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High-resolution angle-resolved lateral piezoresponse force microscopy: Visualization of in-plane piezoresponse vectors
摘要： Piezoresponse force microscopy (PFM) is a widely used tool for ferroelectric domain imaging. Lateral PFM (LPFM) utilizes the torsional vibration mode of a probe cantilever; it can distinguish ferroelectric domains having different polarizations with respect to the axis perpendicular to the cantilever, but it is blind to the parallel axis innately. We introduce a high-resolution angle-resolved-LPFM technique that is capable of visualizing full two-dimensional in-plane piezoresponse vector fields. The LPFM signal is analyzed for each pixel with respect to the sample-probe orientation angle with the aid of an image registration technique, and the corresponding local in-plane piezoresponse vector is deduced from the amplitude and phase of the trigonometric curve fitting. This technique provides a pathway for the visualization of complicated ferroelectric and piezoelectric structures.
关键词： Piezoresponse force microscopy,image registration technique,ferroelectric domain imaging,in-plane piezoresponse vector fields
更新于2025-09-04 15:30:14
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Bismuth Ferrite Second Harmonic Nanoparticles for Pulmonary Macrophage Tracking
摘要： Recently, second harmonic generation (SHG) nanomaterials have been generated that are efficiently employed in the classical (NIR) and extended (NIR-II) near infrared windows using a multiphoton microscope. The aim was to test bismuth ferrite harmonic nanoparticles (BFO-HNPs) for their ability to monitor pulmonary macrophages in mice. BFO-loaded MH-S macrophages are given intratracheally to healthy mice or BFO-HNPs are intranasally instilled in mice with allergic airway inflammation and lung sections of up to 100 μM are prepared. Using a two-photon-laser scanning microscope, it is shown that bright BFO-HNPs signals are detected from superficially localized cells as well as from deep within the lung tissue. BFO-HNPs are identified with an excellent signal-to-noise ratio and virtually no background signal. The SHG from the nanocrystals can be distinguished from the endogenous collagen–derived SHG around the blood vessels and bronchial structures. BFO-HNPs are primarily taken up by M2 alveolar macrophages in vivo. This SHG imaging approach provides novel information about the interaction of macrophages with cells and the extracellular matrix in lung disease as it is capable of visualizing and tracking NP-loaded cells at high resolution in thick tissues with minimal background fluorescence.
关键词： two-photon-laser scanning microscopy,macrophages,third harmonic generation,nanoparticles,second harmonic generation
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Saint Petersburg, Russia (2018.10.22-2018.10.23)] 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Total Internal Reflection Fluorescence Microscopy for Investigation of Dynamics of Single Molecules
摘要： In the work, the study of dynamics of single molecules by means of total internal reflection fluorescence microscopy is suggested. The fluorescence microscopy is directed to detect the single molecules in different fluids. We developed a new experimental scheme of fluorescence microscopy. The developed system based on total internal regime allows studying movements of single chlorophyll particles in the aquatic environment and opens a great prospect for single molecules investigation.
关键词： single molecules,total internal reflection,fluorescence,microscopy
更新于2025-09-04 15:30:14
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Single layer graphene for estimation of axial spatial resolution in confocal Raman microscopy depth profiling
摘要： Single layer graphene (SLG), with its angstrom-scale thickness and strong Raman scattering cross section, was adapted for measurement of the axial (Z-direction) probe beam profile in confocal Raman microscopy depth-profiling experiments. SLG adsorbed to a glass microscope coverslip (SLG/SiO2) served as a platform for estimation of axial spatial resolution. Profiles were measured by stepping the confocal probe volume through the SLG/SiO2 interface while measuring Raman scattering from the sample. Using a high numerical aperture (1.4 NA) oil immersion objective, axial profiles were derived from the graphene 2D vibrational mode and fit to a Lorentzian instrument response function (IRF). Subsequently, the Z-direction spatial resolution in depth-profiling studies of polymer interfaces was estimated through convolution of the Lorentzian IRF with a step function representing the ideal junction separating the phases of interest. In the study of a bipolar polymer membrane, confocal Raman depth profiles of the AEM/CEM (anion exchange membrane / cation exchange membrane) interface show the transition region is broader than the limiting response and are consistent with roughness at the boundary on the order of a few micrometers. Using ClO4- as a Raman active mobile ion probe, application of self-modeling curve resolution (SMCR) to spectral datasets within a profile showed ClO4- ions track the spatial distribution of the AEM phase. Finally, in measurements on a liquid-solid interface formed between 1-octanol and a polydimethylsiloxane (PDMS) membrane, the IRF derived from fitting the experimental profile was slightly narrower than those obtained from profiling SLG, indicating the potential to use polymer-liquid interfaces formed from widely available materials and reagents for estimation of axial spatial resolution in confocal Raman depth-profiling.
关键词： Axial spatial resolution,Polymer interfaces,Confocal Raman microscopy,Single layer graphene,Bipolar membrane,Depth profiling
更新于2025-09-04 15:30:14
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Recent Advances in 3D Structured Illumination Microscopy
摘要： In structured illumination microscopy (SIM) the sample under investigation is illuminated using a structured illumination (SI) pattern. This SI pattern encodes high spatial frequencies of fine features within the sample, which usually are not transferred by the conventional three-dimensional (3D) optical transfer function (OTF) of the imaging system and fills the missing cone of frequencies in the OTF for better discrimination of the out-of- focus light. Thereby, SIM provides super-resolution (SR) performance beyond the diffraction limit and optical- sectioning (OS) capability with the use of data post-processing approaches. 3D structured patterns that include lateral and axial variations in the illumination have attracted more attention recently as they provide OS and SR enhancement in three dimensions. In this paper, we review recent implementations in generating a 3D SI pattern with tunable modulation frequency (independently of both the objective lens and the wavelength used) using a Fresnel biprism or a Wollaston prism. From the raw SIM images, final SIM images with simultaneous OS and SR are retrieved without artifacts due to coherent noise.
关键词： Fresnel biprism,Wollaston prism,structured illumination design,super-resolution,tunable frequency,three-dimensional microscopy
更新于2025-09-04 15:30:14
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High-throughput, non-equilibrium studies of single biomolecules using glass-made nanofluidic devices
摘要： Single-molecule detection schemes offer powerful means to overcome static and dynamic heterogeneity inherent to complex samples. However, probing biomolecular interactions and reactions with high throughput and time resolution remains challenging, often requiring surface-immobilized entities. Here, we introduce glass-made nanofluidic devices for the high-throughput detection of freely-diffusing single biomolecules by camera-based fluorescence microscopy. Nanochannels of 200 nm height and a width of several micrometers confine the movement of biomolecules. Using pressure-driven flow through an array of parallel nanochannels and by tracking the movement of fluorescently labelled DNA oligonucleotides, we observe conformational changes with high throughput. In a device geometry featuring a T-shaped junction of nanochannels, we drive steady-state non-equilibrium conditions by continuously mixing reactants and triggering chemical reactions. We use the device to probe the conformational equilibrium of a DNA hairpin as well as to continuously observe DNA synthesis in real time. Our platform offers a straightforward and robust method for studying reaction kinetics at the single-molecule level.
关键词： fluorescence microscopy,DNA,nanofluidic devices,single-molecule detection,biomolecular interactions
更新于2025-09-04 15:30:14
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A stage-scanning two-photon microscope equipped with a temporal and a spatial pulse shaper: Enhance fluorescence signal by phase shaping
摘要： Here, we present a stage-scanning two-photon microscope (2PM) equipped with a temporal pulse shaper and a spatial light modulator enabling full control over spectral and spatial phases of the exciting laser pulse. We demonstrate the capability of correcting wavefronts and temporal pulse distortions without cross-dependencies induced by optical elements at the same time enhancing the fluorescence signal. We implemented phase resolved interferometric spectral modulation for temporal pulse shaping and the iterative feedback adaptive compensation technique for spatial pulse modulation as iterative techniques. Sample distortions were simulated by cover glass plates in the optical path and by chirping the exciting laser pulses. Optimization of the spectral and spatial phases results in a signal increase of 30% and nearly complete recovery of the losses. Applying a measured spatial compensation phase within a real leaf sample shows the enhancement in contrast due to wavefront shaping with local fluorescence increase up to 75%. The setup allows full independent control over spatial and spectral phases keeping or improving the spatial resolution of our microscope and provides the optimal tool for sensitive non-linear and coherent control microscopy.
关键词： two-photon microscopy,wavefront shaping,spatial light modulator,fluorescence signal enhancement,temporal pulse shaping
更新于2025-09-04 15:30:14
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Two distinct surface terminations of SrVO <sub/>3</sub> (001) ultrathin films as an influential factor on metallicity
摘要： Pulsed laser deposition-grown SrVO3 (001) ultrathin films on SrTiO3 (001) substrates were investigated by in situ low-temperature scanning tunneling microscopy and spectroscopy. SrVO3 (001) ultrathin films showed two distinct surface terminations. One termination was a ((√2 × √2)-R45° reconstruction as was previously observed for SrVO3 (001) thick films, while the other was a ((√5 × √5)-R26.6° reconstruction. Scanning tunneling spectroscopy revealed that the ((√2 × √2)-R45° surface shows a metallic electronic structure, whereas the ((√5 × √5)-R26.6° surface exhibits a significantly reduced density of states at the Fermi level. These results suggest that the surface reconstruction may be an important factor to influence metallicity in epitaxial ultrathin films of transition metal oxides.
关键词： ultrathin films,scanning tunneling microscopy,scanning tunneling spectroscopy,SrVO3,metallicity,surface terminations
更新于2025-09-04 15:30:14
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Atomic-scale structure characteristics of antiferroelectric silver niobate
摘要： Antiferroelectric materials are a kind of functional material, which are widely used in electrostatic energy storage, energy conversion devices, and magnetoelectric coupling devices. As a typical lead-free antiferroelectric material, silver niobate has attracted much attention in recent years due to its excellent performance in energy storage. In this work, using the spherical aberration corrected electron microscopy technique, atomic-resolution images of pure silver niobate were obtained, which revealed typical microscopic physical characteristics of such complex antiferroelectric oxides: in such materials, all cations deviate from the average positions of the main lattice, and the displacement of each kind of cation varies periodically in two opposite directions, resulting in periodic wavy (1–10)c atomic planes, and the period of cation displacement is 15.6 A? . At the same time, the 90(cid:2) antiferroelectric domain boundary and the antiphase domain wall defects are further revealed and analyzed.
关键词： electron microscopy,antiferroelectric,atomic-scale structure,domain boundary,silver niobate
更新于2025-09-04 15:30:14
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Near-Field and Far-Field Thermal Emission of an Individual Patch Nanoantenna
摘要： The far-field spectral and near-field spatial responses of an individual metal-insulator-metal nanoantenna are reported, using thermal fluctuations as an internal source of the electromagnetic field. The far-field spectra, obtained by combining Fourier transform infrared spectroscopy with spatial modulation based on a light falloff effect in a confocal geometry, have revealed two distinct emission peaks attributed to the excitation of the fundamental mode of the nanoantenna at two distinct wavelengths. Superresolved near-field images of the thermally excited mode have been obtained by thermal radiation scanning tunneling microscopy. Experimental results are supported by numerical simulations showing that it is possible to excite the same mode at different wavelengths near a resonance of the insulating dielectric material forming the antenna.
关键词： near-field,nanoantenna,thermal emission,microscopy,spectroscopy,far-field
更新于2025-09-04 15:30:14