Nanometer Resolution Elemental Mapping in Graphene-Based TEM Liquid Cells

Kelly, Daniel J.; Zhou, Mingwei; Clark, Nick; Hamer, Matthew J.; Lewis, Edward A.; Rakowski, Alexander; Haigh, Sarah J.; Gorbachev, Roman

doi:10.1021/acs.nanolett.7b04713

Cited by 123 publications

(153 citation statements)

References 58 publications

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“…1c and d). The wells' ring-shaped top was typically 1-µm wide to provide a sufficiently large atomically-flat area so that no gas diffusion could occur along the resulting 'atomicallytight' sealing with its clean and sharp interface 15,16 . The monocrystalline walls of our microcontainers were also impermeable, as reported previously 17 and confirmed in the present work using wells with walls of different thicknesses.…”

mentioning

confidence: 99%

Limits on gas impermeability of graphene

Sun

Yang

Kuang

et al. 2020

Nature

274

223

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Despite being only one-atom thick, defect-free graphene is considered to be completely impermeable to all gases and liquids [1][2][3][4][5][6][7][8][9][10] . This conclusion is based on theory 3-8 and supported by experiments 1,9,10 that could not detect gas permeation through micrometre-size membranes within a detection limit of 10 5 to 10 6 atoms per second. Here, using small monocrystalline containers tightly sealed with graphene, we show that defect-free graphene is impermeable with an accuracy of eight to nine orders of magnitude higher than in the previous experiments. We could discern permeation of just a few helium atoms per hour, and this detection limit is also valid for all other tested gases (neon, nitrogen, oxygen, argon, krypton and xenon), except for hydrogen. Hydrogen shows noticeable permeation, even though its molecule is larger than helium and should experience a higher energy barrier. The puzzling observation is attributed to a two-stage process that involves dissociation of molecular hydrogen at catalytically active graphene ripples, followed by adsorbed atoms flipping to the other side of the graphene sheet with a relatively low activation energy of about 1.0 electronvolt, a value close to that previously reported for proton transport 11,12 . Our work provides a key reference for the impermeability of two-dimensional materials and is important from a fundamental perspective and for their potential applications.From a theory standpoint, monolayer graphene imposes a very high energy barrier for penetration of atoms and molecules. Density-functional-theory calculations predict that the barrier E is at least several eV 2-6 , which should prohibit any gas permeation under ambient conditions. Indeed, one can estimate that at room temperature T it would take longer than the lifetime of the universe to find an atom energetic enough to pierce a defect-free membrane of any realistic size. These expectations agree with experiments that reported no detectable gas permeation through mechanically-exfoliated graphene. The highest sensitivity was achieved using micrometersize wells etched in oxidized silicon wafers, which were sealed with graphene 1,9,10 . In those measurements, a pressurized gas (e.g., helium) could permeate along the SiO 2 layer and gradually fill the microcontainers making so-called 'nanoballoons'. Their consecutive deflation in air could be monitored using atomic force microscopy (AFM), and it was shown that the leakage occurred only along the SiO 2 surface, within several minutes but independently of the number of graphene layers used for the sealing 1 . These studies allowed a conclusion that graphene membranes were impermeable to all gases, at least with the achieved accuracy of 10 5 -10 6 atoms s -1 . This was further corroborated by creating individual atomic-scale defects in graphene nanoballoons, which resulted in their relatively fast deflation/inflation and confirmed the high sensitivity of the method 9,10 .

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mentioning

confidence: 99%

Limits on gas impermeability of graphene

Sun

Yang

Kuang

et al. 2020

Nature

274

223

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“…Graphene liquid cell has been suggested as a successful platform for EELS analysis . Figure d shows a schematic diagram of ferritin molecules in graphene sandwiches and acquired Fe, N, and O elemental maps from EELS .…”

Section: In Situ Tem In Liquid Environmentmentioning

confidence: 99%

In Situ Transmission Electron Microscopy on Energy‐Related Catalysis

Hwang

Chen

Zhou

et al. 2019

Advanced Energy Materials

106

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Energy‐related catalytic reactions have been extensively investigated in past years in order to efficiently utilize clean and environmentally benign energy sources. In these systems, the catalysts and the catalyst/active medium interfaces play a crucial role in determining their performance. Thus, understanding the physical and chemical properties of catalysts during reactions is of importance to provide fundamental insights for designing the devices. Transmission electron microscopy can provide tremendous information regarding materials' morphology, microstructure, and chemical properties at nanoscales. With in situ electron microscopy, dynamic processes of catalytic reactions in both gas and liquid environments have been investigated in real time. In this paper, the recent research progress of in situ and operando electron microscopy techniques are introduced with the representative works in energy‐related reactions, including electrochemical catalysis in liquid media and heterogeneous catalysis in gas media. The uniqueness of the specific electron microscopy methods and scientific merits of each work are highlighted. Finally, outlooks on emerging research opportunities are discussed.

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“…Development of robust technologies for GLC sample preparation can play a key role in the future of in situ liquid‐cell TEM accordingly. Toward this goal, predetermined and uniform GLC capsules were prepared by loading a lithography patterned h‐BN substrate with liquid sample and encapsulating it with graphene layers . The result was a h‐BN/graphene composite with replicated GLCs of liquid sample within.…”

Section: Future Glc Research Directionsmentioning

confidence: 99%

“…Although the current sample preparation methods do not accommodate such construction, there have been steps taken to achieve novel GLC designs. For instance, sandwiching a lithographically patterned boron nitride substrate between graphene layers on top and bottom is a promising approach to equip GLCs with inlet and outlet channels . Integrating such GLC constructions in a micro‐/nanofluidic device will then facilitate pumping liquids inside the GLC to circulate its content …”

Section: Future Glc Research Directionsmentioning

confidence: 99%

Advances in Graphene‐Based Liquid Cell Electron Microscopy: Working Principles, Opportunities, and Challenges

2019

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Imaging materials and biological structures in a liquid environment pose a significant challenge for conventional transmission electron microscopy (TEM) due to stringent requirement of ultrahigh vacuum design in the microscope column. The most recent liquid‐cell TEM technique, graphene liquid‐cell (GLC) microscopy, employs only layers of graphene to encapsulate liquid specimens. Recent efforts with GLC–TEM have demonstrated superior imaging resolution of beam‐sensitive specimens. Herein, the parameters that affect the quality of GLC analysis, including the graphene transfer onto TEM grids, are reviewed. Several important factors that affect the in situ TEM imaging of specimens, including the variations in GLC geometries and capillary pressure are discussed. The interaction between the electron beam and the liquid along with the possibility for artifacts or the formation of radical ions is also highlighted in this review. The scientific discoveries enabled by GLC–TEM in the areas of nucleation and growth of crystals, corrosion, battery science, as well as high‐resolution imaging of organelles and proteins are also briefly discussed. Finally, possible future research directions of GLC–TEM and the associated challenges are discussed. The synergistic effort to accomplish the proposed research directions has the potential to yield new discoveries in both materials and life sciences.

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Nanometer Resolution Elemental Mapping in Graphene-Based TEM Liquid Cells

Cited by 123 publications

References 58 publications

Limits on gas impermeability of graphene

Limits on gas impermeability of graphene

In Situ Transmission Electron Microscopy on Energy‐Related Catalysis

Advances in Graphene‐Based Liquid Cell Electron Microscopy: Working Principles, Opportunities, and Challenges

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