Characterization of Zirconium Phosphate/Polycation Thin Films Grown by Sequential Adsorption Reactions

Hyuk Nyun Kim, Steven W. Keller, Thomas E. Mallouk, Johannes Schmitt, Gero Decher

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241 Scopus citations

Abstract

Monolayer and multilayer thin films consisting of anionic α-zirconium phosphate (α-ZrP) sheets and polycations (poly(allylamine hydrochloride) (PAH), cytochrome c) were characterized by transmission electron microscopy (TEM), ellipsometry, UV - visible absorbance spectroscopy, reflectance FT-IR, XPS, and X-ray diffraction. Titration and powder X-ray diffraction experiments confirm that exfoliation of α-ZrP begins to occur when enough tetra(n-butylammonium) hydroxide (TBA+OH-) has been added to exceed single-layer packing of TBA+ ions (x ≈ 0.50) in the intercalation compound Zr(HPO4)2-x(TBA+PO4 -)x·H2O. The identical contrast of many sheets in TEM micrographs suggests that the suspension is unilamellar. Alternately dipping cationic substrates into α-ZrP-containing suspensions and aqueous PAH gives a multilayer film that resembles the corresponding bulk intercalation compound. X-ray photoelectron spectra of multilayer films show that they are Zr-rich, relative to α-ZrP, consistent with some corrosion during the exfoliation reaction. The α-ZrP/PAH layer pair thickness is 13/14.7 Å, as measured by ellipsometry/X-ray diffraction, respectively. A 13-layer pair film is sufficiently well-ordered in the stacking direction to give a Bragg peak in the diffraction pattern. The agreement between the bilayer thickness and the total film thickness, measured from Kiessig fringes in the low-angle part of the diffraction pattern, confirms that only a single dense α-ZrP or PAH monolayer is deposited in each adsorption step.

Original languageEnglish (US)
Pages (from-to)1414-1421
Number of pages8
JournalChemistry of Materials
Volume9
Issue number6
DOIs
StatePublished - Jun 1997

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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