Beyond Fragmentation: Unlocking New Frontiers in e-Beam Chemistry

"Electron beams (e-beams) have long been indispensable tools in science and technology, enabling the fabrication and analysis of nanoscale materials. From advanced imaging techniques to precision nanofabrication, e-beams play a crucial role in modern research and industry. However, despite extensive studies on electron-matter interactions at atomic and macroscopic scales, a critical gap remains in understanding these processes at the molecular-to-nano level—the domain most relevant for next-generation nanotechnologies."

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In our recent study we took a significant step forward in bridging this knowledge gap by systematically investigating how e-beams interact with organic molecules at the molecular level. Therefore, we employed operando liquid-phase transmission electron microscopy (TEM), combined with  density functional theory (DFT) calculations and mathematical random search algorithms, to map out and quantify e-beam-induced reactions in real time. Our findings offer fresh insights into the fundamental chemistry of accelerated electrons, paving the way for controlled nanoscale material manipulation.

Fundamental principles of electron beam–matter interactions. a, Molecular-level energy transfer mechanisms during elastic and inelastic electron scattering. b, Electron beam-induced processes in molecules, categorized by their neutral (Neu), oxidative (Ox), and reductive (Red) nature. c, Simplified electronic excitation scheme of molecules and subsequent processes. Intersystem crossing is not included. M: molecule, S₀: singlet ground state, S₁: first singlet excited state, Sₙ: higher singlet excited states, Sₙ*: super-excited state, D₁: first doublet state (radical cation), Dₙ: higher-energy radical cation states. d, Low-magnification post mortem TEM images of irradiated solvents. The green circle highlights the area directly irradiated by the electron beam, while the outer blue circle marks the diffusion region where secondary polymerization was observed.

A New Perspective on e-Beam Chemistry

Traditionally, the effects of electron irradiation on molecules have been understood primarily through the lens of radiolysis—the breaking apart of molecules due to high-energy interactions. While this concept has been extensively studied, especially in the case of water, little was known about how organic molecules undergo transformation under e-beam exposure. This study challenges the oversimplified view of e-beam chemistry as merely a fragmentation process and instead reveals that molecular reactivity is governed by a  interplay of structural and electronic properties.

By analyzing small organic molecules, we identified key parameters that determine polymerization rates under continuous e-beam irradiation. They found that the type of chemical reactions initiated depends on a combination of factors, including the e-beam’s energy, the molecular structure, and the electronic properties of the molecules. This means that electron-induced reactions can be predicted and controlled, much like traditional chemical reactions, if the intrinsic properties of the molecules are well understood.

Transformative Potential for Nanotechnology

The implications of this research extend far beyond fundamental chemistry. The ability to rationally predict and manipulate e-beam-induced reactions opens new avenues for nanotechnology, including:

• Advanced Nanofabrication: Electron beams are widely used in lithography and 3D nano-printing. By tailoring molecular properties, researchers can design materials that selectively resist or undergo controlled transformations, enabling precision fabrication of nanoscale structures.

• Operando Electron Microscopy: Understanding how organic and hybrid materials respond to electron beams enhances our ability to perform real-time imaging and analysis of dynamic processes at the nanoscale with chemically sound interpretation.

• Soft Matter and Biomaterials: The study's findings extend to polymers, biomolecules, and hydrogels, which are critical for applications in medicine, tissue engineering, and soft robotics. Predicting e-beam reactivity can improve material stability and enable new processing methods for functional biomaterials.

• Space Science and Astrophysics: Since ionizing radiation in space interacts with organic and inorganic matter, insights into e-beam chemistry could help model extraterrestrial chemical processes and develop materials for space exploration.

  
  

  

  Post mortem analysis of formed polymer from toluene after disassembly of the liquid chip set. a, Low-magnification TEM image. Scale bar: 5 µm. b, Magnified STEM image showing the spectrum line used for EELS measurement. The starting point is marked as position 1. c, 3D-plot representing energy loss, position, and intensity along the spectrum line shown in b. d, EEL spectra at positions 1, 2, 3, and 4 along the spectrum line. e,  ratio profile of the C K-edge as a function of the analyzed positions along the spectrum line. The yellow box highlights the transition interface at the outer edge of the polymerized region highlighted in b. f, Thickness profile determined by the EELS Log-ratio technique and a model structure that qualitatively describes the variation of the sp²/sp³ ratio throughout the volume of the polymer.

  
  

Towards a New Era of e-Beam-Driven Design

This research marks a paradigm shift in our understanding of electron beam chemistry. By demonstrating that molecular properties dictate e-beam reactivity, scientists and engineers can now approach e-beam applications with a chemistry-driven perspective. This knowledge empowers researchers to develop materials with tailored responses to electron beams, optimizing their use in nanotechnology, imaging, and beyond.

As the field progresses, further studies will refine our ability to predict and control e-beam-induced transformations, making electron beams not just tools of observation but precise instruments for molecular engineering. The future of nanotechnology may well be shaped by a deeper understanding of how electrons interact with matter—one molecule at a time.

This article was published in ACS Nano