Solution Deposition of Self-Assembled Benzoate Monolayers on Rutile (110): Effect of π–π Interactions on Monolayer Structure

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• 作者：Erik S. Skibinski ; Anqi Song ; William J. I. DeBenedetti ; Amnon G. Ortoll-Bloch ; Melissa A. Hines
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：June 2, 2016
• 年：2016
• 卷：120
• 期：21
• 页码：11581-11589
• 全文大小：717K
• 年卷期：0
• ISSN：1932-7455

文摘

High-quality, self-assembled benzoate monolayers were synthesized on rutile (110) using simple aqueous reactions. Sputtering and annealing cycles, which create surface and subsurface defects, were not needed. The monolayers were hydrophobic and remained largely contaminant free during exposures to laboratory air for tens of minutes. During this period, infrared spectroscopy showed that the monolayers did not spontaneously adsorb airborne hydrocarbons or other adventitious aliphatic species. Scanning tunneling microscopy (STM) images, infrared and X-ray photoemission spectra, Monte Carlo simulations, and ab initio calculations were all consistent with benzoate molecules adopting an edge-to-face ring geometry with their four nearest neighbors—a tetrameric bonding geometry. This bonding is further stabilized by a pairing interaction between adjacent benzoate molecules, a pairing that has previously been interpreted as dimerization. The coexistence of paired and unpaired regions of the monolayer is consistent with the relatively small additional energy gained by pairing and the cooperative nature of the pairing interaction. Monolayer stability is driven both by the strong bidentate bonding to unsaturated Ti atoms on the surface as well as by π–π interactions between adsorbates.