Nanosecond electron pulses in the analytical electron microscopy of a fast irreversible chemical reaction

Abstract

We show how the kinetics of a fast and irreversible chemical reaction in a nanocrystalline material at high temperature can be studied using nanosecond electron pulses in an electron microscope. Infrared laser pulses first heat a nanocrystalline oxide layer on a carbon film, then single nanosecond electron pulses allow imaging, electron diffraction and electron energy-loss spectroscopy. This enables us to study the evolution of the morphology, crystallography, and elemental composition of the system with nanosecond resolution. Here, NiO nanocrystals are reduced to elemental nickel within 5 µs after the laser pulse. At high temperatures induced by laser heating, reduction results first in a liquid nickel phase that crystallizes on microsecond timescales. We show that the reaction kinetics in the reduction of nanocrystalline NiO differ from those in bulk materials. The observation of liquid nickel as a transition phase explains why the reaction is first order and occurs at high rates.

Photo‐Thermal Switching of Individual Plasmonically Activated Spin Crossover Nanoparticle Imaged by Ultrafast Transmission Electron Microscopy

“…The temporal resolution in this configuration is approximately 10 ns; however, relative length changes can be recorded with slightly smaller steps. Due to repulsive electron-electron interactions within the intense pulses which cause a loss of coherence and increased energy width, the intensity of the electron pulses had to be limited [52,54] . The pump-probe delay is adjusted by synchronizing the two lasers with an electronic delay unit.…”

“…Due to repulsive electron-electron interactions within the www.advmat.de www.advancedsciencenews.com intense pulses which cause a loss of coherence and increased energy width, the intensity of the electron pulses had to be limited. [52,54] The pump-probe delay was adjusted by synchronizing the two lasers with an electronic delay unit. Since the length changes of the SCO particles were reversible, the experiment was carried out repeatedly for each measurement in a stroboscopic approach with a repetition frequency of 20 Hz.…”

Transient lensing from a photoemitted electron gas imaged by ultrafast electron microscopy

“…Transient lensing from a photoemitted electron gas imaged by ultrafast electron microscopy Omid Zandi 1,2 , Allan E. Sykes 1,2 , Ryan D. Cornelius 1,2 , Francis M. Alcorn 1,2 , Brandon Zerbe 4 , Phillip M. Duxbury 4 , Bryan W. Reed 5 , Renske M. van der Veen 1,2,3 Then…”

“…Ångstroms-micrometers (Å-μm) and femtoseconds-nanoseconds (fs-ns), respectively. In this regard, ultrafast electron microscopy (UEM) has recently emerged as a powerful technique for the study of ultrafast photoinduced processes in nanoscale systems [1][2][3][4][5][6][7][8][9][10][11][12][13][14] . The material is excited by a short fs-ns laser pulse, which is followed by a similarly short electron pulse that probes the ensuing dynamics by means of imaging, diffraction, or spectroscopy inside a transmission electron microscope (TEM).…”

Rapid In Situ Melting and Revitrification as an Approach to Microsecond Time-Resolved Cryo-Electron Microscopy

“…For the purpose of time-resolved cryo-EM experiments, it is crucial to have a detailed understanding of the temperature evolution of the sample, which ultimately determines the attainable time resolution. We therefore characterize the heating and cooling dynamics in situ with time-resolved electron microscopy [34][35][36][37][38] (Note S5 and Figure S2). We heat the sample in Figure 4a, which is held at 100 K, with a 20 µs laser pulse (13 mW).…”