High-resolution Microscopy Techniques Research Articles

Visualising the Cardiovascular System of Embryos of Biomedical Model Organisms with High Resolution Episcopic Microscopy (HREM).

The article will briefly introduce the high-resolution episcopic microscopy (HREM) technique and will focus on its potential for researching cardiovascular development and remodelling in embryos of biomedical model organisms. It will demonstrate the capacity of HREM for analysing the cardiovascular system of normally developed and genetically or experimentally malformed zebrafish, frog, chick and mouse embryos in the context of the whole specimen and will exemplarily show the possibilities HREM offers for comprehensive visualisation of the vasculature of adult human skin. Finally, it will provide examples of the successful application of HREM for identifying cardiovascular malformations in genetically altered mouse embryos produced in the deciphering the mechanisms of developmental disorders (DMDD) program.

Mechanochemical combustion synthesis of vanadium carbide (VC), niobium carbide (NbC) and tantalum carbide (TaC) nanoparticles

The nanoparticles of vanadium, niobium, and tantalum carbides were synthesized by a mechanically induced magnesiothermic combustion in the separate Mg/V2O5/C, Mg/Nb2O5/C, and Mg/Ta2O5/C systems. Initial materials in these systems ignited after short milling times of 10, 10, and 23 min, respectively. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM) and elemental mapping techniques were employed to characterize the combustion products. In this process, magnesium reduces initial oxides to generate elemental V/Nb/Ta to react with carbon, forming the carbide phases.

Micro- and Nanoscale Identification of Rare Earth Element–Mineral Associations in an Acidified Dredge Spoil and Adjacent Reduced Sediments

Although rare earth element (REE) concentrations and speciation are often investigated by chemical extractions of bulk soils and sediments to elucidate site specific environmental processes and anthropogenic influences, micro- and nanoscale investigations provide more precise insights into the REE–mineral associations essential for understanding REE mobility in complex natural landscapes. In this study, we combine the high-resolution microscopic techniques of scanning electron microscopy energy dispersive spectroscopy (SEM-EDS), transmission electron microscopy (TEM), and electron energy-loss spectroscopy (EELS) to characterize micro- and nanoscale REE–mineral associations in an eutrophic estuarine system, specifically at a site containing (1) a coastal acid sulfate soil (CASS) and (2) adjacent estuarine sediments that have received acute acidic drainage from the CASS site for ∼20 years. This study revealed particles with a porous morphology that had a recurring association between Fe and the REE lanthanum (La/Fe/O = 1:1:3) in the sediments, indicating a presence of either a pure orthoferrite ABO3 compound (A = REE, B = metal), or a co-occurrence of REE and Fe minerals (i.e., La2O3 coprecipitated in 1:1 stoichiometry with Fe oxide). Fe(III) minerals are typical of CASS influenced sites and are likely to be essential REE sinks in this system. Additionally, micro- to nanoscale REE–phosphate particles were also widespread here, which may reflect an important REE sink in eutrophic sediments. Specifically, a REE–phosphate particle targeted by SEM was thin sectioned by focused ion beam (FIB) for TEM analysis, revealing a crystal structure (a = 6.6 Å, b = 6.9 Å, α = 90°) consistent with monazite ((REEs, Th)PO4). Usually, a positive Ce anomaly is found more in oxidized solid phase due to less soluble oxidized Ce(IV)O2. Interestingly, our EELS data revealed that Ce was only present as reduced Ce(III) in our solid sample, showing the possibility of Ce3+ incorporating into less soluble minerals such as REE–phosphate, which may explain the higher positive Ce anomaly observed in insoluble phases in reduced sediment. Microtubular cavities, consistent with abiotic processes in REE–phosphate precipitation, were also observed on the cross-sectioned monazite.

Nanoscale Surface Structure-Activity in Electrochemistry and Electrocatalysis.

Nanostructured electrochemical interfaces (electrodes) are found in diverse applications ranging from electrocatalysis and energy storage to biomedical and environmental sensing. These functional materials, which possess compositional and structural heterogeneity over a wide range of length scales, are usually characterized by classical macroscopic or "bulk" electrochemical techniques that are not well-suited to analyzing the nonuniform fluxes that govern the electrochemical response at complex interfaces. In this Perspective, we highlight new directions to studying fundamental electrochemical and electrocatalytic phenomena, whereby nanoscale-resolved information on activity is related to electrode structure and properties colocated and at a commensurate scale by using complementary high-resolution microscopy techniques. This correlative electrochemical multimicroscopy strategy aims to unambiguously resolve structure and activity by identifying and characterizing the structural features that constitute an active surface, ultimately facilitating the rational design of functional electromaterials. The discussion encompasses high-resolution correlative structure-activity investigations at well-defined surfaces such as metal single crystals and layered materials, extended structurally/compositionally heterogeneous surfaces such as polycrystalline metals, and ensemble-type electrodes exemplified by nanoparticles on an electrode support surface. This Perspective provides a roadmap for next-generation studies in electrochemistry and electrocatalysis, advocating that complex electrode surfaces and interfaces be broken down and studied as a set of simpler "single entities" (e.g., steps, terraces, defects, crystal facets, grain boundaries, single particles), from which the resulting nanoscale understanding of reactivity can be used to create rational models, underpinned by theory and surface physics, that are self-consistent across broader length scales and time scales.

Supercritical focusing coherent anti-Stokes Raman scattering microscopy for high-resolution vibrational imaging.

We report the development of, to the best of our knowledge, a novel supercritical focusing coherent anti-Stokes Raman scattering (SCF-CARS) microscopy for high-resolution vibrational imaging. Two optimized phase patterns with a combination of concentric rings with an alternative 0 and π phase are generated by using a spatial light modulator and applied to the pump beam for minimizing its focal spot size. One of the phase patterns is for both the lateral and axial resolution enhancement, and the other can further improve the lateral resolution, but it sacrifices the axial resolution to some extent. We demonstrate this high-resolution SCF-CARS microscopy technique by imaging the polymethyl methacrylate (PMMA) nano-cylinder on a microscope slide and glass-air interface, as well as biomedical samples, for example, tooth.

An explanation for the mysterious distribution of melanin in human skin: a rare example of asymmetric (melanin) organelle distribution during mitosis of basal layer progenitor keratinocytes.

Melanin is synthesized by melanocytes in the basal layer of the epidermis. When transferred to surrounding keratinocytes melanin is the key ultraviolet radiation-protective biopolymer responsible for skin pigmentation. Most melanin is observable in the proliferative basal layer of the epidermis and only sparsely distributed in the stratifying/differentiating epidermis. The latter has been explained as 'melanin degradation' in suprabasal layers. To re-evaluate the currently accepted basis for melanin distribution in human epidermis and to discover whether this pattern is altered after a regenerative stimulus. Normal epidermis of adult human skin, at rest and after tape-stripping, was analysed by a range of (immuno)histochemical and high-resolution microscopy techniques. In vitro models of melanin granule uptake by human keratinocytes were attempted. We propose a different fate for melanin in the human epidermis. Our evidence indicates that the bulk of melanin is inherited only by the nondifferentiating daughter cell postmitosis in progenitor keratinocytes via asymmetric organelle inheritance. Moreover, this preferred pattern of melanin distribution can switch to a symmetric or equal daughter cell inheritance mode under conditions of stress, including regeneration. In this preliminary report, we provide a plausible and histologically supported explanation for how human skin pigmentation is efficiently organized in the epidermis. Steady-state epidermis pigmentation may involve much less redox-sensitive melanogenesis than previously thought, and at least some premade melanin may be available for reuse. The epidermal melanin unit may be an excellent example with which to study organelle distribution via asymmetric or symmetric inheritance in response to microenvironment and tissue demands.

Catalytic conversion of methanol to larger organic molecules over crystalline forsterite: Laboratory study and astrophysical implications

Laboratory catalytic reactions of methanol over heated crystalline silicates (forsterite) lead to the formation of gas-phase olefinic and polycyclic aromatic hydrocarbon (PAH) molecules, and are of potential importance in astrophysical environments including hot molecular cores, protoplanetary disks and shocks. In our experiments the methanol reagent, together with intermediate and product gas-phase molecular species were detected using time-of-flight mass-spectrometry (TOF-MS). A solid deposited on the crystalline forsterite surface was examined subsequently using high-resolution transmission electron microscopy and thermal gravimetric techniques and found to comprise amorphous and graphitic carbon. The chemical players in this work – gas-phase methanol, crystalline silicates and PAHs, have been identified spectroscopically in a range of astrophysical environments including young and evolved stars, protoplanetary disks, comets, captured dust particles and meteorites. It is envisaged that reactions on bare dust grains as studied here both experimentally and theoretically through DFT calculations, can have implications for chemical transformations and conversions, in forming PAH molecules and potentially in the synthesis of prebiotic molecules.

Interfering With DNA Decondensation as a Strategy Against Mycobacteria

Tuberculosis is once again a major global threat, leading to more than 1 million deaths each year. Treatment options for tuberculosis patients are limited, expensive and characterized by severe side effects, especially in the case of multidrug-resistant forms. Uncovering novel vulnerabilities of the pathogen is crucial to generate new therapeutic strategies. Using high resolution microscopy techniques, we discovered one such vulnerability of Mycobacterium tuberculosis. We demonstrate that the DNA of M. tuberculosis can condense under stressful conditions such as starvation and antibiotic treatment. The DNA condensation is reversible and specific for viable bacteria. Based on these observations, we hypothesized that blocking the recovery from the condensed state could weaken the bacteria. We showed that after inducing DNA condensation, and subsequent blocking of acetylation of DNA binding proteins, the DNA localization in the bacteria is altered. Importantly under these conditions, Mycobacterium smegmatis did not replicate and its survival was significantly reduced. Our work demonstrates that agents that block recovery from the condensed state of the nucleoid can be exploited as antibiotic. The combination of fusidic acid and inhibition of acetylation of DNA binding proteins, via the Eis enzyme, potentiate the efficacy of fusidic acid by 10 and the Eis inhibitor to 1,000-fold. Hence, we propose that successive treatment with antibiotics and drugs interfering with recovery from DNA condensation constitutes a novel approach for treatment of tuberculosis and related bacterial infections.

Signal, noise and resolution in linear and nonlinear structured-illumination microscopy.

Structured-illumination microscopy allows widefield fluorescence imaging with resolution beyond the classical diffraction limit. Its linear form extends resolution by a factor of two, and its nonlinear form by an in-principle infinite factor, the effective resolution in practice being determined by noise. In this paper, we analyse the noise properties and achievable resolution of linear and nonlinear 1D and 2D patterned SIM from a frequency-space perspective. We develop an analytical theory for a general case of linear or nonlinear fluorescent imaging, and verify the analytical calculations with numerical simulation for a special case where nonlinearity is produced by photoswitching of fluorescent labels. We compare the performance of two alternative implementations, using either two-dimensional (2D) illumination patterns or sequentially rotated one-dimensional (ID) patterns. We show that 1D patterns are advantageous in the linear case, and that in the nonlinear case 2D patterns provide a slight signal-to-noise advantage under idealised conditions, but perform worse than 1D patterns in the presence of nonswitchable fluorescent background. LAY DESCRIPTION: Structured-illumination microscopy (SIM) is a high-resolution light microscopy technique that allows imaging of fluorescence at a resolution about twice the classical diffraction limit. There are various ways that the illumination can be structured, but it is not obvious how the choice of illumination pattern affects the final image quality, especially in view of the noise. We present a detailed performance analysis considering two illumination techniques: sequential illumination with line-gratings that are shifted and rotated during image acquisition and two-dimensional (2D) illumination structures requiring only shift operations. Our analysis is based on analytical theory, supported by simulations of images considering noise. We also extend our analysis to a nonlinear variant of SIM, with which enhanced resolution can be achieved, limited only by noise. This includes nonlinear SIM based on the light-induced switching of the fluorescent molecules between a bright and a dark state. We find sequential illumination with line-gratings to be advantageous in ordinary (linear) SIM, whereas 2D patterns provides a slight signal-to-noise advantage under idealised conditions in nonlinear SIM if there is no nonswitching background.

Tracking ions and dendrites in batteries

By borrowing a spectroscopy method often used to analyze biological specimens, researchers have developed a high-resolution microscopy technique that can monitor electrochemical processes occurring in batteries in real time. The team used the method to probe quickly changing ion concentrations in an electrolyte solution as well as the mechanism of dendrite growth in lithium batteries. Lithium-ion batteries could hold about 10 times as much energy as today’s commercial varieties do, if the commonly used graphite anodes were replaced with ones made from lithium metal. But that replacement poses safety risks. During charging, lithium can accumulate on the metal anode in the form of dendrites. These spiky structures can grow, pierce the film that separates the positive and negative electrodes, and short-circuit the battery, possibly causing a fire or explosion. To uncover the details of the mechanism behind dendrite growth, researchers have used electron microscopy and other imaging techniques on electrochemical

Structural and spectroscopic properties of Eu3+ doped Y4Al2O9 compounds through a soft chemical process

The present work reports on the synthesis, structural and optical properties of (Y1-xEux)4Al2O9 powders, with x ranging from 0.001 to 0.030. We prepared the materials using a modified polymeric precursors method, and the effect of annealing temperature and Eu3+ concentrations were evaluated. Structural and microstructural parameters, such as cell parameters, crystallite size and grain size were determined and evaluated by using the results from X-ray diffraction and high-resolution transmission electron microscopy techniques. An annealing temperature of 800 °C was enough to obtain single Y4Al2O9 crystalline phase with good distribution of Eu3+ ions. Diffuse reflectance spectra and optical bandgap of 4.52 eV for (Y0.995Eu0.005)4Al2O9 – determined by Kubelka-Munk model – showed good optical quality of the samples, which were considered non-conducting. All doped samples possessed visible photoluminescence emission from Eu3+ ions under excitation at 393 nm, with higher emissions occurring in the red region from 5D0 → 7F2 transition, with R/O relation of 1.69 for the sample with x = 0.010. Analyzing photoluminescence emission spectra, the lifetime values and Judd-Ofelt parameters, we determined that Eu3+ occupied three different sites of the Y4Al2O9 (YAM) structure, replacing Y3+ ions, with the quenching concentration occurring between x = 0.020 and x = 0.030. We noted that Eu3+ ions are in a chemical environment with low polarization, and their degree of covalence is low. Finally, samples with x = 0.020 (Y0.980Eu0.020)4Al2O9 seems to be useful as red phosphors.

Fine nanostructural variation in the wing pattern of a moth Chiasmia eleonora Cramer (1780)

Butterflies and moths possess diverse patterns on their wings. Butterflies employ miscellaneous colour in the wings whereas moths use a combination of dull colours like white, grey, brown and black for the patterning of their wings. The exception is some of the toxic diurnal moths which possess bright wing colouration. Moths possess an obscure pattern in the dorsal part of the wings which may be a line, zigzag or swirl. Such patterns help in camouflage during resting period. Thus, the dorsal wing pattern of the moth is used for both intra- as well as inter-specific signal communication. Chiasmia eleonora is a nocturnal moth of greyish black colouration. The dorsal hindwing possesses yellow and black colour patches. A whitecoloured oblique line crosses both left and right fore- and hindwings to form a V-shaped pattern across the dorsal wing. This V-shaped pattern possesses a UV signal. Closer to the body, the colour appears darker, which fades towards the margin. The fine nanostructural variation is observed throughout the wings. This study elucidates the wing pattern of the geometrid moth C. eleonora using high-resolution microscopy techniques that has not been described in previous studies.

Study of reversible motion of [formula omitted] tensile twin boundaries in a magnesium alloy during strain path changes

Twinning process involving reversible motion of twin boundaries was examined and quantified in a rolled Mg-3Al-1Zn magnesium alloy compressed along two perpendicular directions. The evolution of twinning is analyzed by quasi in-situ electron backscatter diffraction technique, and the detailed structure of the twin boundary is analyzed using high-resolution transmission electron microscopy technique. The results suggest that both twinning and detwinning are attributed to the mobility of twin boundaries. Low-angle boundaries were identified at the prior twin boundaries after detwinning due to the effect of alloying elements, and these low-angle boundaries will affect subsequent deformation. Twin boundary is serrated and consists of 101¯2 coherent twin boundaries and prism-basal boundaries that control twin boundary migration.

Effect of morphology on optical and efficiently enhanced electrical properties of W-ZnS for UV sensor applications

The influence of the morphology on the electron transport properties of ZnS nanostructures has been assessed by the electrical measurements on different ZnS nanostructures. High-quality poly(vinylpyrrolidone) capped wurtzite-ZnS micro- and nanostructures have been prepared by one step hydrothermal methods at low temperatures. Detailed structural investigation based on X-ray diffraction results and morphological analyses have been carried out using field emission scanning electron microscopy, transmission electron microscopy, selected area diffraction pattern, and high-resolution transmission electron microscopy techniques. In order to examine the formation of compound ZnS, the atomic ratio of Zn to S has been found from Energy Dispersion Spectroscopy. The bandgap of the samples has been calculated from the UV-visible absorption spectra in the reflectance mode at room temperature. The dependence of size and shape on excitonic and trap-state emission features of the nanostructures has been studied from the photoluminescence (PL) studies, and the enhancement of PL intensity in 1D nanostructures has also been discussed. High yield and highly crystalline long nanorods and nanowires have been found to be best suited for advanced optoelectronic systems because they have better photoconductivity than microparticles and nanoparticles.

Ag/Au Nanoparticle-Loaded Paper-Based Versatile Surface-Enhanced Raman Spectroscopy Substrates for Multiple Explosives Detection.

We present a systematic study on the fabrication, characterization of versatile, and low-cost filter paper-based surface-enhanced Raman spectroscopy (SERS) substrates loaded with salt-induced aggregated Ag/Au nanoparticles (NPs). These were demonstrated as efficient SERS substrates for the detection of multiple explosive molecules such as picric acid (5 μM), 2,4-dinitrotoluene (1 μM), and 3-nitro-1,2,4-triazol-5-one (10 μM) along with a common dye molecule (methylene blue, 5 nM). The concentrations of the dye and explosive molecules in terms of mass represent 31.98 pg, 11.45 ng, 1.82 ng, and 13.06 ng, respectively. Silver (Ag) and gold (Au) colloidal NPs were prepared by femtosecond laser (∼50 fs, 800 nm, 1 kHz) ablation of Ag/Au-target immersed in distilled water. Subsequently, the aggregated nanoparticles were achieved by mixing the pure Ag and Au NPs with different concentrations of NaCl. These aggregated NPs were characterized by UV–visible absorption and high-resolution transmission electron microscopy techniques. The SERS substrates were prepared by soaking the filter paper in aggregated NPs. The morphologies of the paper substrates were investigated using field-emission scanning electron microscopy technique. We have achieved superior enhancements with high reproducibility and sensitivity for filter paper substrates loaded with Ag/Au NPs mixed for an optimum concentration of 50 mM NaCl.

Tracing the three-dimensional nanochemistry of phase separation in an inverse Ni-based superalloy

Tailoring the properties of intermetallic alloys and phases, which resemble the foundation of a vast variety of high-temperature materials like nickel-based superalloys, is a challenge for improving this class of materials that requires comprehensive understanding of their three-dimensional (3D) nanochemistry. Here we use high-resolution microscopy techniques to reveal the microstructural and 3D nanochemical evolution of disordered γ particles from nanoscale nickel-rich heterogeneities (clusters) to γ spheres and then γ plates in an inverse Ni78Al13Ti9 alloy having an ordered (L12) γ′ matrix. The γ particles require aging to achieve a thermodynamically stable morphology and composition, determined by reducing the Gibbs free energy. The fundamental analogy between γ particles in a γ′ matrix of an inverse alloy and γ particles in γ′ precipitates of a hierarchical Ni86.1Al8.5Ti5.4 alloy is established. Our results demonstrate that this analogy can be harnessed as a novel approach for improving the properties of nickel-based superalloys.

Direct Formation of C-C Double-Bonded Structural Motifs by On-Surface Dehalogenative Homocoupling of gem-Dibromomethyl Molecules.

Conductive polymers are of great importance in a variety of chemistry-related disciplines and applications. The recently developed bottom-up on-surface synthesis strategy provides us with opportunities for the fabrication of various nanostructures in a flexible and facile manner, which could be investigated by high-resolution microscopic techniques in real space. Herein, we designed and synthesized molecular precursors functionalized with benzal gem-dibromomethyl groups. A combination of scanning tunneling microscopy, noncontact atomic force microscopy, high-resolution synchrotron radiation photoemission spectroscopy, and density functional theory calculations demonstrated that it is feasible to achieve the direct formation of C-C double-bonded structural motifs via on-surface dehalogenative homocoupling reactions on the Au(111) surface. Correspondingly, we convert the sp3-hybridized state to an sp2-hybridized state of carbon atoms, i. e., from an alkyl group to an alkenyl one. Moreover, by such a bottom-up strategy, we have successfully fabricated poly(phenylenevinylene) chains on the surface, which is anticipated to inspire further studies toward understanding the nature of conductive polymers at the atomic scale.

Synthesis and Characterization of Nano-Tungsten Oxide Precipitated onto Natural Inorganic Clay for Humidity-Sensing Applications

A wet chemical method was used to obtain tungsten oxide nanoparticles from tungsten tetrachloride and natural microfibrous inorganic clay (sepiolite) as a starting material. Precipitation of tungsten oxide species onto sepiolite under basic conditions and subsequent thermal treatment was investigated, prompted by the abundance of sepiolite in nature and the useful environmental applications that could be attained. Laser granulometry, X-ray diffraction, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), and high-resolution transmission electron microscopy (HR-TEM) techniques were used to study the particle-size distribution, the morphology, and the composition of the prepared sample. Our findings show the presence of tungsten oxide nanoparticles, which are less than 50 nm, on the needles of the modified sepiolite.

Surface Enhanced Raman Spectroscopy and Quantum Chemical Studies on Iminodiacetic Acid Single Crystals

Adsorption behaviour of iminodiacetic acid (IDA) on silver surface were investigated based on surface enhanced Raman spectroscopy (SERS) technique and density functional theory calculations. The single crystals of IDA were grown by slow evaporation method and characterized by powder X-ray diffraction (XRD), dynamic light scattering and scanning electron microscopy techniques. Silver nanoparticles (AgNPs) were prepared by solution combustion method using ananas comosus fruit extract as reducing agent. The AgNPs were characterized by powder XRD and high-resolution transmission electron microscopy techniques. Raman and SERS frequencies were analyzed on the basis of potential energy distribution calculation and compared with the experimental values. The structural parameters of IDA molecule was compared with the experimental values. In frontier molecular orbital analysis, the band gap value was significantly reduced for IDA after adsorption on the silver surface indicates the charge transfer associated with the process of adsorption. The redistribution of electrostatic potential and the reduction in band gap after adsorption on silver surface of IDA, reveals its utility in the design of electro active organic molecular devices. SERS spectral analysis reveals that the IDA adsorbed as a tilted orientation on the silver surface. Localization of electron density and the reduction in band gap after adsorption of silver nanoparticles pave the way for designing the electro active organic molecular devices.

Synthesis and Electrochemical Performance of Novel Peanut-Like SbPO4 Aggregates

Hierarchical SbPO4 peanut-like aggregates are successfully prepared through a facile solvothermal route. The X-ray powder diffraction, scanning electronic microscopy, high-resolution transmission electronic microscopy techniques is utilized to characterize the obtained SbPO4 materials. The experimental results indicate that the SbPO4 peanut-like aggregates are composed of numerous nanoplates in an oriented way via a self-assembly process. Additionally, the electrochemical Na-storage property is also preliminarily investigated.