Sputtering of organic molecules by clusters, with focus on fullerenes

Delcorte, Arnaud; Wehbe, Nimer; Bertrand, Patrick; Garrison, Barbara J.

doi:10.1016/j.apsusc.2008.05.107

Cited by 11 publications

(17 citation statements)

References 29 publications

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“…This interpretation accommodates the observation that the secondary ion yields measured for PS concentrations higher than 1 mg/mL do not decrease but remain almost constant. Even though more sophisticated simulations show that the combined action of 60 carbon atoms induces collective effects, which eventually lead to somewhat larger depth for the projectile penetration and the deposited energy, they qualitatively agree with our interpretation based on TRIM calculations [27,28].…”

Section: Yield Variations As a Function Of The Ps Layer Thicknesssupporting

confidence: 87%

Influence of the organic layer thickness in (Metal-Assisted) secondary ion mass spectrometry using Ga⁺ and C₆₀⁺ projectiles

Wehbe

Mouhib

Prabhakaran

et al. 2009

J. Am. Soc. Mass Spectrom.

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This article investigates the influence of the organic film thickness on the characteristic and molecular ion yields of polystyrene (PS), in combination with two different substrates (Si, Au) or gold condensation (MetA-SIMS), and for atomic (Ga ϩ ) and polyatomic (C 60 ϩ ) projectile bombardment. PS oligomer (m/z ϳ 2000 Da) layers were prepared with various thicknesses ranging from 1 up to 45 nm on both substrates. Pristine samples on Si were also metallized by evaporating gold with three different thicknesses (0.5, 2, and 6 nm). Secondary ion mass spectrometry was performed using 12 keV atomic Ga ϩ and C 60 ϩ projectiles. The results show that upon Ga ϩ bombardment, the yield of the fingerprint fragment C 7 H 7 ϩ increases as the PS coverage increases and reaches its maximum for a thickness that corresponds to a complete monolayer (ϳ3.5 nm). Beyond the maximum, the yields decrease strongly and become constant for layers thicker than 12 nm. In contrast, upon C 60 ϩ bombardment, the C 7 H 7 ϩ yields increase up to the monolayer coverage and they remain constant for higher thicknesses. A strong yield enhancement is confirmed upon Ga ϩ analysis of gold-metallized layers but yields decrease continuously with the gold coverage for C 60 ϩ bombardment. Upon Ga ϩ bombardment, the maximum PS fingerprint ion yields are obtained using a monolayer spin-coated on gold, whereas for C 60 ϩ , the best results are obtained with at least one monolayer, irrespective of the substrate and without any other treatment. The different behaviors are tentatively explained by arguments involving the different energy deposition mechanisms of both projectiles. (J Am Soc

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Section: Yield Variations As a Function Of The Ps Layer Thicknesssupporting

confidence: 87%

Influence of the organic layer thickness in (Metal-Assisted) secondary ion mass spectrometry using Ga⁺ and C₆₀⁺ projectiles

Wehbe

Mouhib

Prabhakaran

et al. 2009

J. Am. Soc. Mass Spectrom.

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“…Therefore, while recombination cannot be entirely discounted, there exists reasonable evidence to support that the Si containing fragments acquired in these experiments do reflect chemical interactions between the porous silicon substrate and organic material loaded therein. Molecular dynamic simulations could be used to investigate this phenomenon more rigorously [27] and could be addressed in the future with greater computational power [28].…”

Section: Resultsmentioning

confidence: 99%

Use of TOF-SIMS to study adsorption and loading behavior of methylene blue and papain in a nano-porous silicon layer

Kempson

Barnes

Prestidge

2010

J. Am. Soc. Mass Spectrom.

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TOF-SIMS was applied to study the cross-sectional distribution of methylene blue and papain in porous silicon layers. Elemental and molecular information were used to study their distributions in the porous region and the chemistry of their adsorption. Methylene blue (MW ϭ 284 Da) [4], and the delivery of active pharmaceutical ingredients [5,6]. The ongoing interest in pSi for use as a therapeutic delivery system is due to the large internal surface area available, the readily modified surface chemistry [7] and, in particular, the excellent in vivo biodegradation and biocompatibility (low toxicity) of the silicon substrate, hydrolysing to form orthosilicic acid, which is readily excreted [8]. The loading dynamics of molecules into a pSi matrix is dependent on wetting and the size of the pores. Likewise, the interaction between a loaded molecule and the pSi substrate is of interest, particularly in the case of protein based therapeutics, whose bioactivity is dependent on remaining in a specific 3D conformation.TOF-SIMS analysis provides information regarding elemental and molecular species present in a sample surface (i.e., within 1-1.5 nm) with high mass resolution (up to ϳ10,000 m/⌬m) and spatial resolution for imaging (ϳ1 micron). Molecular and elemental information is obtained for organic and inorganic materials providing a powerful technique to image organic compounds associated with inorganic substrates or vice versa [9,10]. This has been demonstrated by imaging solid-state pharmaceutical formulations [11][12][13][14], however, to date this has not been extended to porous silicon substrates.In this study, TOF-SIMS was used to map the distribution of methylene blue and papain across porous silicon layers after loading from aqueous solution. Methylene blue (C 16 H 18 N 3 S ϩ , MW ϭ 284.12 g/mol) is a relatively small organic dye molecule commonly used in adsorption studies and can be considered analogous to therapeutic molecules. A molecular mass of 284 g/mol is within a reasonable mass range for a TOF-SIMS' Ga ϩ primary ion beam and can be easily and uniquely identified without interference or confusion from spectral peaks originating from the silicon substrate or in the instance of organic contamination. This molecule was chosen for its convenience, and to assess the ability to use smaller organic fragments to reflect the distribution of the molecule of interest. This is important to be able to extend this work to studying larger molecules, such as proteins and enzymes of pharmaceutical interest, which will not provide a molecular ion in TOF-SIMS. In contrast to methylene blue, papain is a much larger molecule, detailed elsewhere [15], comprising 212 residue units in two domains, giving a molecular weight of 23,406 g/mol. Papain is a cysteine protease hydrolase enzyme present in papaya. This molecular weight is far greater than can be detected with TOF-SIMS, however, fragmentation products can be detected. Smaller organic fragments can be compared with the distribution of methylene blue to investigate si...

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“…Cluster ions typically leave less residual chemical damage due to their lower implantation depths and higher sputter yields. 30–33 For these reasons, there has been a significant increase in the use of cluster ion sources in recent years for applications where high yields of high mass molecular fragments are needed, 34 and most notably in depth profiling applications to map the distribution of specific chemistries within a matrix to create 3D images of organic and biological samples. 35 …”

Section: Introductionmentioning

confidence: 99%

“…30, 33, 36–39 Of particular interest are the implantation and probing depths of the different primary ion species. Depending on the primary cluster size (nuclearity) and on the target properties ( e.g.…”

Section: Introductionmentioning

confidence: 99%

“…25, 40, 42 As most of the ejected fragments typically originate from the impact crater, the C 60 implantation depth is typically similar to the impact crater depth. 30, 38, 43 Therefore, the smaller ejected volume and the low energy of the recoil atoms in inorganic targets make Ga + more surface sensitive (lower sampling depth) in the static ToF-SIMS mode despite its deep implantation depth. Applying the same reasoning to organic samples, the ejection of molecular fragments from monoatomic primary ion impact should primarily occur from the low-energy recoil atoms created by the deep implantation of the primary ions in the sample.…”

Section: Introductionmentioning

confidence: 99%

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Exploring the Surface Sensitivity of TOF-Secondary Ion Mass Spectrometry by Measuring the Implantation and Sampling Depths of Bi_n and C₆₀ Ions in Organic Films

2011

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The surface sensitivity of Binq+ (n = 1, 3, 5, q = 1, 2) and C60q+ (q = 1, 2) primary ions in static time-of-flight secondary ion mass spectrometry (ToF-SIMS) experiments were investigated for molecular trehalose and polymeric tetraglyme organic films. Parameters related to surface sensitivity (impact crater depth, implantation depth, and molecular escape depths) were measured. Under static ToF-SIMS conditions (primary ion doses of 1 × 1012 ions/cm2), the 25 keV Bi1+ primary ions were the most surface sensitive with a molecular escape depth of 1.8 nm for protein films with tetraglyme overlayers, but they had the deepest implantation depth (~18 and 26 nm in trehalose and tetraglyme films, respectively). The 20 keV C60++ primary ions were the second most surface sensitive with a slightly larger molecular escape depth of 2.3 nm. The most important factor that determined the surface sensitivity of the primary ion was its impact crater depth, or the amount of surface erosion. The most surface sensitive primary ions, Bi1+ and C60++, created impact craters with depths of 0.3 and 1.0 nm, respectively, in tetraglyme films. In contrast, Bi5++ primary ions created impact craters with a depth of 1.8 nm in tetraglyme films and were the least surface sensitive with a molecular escape depth of 4.7 nm.

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Sputtering of organic molecules by clusters, with focus on fullerenes

Cited by 11 publications

References 29 publications

Influence of the organic layer thickness in (Metal-Assisted) secondary ion mass spectrometry using Ga⁺ and C₆₀⁺ projectiles

Influence of the organic layer thickness in (Metal-Assisted) secondary ion mass spectrometry using Ga⁺ and C₆₀⁺ projectiles

Use of TOF-SIMS to study adsorption and loading behavior of methylene blue and papain in a nano-porous silicon layer

Exploring the Surface Sensitivity of TOF-Secondary Ion Mass Spectrometry by Measuring the Implantation and Sampling Depths of Bi_n and C₆₀ Ions in Organic Films

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Sputtering of organic molecules by clusters, with focus on fullerenes

Cited by 11 publications

References 29 publications

Influence of the organic layer thickness in (Metal-Assisted) secondary ion mass spectrometry using Ga+ and C60+ projectiles

Influence of the organic layer thickness in (Metal-Assisted) secondary ion mass spectrometry using Ga+ and C60+ projectiles

Use of TOF-SIMS to study adsorption and loading behavior of methylene blue and papain in a nano-porous silicon layer

Exploring the Surface Sensitivity of TOF-Secondary Ion Mass Spectrometry by Measuring the Implantation and Sampling Depths of Bin and C60 Ions in Organic Films

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Influence of the organic layer thickness in (Metal-Assisted) secondary ion mass spectrometry using Ga⁺ and C₆₀⁺ projectiles

Influence of the organic layer thickness in (Metal-Assisted) secondary ion mass spectrometry using Ga⁺ and C₆₀⁺ projectiles

Exploring the Surface Sensitivity of TOF-Secondary Ion Mass Spectrometry by Measuring the Implantation and Sampling Depths of Bi_n and C₆₀ Ions in Organic Films