Tracking single adatoms in liquid in a transmission electron microscope

Abstract

Single atoms or ions on surfaces affect processes from nucleation 1 to electrochemical reactions 2 and heterogeneous catalysis 3 . Transmission electron microscopy (TEM) is a leading approach for visualizing single atoms on a variety of substrates 4,5. It conventionally requires high vacuum conditions, but has been developed for in situ imaging in liquid and gaseous environments 6,7 with a combined spatial and temporal resolution that is unmatched by any other method -notwithstanding concerns about electron beam effects on samples. When imaging in liquid using commercial technologies, electron scattering in the windows enclosing the sample and in the liquid generally limits the achievable resolution to a few nanometres 6,8,9 . Graphene liquid cells, on the other hand, have enabled atomic resolution imaging of metal nanoparticles in liquids 10 . Here we show that a double graphene liquid cell, comprised of a central molybdenum disulphide monolayer separated by hexagonal boron nitride spacers from the two enclosing graphene windows, makes it possible to monitor with atomic resolution the dynamics of platinum adatoms on the monolayer in an aqueous salt solution. By imaging over 70,000 single adatom adsorption sites, we compare the site preference and dynamic motion of the adatoms in both a fully hydrated and vacuum state. We find a modified adsorption site distribution and higher diffusivities for the adatoms in liquid phase compared to those in vacuum. This approach paves the way for in situ liquid phase imaging of chemical processes with single atom precision.

Experimental Guidelines to Image Transient Single-Molecule Events Using Graphene Liquid Cell Electron Microscopy

“…Regarding resolution, motion blurring is a fundamental limitation, yet this limitation could be alleviated using more sophisticated image processing and state-of-the-art direct electron detector and aberration correcting instruments. Indeed, using these approaches single-atom dynamics has been imaged in a GLC …”

“…Indeed, using these approaches single-atom dynamics has been imaged in a GLC. 66 The Supporting Information contains supplementary figures S1 to S11 and legends for movies S1 to S3.…”

High-Resolution Bulgeless Liquid-Cell Electron Microscopy

“…Liquid-cell electron microscopy (LCEM) [1][2][3][4][5][6][7] is a known state-of-the-art technique used to perform high-magnification imaging of nanomaterials and biological specimens which are suspended in a liquid inside of a nanofluidic cell (NFC). There are two types of LCEM systems; those connected to a syringe pump and capable of conferring liquid flow, commonly known as 'flow LCEM systems' [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] , and those which are stationary systems [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] herein referred to as 'static LCEM systems'. Current LCEM technology is limited in its ability to precisely control the effective thickness of the liquid layer.…”

Single Molecule Imaging with Liquid Phase Electron Microscopy

“…The method has contributed tremendously to the understanding of nanoparticle synthesis, assembly, and catalysis, achieving single atom spatial resolution and millisecond temporal resolution. [ 1 ] Due to the notorious problems of imaging organic samples with the electron beam—low contrast and damage‐prone compared with inorganic nanoparticles containing metal elements—similar applications have been greatly retarded. With the synergistic advancements in sample preparation, instrumentation, and data analysis, using low electron dose and with rigorous considerations of electron‐liquid interactions, recent works have successfully imaged the formation and coalescence of polymer micelles, peptide assembly, and crystallization of proteins.…”