Hierarchically Ordered α-Zirconium Phosphate Platelets in Aqueous Phase with Empty Liquid

Abstract

Platelets of α-zirconium phosphate (α-ZrP) obtained from the reflux method in H3PO4 are successfully exfoliated into water via the intercalation of alkanol amines. With volume fractions greater than 0.02 they are stacked into tactoids of few layers with a repeat distance in the order of 10 nm. The tactoids align into nematic liquid crystalline phases with irregularly wide interstices of empty liquid. Colloidal processing involves the freeze-drying of such anisotropic fluids and the dispersion of the restacked tacoids into aqueous dispersions of colloidal polymer particles of largely varying size which occupy the otherwise empty liquid between the α-ZrP tactoids and induce piling of the tactoids into columns. Real-time SAXS on drying films and TEM of the obtained coatings demonstrate that the stacked α-ZrP platelets and the polymer particles comprising liquid dry separately without polymer intercalation, while the morphology of the obtained composites can be tuned primarily by the size of the polymer colloids. Concomitant α-ZrP hydrolysis in the exfoliation step is scrutinized as a function of amine basicity and temperature. The role of zirconium based hydrolysis products in the hierarchical α-ZrP assembly is indirectly though consistently confirmed by opposing impacts of ultra-filtration and added oxoanions on the platelets’ spacing, smoothness and aggregation. HAADF-TEM imaging of scattered, singular platelets and XRD peak analysis of the pristine solid shed light on the α-ZrP synthesis. Coexisting flakes and lacunae, both similar in size to the intra-layer crystal domains, suggest the stitching of proto-α-ZrP flakes into extended layers in accordance with our observations on the aging behaviour of α-ZrP dispersions as well as with literature data on related systems.

Preparation of Zirconium Phosphate Nanomaterials and Their Applications as Inorganic Supports for the Oxygen Evolution Reaction

“…To obtain the protonated ZrP nanosheets, producing the Brönsted acid groups, a follow-up method with an acid can be performed [ 21 ]. The exfoliation of ZrP has also been accomplished by using alkanol amines and other wet methods [ 55 , 56 ].…”

Revisiting the Old and Golden Inorganic Material, Zirconium Phosphate: Synthesis, Intercalation, Surface Functionalization, and Metal Ion Uptake

“…107−111 Intercalation of ZrP has received considerable attention in recent years because of its widespread application in the field of photochemistry, catalysis, drug delivery, and metal ion uptake. 102,103,106,107 The direct intercalation of amines and alkanols containing up to four carbon atoms can be achieved smoothly. However, for larger molecules and ions, intercalation can occur only in the presence of small preintercalated molecules or ions.…”

Freestanding α-zirconium phosphate based nacre-like composite films cast from water

“…Research into α-ZrP is wide with significant interest focused on the intercalation of molecules between the α-ZrP sheets 24,25 and the chemical functionalisation possible at these sites. 19,26,27 There are also reports of composite materials consisting of unidirectional α-ZrP layers within a polymer matrix [28][29][30] or in mono-or multilayer films laid onto substrate surfaces. 19,25,27,[31][32][33] Despite the wealth of research into α-ZrP, there are no reports on freestanding nacre-mimetic materials using these nanoplatelet precursors.…”