C{sub 60}-propylamine adduct monolayers at the gas/water interface: A Brewster angle microscopy and x-ray scattering study
- Department of Physics and Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States)
- Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States)
Brewster angle microscopy (BAM), x-ray specular reflectivity and grazing-incidence x-ray diffraction (GID) studies of C{sub 60}-propylamine adduct monolayers at the gas/water interface as a function of molecular area are reported. At large molecular areas (A{gt}{approximately}150 {Angstrom}{sup 2}/molecule), BAM images reveal macroscopic heterogeneity in the film, consisting of the coexistence between regions covered with uniform solidlike monolayer and bare water surface. After compression to a limiting molecular area of 150 {Angstrom}{sup 2}/molecule, the film is observed to be homogeneous, with the uniform monolayer covering the entire available surface. Both the x-ray reflectivity results and the GID patterns are consistent with the formation of a uniform monolayer at A{approximately}150 {Angstrom}{sup 2}/molecule, while the little dependence that the GID patterns have on the molecular area for A{gt}{approximately}150{Angstrom}{sup 2}/molecule is consistent with the heterogeneity in the film. Upon further compression to higher densities (A{lt}{approximately}120 {Angstrom}{sup 2}/molecule), the x-ray reflectivity results suggest the formation of a partial layer either at the molecule/gas interface or at the molecule/water interface. In this high density regime, the shift in the observed GID pattern with molecular area is much smaller than would be expected if the film were to remain a homogeneous monolayer, also consistent with the formation of an inhomogeneous partial layer. The analysis of the broad GID pattern observed from a uniform monolayer in terms of a model 2D radial distribution function, implies a short range positional correlation, extending to only a few molecular distances. The average nearest neighbor distance (d{approximately}13 {Angstrom}), extracted from the GID analysis, is consistent with the limiting molecular area (A{approximately}150 {Angstrom}{sup 2}/molecule) assuming local hexagonal packing. (Abstract Truncated)
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States)
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 542571
- Journal Information:
- Journal of Chemical Physics, Vol. 107, Issue 14; Other Information: PBD: Oct 1997
- Country of Publication:
- United States
- Language:
- English
Similar Records
Structure of poly([gamma]-benzyl-L-glutamate) monolayers at the gas[endash]water interface: A Brewster angle microscopy and x-ray scattering study
C{sub 60}-propylamine adduct monolayers at the air-water interface