Benzoic Acid and Phthalic Acid on Atomically Well-Defined MgO(100) Thin Films: Adsorption, Interface Reaction, and Thin Film Growth

Beitrag in einer Fachzeitschrift


Details zur Publikation

Autor(en): Xu T, Mohr S, Amende M, Laurin M, Döpper T, Görling A, Libuda J
Zeitschrift: Journal of Physical Chemistry C
Verlag: American Chemical Society
Jahr der Veröffentlichung: 2015
Band: 119
Heftnummer: 48
Seitenbereich: 26968-26979
ISSN: 1932-7447
Sprache: Englisch


Abstract


To better understand the interaction and the growth of thin films of functionalized organic molecules on oxide surfaces, we have studied the adsorption, reaction, and desorption of benzoic acid (BA) and phthalic acid (PA) on a well-ordered MgO(100) thin film grown on a Ag(100) single crystal surface. We have applied isothermal time-resolved infrared reflection absorption spectroscopy (TR-IRAS) and temperature-programmed IRAS (TP-IRAS) under ultrahigh-vacuum (UHV) conditions. BA is dosed using a supersonic molecular beam (SSMB) source while PA is deposited by physical vapor deposition (PVD). For both molecules we have explored the film growth as a function of temperature, both in the monolayer and in the multilayer regime. We have also investigated structural transitions and desorption by temperature-programmed experiments in the range from 100 to 400 K. In addition, we carried out density-functional (DF) calculations. We find that both molecules BA and PA bind through the carboxyl groups to the MgO (100) surface. Upon adsorption at 100 K BA binds in an asymmetric bidentate geometry which exhibits a small tilting angle between the aromatic plane and the surface. Beyond the monolayer, a disordered multilayer film grows, which crystallizes under formation of dimers at around 180 K as indicated by a characteristic splitting of the IR bands. The BA multilayer desorbs at 240 K. Upon adsorption at 300 K, only a BA monolayer forms. Again, BA forms an asymmetric bidentate but with a larger tilting angle compared to low-temperature adsorption. For PA adsorption at 100 K, the adsorption mechanism is observed to change with coverage. At low coverage, both carboxyl groups are deprotonated, and the molecule forms an asymmetric bis-bidentate carboxylate with the aromatic plane nearly perpendicular to the surface. At high coverage, only one carboxyl group binds to the surface and forms an asymmetric bidentate carboxylate while the molecules maintain an upright standing orientation. During PVD of PA, a small fraction of phthalic anhydride (PAA) is formed which coadsorbs at low temperature. Upon annealing, the PAA. desorbs around 250 K, triggering a structural transformation of the PA multilayer during which the PA adopts a more flat lying orientation. The PA multilayer itself desorbs around 310 K. Therefore, only monolayer of PA is stable around 300 K. Again, the adsorption mechanism is coverage dependent, changing from a bis-bidentate carboxylate at lower coverage to a monobidentate carboxylate at higher coverage.



FAU-Autoren / FAU-Herausgeber

Amende, Maximilian
Laurin, Mathias Dr.
Professur für Physikalische Chemie
Lehrstuhl für Physikalische Chemie II
Döpper, Tibor
Lehrstuhl für Theoretische Chemie
Görling, Andreas Prof. Dr.
Lehrstuhl für Theoretische Chemie
Libuda, Jörg Prof. Dr.
Professur für Physikalische Chemie
Mohr, Susanne
Lehrstuhl für Physikalische Chemie II
Xu, Tao
Lehrstuhl für Physikalische Chemie II


Zusätzliche Organisationseinheit(en)
Exzellenz-Cluster Engineering of Advanced Materials


Zitierweisen

APA:
Xu, T., Mohr, S., Amende, M., Laurin, M., Döpper, T., Görling, A., & Libuda, J. (2015). Benzoic Acid and Phthalic Acid on Atomically Well-Defined MgO(100) Thin Films: Adsorption, Interface Reaction, and Thin Film Growth. Journal of Physical Chemistry C, 119(48), 26968-26979. https://dx.doi.org/10.1021/acs.jpcc.5b07591

MLA:
Xu, Tao, et al. "Benzoic Acid and Phthalic Acid on Atomically Well-Defined MgO(100) Thin Films: Adsorption, Interface Reaction, and Thin Film Growth." Journal of Physical Chemistry C 119.48 (2015): 26968-26979.

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Zuletzt aktualisiert 2018-10-08 um 05:12