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PDF 8. Conclusion - Hanoi University of Science and Technology

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Nguyễn Gia Hào

Academic year: 2023

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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).

Figure 1. The structures of typical cations and anions in ionic liquids.
Figure 1. The structures of typical cations and anions in ionic liquids.

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.

Figure 8. SEM images of transverse sections of Fagus crenata (a, c) and Quercus mongolica (b, d) before and after treat‐
Figure 8. SEM images of transverse sections of Fagus crenata (a, c) and Quercus mongolica (b, d) before and after treat‐

Conclusions

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.

Acknowledgements

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.

Author details

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.

Non-Optical Microscopy

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

Introduction

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 [34]; (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.

Figure 1. (A) Top view of a furnace‐based heating holder. The circular hole at the center of the furnace serves as lodg‐
Figure 1. (A) Top view of a furnace‐based heating holder. The circular hole at the center of the furnace serves as lodg‐

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 [90].

Figure 6. (A) Schema of a differentially pumped TEM system after [71]; (B) sequence of HRTEM images and the corre‐
Figure 6. (A) Schema of a differentially pumped TEM system after [71]; (B) sequence of HRTEM images and the corre‐

In situ (S)TEM imaging of liquid specimens

  • The point resolution when using an in situ sample holder for liquids 1. TEM
    • STEM
  • 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-.

Figure 10. Different possible configurations for electron microscopy in liquid. (A) TEM imaging of nanoparticles in a liquid  fully  enclosed  between  two  electron‐transparent  windows
Figure 10. Different possible configurations for electron microscopy in liquid. (A) TEM imaging of nanoparticles in a liquid fully enclosed between two electron‐transparent windows

Conclusions

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.

DOI: 10.2147/NSA.S8984

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.

Liquid Environment

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) [45].

Figure 1. Reaction between wet H 2  gas and an iron foil. Micrographs (a) and (b) were taken after a heavy electron irra‐
Figure 1. Reaction between wet H 2 gas and an iron foil. Micrographs (a) and (b) were taken after a heavy electron irra‐

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.

Figure 10. Images of Zircaloy lamella at nominally atmospheric pressure. (a) Initial structure
Figure 10. Images of Zircaloy lamella at nominally atmospheric pressure. (a) Initial structure

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 .

Figure 3. The principle of scanning tunneling microscopy of a semiconductor. (a) An STM setup, (b) an energy band diagram of a tunnel junction, and (c) a charge balance diagram.
Figure 3. The principle of scanning tunneling microscopy of a semiconductor. (a) An STM setup, (b) an energy band diagram of a tunnel junction, and (c) a charge balance diagram.

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).

Figure 4. Molecule-assisted probing method. (a) A setup. (b) An energy band diagram of a double-barrier junction un‐
Figure 4. Molecule-assisted probing method. (a) A setup. (b) An energy band diagram of a double-barrier junction un‐

Application examples

  • 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.

Figure 6. (a) Topographic image of a cross-section containing two small Si MOSFET devices
Figure 6. (a) Topographic image of a cross-section containing two small Si MOSFET devices

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 [94].

Conclusion

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.

Appendix A

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) ].

Figure 1. (a–c) The dρ = 0.08 eV/Å 3  isosurface of the change in electron density for the (a) He–W[011], (b) He–W[111], and (c) He–W[001] systems
Figure 1. (a–c) The dρ = 0.08 eV/Å 3 isosurface of the change in electron density for the (a) He–W[011], (b) He–W[111], and (c) He–W[001] systems

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[001] 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 [111]‐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[111] 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).

Figure 3. (a) 7.1×7.1 nm 2  STM images of the Si(111)7×7 surface measured at different bias voltages and tunneling cur‐
Figure 3. (a) 7.1×7.1 nm 2 STM images of the Si(111)7×7 surface measured at different bias voltages and tunneling cur‐

Conclusions

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. [1]).

Figure 1. Schematic picture of the electric field produced by a  ET 2 +  and  I 3 −  double layer with the same total charges of each layer in α-(BEDT-TTF) 2 I 3
Figure 1. Schematic picture of the electric field produced by a ET 2 + and I 3 − double layer with the same total charges of each layer in α-(BEDT-TTF) 2 I 3

Wavefunction analysis

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 [1]. 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 [23].

Figure 2. A schematic picture of a donor layer with a flat molecular plane. Electron wavefunctions are described by blue ellipses for π electrons of the donor molecules and a blue circle for s electron of the probe tip
Figure 2. A schematic picture of a donor layer with a flat molecular plane. Electron wavefunctions are described by blue ellipses for π electrons of the donor molecules and a blue circle for s electron of the probe tip

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.

Figure 6. Unit cell structure of α-(ET) 2 I 3  determined by the X-ray analysis at 300 K [23]
Figure 6. Unit cell structure of α-(ET) 2 I 3 determined by the X-ray analysis at 300 K [23]

Conclusion

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.

Figure 1. Appearance of scanning acoustic microscope systems. 1. Signal processor, 2. mechanical scanner with trans‐
Figure 1. Appearance of scanning acoustic microscope systems. 1. Signal processor, 2. mechanical scanner with trans‐

Preparation of sample materials

This relationship shows that Young's modulus (the modulus of elasticity) of the tissue and the SOS are closely related [10].

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

  • Skin
  • Artery
  • Cardiac valve
  • Gastrointestinal tract
  • Placenta
  • Liver and lung
  • Kidney
  • Heart
  • Thyroid
  • Cytology

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.

Figure 4. SOS images of the renal arteries in (RAs) young (A) and elderly (B) subjects
Figure 4. SOS images of the renal arteries in (RAs) young (A) and elderly (B) subjects

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).

Figure 15. SOS image of urothelial carcinoma and glioblastoma. Cells with various different shapes and sizes are present in the urine
Figure 15. SOS image of urothelial carcinoma and glioblastoma. Cells with various different shapes and sizes are present in the urine

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.

Figure 19. Effects of collagenase on SOS values. Changes in the SOS values in a section after collagenase treatment are shown
Figure 19. Effects of collagenase on SOS values. Changes in the SOS values in a section after collagenase treatment are shown

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‐.

Figure 21. Mean and SD of SOS values among various cells in fluids. There SOS values differ significantly among cell types
Figure 21. Mean and SD of SOS values among various cells in fluids. There SOS values differ significantly among cell types

Conclusion

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.

Hình ảnh

Figure 8. SEM images of transverse sections of Fagus crenata (a, c) and Quercus mongolica (b, d) before and after treat‐
Figure 8. SEM images of transverse sections of Fagus crenata (a, c) and Quercus mongolica (b, d) before and after treat‐
Figure 1. (A) Top view of a furnace‐based heating holder. The circular hole at the center of the furnace serves as lodg‐
Figure 2. (A) Representative HRTEM images showing the phase variations of a 7.5 nm wide Au NP as a function of temperature
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