title: Single-nanoparticle phase transitions visualized by four-dimensional electron microscopy.
abstract: The advancement of techniques that can probe the behaviour of individual nanoscopic objects is of paramount importance in various disciplines, including photonics and electronics. As it provides images with a spatiotemporal resolution, four-dimensional electron microscopy, in principle, should enable the visualization of single-nanoparticle structural dynamics in real and reciprocal space. Here, we demonstrate the selectivity and sensitivity of the technique by visualizing the spin crossover dynamics of single, isolated metal-organic framework nanocrystals. By introducing a small aperture in the microscope, it was possible to follow the phase transition and the associated structural dynamics within a single particle. Its behaviour was observed to be distinct from that imaged by averaging over ensembles of heterogeneous nanoparticles. The approach reported here has potential applications in other nanosystems and those that undergo (bio)chemical transformations.
authors.affiliation: Physical Biology Center for Ultrafast Science and Technology, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: Renske M
authors.initials: RM
authors.lastname: van der Veen
authors.forename: Oh-Hoon
authors.initials: OH
authors.lastname: Kwon
authors.forename: Antoine
authors.initials: A
authors.lastname: Tissot
authors.forename: Andreas
authors.initials: A
authors.lastname: Hauser
authors.forename: Ahmed H
authors.initials: AH
authors.lastname: Zewail
mesh_terms: D008854:Microscopy, Electron / Q000379:methods*; D053758:Nanoparticles