Graphene Liquid Cell Electron Microscopy: Progress, Applications, and Perspectives

Abstract

Graphene liquid cell electron microscopy (GLC-EM), a cutting-edge liquid-phase EM technique, has become a powerful tool to directly visualize wet biological samples and the microstructural dynamics of nanomaterials in liquids. GLC uses graphene sheets with a one carbon atom thickness as a viewing window and a liquid container. As a result, GLC facilitates atomic-scale observation while sustaining intact liquids inside an ultra-high-vacuum transmission electron microscopy chamber. Using GLC-EM, diverse scientific results have been recently reported in the material, colloidal, environmental, and life science fields. Here, the developments of GLC fabrications, such as first-generation veil-type cells, second-generation well-type cells, and third-generation liquid-flowing cells, are summarized. Moreover, recent GLC-EM studies on colloidal nanoparticles, battery electrodes, mineralization, and wet biological samples are also highlighted. Finally, the considerations and future opportunities associated with GLC-EM are discussed to offer broad understanding and insight on atomic-resolution imaging in liquid-state dynamics.

Applications of in situ electron microscopy in oxygen electrocatalysis

“…Furthermore, reducing the thickness of the cell window also helps to improve the resolution. For instance, using graphene as the window material could realize atomic-resolution imaging [85] and nm-resolution elemental mapping in LC-(S)TEM [40] . However, current graphene-based TEM liquid cells are difficult to fabricate (very low success rate) and cannot be combined with electrochemistry accessories for electrocatalytic research.…”

“…However, the presence of liquid and the cell windows often significantly reduce the spatial resolution of the acquired images. Consequently, it is generally not possible to achieve atomic resolution in LC-(S)TEM, except in a few cases where graphene is used as the cell window material and the liquid layer is very thin [40][41][42] . Furthermore, the radiolysis of water caused by the electron beam irradiation produces various [71] , (B) an in situ electrochemical liquid cell placed in the optical path of TEM, and (C) an electrochemical microchip with micro-fabricated counter electrode (CE), working electrode (WE) and reference electrode (RE).…”

Recent Notable Approaches to Study Self‐Assembly of Nanoparticles with X‐Ray Scattering and Electron Microscopy

“…Flowcells, temperature control, included electrodes, user friendly dual-chip cells and more have been implemented and with modern microfabrication techniques the reproducibility and control of the geometry and the stability of the closed-cells has improved significantly. [172,174,198] Graphene is in principle superior to SiN as a window material in terms of minimum thickness and stability and used for innovative cell designs [199,200] but graphene-based cells are also more challenging to handle. [172,177] Liquid-phase SEM (LP-SEM) approaches [201] as well as spectroscopy modes [202] are also possible and similar considerations hold true as for ex situ EM, namely, that the resolution of LP-SEM (4-10 nm) is lower than that of LP-TEM but larger structures can be measured.…”

Perspective towards atomic‐resolution imaging of two‐dimensional polymers

“…Liquid‐cell TEM has been applied to reveal the reaction dynamics in situ, offering significant insights into the formation mechanisms of materials, for example, nucleation and growth of nanoparticles, assembly of inorganic and organic matters, biomineralization 36,37 . Notably, recent advancements and implementation of graphene liquid cells have brought liquid‐cell TEM into an atomic‐resolution era 38 . However, for 2D polymers and COFs, the exceedingly high proneness towards electron radiation renders in situ observation extremely challenging, if not impossible, precluding detailed analysis of interfacial growth mechanisms.…”