Laser desorption ion trap mass spectrometry of self-assembled monolayers.
It is demonstrated that laser desorption ion trap mass spectrometry (LD-ITMS) can be successfully applied to the chemical analysis of a monolayer of adsorbates on a solid surface. Negative ion spectra obtained from LD-ITMS of self-assembled monolayers adsorbed from solutions of alkanethiols (CH3(CH2)nSH with n=5, 9, and 15) onto polycrystalline gold surfaces displayed clear ion peaks corresponding to the sulfonate adsorbate species. Sulfonate ions with the general formula CH3(CH2)n SO3 were detected at m/z 165, 221, and 305, respectively, and were derived from the partial oxidation of the corresponding alkanethiol self-assembled monolayers. Little fragmentation and no clustering was observed in these mass spectra. These results indicate that the sensitivity of LD-ITMS is sufficient to allow its application to a wide array of problems in surface science.
Department of Chemistry (M/C 111), University of Illinois at Chicago, 845 West Taylor Street, 60607-7061, Chicago, IL, USA.
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Burroughs
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Hanley