High energy gas cluster ions for organic and biological analysis by time-of-flight secondary ion mass spectrometry

Angerer, Tina B.; Blenkinsopp, Paul; Fletcher, John S.

doi:10.1016/j.ijms.2014.05.015

Cited by 80 publications

(95 citation statements)

References 40 publications

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“…The use of higher energy clusters such as the 40 keV beam used here has recently been shown to produce significant enhancement of lipid signal during tissue analysis compared to the previous state of the art C 60 beams. 21 Large area images were generated by producing a series of individual image "tiles" that were stitched together automatically by the acquisition software. Each tile is comprised of 32 × 32 pixels with each pixel containing a full mass spectrum which is produced by electrostatically scanning the beam over the area of the tile.…”

Section: Methodsmentioning

confidence: 99%

Improved Molecular Imaging in Rodent Brain with Time-of-Flight-Secondary Ion Mass Spectrometry Using Gas Cluster Ion Beams and Reactive Vapor Exposure

et al. 2015

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Imaging mass spectrometry has shown to be a valuable method in medical research and can be performed using different instrumentation and sample preparation methods, each one with specific advantages and drawbacks. Time-of-flight-secondary ion mass spectrometry (TOF-SIMS) has the advantage of high spatial resolution imaging but is often restricted to low mass molecular signals and can be very sensitive to sample preparation artifacts. In this report we demonstrate the advantages of using gas cluster ion beams (GCIBs) in combination with trifluoracetic acid (TFA) vapor exposure for the imaging of lipids in mouse brain sections. There is an optimum exposure to TFA that is beneficial for increasing high mass signal as well as producing signal from previously unobserved species in the mass spectrum. Cholesterol enrichment and crystallization on the sample surface is removed by TFA exposure uncovering a wider range of lipid species in the white matter regions of the tissue, greatly expanding the chemical coverage and the potential application of TOF-SIMS imaging in neurological studies. Ar4000(+) (40 keV) in combination with TFA treatment facilitates high resolution, high mass imaging closing the gap between TOF-SIMS and matrix-assisted laser desorption ionization (MALDI).

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Section: Methodsmentioning

confidence: 99%

Improved Molecular Imaging in Rodent Brain with Time-of-Flight-Secondary Ion Mass Spectrometry Using Gas Cluster Ion Beams and Reactive Vapor Exposure

et al. 2015

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“…Similarly, our laboratory has reported that incorporation of 2~3% CH 4 and 5% HCl into Ar n + also increases the [M + H] + yield, although not quite as much as the [H 2 O] n + beam [19, 20]. In addition, there is evidence that CO 2 - seeded Ar GCIB’s are easier to focus presumably due to better chromaticity in the focusing lenses [21, 22]. …”

Section: Introductionmentioning

confidence: 93%

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

Tian

Maciążek

Postawa

et al. 2016

J. Am. Soc. Mass Spectrom.

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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 when compared to 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 CO2 as a simple alternative to argon. Ionization efficiency, chemical damage, sputter rate and beam focus are investigated on model compounds using a series of CO2 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 Ar2000 and (CO2)2000 on an organic target also confirm that the CO2 molecules in the cluster projectile remain intact, acting as a single particle of m/z 44. The imaging resolution employing CO2 cluster projectiles is improved by more than a factor of 2. The advantage of CO2 vs Ar is also related to the increased stability which, in addition, facilitates the operation of the GCIB system at lower backing pressure.

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“…This finding is in agreement with recently published studies in the static SIMS regime, which state that high energy and larger clusters are beneficial for increasing the molecular ion yield of organic materials. 15,18 ■ EXPERIMENTAL SECTION Material and Sample Preparation. Presliced 5 mm × 5 mm Si wafers (Ted Pella Inc., Reading, CA, USA) were used as substrates for all films.…”

Section: ■ Introductionmentioning

confidence: 99%

Molecular Depth Profiling with Argon Gas Cluster Ion Beams

2015

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Argon gas cluster ion beams (Ar-GCIBs) are remarkable new projectiles for secondary ion mass spectrometry (SIMS) depth profiling of organic materials. However, the optimal cluster size and kinetic energy to provide the best quality of depth profiles, in terms of high ionization efficiency of the target molecules, little chemical damage, and short experiment time, for organic materials is not fully understood. Hence, the effect of cluster size and kinetic energy on the quality of molecular depth profiling is investigated on a simple platform composed of trehalose thin films to acquire more fundamental information about the ion/solid interaction. The results suggest that the sputter yield (Y/n) of argon clusters is linearly dependent upon kinetic energy per atom (E/ n). When E/n > 5 eV/atom, normal depth profiles are obtained with relatively high sputter yields. When E/n ≤ 5 eV/atom, however, distorted depth profiles in the steady state region are observed, which exhibit a low sputter yield and variable ionization efficiency. As a consequence of these observations, it was concluded that high kinetic energy increases the useful molecular ion yield of trehalose and that Ar n + clusters with a small E/n value minimize ion beam bombardment induced chemical damage. Hence optimal conditions for molecular depth profiling will be obtained using the highest kinetic energy with the largest clusters while maintaining a value of E/n near a threshold value of 5 eV/atom. In general, this study provides insight into selecting optimal Ar-GCIB characteristics for molecular depth profiling of organic materials. ■ INTRODUCTIONSecondary ion mass spectrometry (SIMS) has been used as an indepth characterization method for inorganic materials, particularly semiconductors, for many years. 1−3 To expand the scope of this technique into the investigation of organic samples, there has been a growing emphasis on the development of cluster ion sources, such as Au 3 , 4,5 Bi 3 , 6 SF 5 , 7 and C 60 . 4 These probes, particularly C 60 , are more effective than the traditional atomic ion sources, because less chemical damage is accumulated during the interaction of the projectiles with the solid. Molecular depth profiling of a variety of organic materials is now possible, 8−11 providing an important new characterization modality for SIMS. Recently, argon gas cluster ion beams (Ar-GCIBs) 12 have generated a great deal of excitement, because they appear to yield better depth resolution and produce less chemical damage than C 60 , 13−16 broadening the scope of this technology even further.There is flexibility associated with the implementation of GCIBs. For example, the nature of the chemical composition of these clusters can be varied, consisting of water clusters 17,18 or Ar clusters doped with other species such as CO 2 15 and CH 4 , 19 or other molecules such as N 2 20 and C 2 H 5 OH. 21,22 The idea behind many of these experiments is to increase the ionization efficiency of the target molecules by providing a source of protons for making [M + H...

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High energy gas cluster ions for organic and biological analysis by time-of-flight secondary ion mass spectrometry

Cited by 80 publications

References 40 publications

Improved Molecular Imaging in Rodent Brain with Time-of-Flight-Secondary Ion Mass Spectrometry Using Gas Cluster Ion Beams and Reactive Vapor Exposure

Improved Molecular Imaging in Rodent Brain with Time-of-Flight-Secondary Ion Mass Spectrometry Using Gas Cluster Ion Beams and Reactive Vapor Exposure

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

Molecular Depth Profiling with Argon Gas Cluster Ion Beams

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High energy gas cluster ions for organic and biological analysis by time-of-flight secondary ion mass spectrometry

Cited by 80 publications

References 40 publications

Improved Molecular Imaging in Rodent Brain with Time-of-Flight-Secondary Ion Mass Spectrometry Using Gas Cluster Ion Beams and Reactive Vapor Exposure

Improved Molecular Imaging in Rodent Brain with Time-of-Flight-Secondary Ion Mass Spectrometry Using Gas Cluster Ion Beams and Reactive Vapor Exposure

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

Molecular Depth Profiling with Argon Gas Cluster Ion Beams

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