The University of Massachusetts Amherst
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Layer-by-layer assembly of sol-gel oxide “glued” montmorillonite-zirconia multilayers

TitleLayer-by-layer assembly of sol-gel oxide “glued” montmorillonite-zirconia multilayers
Publication TypeJournal Article
Year of Publication2010
AuthorsChen H, Zhang G, Wei Z, Cooke KM, Luo J
JournalJournal of Materials Chemistry
Start Page4925
Date Published04/2010

This paper reports the layer-by-layer synthesis and  growth  kinetics of a new class of nanostructured multilayers consisting of montmorillonite ( MMT ) nanoclays “glued” by sol–gel oxides, such as  zirconia  (ZrO2) and tin oxide (SnO2), {MMTx-(sol–gel  oxide)}n . The multilayers possess an ordered layer structure with tunable nanoscale periods of thickness. Systematic investigation of  growth  kinetics revealed unique underlying film  growth  mechanisms. The  growth of the  MMT  and sol–gel ZrO2 layers is strongly coupled. For fresh aqueous ZrO2 precursors, the growth  rates of sol–gel ZrO2 layers on  MMT  surfaces as functions of time and precursor concentration do not follow the standard mass transfer or interfacial reaction controlled kinetic models. Furthermore, the  growth  of the sol–gel  oxide  layers on  MMT  surfaces is self-limited to a maximum thickness of ∼50–60 nm. These observations suggest a surface-mediated  growth  of sol–gel  oxide  layers on  MMT  surfaces, and such  growth  is likely influenced or controlled by electrostatic interactions. For the aged precursors, the  growth  mechanism differs; the  growth  of sol–gel  oxide  layers is controlled by hydrodynamics and follows the Landau–Levich model. These new findings on detailed  growth  kinetics, which have been difficult to observe and quantify via the synthesis of more prevailing  polyelectrolyte -based multilayers, significantly advance the general understanding of the layer-by-layer electrostatic  assembly . Overall,  layer-by-layer assembly  of multilayers using sol–gel oxides, instead of  polyelectrolytes , as both adhesive and functional components in the structure, is a new concept of nanoscale fabrication, which can lead to the development of a broad range of inorganic nanostructured films. The mechanical properties and potential applications of this new class of multilayers are briefly discussed.