scholarly journals Single-Molecule van der Waals Compass

2020 ◽  
Author(s):  
Xiao Chen ◽  
Boyuan Shen ◽  
Huiqiu Wang ◽  
Hao Xiong ◽  
Weizhong Qian ◽  
...  
Keyword(s):  
Single Molecule ◽  
Potential Field ◽  
Van Der Waals ◽  
Real Space ◽  
Channel Structure ◽  
Transmission Electron ◽  
Imaging Results ◽  
Scanning Transmission ◽  
Para Xylene ◽  
Temporal Dimensions

Abstract Imaging the single molecules is always challenging under the diverse microscopes, but highly demanded for investigating the intermolecular interactions at the molecular level1-6. The van der Waals (vdW) interactions at sub-nanometer scale will deeply influence various molecular behaviors under the confinement conditions7-11. Here, inspired by the traditional compass12, we introduce a classical strategy using a vertical para-xylene (PX) molecule as a rotating pointer to detect the vdW potential field in a MFI straight channel. Based on the integrated differential phase contrast scanning transmission electron microscopy (iDPC-STEM)13-17, we achieve the real-space imaging of single PX molecule pointer in each channel with a certain orientation. The solid relation between the pointer orientation and atomic channel structure in this vdW compass is established by combining the calculations and imaging results. Thus, these PX orientations help us identify the varied vdW potential field related to the channel geometry both in the spatial and temporal dimensions. This work not only provides a visible and sensitive pointer to investigate the host-guest vdW interactions in porous materials at the molecular level, but also promotes the further imaging and study of other single-molecule behaviors by the iDPC-STEM.

Three-dimensional real-space crystallography of MCM-48 mesoporous silica revealed by scanning transmission electron tomography

2006 ◽  
Vol 418 (4-6) ◽  
pp. 540-543 ◽  
Author(s):  
Timothy J.V. Yates ◽  
John Meurig Thomas ◽  
Jose-Jesus Fernandez ◽  
Osamu Terasaki ◽  
Ryong Ryoo ◽  
...  
Keyword(s):  
Mesoporous Silica ◽  
Electron Tomography ◽  
Three Dimensional ◽  
Real Space ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

Thickness and Stacking Sequence Determination of Exfoliated Dichalcogenides (1T-TaS2, 2H-MoS2) Using Scanning Transmission Electron Microscopy

2018 ◽  
Vol 24 (4) ◽  
pp. 387-395 ◽  
Author(s):  
Robert Hovden ◽  
Pengzi Liu ◽  
Noah Schnitzer ◽  
Adam W. Tsen ◽  
Yu Liu ◽  
...  
Keyword(s):  
Transition Metal Dichalcogenides ◽  
Single Layer ◽  
Atomic Layer ◽  
Real Space ◽  
Dark Field ◽  
Crystal Thickness ◽  
Stacking Sequence ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

AbstractLayered transition metal dichalcogenides (TMDs) have attracted interest due to their promise for future electronic and optoelectronic technologies. As one approaches the two-dimensional (2D) limit, thickness and local topology can greatly influence the macroscopic properties of a material. To understand the unique behavior of TMDs it is therefore important to identify the number of atomic layers and their stacking in a sample. The goal of this work is to extract the thickness and stacking sequence of TMDs directly by matching experimentally recorded high-angle annular dark-field scanning transmission electron microscope images and convergent-beam electron diffraction (CBED) patterns to quantum mechanical, multislice scattering simulations. Advantageously, CBED approaches do not require a resolved lattice in real space and are capable of neglecting the thickness contribution of amorphous surface layers. Here we demonstrate the crystal thickness can be determined from CBED in exfoliated 1T-TaS2 and 2H-MoS2 to within a single layer for ultrathin ≲9 layers and ±1 atomic layer (or better) in thicker specimens while also revealing information about stacking order—even when the crystal structure is unresolved in real space.

Identification of site-specific isotopic labels by vibrational spectroscopy in the electron microscope

Science ◽  
2019 ◽  
Vol 363 (6426) ◽  
pp. 525-528 ◽  
Author(s):  
Jordan A. Hachtel ◽  
Jingsong Huang ◽  
Ilja Popovs ◽  
Santa Jansone-Popova ◽  
Jong K. Keum ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Spatial Resolution ◽  
Theoretical Calculations ◽  
Scanning Transmission Electron Microscope ◽  
Real Space ◽  
Site Specific ◽  
Spatially Resolved ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Isotopic Labels

The identification of isotopic labels by conventional macroscopic techniques lacks spatial resolution and requires relatively large quantities of material for measurements. We recorded the vibrational spectra of an α amino acid, l-alanine, with damage-free “aloof” electron energy-loss spectroscopy in a scanning transmission electron microscope to directly resolve carbon-site–specific isotopic labels in real space with nanoscale spatial resolution. An isotopic red shift of 4.8 ± 0.4 milli–electron volts in C–O asymmetric stretching modes was observed for 13C-labeled l-alanine at the carboxylate carbon site, which was confirmed by macroscopic infrared spectroscopy and theoretical calculations. The accurate measurement of this shift opens the door to nondestructive, site-specific, spatially resolved identification of isotopically labeled molecules with the electron microscope.

Energy-filtered electron diffraction from amorphized solids in the dedicated scanning transmission electron microscope (STEM)¶

1996 ◽  
Vol 54 ◽  
pp. 702-703
Author(s):  
A. N. Sreeram ◽  
L.-C. Qin ◽  
A. J. Garratt-Reed ◽  
L. W. Hobbs
Keyword(s):  
Electron Diffraction ◽  
Diffraction Data ◽  
Scanning Transmission Electron Microscope ◽  
Real Space ◽  
Distribution Functions ◽  
Space Distribution ◽  
Electron Diffraction Data ◽  
X Rays ◽  
Transmission Electron ◽  
Scanning Transmission

There is significant current interest in understanding the structure of aperiodic solids, such as originally crystalline material amorphized by ion implantation, impact or application of massive pressures, or deposited amorphous thin films, which occupy small volumes. Radially-averaged real-space distribution functions can be derived from diffraction data, the best of which come from thermal neutron diffraction, which inconveniently requires large volumes. Neutron data are collectable in reciprocal space out to q ≡ 2sin(Θ/2)/λ = 70 nm-1, where Θ is the scattering angle and λ the wavelength, or about twice as far as for X-rays, which also require large diffracting volumes. Electron diffraction is the only recourse for very small volumes because of the much stronger interaction of the electron, but spectra must be energy filtered to remove the large inelastic scattering component. Recently, it has been shown that useful electron diffraction data can be collected conveniently to at least q = 16 nm-1 in the VG HB5 dedicated 100-kV field-emission STEM. This contribution details our experiences with improved collection in the VG HB603 instrument operating at 250 kV.

scholarly journals Metal atom–guided conformational analysis of single polynuclear coordination molecules

2021 ◽  
Vol 7 (32) ◽  
pp. eabd9887
Author(s):  
Kenji Takada ◽  
Mari Morita ◽  
Takane Imaoka ◽  
Junko Kakinuma ◽  
Ken Albrecht ◽  
...  
Keyword(s):  
Single Molecule ◽  
Microscopic Observation ◽  
Electron Microscopic Observation ◽  
Dark Field ◽  
Electron Microscopic ◽  
Electron Dose ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Planar Molecules

Microscopic observation of single molecules is a rapidly expanding field in chemistry and differs from conventional characterization techniques that require a large number of molecules. One of such form of single-molecule microscopy is high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), which is especially suitable for coordination compounds because of its atomic number–dependent contrast. However, to date, single-molecule observations using HAADF-STEM has limited to simple planar molecules. In the present study, we demonstrate a direct structural investigation of nonplanar dendronized polynuclear Ir complexes with subnanometer resolution using Ir as an atomic label. Decreasing the electron dose to the dendrimer complexes is critical for the single-molecule observation. A comparison with simulated STEM images of conformational isomers is performed to determine the most plausible conformation. Our results enlarge the potential of electron microscopic observation to realize structural analysis of coordination macromolecules, which has been impossible with conventional methods.

scholarly journals Resolving atomic SAPO-34/18 intergrowth architectures for methanol conversion by identifying light atoms and bonds

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Boyuan Shen ◽  
Xiao Chen ◽  
Xiaoyu Fan ◽  
Hao Xiong ◽  
Huiqiu Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Methanol Conversion ◽  
Real Space ◽  
Zeolite Catalysts ◽  
Structure Property ◽  
Synthesis Conditions ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Micro Structures ◽  
Catalytic Performances

AbstractThe micro-structures of catalyst materials basically affect their macro-architectures and catalytic performances. Atomically resolving the micro-structures of zeolite catalysts, which have been widely used in the methanol conversion, will bring us a deeper insight into their structure-property correlations. However, it is still challenging for the atomic imaging of silicoaluminophosphate zeolites by electron microscopy due to the limits of their electron beam sensitivity. Here, we achieve the real-space imaging of the atomic lattices in SAPO-34 and SAPO-18 zeolites, including the Al–O–P atoms and bonds, by the integrated differential phase contrast scanning transmission electron microscopy (iDPC-STEM). The spatial distribution of SAPO-34 and SAPO-18 domains in SAPO-34/18 intergrowths can be clearly resolved. By changing the Si contents and templates in feed, we obtain two SAPO-34/18 catalysts, hierarchical and sandwich catalysts, with highly-mixed and separated SAPO-34 and SAPO-18 lattices respectively. The reduced diffusion distances of inside products greatly improve the catalytic performances of two catalysts in methanol conversion. Based on the observed distributions of lattices and elements in these catalysts, we can have a preliminary understanding on the correlation between the synthesis conditions and structures of SAPO-34/18 intergrowth catalysts to further modify their performances based on unique architectures.

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