Observation of a new type of nanoscale ferroelectric domains, termed as “bubble domains”—laterally confined spheroids of sub‐10 nm size with local dipoles self‐aligned in a direction opposite to the ...macroscopic polarization of a surrounding ferroelectric matrix—is reported. The bubble domains appear in ultrathin epitaxial PbZr0.2Ti0.8O3/SrTiO3/PbZr0.2Ti0.8O3 ferroelectric sandwich structures due to the interplay between charge and lattice degrees of freedom. The existence of the bubble domains is revealed by high‐resolution piezoresponse force microscopy (PFM), and is corroborated by aberration‐corrected atomic‐resolution scanning transmission electron microscopy mapping of the polarization displacements. An incommensurate phase and symmetry breaking is found within these domains resulting in local polarization rotation and hence impart a mixed Néel–Bloch‐like character to the bubble domain walls. PFM hysteresis loops for the bubble domains reveal that they undergo an irreversible phase transition to cylindrical domains under the electric field, accompanied by a transient rise in the electromechanical response. The observations are in agreement with ab‐initio‐based calculations, which reveal a very narrow window of electrical and elastic parameters that allow the existence of bubble domains. The findings highlight the richness of polar topologies possible in ultrathin ferroelectric structures and bring forward the prospect of emergent functionalities due to topological transitions.
Nanoscale spheroid domains—“bubble domains”—sub‐10 nm in lateral size with local dipoles self‐aligned in a direction opposite to the polarization of the surrounding ferroelectric matrix are reported in ultrathin epitaxial ferroelectric heterostructures. Incommensurate dipolar order and symmetry breaking is found within these domains, which leads to local polarization rotation and consequently mixed Néel–Bloch‐like character to the bubble domain walls.
The Energy Dispersive X-ray (EDX) microanalysis is a technique of elemental analysis associated to electron microscopy based on the generation of characteristic Xrays that reveals the presence of ...elements present in the specimens. The EDX microanalysis is used in different biomedical fields by many researchers and clinicians. Nevertheless, most of the scientific community is not fully aware of its possible applications. The spectrum of EDX microanalysis contains both semi-qualitative and semi-quantitative information. EDX technique is made useful in the study of drugs, such as in the study of drugs delivery in which the EDX is an important tool to detect nanoparticles (generally, used to improve the therapeutic performance of some chemotherapeutic agents). EDX is also used in the study of environmental pollution and in the characterization of mineral bioaccumulated in the tissues. In conclusion, the EDX can be considered as a useful tool in all works that require element determination, endogenous or exogenous, in the tissue, cell or any other sample.
Cover Image Papazoglou, Sebastian; Ashtarayeh, Mohammad; Oeschger, Jan Malte ...
NMR in biomedicine,
03/2024, Volume:
37, Issue:
3
Journal Article
Peer reviewed
The cover image is based on the Research Article Insights and improvements in correspondence between axonal volume fraction measured with diffusion‐weighted MRI and electron microscopy by Sebastian ...Papazoglou et al., https://doi.org/10.1002/nbm.5070.
We describe the simple, scalable, single‐step, and polar‐solvent‐free synthesis of high‐quality colloidal CsPbX3 (X=Cl, Br, and I) perovskite nanocrystals (NCs) with tunable halide ion composition ...and thickness by direct ultrasonication of the corresponding precursor solutions in the presence of organic capping molecules. High angle annular dark field scanning transmission electron microscopy (HAADF‐STEM) revealed the cubic crystal structure and surface termination of the NCs with atomic resolution. The NCs exhibit high photoluminescence quantum yields, narrow emission line widths, and considerable air stability. Furthermore, we investigated the quantum size effects in CsPbBr3 and CsPbI3 nanoplatelets by tuning their thickness down to only three to six monolayers. The high quality of the prepared NCs (CsPbBr3) was confirmed by amplified spontaneous emission with low thresholds. The versatility of this synthesis approach was demonstrated by synthesizing different perovskite NCs.
Under ultrasonication: Perovskite nanocrystals and nanoplatelets with controlled halide composition and thickness were prepared by direct ultrasonication of the corresponding precursor solutions in the presence of organic capping molecules. The optical properties of the as‐prepared CsPbX3 NCs can be tuned across the entire visible range by changing either the composition or thickness.
Graphene liquid cells (GLCs) for transmission electron microscopy (TEM) enable high‐resolution, real‐time imaging of dynamic processes in water. Large‐scale implementation, however, is prevented by ...major difficulties in reproducing GLC fabrication. Here, a high‐yield method is presented to fabricate GLCs under millimeter areas of continuous graphene, facilitating efficient GLC formation on a TEM grid. Additionally, GLCs are located on the grid using correlated light‐electron microscopy (CLEM), which reduces beam damage by limiting electron exposure time. CLEM allows the acquisition of reliable statistics and the investigation of the most common shapes of GLCs. In particular, a novel type of liquid cell is found, formed from only a single graphene sheet, greatly simplifying the fabrication process. The methods presented in this work—particularly the reproducibility and simplicity of fabrication—will enable future application of GLCs for high‐resolution dynamic imaging of biomolecular systems.
Graphene liquid cells are femtoliter pockets of water confined between two layers of graphene, allowing real‐time transmission electron microscopy on liquid, room‐temperature samples. Light electron microscopy is used to efficiently locate graphene liquid cells on a transmission electron microscopy grid, assembled through the reliable loop‐assisted transfer method for free‐standing graphene sheets.
This paper provides a brief summary of the history, development and variety of applications of electron microscopy techniques to analyze coals, organic-rich shales, and carbonaceous materials. ...General construction and principles of operation of transmitted (TEM) and scanning electron microscope (SEM) are outlined, along with guidance on specimen preparation, and a brief overview of published TEM and SEM applications related to coal, shales, and carbonaceous materials. This work was accepted as the chapter 18.2 of International Committee for Coal and Organic Petrology Methods Handbook at the ICCP Plenary Session on September 27, 2018 in Brisbane (Australia).
•Construction and operational principles of a TEM and SEM.•Specimens’ preparation techniques used for TEM and SEM study.•Application of TEM to study coals and carbon materials.•Application of SEM to study coals, organic-rich shales and carbonaceous matter.
Among 2D materials that recently have attracted enormous interest, black phosphorus (BP) is gaining a rising popularity due to its tunable band‐gap structure, which is strongly correlated to the ...thickness and can enable its use in optoelectronic and electronic applications. It is therefore important to provide a facile and scalable methodology to prepare single or few‐layer BP nanosheets. We propose herein a simple and fast top‐down method to exfoliate a BP crystal into nanosheets of reduced thickness by using electrochemistry. The application of an anodic potential to the crystal in an acidic aqueous solution allows control over the exfoliation efficiency and quality of the nanosheets produced. X‐ray photoelectron spectroscopy (XPS), Raman spectroscopy, and scanning transmission electron microscopy (STEM) have been applied to fully characterize the exfoliated material, which presented significantly reduced layer thickness compared to the starting bulk material.
A layered approach: A simple and fast top‐down electrochemical method for exfoliating a BP crystal into nanosheets of reduced thickness is proposed. The application of an anodic potential to the crystal in an acidic solution allows control over the exfoliation efficiency and quality of the nanosheets produced.
•CoFe2O4 nanoparticles were prepared by co-precipitation using 4 precipitating agents.•The intermediate products were calcined at 600 °C for 4 h.•X-ray peak profile analysis (XPPA) were used to ...estimate the physical parameters.•D-S method, W-H plot, H-W plot & SSP technique results were highly intercorrelated.•XRD, SEM, TEM, DLS & ζ-potential results indicate KOH as the most suitable alkali.
Cobalt ferrite (CoFe2O4) nanoparticles have been developed by co-precipitation technique using four distinct precipitating agents, e.g., mixture of sodium hydroxide (NaOH) and sodium carbonate (Na2CO3), sodium hydroxide (NaOH), ammonium hydroxide (NH4OH), potassium hydroxide (KOH). The prepared systems had been investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Nanoparticle analyzer and Transmission electron microscopy (TEM). X-ray peak profile analysis (XPPA) had been used to estimate the physical parameters such as crystallite size and lattice strain by Debye-Scherrer (D-S) method, Williamson-Hall (W-H) plot, Halder-Wagner (H-W) technique and Size-Strain plot (SSP) technique. Different precipitating agents influence strongly the structure, size distribution, morphology and stability of the nanoparticles and on the basis of these parameters an optimum sample had been selected. The crystallite size calculated from XRD and particle size calculated from SEM shows a narrow size distribution with averages between 26.6–50.4 nm and 54–98 nm respectively, for all the samples. The particle size obtained from TEM shows high compatibility with XRD results with averages between 20 and 50 nm. The average lattice strain, dislocation density, lattice constant, cell volume, zeta potential was between 0.00094 and 0.0015, (4.34–14.13) × 1014 (lines/m2), 8.36870–8.38558 Å, 586.10–589.65 Å3, −87.8–27.7 mV respectively. The results estimated from the D-S method, W-H plot, H-W plot, SSP technique, SEM, Nanoparticle Analyzer and TEM regarding the structural and morphological parameters of the CoFe2O4 nanoparticles had been highly intercorrelated. Among the XPPA methods, SSP method is the most compatible one since the data points more accurately fits in this method with average correlation coefficient value (R2) of 0.99 that has been reinforced from TEM results as well. The synthesized CoFe2O4 nanoparticles can be applicable as liquid black coloring agent on ceramic surface after mixing with suitable solvent.
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