Antibacterial action of lipidic nanoemulsions using atomic force microscopy and scanning electron microscopy on Escherichia coli

The present study demonstrates the mechanism of bactericidal effect rendered by cationic and non-cationic lipidic emulsions using atomic force microscopy (AFM) and scanning electron microscopy. The AFM images of treated Escherichia coli cells indicated the conformational alteration from rod-shaped bacteria to a fluid-flattened structure with the presence of pore in the centre of bacterium, indicating the cell lysis. Root mean square roughness increased substantially due to exposure of underlying rugose peptidoglycan layer when treated with non-cationized lipidic nanoemulsions (NCLE). The cationised-lipidic-emulsion (CLE) treated E. coli cells frequently showed division septa along the length of E. coli which was not visible in non-cationised treated bacterial cells. The enhanced adhesion between CLE and negatively charged bacteria leads to lesser time required to kill the bacteria as compared to NCLE.     

Quantitative characterization of clay dispersion in polypropylene-clay nanocomposites by combined transmission electron microscopy and optical microscopy

This paper presents a novel method to describe the microstructure of polymer/clay nanocomposites quantitatively. Based on the image analyses of transmission electron microscopy (TEM) and optical microscopy micrographs, two parameters, degree of dispersion (χ) and mean interparticle distance per unit volume of clay (λ_V) are proposed to describe the level of clay dispersion. The degree of dispersion gives the percentage of exfoliation, and λ_V is a measure of spatial separation between particles relative to clay loading. A polypropylene/clay system was chosen as an example to show the effects of processing conditions and biaxial stretching on clay dispersion using the proposed quantifiers. It provides insights into the ‘real’ clay dispersion using a combination of both microscopical and macroscopical aspects.     

Finestructures study of the diamond/titanium interface by transmission electron microscopy

It is well known that a TiC layer can be formed and should act as a buffer layer in diamond films deposited on Ti alloy. Through our cross-sectional investigation in HRTEM, a thin layer (20–30 nm) was first identified between the outermost diamond film and the inner reactive TiC layer adjacent to the substrate. This layer consists of numerous crystalline nanoparticles with grain sizes of 5–20 nm. Through electron nanodiffraction patterns combined with EDS and EELS analysis, these nanoparticles can be identified as a TiC_1−xO_x phase with a similar structure to cubic TiC. Besides, C atoms and O atoms in TiC_1−xO_x randomly occupy the vacancies of C in TiC. The thickness of this TiC_1−xO_x layer does not change significantly with increasing deposition time, and the diamond phase directly nucleates and grows on it.     

Three-dimensional atomic imaging of Y and (B12)13 clusters in YB56 by HREM and crystallographic image processing

The three-dimensional atomic image of YB₅₆ was obtained by inverse Fourier transformation of three-dimensional phases and amplitudes in three high-resolution images along [100], [110] and [111] of YB₅₆ crystals. After crystallographic image processing, the image directly showed the three-dimensional potential map of the crystal, which showed (B₁₂)₁₃ clusters and Y atom positions. The present method would be useful for three-dimensional structure analysis in nanoscale regions.     

Structural characterization of a Cu/MgO(001) interface using CS-corrected HRTEM

Epitaxial Cu(001) layers were deposited on MgO(001) substrates by magnetron sputtering and the atomic structure of the Cu-MgO interface was characterized by spherical aberration (C_S)-corrected high-resolution transmission electron microscopy (HRTEM). The interface structure and the misfit dislocation network were determined by imaging in both the <100> and <110> directions. The dislocation network was found to lie along the <100> directions with a Burgers vector of ½ a_Cu <100> deduced from HRTEM images and geometrical phase analysis. The dislocations do not fully accommodate the lattice mismatch, yielding residual stress at the interface and an elongation of the Cu lattice along the [001] direction.     

Observation of submicronic contacts and vias by scanning ion and electron microscopy

Scanning ion and electron microscopy of focused ion beam cross-sections has been used to observe 0·6 μm contacts and 0·7 μm vias of a 0·5 μm CMOS technology. Three different kinds of cross-sections have been tested to improve the observation quality. The comparison of images obtained with ions and electrons provides information on ion and electron contrast mechanisms. This technique has been used to identify very small defects in interconnection structures and to evaluate the 0·5 μm CMOS metallization process.     

Transmission electron microscopy/electron energy loss spectroscopy measurements and ab initio calculation of local magnetic moments at nickel grain boundaries

We have determined local magnetic moments at nickel grain boundaries using a transmission electron microscopy/electron energy loss spectroscopy method assuming that the magnetic moment of Ni atoms is a linear function of the L₃/L₂ (white-line ratio) in the energy loss spectrum. The average magnetic moment measured in the grain interior was 0.55 μ_B, which agrees well with the calculated magnetic moment of pure nickel (0.62 μ_B). The local magnetic moments at the grain boundaries increased up to approximately 1.0 μ_B as the mis-orientation angle increased, and showed a maximum around 50°. The respective enhancement of local magnetic moments at the Σ5 (0.63 μ_B) and random (0.90 μ_B) grain boundaries in pure nickel was approximately 14 and 64% of the grain interior. In contrast, the average local magnetic moment at the (111) Σ3 grain boundary was found to be 0.55 μ_B and almost the same as that of the grain interior. These results are in good agreement with available ab initio calculations.     

Visualization of battery materials and their interfaces/interphases using cryogenic electron microscopy

Future innovations and developments in advanced rechargeable batteries require atomic-scale observation and understanding of the failure mechanisms of secondary batteries. Unfortunately, battery chemistry is highly sensitive to air or moisture and cannot stand electron beam radiation at high dose rates essential for atomic-scale resolution, hence limiting the use of conventional electron or optical microscopes. Recently, cryogenic electron microscopy (cryo-EM) has shown that battery-sensitive materials and interface/interphases can be protected, stabilized, and imaged under cryogenic conditions, facilitating novel insights into key components and phenomena that have a substantial impact on the cell operation. Herein, we highlight the significance and essential role of cryo-EM in characterizing sensitive battery materials (such as Li/Na/K metal anodes, sulfur, lithiated silicon, etc.), key components and interfaces, and summarize the recent contributions and discoveries enabled by cryo-EM. The chemistries and evolving nanostructures at electrode/electrolyte interphase in various electrolytes (both solid and liquid), hosts, artificial interphases, and temperature ranges for lithium-based batteries, and beyond are discussed in detail. Finally, the conclusions and the perspectives on the future direction of cryo-EM in analyzing the battery materials and interfaces are briefly discussed. We believe that the insights and discoveries obtained from this characterizing tool will provide guidelines for developing energy materials with improved electrochemical performance.     

La0.7Ca0.3MnO3薄膜微观结构的HRTEM表征

利用透射电子显微镜研究了衬底温度600～800℃条件下采用脉冲激光法在(001)LaAlO3(LAO)衬底上制备的La0.7Ca0.3MnO3(LCMO)薄膜的微观结构。结果表明薄膜由大量柱状晶组成且与LAO衬底形成良好外延关系。LCMO薄膜与LAO衬底的取向关系可以描述为:(ⅰ)(100)f∥(001)s、[011]f∥[100]s;(ⅱ)(011)f∥(001)s、[100]f∥[100]s。LCMO显示层状畴结构,即在衬底上初始生长的薄膜为(ⅱ)型畴,在此之上生长的薄膜为(ⅰ)类和(ⅱ)类型畴的混合体。薄膜中可观察到一些反向畴与孪晶等缺陷。薄膜与衬底界面少见错配位错,薄膜以Stranski-Krastanov模式生长。     

Characterization of thermally stable W/Ni multilayers by X-rays and cross-sectional transmission electron microscopy

W/Ni multilayer structures (MLS) composed of 5 and 10 bilayers, with composition W(15 Å)/Ni(55 Å), have been deposited on float glass substrate using ion-beam sputtering. X-ray reflectivity and wide-angle X-ray diffraction techniques have been used to study their interface characteristics, such as layer thickness, interface roughness and change in structural parameters. The fabricated MLS were found to be oriented along (111) of Ni having superlattice modulation perpendicular to the film plane. Thermal annealing studies on these multilayers showed that these were stable up to 500 °C. Cross-sectional transmission electron microscopy and selected area electron diffraction studies on as-deposited W/Ni MLS of 10 bilayers revealed well formed interfaces without any correlated roughness. The thicknesses of different layers were found to vary along the film thickness.     

Direct observation of ferrielectricity at ferroelastic domain boundaries in CaTiO3 by electron microscopy

High-resolution aberration-corrected transmission electron microscopy aided by statistical parameter estimation theory is used to quantify localized displacements at a (110) twin boundary in orthorhombic CaTiO(3). The displacements are 3-6 pm for the Ti atoms and confined to a thin layer. This is the first direct observation of the generation of ferroelectricity by interfaces inside this material which opens the door for domain boundary engineering.     

Ellipsometry and transmission electron microscopy study of MoSi2 coatings after oxidation at high temperature in air

MoSi₂ coatings were deposited on Si (100) substrates by means of magnetron sputtering. The structural and optical properties of the coatings were then investigated through transmission electron microscopy (TEM) and UV-visible-near IR ellipsometry after heat treatments in air at two temperatures (1100 K and 1600 K). After annealing at 1100 K, no silica layer could be observed by TEM at the surface of the MoSi₂ coating, whereas annealing at 1600 K gave rise to a protective silica layer. As observed by TEM, this silica layer contained nanometric molybdenum silicide crystals. Increasing the annealing time at 1600 K from 20 min to 2 h resulted in both a higher concentration and growth of these molybdenum silicide crystals in the silica layer. An optical model, taking into account the observed microstructure and allowing a good fit of the ellipsometry data, was developed. It is also shown that the dielectric constants of the non-oxidized part of the MoSi₂ layer became modified when the annealing temperature (1100 K versus 1600 K) and the annealing time at 1600 K (20 min versus 2 h) were increased.     

Transmission electron microscopy characterization of TiN/SiNx multilayered coatings plastically deformed by nanoindentation

Plastic deformation of TiN_5 nm/SiN_0.5 nm multilayers by nanoindentation was investigated by transmission electron microscopy in order to identify deformation mechanisms involved in film failure resulting from severe plastic deformation. The TiN layers exhibited a crystalline fcc structure with a [002] preferential orientation; further crystal growth was interrupted by the amorphous SiN_x layers. After severe plastic deformation collective vertical displacement of slabs of several TiN/SiN_x-bilayers, which resulted from shear sliding at TiN/TiN grain boundaries, was observed. They are, together with horizontal fractures along the SiN_x layers, vertical cracks under the indenter tip following the TiN grain boundaries and delamination from the substrate, the predominant failure mechanisms of these coatings. The deformation behaviour of these films provides an experimental support for the absence of dislocation activity in grains of 5 nm size.     

High-resolution electron microscopy and low-temperature electron diffraction studies of a Bi2212 single crystal grown by the floating zone method

High-resolution electron microscopy of a Bi₂Sr₂CaCu₂O₈ (Bi2212) single crystal prepared by the floating zone method shows that the single crystal is of high quality; there is no intergrowth faulting in the layered structure along thec-axis. Low-temperature selected area diffraction and convergent beam electron diffraction (CBED) studies of this high-quality single crystal show that there is no detectable change for both the point group symmetry of the basic structure and the modulated structure from room temperature to about 15 K. However, a lattice anomaly around 215 K was suggested by measuring the temperature dependence of the ratio between the cross-point distances of the HOLZ lines in high-index CBED patterns. The presence of the lattice anomaly was further confirmed by low-temperature X-ray diffraction.     

Identification of molecular flipping of an asymmetric tris(phthalocyaninato) lutetium triple-decker complex by scanning tunneling microscopy/spectroscopy

The assembling behavior and electronic properties of asymmetric tris(phthalocyaninato) lutetium tripledecker sandwich complex molecules (Lu₂Pc₃) on highly oriented pyrolytic graphite (HOPG) surfaces have been studied by scanning tunneling microscopy/spectroscopy (STM/STS) methods. Phase transitions were observed at different bias polarities, involving an ordered packing arrangement with fourfold symmetry at negative bias and an amorphous arrangement at positive bias. Molecular switching behaviour for individual Lu₂Pc₃ molecules was reported here according to the bias-polarity-induced flipping phenomena and the peak shift in dI/dV versus V curves at different voltage scanning directions. The sensitive response of the strong intrinsic molecular dipole to an external electric field is proposed to be responsible for molecular switching of Lu₂Pc₃ at the solid/liquid interface. This article is published with open access at Springerlink.com     

Site occupancy determination of Eu/Y doped in Ca2SnO4 phosphor by electron channeling microanalysis

Energy-dispersive X-ray analysis based on electron channeling effects in transmission electron microscopy (TEM) was performed on Ca₂SnO₄ phosphor materials doped with Eu³⁺/Y³⁺ at various concentrations, which showed red photoluminescence associated with the Eu³⁺⁵D₀-⁷F₂ electric dipole transition. The method provided direct information on which host element site impurity elements occupy. The local atomic configurations and chemical bonding states associated with dopant impurities with different ionic radii were also examined by TEM-electron energy-loss spectroscopy (TEM-EELS).     

Transmission electron microscopy characterization of Al2Cu precipitate growth kinetics by in situ heat treatment

Growth kinetics of the Al₂Cu (θ) precipitate in an Al-1.5Cu alloy thin film were characterized in situ using transmission electron microscopy (TEM). The sizes of θ precipitates during isothermal growth in TEM were measured during aging at 250, 275 and 300 °C. The results of precipitate growth were analyzed based on the model of the “collector plate mechanism” for bulk alloys. The lengthening of the θ precipitate in thin film varies as t^0.29 for short annealing times (up to ∼10-20 min) at temperatures between 250 and 300 °C. This is in good agreement with the analysis in bulk alloys. For longer annealing time, however, the t^0.29 time law does not fit as the distances of Cu volume diffusion exceed one half of the film thickness.     

Comparative determination of the α/β phase fraction in α+β-titanium alloys using X-ray diffraction and electron microscopy

A comparison is made between the measured α/β phase fractions in Ti-6246 using X-ray diffraction (XRD) and electron microscopy. Image analysis of SEM and TEM images was compared to the phase fraction estimate obtained using electron backscattered diffraction, lab and high-energy synchrotron XRD. There was a good agreement between the electron microscopic and diffraction techniques, provided that the microstructural parameters of grain size and texture are estimated correctly when using quantitative Rietveld refinement.     

Functionality improvement of Nimesulide by eutectic formation with nicotinamide: Exploration using temperature-composition phase diagram

The aim of present work was to explore the temperature-composition phase diagram for detection of formation of a multi-component system. Fusion of model drug Nimesulide (NIM) and Nicotinamide (NIC) was prepared and evaluated for possible interaction using thermal analysis. Phase diagram and the appearance of single endotherm confirmed Eutectic formation with the molar ratio of 1:2 (NIM: NIC). Spray dried powder in same molar ratio showed improved functionality in terms of solubility (14 folds), dissolution (2 folds) in distilled water and drug content (92.27%). SEM study revealed that the particles of eutectic mixture were of nearly same size in all directions in shape with bigger particle size compared to the pure drug, which was responsible for its improved flow. The compressibility of prepared eutectic was greatly enhanced which was followed by formation of directly compressible tablets. FT-IR study explained the possibility of formation of hydrogen bond between both the components. Stability data proved the stable nature of the eutectic mixture as well as its prepared formulation. The study explained the way to prepare thermal phase diagram by taking solidus and liquidus points in DSC diagram, which was finally used as a confirmatory parameter for the formation of the eutectic. Simultaneous improvement in physicochemical and mechanical properties was highlighted.