Formation of Vertically Oriented Channels during Calcination of Surfactant-Templated Titania-Doped Mesoporous Silica Thin Films

Yuxin He, M. Arif Khan, Andrew Drake, Ramy Ghanim, Joshua Garay, Aniruddha Shirodkar, Joseph Strzalka, Qingteng Zhang, Barbara L. Knutson, Stephen E. Rankin

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Mesoporous structure development during calcination of titania-doped mesoporous silica thin films is characterized byin situgrazing-incidence small-angle X-ray scattering (GISAXS). Varying amounts of titania (≤6 mol %) are incorporated in cetyltrimethylammonium bromide (CTAB)-templated films by two methods in this study: dispersion of titania in the silica matrix and fixing titania at the pore surface by complexation of the titania precursor with a sugar-based cosurfactant, dodecyl maltoside (C12G2). Before calcination, films templated with only CTAB display a mesoporous structure with a mixture of in-plane two-dimensional (2D) hexagonal and randomly oriented porous structure, while the C12G2-complexed film possessed randomly oriented mesostructure only. Both methods yield a final structure of hexagonal close-packed pores orthogonally oriented to the substrate after calcination at 500 °C. This is attributed to weak Si-O-Ti bonds, which allow sintering to occur at 500 °C, combined with unidirectional thermal contraction of the film in the vertical direction. Anisotropic stress and annealing of the films allow the randomly oriented pores to merge vertically and form channels with a pore diameter of 2.3 ± 0.3 nm. Titania doping greater than 1% is required for this transformation in films with no C12G2surfactant used, while transformation was observed for films with C12G2complexation even at low (0.005%) titania doping, perhaps accentuated by orientational disorder introduced by the sugar surfactant.

Original languageEnglish
Pages (from-to)22262-22273
Number of pages12
JournalJournal of Physical Chemistry C
Volume125
Issue number40
DOIs
StatePublished - Oct 14 2021

Bibliographical note

Publisher Copyright:
© 2021 American Chemical Society

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • General Energy
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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