Photoinitiated Dynamics in Amorphous Solid Water via Nanoimprint Lithography

Area of Science:

• Materials Science
• Physical Chemistry
• Nanotechnology

Background:

• Single-pulse data collection is crucial for analyzing fragile samples like amorphous solid water (ASW) without irreversible alteration.
• Previous methods lacked well-defined molecular pathways in ASW and sample sizes suitable for molecular dynamics (MD) modeling.
• Overcoming these limitations is essential for advancing the study of molecular dynamics in condensed phases.

Purpose of the Study:

• To develop a method for single-pulse analysis of ASW samples.
• To enable atomistic molecular dynamics modeling of ejected molecular clusters.
• To demonstrate an application in chemical analysis using laser-induced desorption.

Main Methods:

• Combining nanoimprint lithography and photoinitiation to create arrays of gold nanoparticles.
• Irradiating nanoparticles with pulsed laser (532 nm) to eject doped ASW films at ~100 K.
• Utilizing nanoparticle spacing for independent "nanoexperiments" and high signal-to-noise ratios.

Main Results:

• Achieved high single-pulse signal-to-noise ratios through summation of ~10^6 nanoexperiments.
• Enabled atomistic (molecular) level modeling and simulation of ejected material due to small sample size.
• Demonstrated H/D scrambling in D2O/H2O films upon NO2 deposition, indicating proton presence via nitric acid catalysis.

Conclusions:

• The developed technique overcomes previous limitations in studying ASW and enables single-pulse analysis.
• The method facilitates unprecedented atomistic simulations of laser-ejected molecular systems.
• This approach offers a powerful tool for chemical analysis and understanding molecular dynamics in condensed phases.