Unusual molecular material formed through irreversible transformation and revealed by 4D electron microscopy

Veen, Renske M. van der; Tissot, Antoine; Hauser, Andreas; Zewail, Ahmed H.

doi:10.1039/c3cp51011e

Cited by 16 publications

(12 citation statements)

References 18 publications

(46 reference statements)

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“…The remaining material still displays a thermal expansion behavior. Indeed, it was shown that under certain favorable conditions, the Fe(pyrazine)Pt(CN) 4 nanoparticles can undergo a chemical transformation that involves the removal of pyrazine molecules from the 3D framework structure 52 . The remaining crystalline material does no longer display SCO, but it exhibits an exceptionally large negative thermal expansion coefficient in the a , b -plane.…”

Section: Resultsmentioning

confidence: 99%

Modeling nonequilibrium dynamics of phase transitions at the nanoscale: Application to spin-crossover

Park

Veen

2017

Structural Dynamics

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In this article, we present a continuum mechanics based approach for modeling thermally induced single-nanoparticle phase transitions studied in ultrafast electron microscopy. By using coupled differential equations describing heat transfer and the kinetics of the phase transition, we determine the major factors governing the time scales and efficiencies of thermal switching in individual spin-crossover nanoparticles, such as the thermal properties of the (graphite) substrate, the particle thickness, and the interfacial thermal contact conductance between the substrate and the nanoparticle. By comparing the simulated dynamics with the experimental single-particle diffraction time profiles, we demonstrate that the proposed non-equilibrium phase transition model can fully account for the observed switching dynamics.

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Section: Resultsmentioning

confidence: 99%

Modeling nonequilibrium dynamics of phase transitions at the nanoscale: Application to spin-crossover

Park

Veen

2017

Structural Dynamics

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“…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).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

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Understanding and controlling ultrafast charge carrier dynamics is of fundamental importance in diverse fields of (quantum) science and technology. Here, we create a three-dimensional hot electron gas through two-photon photoemission from a copper surface in vacuum. We employ an ultrafast electron microscope to record movies of the subsequent electron dynamics on the picosecond-nanosecond time scale. After a prompt Coulomb explosion, the subsequent dynamics is characterized by a rapid oblate-to-prolate shape transformation of the electron gas, and periodic and long-lived electron cyclotron oscillations inside the magnetic field of the objective lens. In this regime, the collective behavior of the oscillating electrons causes a transient, mean-field lensing effect and pronounced distortions in the images. We derive an analytical expression for the time-dependent focal length of the electron-gas lens, and perform numerical electron dynamics and probe image simulations to determine the role of Coulomb self-fields and image charges. This work inspires the visualization of cyclotron dynamics inside two-dimensional electron-gas materials and enables the elucidation of electron/plasma dynamics and properties that could benefit the development of high-brightness electron and X-ray sources.

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“…[22][23][24][25] In order to both understand these switching mechanisms and to design efficient integrated ST materials, grafting Fe(II) compounds to nanoparticles provides a relevant approach for experimentation. 31,32 Furthermore, ST polymeric chains of [Fe(aminotriazole) 3 ] n 2+ compounds have been processed into composite nanoparticles showing the consistency of their properties. 29,30 The photocommutation of three-dimensional Hoffmann clathrate [Fe II (pyrazine)][Pt(CN) 4 ] n nanocrystals has also been achieved and studied by 4D electronic microscopy.…”

Section: Introductionmentioning

confidence: 99%

Versatile nano-platforms for hybrid systems: expressing spin-transition behavior on nanoparticles

et al. 2015

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International audiencea The aim of this paper is to demonstrate the possibility of expressing molecular magnetic phenomena on hybrid nano-particles. The advantage of such composite materials is their wonderful versatility, in terms of choice of molecular compounds to be grafted on, and in terms of possibilities for integration in devices. As a first example, we designed a composite made of silica nanoparticles as cores on which Fe(II) coordination complexes displaying spin-crossover (SCO) phenomenon have been grafted in three steps involving the silanization of the SiO 2 core, the anchoring of bis(1-methylimidazolyl)-type ligands and at last the coordination of octahedral Fe(II) complexes at the surface of the nanoparticles. This step-by-step procedure enables an adequate coverage of the Fe(II) complexes at the surface of the nanoparticles that allows for the appearance of the spin-transition (ST) behavior at a level detectable by SQUID magnetometry. These tailor-made particles can thus be considered as nanometric switchable units

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Unusual molecular material formed through irreversible transformation and revealed by 4D electron microscopy

Cited by 16 publications

References 18 publications

Modeling nonequilibrium dynamics of phase transitions at the nanoscale: Application to spin-crossover

Modeling nonequilibrium dynamics of phase transitions at the nanoscale: Application to spin-crossover

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

Versatile nano-platforms for hybrid systems: expressing spin-transition behavior on nanoparticles

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