Chemically modified porous silicon for laser desorption/ionization mass spectrometry of ionic dyes |
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Authors: | I. V. Shmigol S. A. Alekseev O. Yu. Lavrynenko N. S. Vasylieva V. N. Zaitsev D. Barbier V. A. Pokrovsky |
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Affiliation: | 1. A. A. Chuiko Institute of Surface Chemistry, NAS of Ukraine, 17 General Naumov St., 03164 Kiev, Ukraine;2. Chemistry Department, Kiev National Taras Shevchenko University, 60 Vladimirskaya St., 01033 Kiev, Ukraine;3. Lyon Institute of Nanotechnologies, INL, CNRS UMR‐5270, INSA de Lyon, 7 avenue Jean Capelle, Bat. Blaise Pascal, 69621 Villeurbanne cedex, France |
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Abstract: | Desorption/ionization on silicon (DIOS) mass spectra of model ionic dyes methylene blue (MB+Cl?) and methyl orange (Na+MO?) were studied using p+ type‐derived porous silicon (PS) free layers. As‐prepared PS (PS‐H), the PS thermally oxidized at 300 °C (PS‐OX), PS with chemically grafted cation‐exchanging alkylsulfonic acid (PS‐SO3H) and anion‐exchanging propyl‐octadecyldimethylammonium chloride (PS‐ODMA+Cl?) groups was tested as ionization platforms. Two mechanisms of the methylene blue desorption/ionization were found: (1) the formation of [MB + H]+? ion due to the reduction/protonation of MB+, which is predominant for PS‐H and PS‐OX platforms and (2) direct thermal desorption of the MB+ cation, prevailing for PS‐SO3H. The fragmentation of the cation is significantly suppressed in the latter case. The samples of PS‐SO3H and PS‐ODMA+ Cl? efficiently adsorb the dyes of the opposite charge from their solutions via the ion‐exchange. Consequent DIOS MS studies allow to detect only low fragmented ions (MB+ and MO?, respectively), demonstrating the potential of the ion‐exchange adsorption combined with DIOS MS for the analysis of ionic organic compounds in solutions. Copyright © 2009 John Wiley & Sons, Ltd. |
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Keywords: | porous silicon DIOS MS ionic dyes sulfonic acid quaternary ammonium salt desorption/ionization mechanism |
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