Lenaerts Jens, Van Vaeck Luc, Gijbels Renaat
Department of Chemistry, University of Antwerp, B-2610 Wilrijk, Belgium.
Rapid Commun Mass Spectrom. 2003;17(18):2115-24. doi: 10.1002/rcm.1160.
Time-of-flight static secondary ion mass spectrometry (TOF-S-SIMS) was used to characterize thin layers of oxy- and thiocarbocyanine dyes on Ag and Si. Apart from adduct ions a variety of structural fragment ions were detected for which a fragmentation pattern is proposed. Peak assignments were confirmed by comparing spectra of dyes with very similar structures. All secondary ions were assigned with a mass accuracy better than 50 ppm. The intensity of molecular ions as well as fragment ions has been studied as a function of the type of organic dye, the substrate, the layer thickness and the type of primary ion. A large yield difference of two orders of magnitude was observed between the precursor ions of cationic carbocyanine dyes and the protonated molecules of the anionic dyes. Fragment ions, on the other hand, yielded similar intensities for both types of dye. As the dye layers deposited on an Ag substrate yielded higher secondary ion intensities than those deposited on a Si substrate, the Ag metal clearly acts as a promoting agent for secondary ion formation. The effect was more pronounced for precursor signals than for fragment ions. The promoting effect decreased as the deposited layer thickness of the organic dye layer was increased.
飞行时间静态二次离子质谱法（TOF-S-SIMS）用于表征银和硅上的氧代和硫代碳菁染料薄层。除加合离子外，还检测到多种结构碎片离子，并提出了其碎裂模式。通过比较结构非常相似的染料的光谱，确认了峰的归属。所有二次离子的质量准确度均优于50 ppm。研究了分子离子和碎片离子的强度与有机染料类型、基底、层厚度和一次离子类型的关系。观察到阳离子碳菁染料的前体离子与阴离子染料的质子化分子之间的产率差异有两个数量级。另一方面，两种类型染料的碎片离子产生相似的强度。由于沉积在银基底上的染料层产生的二次离子强度高于沉积在硅基底上的染料层，银金属显然是二次离子形成的促进剂。这种效应在前体信号中比在碎片离子中更明显。随着有机染料层沉积层厚度的增加，促进作用减弱。
