several screening and staining methods on D. melanogaster, a fruit fly, as a model.

Structural, optical and giant dielectric constant properties of pure ktenasite and schulenbergite/CuO minerals

In this study, schulenbergite [(Cu,Zn)7(SO4)2(OH)10·3H2O)]/CuO and pure ktenasite [(Cu,Zn)5(SO4)2(OH)6·6H2O)] minerals were simply synthesized via addition of sodium sulfide (Na2S) to a mixture of nanosized CuO powder dispersed into Zn(NO3)2·6H2O solution. The X-ray diffraction patterns illustrate the formation of schulenbergite/CuO mineral with ratio of 69:31% and 87/13% owing to additions of 0.1 and 0.2 mol L−1 Na2S, respectively. The addition of 0.4 mol L−1 Na2S substance lead to formation of pure ktenasite [(Cu,Zn)5(SO4)2(OH)6·6H2O)] mineral. The absorption vibration modes based on Fourier-transform infrared (FTIR) analysis verified the formation of schulenbergite/CuO and pure ktenasite compositions. The scanning electron microscope micrographs of schulenbergite/CuO and pure ktenasite samples reveal the formation of mixed grains with needle, sheets, cotton and wool shapes. The selected area electron diffraction images of the synthesized powders show strong dot-rings, indicating polycrystalline nature. Optically, all samples possess a high absorption ability for infrared-visible light wavelengths. At lower frequencies, the pellet of pure ktenasite sample exhibits giant dielectric constant characteristics. Exactly, pure ktenasite sample reveals a dielectric constant value of ~ 1.3 × 106 at frequency of 42 Hz. For schulenbergite/CuO (87/13%) sample, a large dielectric constant value of ~ 5311 was measured at frequency of 42 Hz. The colossal and variable relative permittivity values make the pure ktenasite [(Cu,Zn)5(SO4)2(OH)6·6H2O)] mineral is a suggested material for energy storage applications.

Effects of Heat Treatment in Air Atmosphere on Dip Coating Deposited CdS Thin Films for Photo Sensor Applications

Objective: In this report, photo sensitive materials with enhanced charge carriers have been prepared using dip coating technique. Methods: Cadmium sulphide (CdS) is N-type semiconductor compound belonging to II-VI group. CdS nanoparticles were synthesized using non-aqueous chemical method and characterized by ultraviolet-visible (UV-Vis) absorption spectroscopy, photoluminescence (PL) and transmission electron microscopy. CdS films were deposited on fluorine doped tin oxide (FTO) glass slides using dip coating method at different dip times and heat treated in air and analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis by X-rays (EDAX), mapping and atomic force microscopy (AFM). Results: Quantum confinement effect was observed in UV-Vis absorption spectra of CdS nanoparticles. Quenching of luminescence intensity and blue shift at smaller wavelengths were observed in PL spectra. Presence of highly dense rectangular shaped grains in CdS films and increment in particle sizes with increase in dip time were shown by AFM images. Selected area electron diffraction images showed ring patterns indicating polycrystalline nature of CdS nanoparticles. Increase in crystallite size and decrease in crystal defects by heat treatment in air and increment in grain size with increase in dip time were shown by SEM images. XRD analysis of CdS films showed polycrystalline nature. Conclusion: In previous work, preparation of dip coating deposited CdS films on FTO glass substrates for optoelectronic device applications such as photo sensors has not been reported. In this study, I-V characteristics of heterojunctions under dark and illumination conditions were discussed. Experimental results obtained in our study and their comparison with previous reports were also discussed.

Demonstration of Bixbyite-Structured δ-Ga2O3 Thin Films Using β-Fe2O3 Buffer Layers by Mist Chemical Vapor Deposition

Gallium oxide (Ga2O3) possesses five polymorphs: α, β, γ, κ (ε), and δ. Although the first four polymorphs have been well-studied, there are few reports on δ-Ga2O3. Here, we demonstrate the epitaxial growth of metastable δ-Ga2O3 thin films by mist chemical vapor deposition using β-Fe2O3 buffer layers. X-ray diffraction (XRD) 2θ–ω scan pattern revealed that (004) κ-Ga2O3 grew on (111) yttria-stabilized zirconia (YSZ) without a buffer layer or with a bcc-In2O3 buffer layer, whereas (222) δ-Ga2O3 grew on (222) β-Fe2O3. The β-Fe2O3 buffer layer led to the epitaxial growth of the δ-Ga2O3 thin film. The lattice mismatch between the equivalent crystal structures of β-Fe2O3 and δ-Ga2O3 triggered this growth. XRD analysis shows that δ-Ga2O3 grew epitaxially on the β-Fe2O3 buffer layer/YSZ substrate in both the out-of-plane and in-plane orientations, and the lattice constant inferred from the diffraction peaks was estimated to be 9.255 Å. Reciprocal space mapping results indicated that the δ-Ga2O3 grown on β-Fe2O3 was fully relaxed. Selected area electron diffraction images confirmed that the δ-Ga2O3 exhibited a cubic bixbyite structure. The optical band gap of δ-Ga2O3 was 4.3 or 4.9 eV, as calculated from reflection electron energy loss spectroscopy. We successfully grew a δ-Ga2O3 epitaxial thin film for the first time.

Edge-Plane Exposed N-Doped Carbon Nanofibers Toward Fast K-Ion Adsorption/Diffusion Kinetics for K-Ion Capacitors

Sluggish kinetics severely limit the development of potassium-ion hybrid capacitors (PIHCs). Exposing active sites is recognized as an ideal strategy to resolve this issue, but the corresponding ma...

Optical and highly enhanced solar light-driven photocatalytic activity of reduced graphene oxide wrapped α-MoO3 nanoplates

Herein, we prepared reduced graphene oxide (rGO) wrapped Molybdenum trioxide (MoO3) nanoplates through direct precipitation followed by a post-annealing method. Morphologies of the prepared samples were identified by field emission scanning electron microscopy and high-resolution transmission electron microscopy along with selected area electron diffraction images. Optical absorption spectra of the samples were deconvoluted by Lorenztian multiple peak fitting and discussed using crystal field theory. The observed strong violet emission under 330 nm excitation was explained by the molybdenum interstitials defects. Moreover, the prepared materials have been used to degrade the Methylene blue dye under the sun light illumination. The 30 mg of rGO loading was completely wrapped over MoO3 and shows better photocatalytic efficiency than the MoO3. The wrapping of rGO over MoO3 was not only promote the separation of photo induced electrons and holes but also it protect the MoO3 nanoplates from the dissolution. The improvement in the catalytic activity is explained by the photogenerated electron transfer at the interface leads to the electron-hole recombination delay in the rGO wrapped MoO3 nanoplates composites.

Investigation of microstructure and temperature and frequency dependent dielectric relaxation of Molybdenum-zinc-selenite glass nanocomposite systems

Transition metal oxide doped glass nanocomposite bulk samples of the composition xMoO3–(1-x) (0.5ZnO–0.5SeO2), for x = 0.05, 0.1, 0.2 and 0.3 weight percent, have been developed via the process of slow cooling of the melt. The dependency of dielectric properties on temperature and frequency has been studied. Using transmission electron microscopy (TEM) micrographs, the growth of nanocrystallites and their lattice fringes have been noticed and selected area electron diffraction images have as well been observed. The results of the differential scanning calorimetric (DSC) process describe the thermal property of these compositions. The dielectric constant (ε/) and dielectric loss (ε//) value increases with the increment in temperature and reduces as frequency increases considerably. The dynamic conductivity relaxation process is non-Debye type as Kohlrausch stretching exponent (β) value is not equal to unity and obtained relaxation time shows Arrhenius behavior. The scaled electric okmodulus (complex) spectra discloses that the dynamic conductivity relaxation process depends on the composition but does not depend on temperature.

The effect of Nd8Cu2 alloy on the microstructure and magnetic properties of (Nd, MM)-Fe-B sintered magnets

Abstract Multi-main-phase (MM0.3Nd0.7)-Fe-B (MM = Misch Metal) magnets were prepared by sintering the mixture of Nd-Fe-B and MM-Fe-B powders. In order to further enhance the coercivity of the magnet, Nd8Cu2 eutectic alloy powders were added to the magnets as a variable. When the addition of the Nd8Cu2 powders increases from 0 to 5 wt%, the Hcj of the magnets increases by 56.8% (7.01–10.99 kOe). Microstructural investigations show that after the addition of 5 wt% Nd8Cu2 powders, the thickness of continuous grain boundary layers are over 2.1 nm, which effectively block the short-range exchange coupling between adjacent grains, contributing to the improvement of Hcj. The Selected Area Electron Diffraction images show that the Cu exists in the form of NdCu2 in the grain boundary layers.

Quantitative study of the effect of stress on the precipitation in an Al-Cu-Mg-Ag alloy single crystal

Al-1.96Cu-0.24Mg-0.18Ag alloy single crystal with (2¯15) plane orientation has been used to investigate the effect of external stresses (50, 100, 134, 160 and 200 MPa) on the precipitation behavior of Ω, θ′ and S precipitates. The microstructure of the aged specimens was observed by transmission electron microscopy (TEM), selected area electron diffraction (SAED) and scanning transmission electron microscopy (STEM). X-ray elemental mapping under high-angle annular dark-field (HAADF) was used to analyze the elements in the precipitates. TEM images showed that the amount and distribution of the three types of precipitates are different in specimens aged under different external stresses. Along with the SAED and STEM images, the type, amount and distribution of Ω, θ′ and S precipitates were quantitatively measured. Compared to the results on stress-free aged specimen, the amount of Ω precipitates decreases in stress aged samples, while that of the S precipitates increases, and the amount of θ′ precipitates is constant with low value. The orienting effect of stress on Ω precipitates gets serious at 100 MPa, but it decreases at 200 MPa. The orienting effect of stress on S precipitates is quite similar to that in the case of the Ω phase. As the competition of acquiring Mg and Cu atoms between S and Ω precipitates, the orienting effect of stress on S precipitates is serious from 100 to 160 MPa. Both the orienting effect of stress on Ω and S precipitates decreased because of the inhibiting effect of dislocations at 200 MPa. The orienting effect on θ′ variants is different from that of Ω precipitates. It is serious at 50 MPa and gets weaker at 100–200 MPa.

ENHANCED UV EMISSION IN YTTRIUM-DOPED ZnS NANOPARTICLES SYNTHESIZED BY PRECIPITATION METHOD

This paper deals with the effect of yttrium doping on the structural and optical properties of zinc sulphide (ZnS) nanoparticles with nanoparticulated mesoporous. The morphology of the nanoparticles is determined by FESEM and it shows that the particles are spherical shape. HRSEM images show that particle size and agglomerated nature of the samples are augmented when doping concentration increases. Transmission electron microscope images probe the spherical shape of the nanoparticles as well as small number of inter particle mesoporous with intra-particles. The selected area electron diffraction images validate the crystalline and cubic nature of the synthesized samples. The presence of intra-particles is corroborated by XRD and FTIR spectra. X-ray diffraction’s results also confirm that the synthesized nanoparticles are crystallized in zinc blende structure. The diffuse reflectance spectra indicate that 5[Formula: see text]wt.% of yttrium-doped zinc sulphide shows higher reflectance than the undoped ZnS. Thus photoluminescence studies suggest that 5[Formula: see text]wt.% of yttrium-doped ZnS sample may be used for the development of supersensitive ultraviolet detector.

A simple hydrothermal route for the low-temperature processing of nanocrystalline TiO2

Well-shaped pure anatase TiO2 nanocrystals were successfully synthesized using an indirect approach by hydrolysis of titanium n-butoxide in 2-propanol, 2-butanol, and 2-pentanol. TiO2 nanocrystals formed without any auxiliary reactants or surfactants at a temperature as low as 200 °C using a simple hydrothermal-assisted sol–gel processing method. The effect of the chain length of alcohol on the degree of crystallinity, particle size, porosity, and pore size was investigated by low-angle and wide-angle X-ray diffraction (XRD), scanning electron microscope, energy-dispersive X-ray, transmission electron microscopy, high-resolution transmission electron microscopy (HR-TEM), selected-area electron diffraction (SAED), and N2 adsorption–desorption analyses. XRD techniques confirmed the crystalline nature and mesostructure of the as-prepared samples. HR-TEM images for the prepared sample in 2-propanol (Ti-1) which is obtained without any calcination show the well-crystallized structure having equilateral hexagonal shape and uniform size. In accordance with XRD data, SAED image shows distinct electron diffraction rings of the set of interplanar distances which could be indexed to the tetragonal phase of TiO2.

Nitrogen-Incorporated SBA-15 Mesoporous Molecular Sieve Supported Palladium for Solvent-Free Aerobic Oxidation of Benzyl Alcohol

Palladium catalysts supported on nitrogen-incorporated SBA-15(SBA-15-N) prepared using sol-immobilization are found to be highly efficient and reusable catalysts for the solvent-free oxidation of benzyl alcohol using molecular oxygen under low pressure. The samples were characterized by XRD, N2 adsorption- desorption, ICP, EA, FTIR, Pyridine-IR and TEM techniques. The results indicated that nitrogen was incorporated into the SBA-15 framework, and the nitridation treatment was an alternative and effective way to modify the properties of the SBA-15 for immobilizing Pd. It was supposed that the interaction between the surface-NHx groups and Pd precursors was the key to immobilizing Pd. The catalyst displayed an obvious improvement in catalytic activity, showing a high selectivity of benzyl alcohol oxidation. The 2 %Pd/SBA-15-900 N catalyst also can be readily recovered and reused at least five consecutive cycles without significant leaching and lose its catalytic activity. Selected area electron diffraction image of 2 %Pd/SBA-15-900 N

Structural – Electrical property correlation in defect induced nanostructured off-stoichiometric bismuth ferrite: A defect analysis

In order to increase magnetization, an attempt has been made to synthesize nanostructured bismuth ferrite using high energy planetary ball milling (HEPBM). In this process local heating in HEPBM and Bi-volatility has eventually led to the formation of BiFe5O12 (off stoichiometric bismuth iron garnet (BIG)). Electrical characterization has been done in order to identify the nature of defects and diffusion mechanism which has been supported by high resolution transmission electron microscopy and selected area electron diffraction images. The simultaneous analysis of current density-applied voltage (J–V) and current density-frequency (J–ν) curves gives insight mechanism for defect formation and how surface charge density depends on relaxation time and frequency of field applied.

Deformation microstructures of glaucophane and lawsonite in experimentally deformed blueschists: Implications for intermediate‐depth intraplate earthquakes

AbstractA series of simple‐shear experiments on blueschist was performed at 400–500°C and 1–2.5 GPa to understand the deformation of seismically active, subducting oceanic crust. The experiments show that brittle microstructures are mainly found at pressures of 1–2 GPa, whereas ductile microstructures form at 2.5 GPa. J‐indices (a measure of fabric intensity) of glaucophane crystal preferred orientations change systematically with changing shear strain and confining pressure, and the angle between the slip plane and the shear direction of samples deformed at >2 GPa is similar to that of a strain ellipsoid. These results, together with the variable orientations of fine grains in a selected area electron diffraction image at 2 GPa, indicate that the brittle–ductile transition for glaucophane occurs at ~2 GPa. In contrast to this, lawsonite in the experiments show abundant fracturing in most specimens and a poor correlation between the J‐index, shear strain, and confining pressure. This demonstrates that lawsonite deformed by brittle failure under all experimental conditions. In the case of a starting material that has a strong fabric and deformed under dry experimental conditions, the brittle–ductile transition zone of glaucophane will be much shallower than 2 GPa. Therefore, our initial experimental results on the deformation behavior of blueschist indirectly support the dehydration embrittlement of subducting oceanic crust (glaucophane) as an important factor in the origin of intraplate earthquakes.

U(VI) behaviour in hyperalkaline calcite systems

The behaviour of U(VI) in hyperalkaline fluid/calcite systems was studied over a range of U(VI) concentrations (5.27×10−5μM to 42.0μM) and in two high pH systems, young and old synthetic cement leachate in batch sorption experiments. These systems were selected to be representative of young- (pH 13.3) and old-stage (pH 10.5) leachate evolution within a cementitious geological disposal facility. Batch sorption experiments, modelling, extended X-ray absorption fine structure spectroscopy, electron microscopy, small angle X-ray scattering and luminescence spectroscopy were used to define the speciation of U(VI) across the systems of study. At the lowest concentrations (5.27×10−5μM 232U(VI)) significant U removal was observed for both old and young cement leachates, and this was successfully modelled using a first order kinetic adsorption modelling approach. At higher concentrations (>4.20μM) in the young cement leachate, U(VI) showed no interaction with the calcite surface over an 18month period. Small angle X-ray scattering techniques indicated that at high U concentrations (42.0μM) and after 18months, the U(VI) was present in a colloidal form which had little interaction with the calcite surface and consisted of both primary and aggregated particles with a radius of 7.6±1.1 and 217±24Å, respectively. In the old cement leachate, luminescence spectroscopy identified two surface binding sites for U(VI) on calcite: in the system with 0.21μM U(VI), a liebigite-like Ca2UO2(CO3)3 surface complex was identified; at higher U(VI) concentrations (0.42μM), a second binding site of undetermined coordination was identified. At elevated U(VI) concentrations (>2.10μM) in old cement leachate, both geochemical data and luminescence spectroscopy suggested that surface mediated precipitation was controlling U(VI) behaviour. A focused ion beam mill was used to create a section across the U(VI) precipitate–calcite interface. Transmission electron microscope images of the section revealed that the calcite surface was coated with a nano crystalline, U containing phase. Selected area electron diffraction images of the U precipitate which was formed at a U(VI) concentration of 4.20μM were consistent with the formation of calcium uranate. XAS spectroscopy at higher concentrations (⩾21.0μM) suggested the formation of a second U(VI) phase, possibly a uranyl oxyhydroxide phase.These results indicated that in the young cement leachate, U(VI) did not react with the calcite surface unless U(VI) concentrations were very low (5.27×10−5μM). At higher concentrations, speciation calculations suggested that U(VI) was significantly oversaturated and experimental observations confirmed it existed in a colloidal form that interacted with the mineral surface only weakly. In the old cement leachate systems at low concentrations batch sorption and luminescence data suggested that U(VI) removal was being driven by a surface complexation mechanism. However, at higher concentrations, spectroscopic methods suggest a combination of both surface complexation and surface mediated precipitation was responsible for the observed removal. Overall, U(VI) behaviour in hyperalkaline calcite systems is distinct from that at circumneutral pH conditions: at high pH and anything but low U(VI) concentrations, a surface mediated precipitation mechanism occurs; this is in contrast to circumneutral pH conditions where U(VI) surface complexation reactions tend to dominate.

Determination of the crystal structure of U6Fe5Al8Si9 by electron crystallography

The crystal structure of U6Fe5Al8Si9 was re-determined by electron crystallography, using selected area electron diffraction (SAED) and high resolution (HRTEM) images, taken along the [001] direction. The obtained results are very similar to those found previously by X-ray powder diffraction. The differences between the atomic positions found by SAED and HRTEM images and those found by X-ray powder diffraction were 0.11 and 0.08Å, respectively.

Solid–solid and gas–solid interactions induced during high-energy milling to produce PbTe nanopowders

Transformations from precursors to nanoparticles by high-energy milling are promoted by two major driving forces, namely physical and/or chemical. While the former has been difficult to trace since stress, strain and recovery may occur almost simultaneously during milling, the latter has been sequentially followed as an evolution from precursors to intermediate phases and thereof to high purity nanocrystals. The specific objective of this work is to discern how solid–solid and partially solid–gas reactions manifest themselves correspondingly as a short-range diffusion through an interface or how vapor species, as a subliming phenomenon, grows as a different phase on an active local surface. These series of changes were traced by sub-cooling the as-milled powders extracted during a milling cycle. Through this experimental technique, samples were electron microscopically analyzed and where it was required, selected area electron diffraction images were obtained. High-resolution transmission electron microscopy results, unambiguously, confirm that nanocrystals in the last stage show a cubic morphology which average size distributions are around 17 nm.

Synthesis and characterization of crystalline carbon nitride nanowires

Carbon nitride nanowires were synthesized by thermal nitridation of multiwalled carbon nanotubes in a horizontal tube furnace. Scanning electron microscopy and transmission electron microscopy images revealed the large-scale formation of nanowires. Selected-area electron diffraction images and high-resolution transmission electron microscopy images show that the as-synthesized nanowires grow preferentially along the [110] direction, with diameters of 15 to 100 nm and lengths from several tens of micrometers to several millimeters. Here, the growth mechanism of these nanowires is proposed.

Characteristics of La 2CaB 10O 19 crystallization from glass

The characteristics of La 2CaB 10O 19 (LCB) crystallization from a La 2O 3–CaO–B 2O 3 glass were studied. The crystal growth rate ( U) was estimated from the crystalline layer thicknesses to obtain the activation energy for growth ( E G), which was found to be 418 kJ/mol. The activation energy for overall crystallization ( E), obtained from non-isothermal differential thermal analysis (DTA) by the methods of Kissinger and Ozawa, was in the range of 398–417 kJ/mol. A comparison of the activation energies showed that E ≅ E G. X-ray diffraction (XRD) patterns, light microscopy images and second harmonic generation tests, confirmed that LCB is the dominant phase crystallizing from the glass. Nucleation-rate type curves derived from DTA measurements showed that the annealed glass behaved as a nuclei site-saturated matrix. Transmission electron microscopy and selected area electron diffraction images of fine glass powders indicated the presence of crystalline clusters of 30–50 nm, which are related to the phases detected by XRD. The crystallization of LCB from the glass was characterized by a growth process from a nuclei site-saturated matrix and could be analyzed by the Johnson-Mehl-Avarmi kinetic model.

CHROMATICITY DEPENDENCE ON Eu CONCENTRATION IN Y2O3:Eu NANOPOWDERS

Y2O3:Eu nanopowders were synthesized by urea combustion method containing different concentration of Eu . The synthesized Y2O3:Eu nanopowders were characterized by X-ray diffractometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), energy dispersive X-ray analysis (EDX) and photoluminescence spectroscopy (PL). The particle size was calculated to be in the range of 15–30 nm using Scherrer's formula. The Ia-3 structure of synthesized Y2O3:Eu nanopowders were confirmed with X-ray diffractometry. The crystallinity of Y2O3:Eu nanopowders were confirmed by SAED and TEM images. The 5D0–∑7F J (J = 0, 1, 2, 3) and 5 D 1–7 F 1 transitions bands were observed at 575–650 and 530–550 ranges in the photoluminescence spectrum. The concentration quenching was estimated to be about 5 mol% of Eu . The best chromaticity to the standard red color was observed with the sample containing 3 mol% of Eu .