Controlled beams of shockfrozen, isolated, biological and artificial nanoparticles

TL;DR

This paper demonstrates rapid shock-freezing of isolated biological and artificial nanoparticles in a gas phase, enabling high-resolution imaging and nanoscience applications through improved sample delivery methods.

Contribution

It introduces a novel shock-freezing technique for nanoparticles, achieving microsecond cooling in a helium buffer gas, and characterizes the resulting nanoparticle beams with microscopy and simulations.

Findings

Nanoparticles can be transferred into the gas phase and shock-frozen within microseconds.

Particle beams can be focused to less than 100 micrometers and characterized accurately.

The method is suitable for advanced imaging and nanoscience applications.

Abstract

X-ray free-electron lasers (XFELs) promise the diffractive imaging of single molecules and nanoparticles with atomic spatial resolution. This relies on the averaging of millions of diffraction patterns of identical particles, which should ideally be isolated in the gas phase and preserved in their native structure. Here, we demonstrated that polystyrene nanospheres and Cydia pomonella granulovirus can be transferred into the gas phase, isolated, and very quickly shockfrozen, i.e. cooled to 4~K within microseconds in a helium-buffer-gas cell, much faster than state-of-the-art approaches. Nanoparticle beams emerging from the cell were characterized using particle-localization microscopy with light-sheet illumination, which allowed for the full reconstruction of the particle beams, focused to $<100\:\mu\text{m}$, as well as for the determination of particle flux and number density. The experimental results were quantitatively reproduced and rationalized through particle-trajectory simulations. We propose an optimized setup with cooling rates for few-nanometers particles on nanoseconds timescales. The produced beams of shockfrozen isolated nanoparticles provide a breakthrough in sample delivery, e.g. for diffractive imaging and microscopy or low-temperature nanoscience.