Microscopy (Oxford, England)最新文献

Electron-beam irradiation often induces unintended structural and chemical changes in materials. Here, we show that damage and reduction in tungsten trioxide (WO3) nanowires are primarily driven by a carrier-mediated ionization process. In situ electron microscopy and electron energy-loss spectroscopy reveal structural degradation accompanied by the reduction of W6+ to W5+, while carrier dynamics simulations identify persistent, high-density electron-hole populations. Quantitative analyses and control experiments indicate that knock-on displacement and heating contribute minimally. This study establishes a microscopy-based quantitative framework for understanding electron-beam-induced damage and redox processes, highlighting the potential of electron microscopy for mechanistic insights and nanoscale chemical patterning in oxides.

Si-photodiode is commonly used for the backscattered electron (BSE) detector in scanning electron microscope (SEM). However, it is difficult to detect low-energy electrons below 3 kV. We have developed a thin microchannel plate (MCP) chip with an energy filter grid as an alternative BSE detector for low-energy SEM observations. The MCP can get enough signals even at 1 keV electron beam operation. The energy filtering operation revealed that the MCP image is composed of SE and BSE signals. By filtering SE component, the low-energy BSE images are easily obtained, which will open-up the new observation method of SEM using low-BSE image.

Ion gradients and membrane potential are fundamental to bacterial physiology, driving essential processes such as ATP synthesis, nutrient uptake, motility and stress adaptation. Visualizing these ion dynamics has become increasingly feasible through the use of fluorescent probes. This review provides a comprehensive overview of both synthetic dyes and genetically encoded indicators developed or adapted for bacterial systems. This review describes the principles underlying ion detection, highlights representative fluorescent probe tools and assesses their application in monitoring cytoplasmic ions and membrane potential in living bacterial cells. Specific challenges in bacterial imaging, such as cell size, membrane permeability, dye efflux and signal quantification, are discussed alongside recent advances in probe design and imaging platforms. This review aims to guide future research by outlining current capabilities, identifying limitations and suggesting opportunities for innovation in bacterial ion imaging.

Crystal defects are intrinsically linked to the electrical and optical properties of semiconductor materials, making their nanoscale detection essential across all phases (from research and development to manufacturing). Electron energy loss spectroscopy (EELS) in scanning transmission electron microscopy (STEM) has emerged as a promising technique for detecting even point defects due to the shape modulation in valence-loss spectra induced by defects. However, previous studies have primarily focused on qualitative detection, leaving the detection limit, i.e. the minimum detectable concentration, insufficiently explored. To experimentally evaluate the detection limit of defects and clarify the application scope of valence EELS, we prepared GaN samples with controlled defect concentrations along the depth direction using multi-step He-ion implantation and acquired valence-loss spectra at each depth. Based on the simulated depth profile of defects, we evaluated the detection limit from the depth at which significant modulation in the spectral shape was observed. The detection limit fundamentally depends on the signal-to-noise ratio of the valence-loss spectra. Under typical STEM conditions with an electron dose of 5 × 105 e-/Å2, the detection limit of defects in GaN was determined to be 0.35% (3500 ppm). Detailed structural analysis revealed that GaN contains implantation-induced defects and their clusters, and exhibits lattice strain and local disorder while retaining its wurtzite structure. The shape modulation in the valence-loss spectra was attributed to the indirect detection of defects through the surrounding strain fields.

Using an electron microscope, thick (30-100 nm wide), linear (not branched), cross-striated protein fibrils with an axial repeat of about 65 nm were detected in mammalian cell nuclei. These fibrils differ from the thin filaments of the nuclear matrix described in the literature. Therefore, in this work, the main efforts were aimed at demonstrating the nuclear origin of thick fibrils. Their presence in the material of nuclei destroyed by ultrasound, their contact with isolated nucleoli, and their presence in residual nuclei (nuclear matrix) are shown. Contacts of thick fibrils with both chromatin and the network of filaments of the nuclear matrix were observed. Thick fibrils, which are axial components of condensed chromosomes, are preserved during mitosis. It is likely that their contacts with chromatin and elements of the nuclear matrix are also preserved, ensuring the reproduction of the internal structure of the nuclei in daughter cells. Thick fibrils disintegrate in a medium with low ionic strength. Perhaps this is the reason for their absence in other authors' nuclear matrix preparations. In this work, the nuclei were isolated, and all experiments were carried out in a "complete medium" simulating the intranuclear salt content.

Lamellipodia are generally defined as thin, sheet-like cell protrusions that constitute the actin cytoskeleton-based motile apparatus, which promotes the movement of migrating cells. Recently, we identified a novel type of lamellipodia, termed ruffle-edge lamellipodia, which have α-actinin-4 (ACTN4)-enriched multilayer membrane folds at their leading edges in certain invasive cancer cell lines. In this study, the role of unconventional myosin-1e (Myo1E) in ACTN4-enriched ruffle-edge lamellipodia was analyzed using live-cell imaging, immunofluorescence, and scanning electron microscopy. Immunofluorescence microscopy for endogenous Myo1E and live-cell imaging of mApple-Myo1E-expressing cells showed that Myo1E was localized to ACTN4-rich lamellipodia tips in A549 cells. The wound-healing assay and live-cell movies showed that Myo1E small interfering RNA knockdown significantly suppressed cell migration and ruffle-edge lamellipodia formation. Furthermore, scanning electron microscopy demonstrated that Myo1E knockdown significantly reduced ruffle-edge structures. These results suggest that Myo1E may play an important role not only in the motility of ruffle-edge lamellipodia but also in the construction of ruffle-edge structures, which are probably associated with cancer cell invasion and metastasis.

Electron microscopy using an environmental cell is a powerful tool for observing catalysts and other nanomaterials in gases and liquids. An environmental cell must contain amorphous silicon-nitride membranes because they protect the sample environment from the vacuum of the electron microscope and enable the electron beam to pass through the cell. However, the membranes superimpose non-uniform contrast on the projected image, degrading image quality. We propose a method for removing the noise derived from the membranes using Noise2Noise, a deep-learning method, for a series of transmission-electron-microscope images with slight electron-beam tilt and evaluated its effectiveness. We succeeded in removing the membrane-derived noise while retaining the information of the sample in the cell. We also succeeded in efficiently removing Poisson noise. We believe this method will enable measurements requiring high signal-to-noise ratios, which could previously only be observed in a vacuum, to be conducted in an environmental cell.

Scanning electron microscope (SEM) observation in low vacuum can overcome the issue of charge-up at the specimen surface, allowing for the observation of insulating samples without sample pretreatment. The ultra-variable-pressure detector (UVD) was developed as a secondary electron (SE) detector for the low-vacuum observation in SEM. It works by collecting the light signal released from the collision between SEs and gas molecules. In this study, we propose a simple method using a stainless-steel sphere to characterize the feature of UVD signal in low-vacuum SEM and compare it with the traditional Everhart-Thornley (E-T) detector in normal SEM. The UVD signal showed characteristic features, namely a two-round-peak feature in the profile, which is different from that of E-T detector. Through experiment and simulation, we revealed that at higher vacuum levels (as a few Pa), SEs provide the primary contribution to the UVD signal, exhibiting a profile similar to that of the E-T signal. As the vacuum deteriorates, as 30 Pa, the main contribution to the UVD signal shifts from SEs to low-energy backscattered electrons (BSEs). Our finding indicates that by tuning the chamber pressure, we can vary the UVD image between SE and low-energy BSE features.

Organosilica nanoparticles are considered one of the promising nanomaterials for biomedical imaging and clinical applications due to their tunable properties, biocompatibility and multimodal imaging ability. In this review, we summarize the synthesis and functionalization of organosilica nanoparticles with a particular focus on their importance in biomedical imaging. By their high fluorescence intensity and unique photostability, organosilica nanoparticles provide capabilities for high-resolution and long-term imaging for in vivo, mesoscopic and microscopic applications. In addition, surface modifications of organosilica nanoparticles control cellular interactions, facilitating the accurate monitoring of cellular uptake, mitochondrial activity and endosomal sorting. Incorporating recent progress and experimental results, this review summarizes the multiformity and extensive prospects of organosilica nanoparticle-based imaging modalities and offers perspectives on future development in nanoparticle-driven biomedical imaging and therapeutic strategies.

Compact soft-X-ray emission spectroscopy (SXES) instrument, which was first applied to transmission electron microscope, was recently applied to scanning electron microscope and electron-probe microanalyzer, which improved the practical applicability of SXES as a tool investigating chemical bonding state of elements in bulk materials. Intensity profiles of Al-L, B-K and Si-L emission spectra which directly reflect the partial density of state of valence band (VB) were explained. Those energy positions are affected by core-level shift (chemical shift; CS) and a change of density of state (DOS) of VB, for example a bandgap formation. Those VB DOS measurements combined with electron-beam scanning technique can conduct a chemical bond mapping of a bulk material. It was presented that L-emission spectra of 3d transition-metal elements gives DOS+CS information in Lα,β emission, dielectric information in Lℓ,η, and the number of 3d electrons in the integrated intensity ratio of Lα,β/(Lα,β+ Lℓ,η). Since the electron-beam excited SXES experiment for bulk specimens can control the self-absorption effect, L-absorption profile of 3d-TM elements is obtainable from L-emission measurements by changing the accelerating voltage. Furthermore, CB information can be obtained from SXES spectra of semiconductor materials, Si and diamond cases were presented, by using the self-absorption effect on the background intensity of bremsstrahlung (BS) caused by electron-beam irradiation of the specimen.