Influence of Alkyl Chain Length on Phosphate Self-Assembled Monolayers
| Autor: | Nicholas D. Spencer, Stefan Zürcher, Samuele Tosatti, Doris M. Spori, Nagaiyanallur V. Venkataraman, Firat Durmaz |
|---|---|
| Rok vydání: | 2007 |
| Předmět: |
chemistry.chemical_classification
Alkyl phosphate Analytical chemistry Infrared spectroscopy Self-assembled monolayer Surfaces and Interfaces Condensed Matter Physics Contact angle Crystallinity chemistry.chemical_compound Crystallography X-ray photoelectron spectroscopy chemistry Monolayer Electrochemistry lipids (amino acids peptides and proteins) General Materials Science Spectroscopy Alkyl |
| Zdroj: | Langmuir. 23:8053-8060 |
| ISSN: | 1520-5827 0743-7463 |
| Popis: | A series of alkyl phosphates with alkyl chain lengths ranging from C10 to C18 have been synthesized. Self-assembled monolayers (SAMs) of these molecules were prepared on titanium oxide surfaces by immersion of the substrates in alkyl phosphate solutions of 0.5 mM concentration in n-heptane/isopropanol. The SAMs were characterized by means of dynamic water contact angle (dCA) measurements, variable-angle spectroscopic ellipsometry (VASE), X-ray photoelectron spectroscopy (XPS), and polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS). A higher degree of order and packing density within the monolayers was found for alkyl phosphates with alkyl chain lengths exceeding 15 carbon atoms. This is reflected in a lower dCA hysteresis, as well as a film thickness measured by VASE and XPS close to the expected values for SAMs with an average alkyl chain tilt angle of 30 degrees to the surface normal. Additionally a shift of the symmetric and antisymmetric C-H stretching modes in the PM-IRRAS spectra to lower wave numbers was observed. These findings imply a higher two-dimensional crystallinity of the films derived from alkyl phosphates with a longer alkyl chain length. |
| Databáze: | OpenAIRE |
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