CO2 Cluster Ion Beam, an Alternative Projectile for Secondary Ion Mass Spectrometry

The emergence of argon-based gas cluster ion beams for SIMS experiments opens new possibilities for molecular depth profiling and 3D chemical imaging. These beams generally leave less surface chemical damage and yield mass spectra with reduced fragmentation compared with smaller cluster projectiles....

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Bibliographic Details
Published in:Journal of the American Society for Mass Spectrometry 2016-09, Vol.27 (9), p.1476-1482
Main Authors: Tian, Hua, Maciążek, Dawid, Postawa, Zbigniew, Garrison, Barbara J., Winograd, Nicholas
Format: Article
Language:English
Subjects:
Analytical Chemistry
Argon
Bioinformatics
Biotechnology
Carbon dioxide
Chemical damage
Chemistry
Chemistry and Materials Science
Clusters
Computer simulation
Depth profiling
Image resolution
Ion beams
Ionization
Mass spectra
Mass spectrometry
Medical imaging
Organic Chemistry
Projectiles
Proteomics
Research Article
Secondary ion mass spectrometry
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Summary:The emergence of argon-based gas cluster ion beams for SIMS experiments opens new possibilities for molecular depth profiling and 3D chemical imaging. These beams generally leave less surface chemical damage and yield mass spectra with reduced fragmentation compared with smaller cluster projectiles. For nanoscale bioimaging applications, however, limited sensitivity due to low ionization probability and technical challenges of beam focusing remain problematic. The use of gas cluster ion beams based upon systems other than argon offer an opportunity to resolve these difficulties. Here we report on the prospects of employing CO 2 as a simple alternative to argon. Ionization efficiency, chemical damage, sputter rate, and beam focus are investigated on model compounds using a series of CO 2 and Ar cluster projectiles (cluster size 1000–5000) with the same mass. The results show that the two projectiles are very similar in each of these aspects. Computer simulations comparing the impact of Ar 2000 and (CO 2 ) 2000 on an organic target also confirm that the CO 2 molecules in the cluster projectile remain intact, acting as a single particle of m/z 44. The imaging resolution employing CO 2 cluster projectiles is improved by more than a factor of two. The advantage of CO 2 versus Ar is also related to the increased stability which, in addition, facilitates the operation of the gas cluster ion beams (GCIB) system at lower backing pressure. Graphical Abstract ᅟ
ISSN:1044-0305
1879-1123
DOI:10.1007/s13361-016-1423-z