Molecular architecture: construction of self-assembled organophosphonate duplexes and their electrochemical characterization
| Autor: | Bert Nickel, Achyut Bora, Christian Hundschell, Gerhard Abstreiter, Jeffrey Schwartz, Kung-Ching Liao, Anshuma Pathak, Marc Tornow, Anna Cattani-Scholz |
|---|---|
| Rok vydání: | 2012 |
| Předmět: |
Anthracenes
Materials science Silicon Inorganic chemistry Stacking Organophosphonates chemistry.chemical_element Surfaces and Interfaces Condensed Matter Physics Electrochemistry Microscopy Atomic Force Dielectric spectroscopy X-ray reflectivity Crystallography chemistry X-Ray Diffraction Duplex (building) Electrode Monolayer General Materials Science Spectroscopy |
| Zdroj: | Langmuir : the ACS journal of surfaces and colloids. 28(20) |
| ISSN: | 1520-5827 |
| Popis: | Self-assembled monolayers of phosphonates (SAMPs) of 11-hydroxyundecylphosphonic acid, 2,6-diphosphonoanthracene, 9,10-diphenyl-2,6-diphosphonoanthracene, and 10,10'-diphosphono-9,9'-bianthracene and a novel self-assembled organophosphonate duplex ensemble were synthesized on nanometer-thick SiO(2)-coated, highly doped silicon electrodes. The duplex ensemble was synthesized by first treating the SAMP prepared from an aromatic diphosphonic acid to form a titanium complex-terminated one; this was followed by addition of a second equivalent of the aromatic diphosphonic acid. SAMP homogeneity, roughness, and thickness were evaluated by AFM; SAMP film thickness and the structural contributions of each unit in the duplex were measured by X-ray reflection (XRR). The duplex was compared with the aliphatic and aromatic monolayer SAMPs to determine the effect of stacking on electrochemical properties; these were measured by impedance spectroscopy using aqueous electrolytes in the frequency range 20 Hz to 100 kHz, and data were analyzed using resistance-capacitance network based equivalent circuits. For the 11-hydroxyundecylphosphonate SAMP, C(SAMP) = 2.6 ± 0.2 μF/cm(2), consistent with its measured layer thickness (ca. 1.1 nm). For the anthracene-based SAMPs, C(SAMP) = 6-10 μF/cm(2), which is attributed primarily to a higher effective dielectric constant for the aromatic moieties (ε = 5-10) compared to the aliphatic one; impedance spectroscopy measured the additional capacitance of the second aromatic monolayer in the duplex (2ndSAMP) to be C(Ti/2ndSAMP) = 6.8 ± 0.7 μF/cm(2), in series with the first. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|