Trevor J L, Mencer D E, Lykke K R, Pellin M J, Hanley L
Materials Science and Chemistry Divisions, Argonne National Laboratory, Argonne, Illinois 60439, Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois 60607, and Department of Chemistry, The Pennsylvania State University [Formula: see text] Hazelton, Hazelton, Pennsylvania 18533.
Anal Chem. 1997 Nov 1;69(21):4331-8. doi: 10.1021/ac970283m.
Biotin and biotinylated self-assembled monolayers (SAMs) on gold have been investigated using time-of-flight secondary ion mass spectrometry, direct laser desorption, laser desorption with 193 nm photoionization of ion- and laser-desorbed species, and laser desorption with vacuum ultraviolet (VUV, 118 nm) photoionization. Our results indicate that direct laser desorption and laser desorption combined with 193 nm multiphoton ionization can detect a chromophoric molecule like biotin that is covalently bound to a SAM. However, secondary ion mass spectra were dominated by fragmentation, and ion desorption/193 nm photoionization detected no species related to biotin. The dominant features of the laser desorption/VUV mass spectra were neat and Au-complexed dimers of intact and fragmented biotinylated SAM molecules. Multiphoton and single-photon ionization of laser-desorbed neutrals from biotinylated SAMs both led to the production of ions useful for chemical analysis of the monolayer. Multiphoton ionization with ultraviolet radiation was experimentally less challenging but required a chromophore for ionization and resulted in significant fragmentation of the adsorbate. Single-photon ionization with VUV radiation was experimentally more challenging but did not require a chromophore and led to less fragmentation. X-ray photoelectron spectra indicated that the biotinylated SAM formed a disordered, 40-60 Å thick monolayer on Au. Additionally, projection photolithography with a Schwarzschild microscope was used to pattern the biotinylated SAM surface and laser desorption/photoionization was used to detect biotinylated adsorbates from the ∼10 μm sized pattern.
利用飞行时间二次离子质谱、直接激光解吸、对离子和激光解吸物种进行193nm光电离的激光解吸以及真空紫外（VUV，118nm）光电离对生物素和金表面的生物素化自组装单分子层（SAMs）进行了研究。我们的结果表明，直接激光解吸以及与193nm多光子电离相结合的激光解吸能够检测到与SAM共价结合的发色分子，如生物素。然而，二次离子质谱主要由碎片主导，并且离子解吸/193nm光电离未检测到与生物素相关的物种。激光解吸/VUV质谱的主要特征是完整的和碎片化的生物素化SAM分子的纯净二聚体和与金络合的二聚体。来自生物素化SAMs的激光解吸中性粒子的多光子电离和单光子电离都导致产生了可用于单分子层化学分析的离子。用紫外辐射进行多光子电离在实验上难度较小，但需要一个发色团进行电离，并且会导致吸附质的显著碎片化。用VUV辐射进行单光子电离在实验上更具挑战性，但不需要发色团，并且导致的碎片化较少。X射线光电子能谱表明，生物素化SAM在金上形成了一个无序的、40 - 60 Å厚的单分子层。此外，使用施瓦兹希尔德显微镜的投影光刻技术对生物素化SAM表面进行图案化处理，并使用激光解吸/光电离来检测来自约10μm大小图案的生物素化吸附质。
