Interactions between self-assembled monolayers and an organophosphonate: A detailed study using surface acoustic wave-based mass analysis, polarization modulation-FTIR spectroscopy, and ellipsometry
- Texas A&M Univ., College Station, TX (United States). Dept of Chemistry; and others
Self-assembled monolayers (SAMs) having surfaces terminated in the following functional groups: -CH{sub 3}, -OH, -COOH, and (COO{sup -}){sub 2}Cu{sup 2+} (MUA-Cu{sup 2+}) have been prepared and examined as potential chemically sensitive interfaces. Mass measurements made using surface acoustic wave (SAW) devices indicate that these surfaces display different degrees of selectivity and sensitivity to a range of analytes. The response of the MUA-Cu{sup 2+} SAM to the nerve-agent simulant diisopropyl methylphosphonate (DIMP) is particularly intriguing. Exposure of this surface to 50%-of-saturation DIMP yields a surface concentration equivalent to about 20 DIMP monolayers. Such a high surface concentration in equilibrium with a much lower-than-saturation vapor pressure has not previously been observed. Newly developed analytical tools have made it possible to measure the infrared spectrum of the chemically receptive surface during analyte dosing. Coupled with in-situ SAW/ellipsometry measurements, which permit simultaneous measurement of mass and thickness with nanogram and Angstrom resolution, respectively, it has been possibly to develop a model for the surface chemistry leading to the unusual behavior of this system. The results indicate that DIMP interacts strongly with surface-confined Cu{sup 2+} adduct that nucleates growth of semi-ordered crystallites having substantially lower vapor pressure than the liquid.
- Research Organization:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 542066
- Report Number(s):
- SAND-97-2140C; CONF-970997-; ON: DE98000173; TRN: 97:005615
- Resource Relation:
- Conference: Interaction of acoustic waves with thin films and interfaces, Leicester (United Kingdom), 8-10 Sep 1997; Other Information: PBD: 24 Jun 1997
- Country of Publication:
- United States
- Language:
- English
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