Layer-by-layer assembly of sol–gel oxide “glued” montmorillonite-zirconia multilayers

Abstract

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 (ZrO 2 ) and tin oxide (SnO 2 ), {MMT x -(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 ZrO 2 layers is strongly coupled. For fresh aqueous ZrO 2 precursors, the growth rates of sol-gel ZrO 2 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.

Effective Air‐Spray Deposition of Thin Films Obtained by Sol–Gel Process onto Complex Pieces of Sanitary Ware

“…Each viscosity versus aging time curve has a linear behavior for short times, and can be approximated to a first‐order exponential growing near the gelation time, which corresponds to chemical reactions with first‐order kinetics …”

Micromechanical Properties of Nanostructured Clay-Oxide Multilayers Synthesized by Layer-by-Layer Self-Assembly

“…A similar LbL deposition technique was employed to prepare clay-zirconia multilayered films [15,16]. Two kinds of sodium-rich montmorillonite (Na-MMT) clay minerals, Cloisite ® Na + , and SWy-2, obtained from Southern Clay Products Inc. (Gonzales, TX, USA) and the Clay Minerals Society Repository (Purdue University, West Lafayette, IN, USA), respectively, were used to prepare 0.03 wt % and/or 0.4 wt % clay suspension.…”

“…Nanostructured clay-oxide multilayers prepared by the LbL self-assembly technique has been reported by Chen and Zhang et al [15,16,17]. In these studies, the exfoliated clay platelet (montmorillonite, MMT) having a high aspect ratio with thickness in nanometer scale and bearing negative surface charges is used as an anionic component.…”

Tb3+-containing supramolecular hydrogels: luminescence properties and reversible sol–gel transitions induced by external stimuli

“…Supramolecular gels have attracted considerable attention due to their unique structures and wide applications 1,2 in biomaterials, [3][4][5] liquid-crystalline materials, 6,7 stimuli-responsive materials, 8,9 nanoscale inorganic materials, and so on. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] These self-assembly nanoscale structures of gelators, such as fibers, rods and ribbons, are capable of entrapping a large amount of organic solvent or water via non-covalent interactions to afford a solid-like appearance, that is, forming supramolecular organogels or hydrogels. 25 Stimuli can induce the release of entrapped solvent molecules, resulting in shrinking or even a gel-to-sol transition of supramolecular gels.…”