Large cluster ions: soft local probes and tools for organic and bio surfaces

Abstract

Large cluster projectiles boost molecular sensitivity in mass spectrometry and open new avenues for physical characterization and nanofabrication.

Direct Analysis of Ion-Induced Peptide Fragmentation in Secondary-Ion Mass Spectrometry

“…In contrast, for Bi + , the SIMS signal behaves similar to the DINeC signal. This indicates a larger information depth for the Ar 1000 + primary ions in agreement with the, in general, higher sputter yield for cluster ions. − …”

“…This pronounced difference between the DINeC and SIMS signals can be explained when taking into account the two different desorption/sputter processes operative for the two methods. Although SIMS is known as a surface-sensitive method, experiments and simulations show that, depending on the primary-ion species and E / n values, molecules can also be sputtered from subsurface layers, in particular for large cluster ions with higher E / n . − As a consequence, signal intensities in SIMS spectra of our experiment typically reflect the signal averaged over an information depth which extends into the bulk material. In contrast, the SO 2 clusters used in DINeC experiments do not have enough energy to sputter the sample surface; hence, only molecules from the topmost surface layer can be desorbed via a dissolvation process in the cluster. ,, This is also reflected in the comparably low amount of removed material per SO 2 cluster .…”

Investigating the relationship between the mechanical properties of plasma polymer-like thin films and their glass transition temperature

“…The determination of the surface transition temperature (TT), strongly correlated to the glass transition temperature (Tg), of PPF as a function of Ts has been achieved through ToF-SIMS measurements. [42][43][44] The films have been analyzed less than 24h after their synthesis. Static ToF-SIMS data have been acquired in positive mode using a ToF-SIMS V instrument provided by ION TOF GmbH.…”

Deposition of Intact and Active Proteins In Vacuo Using Large Argon Cluster Ion Beams

“…The ultrahigh vacuum inherent to ToF-SIMS allows the production of dry films (in contrast with adsorption methods), and the fact that charged as well as neutral species are deposited largely improves the efficacy in regards with other preparative mass spectrometry techniques. We are confident that the transfer of larger proteins will be possible, since recent molecular dynamic simulations indicate that similar Ar clusters can desorb larger organic molecules (∼60 kDa) without fragmentation . It will remain very important to check whether these transferred proteins do keep their activity, since uncertainties remain regarding the potential conformation changes that could occur.…”

“…We are confident that the transfer of larger proteins will be possible, since recent molecular dynamic simulations indicate that similar Ar clusters can desorb larger organic molecules (∼60 kDa) without fragmentation. 40 It will remain very important to check whether these transferred proteins do keep their activity, since uncertainties remain regarding the potential conformation changes that could occur. In addition, modifications could be implemented in order to construct more homogeneous films (ultimately allowing a fine thickness control, from (sub)mono-to multilayers) or to be able to control the deposition pattern.…”