Delcorte A, Yunus S, Wehbe N, Nieuwjaer N, Poleunis C, Felten A, Houssiau L, Pireaux J-J, Bertrand P
PCPM, Université Catholique de Louvain, Croix du Sud 1, B-1348 Louvain-la-Neuve, Belgium.
Anal Chem. 2007 May 15;79(10):3673-89. doi: 10.1021/ac062406l. Epub 2007 Apr 7.
The advantages and drawbacks of using either monatomic or buckminsterfullerene primary ions for metal-assisted secondary ion mass spectrometry (MetA-SIMS) are investigated using a series of organic samples including additive molecules, polyolefins, and small peptides. Gold deposition is mostly performed by sputter-coating, and in some cases, the results are compared to those of thermal evaporation (already used in a previous article: Delcorte, A.; Médard, N.; Bertrand, P. Anal. Chem. 2002, 74, 4955). The microstructure of the gold-covered sample surfaces is assessed by scanning and transmission electron microscopies. The merits of the different sets of experimental conditions are established via the analysis of fragment and parent-like ion yields. For most of the analyzed samples, the highest yields of fragment and parent-like ions are already reached with the sole use of C60+ projectiles. Metallization of the sample does not lead to a significant additional enhancement. For polyethylene and polypropylene, however, gold metallization associated with Ga+/In+ projectiles appears to be the only way to observe large cationized, sample-specific chain segments (m/z approximately 1000-2000). A detailed study of the polypropylene mass spectra as a function of gold coverage shows that the dynamics of yield enhancement by metal nanoparticles is strongly dependent on the choice of the projectile, e.g., a pronounced increase with Ga+ and a slow decay with C60+. The cases of Irganox 1010, a polymer antioxidant, and leucine enkephalin, a small peptide, allow us to investigate the specific influence of the experimental conditions on the emission of parent(like) ions such as M+, (M + Na)+, and (M + Au)+. The results show a dependence on both the type of sample and the considered secondary ion. Using theoretical and experimental arguments, the discussion identifies some of the mechanisms underlying the general trends observed in the results. Guidelines concerning the choice of the experimental conditions for MetA-SIMS are provided.
使用包括添加剂分子、聚烯烃和小肽在内的一系列有机样品，研究了在金属辅助二次离子质谱（MetA-SIMS）中使用单原子或巴基球富勒烯初级离子的优缺点。金沉积大多通过溅射镀膜进行，在某些情况下，将结果与热蒸发的结果进行比较（热蒸发已在之前的一篇文章中使用：德尔科特，A.；梅达尔，N.；伯特兰，P.《分析化学》2002年，74卷，4955页）。通过扫描电子显微镜和透射电子显微镜评估金覆盖的样品表面的微观结构。通过分析碎片离子和类母离子产率确定不同组实验条件的优点。对于大多数分析的样品，仅使用C60 + 弹丸就已经达到了碎片离子和类母离子的最高产率。样品的金属化不会导致显著的额外增强。然而，对于聚乙烯和聚丙烯，与Ga + /In + 弹丸相关的金金属化似乎是观察到大的阳离子化的、特定于样品的链段（m/z约为1000 - 2000）的唯一方法。对聚丙烯质谱随金覆盖率变化的详细研究表明，金属纳米颗粒增强产率的动力学强烈依赖于弹丸的选择，例如，Ga + 导致产率显著增加，而C60 + 导致产率缓慢下降。聚合物抗氧化剂Irganox 1010和小肽亮氨酸脑啡肽的情况使我们能够研究实验条件对诸如M + 、(M + Na)+ 和(M + Au)+ 等母（类）离子发射的特定影响。结果表明这取决于样品类型和所考虑的二次离子。通过理论和实验论证，讨论确定了结果中观察到的一般趋势背后的一些机制。提供了关于MetA-SIMS实验条件选择的指导原则。
