On the mechanism of laser-induced desorption-ionization of organic compounds from etched silicon and carbon surfaces
On the mechanism of laser-induced desorption-ionization of organic compounds from etched silicon and carbon surfaces
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DOI：
10.1063/1.1381531
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发表时间：
2001-07-22
影响因子：
4.4
通讯作者：
Sunner, J
中科院分区：
文献类型：
--
作者：
Alimpiev, S;Nikiforov, S;Sunner, J
研究了有机化合物在碳和硅衬底上的激光诱导脱附/电离。使用两种不同的蚀刻程序。硅表面被腐蚀或者通过恒电流阳极氧化产生多孔硅，或者通过超高温（类似于5eV）F原子束产生无孔硅。原子力显微镜（AFM）的图像显示，这两个蚀刻程序产生的表面与亚微米结构。高定向热解石墨与超高温O原子蚀刻。使用337 nm紫外（UV）激光和3.28 μ m红外（IR）激光进行解吸。分析物从液相或气相沉积在基底上。如果满足三个条件，则获得质谱。首先，必须吸收足够的激光。当采用IR激光器时，需要薄的物理吸附溶剂层以发生足够的激光吸收。虽然所需的红外和紫外光通量相差约20倍，但计算出的最高表面温度相似，约为1000 K。第二个要求是基底具有“粗糙”表面。对于质子化分析物的观察，第三个要求是分析物的水溶液pK（a）值大于约4。这些观察结果支持的结论是，从多孔和无孔表面的分析物的解吸电离机制是非常相似的或基本相同的。(C)2001年美国物理学会。
The laser-induced desorption/ionization of organic compounds from etched carbon and silicon substrate surfaces was investigated. Two different etching procedures were used. Silicon surfaces were etched either by galvanostatic anodization to produce porous silicon or by a hyperthermal (similar to5 eV) F-atom beam to produce nonporous silicon. Atomic force microscopy (AFM) images showed that both etching procedures yielded surfaces with sub-micrometer structures. Highly oriented pyrolytic graphite was etched with hyperthermal O atoms. A 337 nm ultraviolet (UV) laser and a 3.28 mum infrared (IR) laser were used for desorption. Analytes were deposited on the substrates either from the liquid or the gas phase. Mass spectra were obtained provided that three conditions were fulfilled. First, sufficient laser light had to be absorbed. When the IR laser was employed, a thin physisorbed solvent layer was required for sufficient laser light absorption to occur. Though the required fluence of IR and UV light differed by a factor of about 20, the calculated maximum surface temperatures were similar, about 1000 K. The second requirement was that the substrate had a "rough" surface. The third requirement, for the observation of protonated analytes, was that the aqueous pK(a)-value of the analyte be larger than about 4. These observations support the conclusion that the desorption-ionization mechanisms of analytes from porous and nonporous surfaces are very similar or essentially the same. (C) 2001 American Institute of Physics.