Highly ordered self-assembled monolayer film of an azobenzenealkanethiol on Au(111). Electrochemical properties and structural characterization by synchrotron in-plane X-ray diffraction, atomic force microscopy, and surface-enhanced Raman spectroscopy
- Northwestern Univ., Evanston, IL (United States)
- Argonne National Lab., IL (United States)
The synthesis and characterization of p-HS(CH{sub 2}){sub 11}OC{sub 6}H{sub 4}N=NC{sub 6}H{sub 5}, compound 1d, is reported. Compound 1d self-assembles onto Au(111) substrates into highly ordered monolayer films. Self-assembled monolayer films (SAMs) of 1d on Au(111)/mica have been characterized by ellipsometry, surface-enhanced Raman spectroscopy (SERS), and atomic force microscopy (AFM). We also report the characterization of SAMs of 1d on bulk single crystal Au(111) by synchrotron in-plane X-ray diffraction (XRD) measurements. AFM and in-plane XRD suggest that a SAM of 1d is comprised of domains of 1d which form a hexagonal lattice (4.50 {+-} 0.06 A nearest neighbor spacing) that is incommensurate with the underlying Au(111) lattice. A model is proposed to describe the SAM structure. In such a model, small bundles (nearly 80 molecules) of ordered azobenzene moieties that rest over a set of inward tilting alkyl surface tethering groups make up the individual domains. Thermal annealing of the as-deposited SAM of 1d results in a modest increase in domain size from nearly 45 to around 55 A and a change in azobenzene tilt angle from 20-30{degree} to approximately 0{degree} with no change in nearest neighbor spacing. The redox activity of the azobenzene group is significantly affected by monolayer film structure. Only 2% of the azobenzene groups within a SAM of 1d are electrochemically accessible through cyclic voltammetry in a THF/0.1 M n-Bu{sub 4}NPF{sub 6} electrolyte. 46 refs., 13 figs.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 70341
- Journal Information:
- Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 22 Vol. 117; ISSN JACSAT; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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