Title: Advanced Electron Microscopy of Clusters Grown Inside Superfluid Helium Droplets: Advances, Challenges, and Perspectives
Authors: Daniel Knez, Wolfgang E. Ernst, Gerald Kothleitner, Ferdinand Hofer
Date: 2026-02-19
Working Group: AND, WG3, WG4
Grant Period: GP4
Grant Period Goal (number): GAPG-6, GAPG-7
Covered deliverables from the MoU (number): 4.1.1, 4.1.2
Countries involved: Austria
Number of female/young/ITC coauthors: 0/1/0
Is the publication open access?: Yes
Is the publication co-lead by a YRI?: Yes
Abstract: Superfluid helium nanodroplets act as ultracold, nanoscale “cryostats” that enable the synthesis of exceptionally pure metallic,
bimetallic, and hybrid nanoparticles with precise control over size and architecture. This review highlights how advanced electron
microscopy—particularly aberration-corrected scanning transmission electron microscopy combined with spectroscopy—reveals
the structure, composition, and three-dimensional morphology of these particles at near-atomic resolution. In situ heating and
cooling experiments uncover unique thermodynamic behaviors, such as nanowire breakup, alloying, and structural inversion,
while studies on beam-induced effects expose atomic displacements and radiolysis-driven chemistry. The soft-landing deposition
of the helium droplet method preserves metastable configurations and facilitates the creation of nanoparticle architectures that
are unattainable by conventional routes. Looking ahead, emerging low-dose imaging techniques, phase-sensitive methods, and
machine learning-driven analyses promise to further expand our ability to design and study functional nanomaterials for use in
catalysis, plasmonics, and quantum technologies.
