Chemistry Department, The Pennsylvania State University, 215 Chemistry Building, University Park, PA, 16802, USA.
Smoluchowski Institute of Physics, Jagiellonian University, ulica Lojasiewicza 11, 30-348, Krakow, Poland.
J Am Soc Mass Spectrom. 2019 Mar;30(3):476-481. doi: 10.1007/s13361-018-2102-z. Epub 2018 Nov 14.
A gas cluster ion beam (GCIB) source, consisting of CO clusters and operating with kinetic energies of up to 60 keV, has been developed for the high resolution and high sensitivity imaging of intact biomolecules. The CO molecule is an excellent molecule to employ in a GCIB source due to its relative stability and improved focusing capabilities, especially when compared to the conventionally employed Ar cluster source. Here we report on experiments aimed to examine the behavior of CO clusters as they impact a surface under a variety of conditions. Clusters of (CO) (n = 2000~10,000) with varying sizes and kinetic energies were employed to interrogate both an organic and inorganic surface. The results show that C-O bond dissociation did not occur when the energy per molecule is less than 5 eV/n, but that oxygen adducts were seen in increasing intensity as the energy is above 5 eV/n, particularly, drastic enhancement up to 100 times of oxygen adducts was observed on Au surface. For Irganox 1010, an organic surface, oxygen containing adducts were observed with moderate signal enhancement. Molecular dynamics computer simulations were employed to test the hypothesis that the C-O bond is broken at high values of eV/n. These calculations show that C-O bond dissociation occurs at eV/n values less than the C-O bond energy (8.3 eV) by interaction with surface topological features. In general, the experiments suggest that the projectiles containing oxygen can enhance the ionization efficiency of surface molecules via chemically induced processes, and that CO can be an effective cluster ion source for SIMS experiments. Graphical Abstract.
一种气体团簇离子束（GCIB）源，由 CO 团簇组成，工作动能高达 60keV，已被开发用于完整生物分子的高分辨率和高灵敏度成像。由于其相对稳定性和改进的聚焦能力，CO 分子是 GCIB 源中一种极好的分子，特别是与传统使用的 Ar 团簇源相比。在这里，我们报告了旨在研究 CO 团簇在各种条件下撞击表面时的行为的实验。使用具有不同大小和动能的（CO）（n=2000~10000）团簇来研究有机和无机表面。结果表明，当每个分子的能量小于 5eV/n 时，C-O 键不会发生解离，但当能量高于 5eV/n 时，会看到氧加合物的强度增加，特别是在 Au 表面上观察到高达 100 倍的氧加合物的剧烈增强。对于有机表面 Irganox 1010，观察到含氧加合物，信号增强适中。采用分子动力学计算机模拟来检验 C-O 键在高 eV/n 值下断裂的假设。这些计算表明，C-O 键的解离发生在 eV/n 值小于 C-O 键能（8.3eV）的情况下，这是通过与表面拓扑特征相互作用实现的。总的来说，实验表明，含氧的射弹可以通过化学诱导过程提高表面分子的电离效率，并且 CO 可以成为 SIMS 实验的有效团簇离子源。
