Changes in the cell wall area of fibrous cells in the earlywood and latewood of various wood species during [C2mim][Cl] treatment at 120°C [35, 36]. The cell walls of both earlywood and latewood were swollen by [EtPy][Br] treatment (Figure 5c).
Scanning electron microscopy observations
In polarized light micrographs, the brightness from the birefringence of cellulose showed no changes upon [EtPy][Br] treatment (Figure 5d). This result implies that [EtPy][Br] treatment has no significant effect on the crystalline structure of cellulose in wood cell walls.
Confocal Raman microscopy analysis
Raman spectra for S2 of Fagus crenata wood fibers after treatment with [C2mim][Cl] (a) and [EtPy][Br]. After treatment, changes in the distribution of chemical compounds were similar for tracheids of Cryptomeria japonica and wood fibers of Fagus crenata.
In addition, the intensity of the lignin band at 1657 cm-1 decreased significantly for all regions measured except for the axial parenchyma cell sample. Morphological and topochemical characteristics of wood cell walls treated with ionic liquids were studied using various microscopic techniques.
During the liquefaction processing of wood in ionic liquids, the ultrastructure and chemical compositions of wood showed inhomogeneous-. The development of sensitive analytical methods on wood cell walls for chemical information with much higher spatial resolution will open a new field of wood science and technology.
The trend of the spectral changes is consistent with the morphological changes observed by SEM (Figure 8). These results will serve to cultivate a better understanding of the liquefaction mechanism of woody biomass in ionic liquids and accelerate the development of ionic liquid treatment for wood-based biorefinery.
Effect of reaction atmosphere on the liquefaction and depolymerization of wood in the ionic liquid 1-ethyl-3-methylimidazolium chloride. Topochemical and morphological characterization of wood cell wall treated with the ionic liquid, 1-ethylpyridinium bromide.
FT-Raman spectroscopy of wood: Identification of the contributions of lignin polymers and carbohydrates to the spectrum of black spruce (Picea mariana).
The New Youth of the In Situ Transmission Electron Microscopy
Due to the current and ever-expanding scope of the in situ (S)TEM field, this chapter presents only some of the latest and most exciting innovations and results achieved in this field. In the following section, attention is then focused on a kind of "variation on a theme" of the in situ sample heating.
In situ heating TEM experiments in vacuum
- In situ TEM heating in Au nanoparticles
- In situ chemical reactions of semiconductor‐based materials
- In situ TEM heating for graphene studies
- New directions and perspectives of in situ TEM annealing
Adapted with permission from ; (B) dissolution of the SnO2 nanowire in the Au catalyst tip during in situ heating experiments. An alternative approach to in situ experiments uses annealing to introduce chemical transformations into candidate materials.
In situ gas‐solid reactions in environmental (S)TEM
- The differentially pumped system
- The window‐closed E‐cell
The corresponding EEL spectra of the peripheral region (below) show the coexistence of Cu metal moieties (marker 1) in the Cu2O nanocube (marker 2). Such is the case of the study on yttria-stabilized zirconia (YSZ) NPs as a treatment device for soot exhaust products due to their oxygen scavenging ability .
In situ (S)TEM imaging of liquid specimens
- The point resolution when using an in situ sample holder for liquids 1. TEM
- In situ liquid TEM for materials science studies
- In situ liquid TEM for biological sciences studies
This kind of E cell was just put in a normal TEM holder instead of the grid. They consisted in showing not only the nucleation and growth of the Pt nanoclusters over time in the sealed E-.
The evolution of PVP‐GNRs within the GSCs was then followed for a total time of 30 s, using classical TEM geometry performed at medium magnification, and with a high contrast objective lens and an electron beam acceleration voltage of 120 kV. As shown in Figure 14B, the movement of PVP-GNRs inside GSCs is similar for both incubation times: a local displacement of PVP-GNRs and their surrounding solution was observed.
Nanoparticle metamorphosis: an in situ high temperature transmission electron microscopy study of the structural evolution of heterogeneous Au:Fe2O3 nanoparti-. Design and applications of environmental cell transmission electron microscope for in situ observations of gas-solid reactions.
Sealed gas cells
- Interactions between materials and gases
- Suppression of specimen evaporation
- Oxidation and reduction of metals
- In situ growth of nanostructures
- Reactions with atomic/ionized gases
- Dynamic observation of catalysts and catalytic reactions
- Biological studies
- In situ investigations on cladding materials
Their grid spacing corresponds to the distance from the origin and re‐. The large, red circle corresponds to a spacing of 0.21 nm. The orientation of the observed Pt(111) lattice edges is consistent with the superimposed crystal lattice vectors and the zone axis (color online) .
Sealed liquid cells
Lithiation of a Si nanowire immersed in a liquid electrolyte proceeded in a core-shell manner. In situ TEM observation of Cu-coated Si (Cu-Si) NW lithiation.
Summary and future research directions
In situ transmission electron microscopy observation of microstructure and phase evolution in a SnO2 nanowire during lithium intercalation. Investigation of the degradation mechanisms in electrolyte solutions for Li-ion batteries by in situ transmission electron microscopy.
Advanced Scanning Tunneling Microscopy for Nanoscale Analysis of Semiconductor Devices
Preparation of Si device cross-sections
- Passivation by hydrogenation
- Passivation by an ultrathin oxide
- Formation of C 60 monolayer films
Chemical and electrical passivation of solid surfaces is the subject of extensive research in catalysis to control the charge transfer process and chemical reactions in solid-liquid and solid-state. Therefore, passivation of Si surfaces by hydrogenation or oxidation has been applied to reproducibly prepare uniform surfaces of device cross-sections and to obtain a very low density of surface states.
Tunneling microscopy: basics
The shape of the tunnel barrier determines the electron transmission factor and the value of the tunnel current. The depth of the band bending region (w) depends on the electric field shielding by the electric charge in the semiconductor and is given by .
Advanced STM modes
- Vacuum gap modulation method
- Molecule-assisted probing method
- A dual-imaging method
At the resonance state, the Fermi energy of the STM tip aligns with the lowest unoccupied molecular orbital (LUMO), and thus the strength of electric field in the vacuum gap is given by F = (ΦM − EA)/Z0. The spatial variation of the frequency shift (Δf) reflects variations in the interaction force caused by charge carriers, impurity charges and surface imperfections as illustrated in Figure 5(b).
- Channel length in small MOSFET
- Super-junction devices fabricated by the channeling ion implantation
- Length-dependent resistivity of Si nanowires
- Wavelength-dependent photocarrier distribution across strained Si stripes
The interaction strength depends on the depth of the donor site and the electrostatic screening by mobile carriers. We see in Figure 8(c) that the current gradually decreases in the NW interior with distance from the Si pad due to the dependence of the NW resistance on its length.
Simulations of tunneling current spectra
The light intensity was mechanically modulated at a frequency of ∼3 kHz, and the computer signal was measured by an embedding unit. The current continuity model accounts for charge carrier transport between states in an STM probe and the conduction and valence band of Si and is implemented on the basis of a technological computer-aided design (TCAD) semiconductor device simulator code .
Accuracy relies on the simulation's ability to account for quantum phenomena, and further development of simulations based on the current continuum model will be essential. The capability of the molecular-assisted test method has been demonstrated using C60 molecules.
32] Nishizawa M., Bolotov L., Tada T., and Kanayama T.: Scanning tunneling microscopy detection of individual dopant atoms on wet-prepared Si(111):H surfaces. 40] Kanayama T., Nishizawa M., and Bolotov L.: Dopant and carrier concentration profiling at atomic resolution by scanning tunneling microscopy.
Electron Orbital Contribution in Distance‐Dependent STM Experiments
Role of the electron orbitals and tip-surface distance in STM experiments: theory
- Spatial resolution with different atomic orbitals at the tip apex
- Electronic structure of realistic tips at small tunneling gaps
- Role of atomic relaxations at small tip-surface distances
- Reduction in tunneling current channels with decreasing tip‐surface distance
The role of electron orbitals and tip-surface distance in STM experiments: theoretical experiments: theory. At large tip-sample distances, there is no significant vertical displacement of the adatom [ Figure 2(c) ].
Electron orbital resolution in distance‐dependent STM experiments
- Tip orbitals resolved using p z states of the Si(111)7×7 surface atoms
- d yz electron orbital of a MnNi tip resolved in STM experiments on the Cu(014)–O surface Figure 4(a) shows the STM image of the Cu(014)–O surface measured using a polycrystalline
- Distance dependence of the W tip orbital contribution in STM experiments on graphite
- d xz ‐orbitals of the surface atoms resolved using tungsten tips
- STM imaging of graphite (0001) using a ‐oriented diamond tip
- STM experiments with functionalized tips terminated by a light element atom The experiments with the diamond tip (Figure 7) show that an enhancement of the spatial
- STM imaging of the random bond length distortions in graphene using a W tip Figure 9 demonstrates the picometer lateral resolution achieved in high‐resolution STM
This can be explained by a large contribution of special electron orbitals of the tip atom at certain distances of the tip sample [ Figure 5(a) ]. STM images of graphene synthesized on SiC(001) demonstrating atomic-scale waviness (a) and random picoscale distortions of carbon bond lengths in the graphene lattice (b, c).
Effect of orbital symmetry of the tip on scanning tunneling spectra of Bi2Sr2CaCu2O8+δ. Different tips for high-resolution atomic force microscopy and scanning tunneling microscopy of single molecules.
Wavefunction Analysis of STM Image: Surface Reconstruction of Organic Charge Transfer Salts
Surface states of charge transfer salts
Schematic image of the electric field produced by an ET2+ and I3− bilayer with the same total charges of each layer in α-(BEDT-TTF)2I3. Thus, the surface ET layer approximately only senses the electric field of the I3 layer within the double layer (reused from Ref. ).
At the second point, the partner anion layer of the bilayer generally forms a flat sheet and creates an approximately uniform electric field normal to the anion layer . ΔS,i is the relative height difference of the corresponding sulfur atom with respect to ET(B), measured from the a−b plane, obtained from the structural data .
Surface reconstruction in charge transfer salts
- Charge redistribution in α-(BEDT-TTF) 2 I 3
- Translational reconstruction in β-(BEDT-TTF) 2 I 3
- Rotational reconstruction in (EDO-TTF) 2 PF 6
Based on the analyzed result of α-(ET)2I3 in the previous section, the missing steric hindrance of the surface (ET)2 layer with the I3− layer is also expected to have some effects on the surface electronic states of (ET)2. Topographies (A) along the oxygen pair of the EDO group and (B) along the oxygen and carbon atoms of the EDO-TTF molecules.
The first operation deletes the second half of the O2p orbital, which is not observed in the STM image. Comparison of symmetry breaking in the surface molecular structures of one- and two-dimensional bis(ethylenedithio)tetrathiafulvalene compounds.
Application of Scanning Acoustic Microscopy to Pathological Diagnosis
Principles of acoustic microscopy
Ultrasound waves from the transducer reflect from both the glass plate and sample sec. The waves reflected from both the glass and the samples are then collected by the same lens.
Preparation of sample materials
This relationship shows that Young's modulus (the modulus of elasticity) of the tissue and the SOS are closely related .
Observation procedure of SAM
After mechanical X-Y scanning, the SOS was calculated from each point on the cross-section and plotted on screen to create two-dimensional, color-coded images. Other data, such as section thickness and AOS, were also obtained from each point and displayed on the screen.
Application of SAM to tissue and cytology diagnosis
- Cardiac valve
- Gastrointestinal tract
- Liver and lung
The broad internal elastic lamina (arrows) has higher SOS values than those of the intima and media. Necrotic areas have higher SOS values than intact heart muscle on the more endocardial side.
Differentiation between malignant and benign effusions
The bipolar images on the right were obtained based on the upper and lower cut point values. These images were obtained by limiting the range of the color scale bar on the right side of the screen (yellow arrows).
SOS changes by fixation
Effects of PAS reaction on SOS imaging
Using tannic acid fixation, the SOS values increase according to the concentration and duration of fixation (Figure 17). After fixation, the SOS values in the adenocarcinoma increased, indicating that the cells had hardened.
Effects of collagenase on SOS values
Differences in SOS values and thickness were also compared using formalin and ethanol fixation. After the PAS reaction, SOS values increase according to optical staining strength (Figure 18), with more glycosylated regions appearing as higher SOS areas.
Statistical analysis of SOS
Skin SOS values of juvenile skin gradually decreased, while those of elderly skin were stable. The group of malignant cells has significantly greater SOS values than the group of benign cells (P < 0.01), and epi‐.
In tissue sections, each tissue component has a specific SOS value, as shown in Figure 22 and Table 2 for the stomach walls, where the mucosal layers have lower SOS values than the muscularis mucosae or muscularis propria layers. Carcinomas arising from the mucosal epithelium have almost the same SOS values as the mucosal layer, but poorly differentiated carcinomas have higher SOS values because of their desmoplastic reactions.