Charged Nanoparticle Dynamics in Water Induced by Scanning Transmission Electron Microscopy

Abstract

Using scanning transmission electron microscopy we image ~ 4 nm platinum nanoparticles deposited on an insulating membrane, where the membrane is one of two electron-transparent windows separating an aqueous environment from the microscope’s high vacuum. Upon receiving a relatively moderate dose of ~ 104 e/nm2, initially immobile nanoparticles begin to move along trajectories that are directed radially outward from the center of the field of view. With larger dose rates the particle motion becomes increasingly dramatic. These observations demonstrate that even under mild imaging conditions, the in situ electron microscopy of aqueous environments can produce electrophoretic charging effects that dominate the dynamics of nanoparticles under observation.

Understanding the Role of Solvation Forces on the Preferential Attachment of Nanoparticles in Liquid

“…Due to beam charging effects, it is possible that the silver nanorods could obtain net, positive charges. 21,28 As the nanorods are suspended in dielectric liquid, discharge into solution is expected. Based on the characteristic time scale for electrical discharge obtained from Maxwell's equations, the discharge time of a nanoparticle in a dilute electrolyte is on the order of nanoseconds.…”

“…[12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] Particle coalescence has been observed for haematite, iron oxyhydroxide, platinum-iron alloy, platinum, silver, and gold, allowing for assessment of coalescence features such as preferred particle orientations and kinetics. [12][13][14][24][25][26] When performing these experiments, care must be taken to avoid electron beam artifacts, such as specimen charging/reduction, flow effects, and bubbles, that can influence specimen behavior.…”

“…[12][13][14][24][25][26] When performing these experiments, care must be taken to avoid electron beam artifacts, such as specimen charging/reduction, flow effects, and bubbles, that can influence specimen behavior. 18,21,22,27,28 However, recent experimental observations have shown that these effects can be quantified, controlled and mitigated using calibrated electron doses. [28][29][30] As a result, in situ TEM observations can be used as an accurate starting point for understanding nanoparticle behavior in liquids.…”

Bubble and Pattern Formation in Liquid Induced by an Electron Beam

“…[13][14][15][16][17][18] The beam can be used to charge nanoparticles and affect their motion. 11 Microstructural changes 25 as well as formation and dynamics of bubbles or voids due to the beam have been reported. 20,[26][27][28] Amongst a variety of potential beam effects, 29 radiation chemistry, or interaction of ionizing radiation with the fluid medium, is critically important.…”

Membrane protein stoichiometry studied in intact mammalian cells

“…It would not be possible to achieve nanoscale resolution at these thicknesses with transmission electron microscopy. Furthermore, although it has been suggested that Brownian motion should blur the images, this is not seen experimentally; instead, nanoparticles in close proximity to a membrane move several orders of magnitude slower than what would be expected for a bulk liquid (Ring & de Jonge, 2012;White et al, 2012;Verch et al, 2015).…”