The true structure of hexagonal mesophase-templated silica films as revealed by X-ray scattering: Effects of thermal treatments and of nanoparticle seeding
M. Klotz et al., The true structure of hexagonal mesophase-templated silica films as revealed by X-ray scattering: Effects of thermal treatments and of nanoparticle seeding, CHEM MATER, 12(6), 2000, pp. 1721-1728
This work describes the detailed structural investigation of mesophase-temp
lated mesoporous silica films by 1D and 2D X-ray scattering techniques and
transmission electron microscopy. The films are prepared by sol-gel dip coa
ting with 2D hexagonal templating mesophases, yielding 2D mesoporous struct
ures consisting of cylindrical pores whose axes are aligned parallel to the
surface. It is shown that drying and thermal treatments induce an unidirec
tional shrinkage of the layers in the direction of the normal of the film.
The true rectangular symmetry is only evidenced by 2D X-ray scattering in t
wo different scattering geometries. 1D diffraction gives only an apparent h
exagonal symmetry. It is furthermore shown that although the cylinder axes
are randomly orientated within the plane parallel to the surface, there are
large domains with well aligned 2D planar unit cells perpendicular to the
surface. It is demonstrated that this preferential ordering is destroyed by
nanoparticle seeding with amorphous silica or maghemite particles.