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Enhanced Ion Yields Using High Energy Water Cluster Beams for Secondary Ion Mass Spectrometry Analysis and Imaging

Lookup NU author(s): Dr Sadia Sheraz, Professor John Vickerman, Professor Peter Cumpson

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Abstract

Previous studies have shown that the use of a 20 keV water cluster beam as a primary beam for the analysis of organic and bio-organic systems resulted in a 10-100 times increase in positive molecular ion yield for a range of typical analytes compared to C60 and argon cluster beams. This resulted in increased sensitivity to important lipid molecules in the bioimaging of rat brain. Building on these studies, the present work compares 40 and 70 keV water cluster beams with cluster beams composed of pure argon, argon and 10%CO2, and pure CO2. First, as previously, we show that for E/nucleon about 0.3 eV/nucleon water and nonwater containing cluster beams generate very similar ion yields, but below this value, the water beams yields of BOTH negative and positive "molecular" ions increase, in many cases reaching a maximum in the <0.2 region, with yield increases of ∼10-100. Ion fragment yields in general decrease quite dramatically in this region. Second, for water cluster beams at a constant E/nucleon, "molecular" ion yield increases with beam energy and hence cluster size due to increased sputter yield (ionization probability is constant). Third, as a consequence of the increased ion yield and the improved focusability using high-energy cluster beams, imaging in the 1 μm spatial resolution region is demonstrated on HeLa cells and rat brain tissue, monitoring molecules that were previously difficult to detect with other primary beams. Finally, the suggestion that the secondary ion emission zone has quasi-aqueous character seems to be sustained.

Publication metadata

Author(s): Sheraz S, Tian H, Vickerman JC, Blenkinsopp P, Winograd N, Cumpson P

Publication type: Article

Publication status: Published

Journal: Analytical Chemistry

Year: 2019

Volume: 91

Issue: 14

Pages: 9058-9068

Print publication date: 16/07/2019

Online publication date: 28/05/2019

Acceptance date: 23/05/2019

ISSN (print): 0003-2700

ISSN (electronic): 1520-6882

Publisher: American Chemical Society

URL: https://doi.org/10.1021/acs.analchem.9b01390

DOI: 10.1021/acs.analchem.9b01390

PubMed id: 31136149

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