Optimizing the geometry of aerodynamic lens injectors for single-particle coherent diffractive imaging of gold nanoparticles

Lena Worbs; Nils Roth; Jannik Lübke; Armando D Estillore; P Lourdu Xavier; Amit K Samanta; Jochen Küpper

doi:10.1107/S1600576721009973

Optimizing the geometry of aerodynamic lens injectors for single-particle coherent diffractive imaging of gold nanoparticles

J Appl Crystallogr. 2021 Nov 16;54(Pt 6):1730-1737. doi: 10.1107/S1600576721009973. eCollection 2021 Dec 1.

Authors

Lena Worbs^{1

2}, Nils Roth^{1

2}, Jannik Lübke^{1

2

3}, Armando D Estillore¹, P Lourdu Xavier^{1

4}, Amit K Samanta¹, Jochen Küpper^{1

2

3}

Affiliations

¹ Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany.
² Department of Physics, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany.
³ Center for Ultrafast Imaging, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany.
⁴ Max Planck Institute for the Structure and Dynamics of Matter, Luruper Chaussee 149, 22761 Hamburg, Germany.

Abstract

Single-particle X-ray diffractive imaging (SPI) of small (bio-)nanoparticles (NPs) requires optimized injectors to collect sufficient diffraction patterns to allow for the reconstruction of the NP structure with high resolution. Typically, aerodynamic lens-stack injectors are used for NP injection. However, current injectors were developed for larger NPs (>100 nm), and their ability to generate high-density NP beams suffers with decreasing NP size. Here, an aerodynamic lens-stack injector with variable geometry and a geometry-optimization procedure are presented. The optimization for 50 nm gold-NP (AuNP) injection using a numerical-simulation infrastructure capable of calculating the carrier-gas flow and the particle trajectories through the injector is also introduced. The simulations were experimentally validated using spherical AuNPs and sucrose NPs. In addition, the optimized injector was compared with the standard-installation 'Uppsala injector' for AuNPs. Results for these heavy particles showed a shift in the particle-beam focus position rather than a change in beam size, which results in a lower gas background for the optimized injector. Optimized aerodynamic lens-stack injectors will allow one to increase NP beam density, reduce the gas background, discover the limits of current injectors and contribute to structure determination of small NPs using SPI.

Keywords: X-ray free-electron lasers; XFELs; coherent diffractive imaging; high-density beams; injectors; nanoparticles; numerical simulations; sample delivery; single particles.

Grants and funding

This work was funded by European Research Council, FP7 Ideas: European Research Council grant 614507; Deutsche Forschungsgemeinschaft; Deutsches Elektronen-Synchrotron; Joachim Herz Stiftung.