Public Thesis Defense of Benjamin TOMASETTI - IMCN
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Deposition of Biomolecular Layers via Gas Cluster Ion Beams: Instrument Conception and Applications
Thursday December 18th, 2025 - 4pm - Auditorium BARB91 - Place Sainte-Barbe, 1 - 1348 Louvain-la-Neuve
Gas Cluster Ion Beam (GCIB)-assisted deposition is a method that utilizes the gentle sputtering caused by large ion clusters to transfer molecules from one surface to another. The impact of large clusters composed of a few thousands of atoms is sufficiently soft to transfer large molecules such as proteins intact. Indeed, the internal energy of the desorbed molecules is low enough to result in a reduced amount of fragmentation.
At the beginning of this doctoral work, a commercial GCIB source was used to answer fundamental questions and make progress toward practical applications. Deposition rate and fragmentation were assess under Arn+ bombardment for different cluster sizes (n = 1500 - 7000) and energy (5 – 10 keV). A first application was the soft transfer of a large quantity of neutral molecules from a tissue sample to another surface. This method, called microvolume expansion, aims to enhance ionization in secondary ion mass spectrometry (SIMS) analysis—an aspect that often presents a limitation for this technique. The second application demonstrates the construction of dry multilayers and molecular architectures that cannot be achieved using solvent-based methods. Glucose oxidase (GOx, ≈ 80 kDa) and horseradish peroxidase (HRP, ≈ 40 kDa)—two enzymes involved in the same catalytic cascade—are successively deposited onto β-D-glucose. This results in the formation of an on-demand release material, where the enzymes and substrate are combined into a dry trilayer structure. The enzymatic reaction is triggered only upon rehydration, enabling precise control over the activation of the system.
In parallel with these results, a molecular transfer and soft-landing instrument named CLASH (Cluster-Assisted Soft-Landing Hub) was developed from scratch. The system, described in this work, comprises two vacuum chambers: one for supersonic jet generation and cluster formation, and another for sample impact. Mass-selected large Arn+ and (CO2)n+ clusters were obtained and analyzed using time-of-flight spectrometry. This setup enables new deposition experiments through its advanced cluster generation (via a home-built pulsed valve) and high adaptability.
Jury members :
Prof. Delcorte Arnaud (UCLouvain), Supervisor
Prof. Lauzin Clément (UCLouvain), Supervisor
Prof. Dupont Christine (UCLouvain), Secretary
Prof. Urbain Xavier (Uclouvain), Chairperson
Prof. Gilmore Ian (National Physical Lab, UK)
Prof. Lengyel Josef (TUM, Germany)