Mesostructured Silica Thin Films Research Articles

Phase Transformation from Lamellar to Hexagonal in Mesostructured Silica Thin Films by a Water Vapor Hydrothermal Method

Abstract The phase transformation from lamellar to 2-dimensional (2D) hexagonal structure has been observed in mesostructured silica thin films, synthesized using a self-assembly triblock copolymer (EO20PO70EO20, P123) as a template, during heat treatment under water vapor hydrothermal conditions.

Directing role of pH and ethanol vapour on the formation of 2D or 3D mesostructured silica and hybrid organo-silica thin films

A simple synthetic route leading to ordered mesostructured silica and organo-silica thin films is investigated by in situ X-ray experiments. The mesophase directing role of pH and of ethanol vapour pressure during film formation is demonstrated. Modifications of these two parameters during dip coating results in three different 2D or 3D mesostructures (p6mm, P63/mmc, or Pm3n).

Patterning of dye-doped mesostructured silica thin films and lasing actions in their films

Patterning of dye-doped mesostructured silica thin films and lasing actions in their films

Molecular Motion and Environmental Rigidity in the Framework and Ionic Interface Regions of Mesostructured Silica Thin Films

The rigidochromic probe molecule ClRe(CO)3-2,2‘-bipyridine is used to study the properties of mesostructured silica thin films. The probe serves dual functions: its emission band maximum shifts to higher energy with increasing rigidity of its environment and simultaneously the fluorescence depolarization measures the mobility of the probe molecule itself. Dip-coated, mesostructured 2-d hexagonal thin films doped with ClRe(CO)3-2,2‘-bipyridine are prepared by a one-step, one-pot synthesis procedure using tetraethoxysilane as the silicon source and cetyltrimethylammonium bromide as the structure directing agent. Amorphous silicate films prepared without the surfactant are used as controls. In the freshly prepared mesostructured films, the probe molecules reside in both the silica framework (in a rigid environment) and the ionic interface region near the surfactant headgroups (in a nonrigid environment) as shown by the rigidochromic shift. The fluorescence depolarization confirms the rigidity; the molecule is fixed in position in the silica framework but rotates in the interface region. The spectra of the probe in dried and frozen films show that maximum rigidity is achieved at low temperature.

X-ray micro diffraction study on mesostructured silica thin films

The local structure of highly ordered mesostructured silica films was investigated by using a synchrotron X-ray microbeam and a CCD X-ray detector. Two-dimensional X-ray diffraction patterns clearly showed the detailed arrangement of the mesostructures, in which the hexagonal mesochannels aligned uniaxially in the mesostructured silica films formed on a silica glass substrate with a rubbing-treated thin polyimide coating. The alignment direction was shown to be perpendicular to the rubbing direction. The grazing incidence condition revealed the structural anisotropy of the mesostructures, while normal incidence X-ray diffraction data indicated the in-plane structural uniformity of the films. Extra spots were observed in the diffraction patterns. This suggested that the X-ray beam reflected at the boundary of the mesostructured silica film and the substrate.

In situ Brewster angle microscopy and surface pressure studies on the interfacial growth of mesostructured silica thin films

Growth of a mesostructured silica thin film at the air/water interface was observed in situ using Brewster angle microscopy and surface pressure measurements allowing real time observation of nucleation of the film and its rapid growth to full surface coverage at the end of the induction period.