Exfoliation of α-Zirconium Phosphate Using Tetraalkylammonium Hydroxides

Abstract

α-Zirconium phosphate (α-ZrP), a classical layered compound, has found widespread application. Exfoliation of α-ZrP has been mainly achieved by propylamine (PA) or tetrabutylammonium hydroxide (TBAOH), but the exact mechanism of exfoliation has not been completely elucidated. We examined the feasibility of exfoliation utilizing tetraalkylammonium hydroxide (TXAOH) and investigated the stepwise intercalation/exfoliation mechanism of α-ZrP. All of the TXAOHs examined (carbon number of the branches: 1−4) were able to exfoliate α-ZrP in an aqueous dispersion under ultrasonication. Furthermore, exfoliation of α-ZrP by two different exfoliators (either a mixture of two or sequentially) was also investigated to pinpoint the exfoliation mechanism. Our results indicate that small TXA cations are kinetically preferred to diffuse into the galleries of α-ZrP, while large TXA cations can help open up the galleries and facilitate transport of the already intercalated cations. These findings should help fellow researchers to choose the most suitable exfoliators for their own projects and develop better intercalation/exfoliation systems.

Gelation Based on Host–Guest Interactions Induced by Multi-Functionalized Nanosheets

“…In this work, we proposed a design of a gelation system, making use of abundant host-guest interactions, as shown in Figure 1. α-ZrP microcrystals (Figure 1a) could be exfoliated by propylamine or TXA [36] in an aqueous system into single-layer nanosheets, forming a homogenous colloid dispersion (Figure 1b). The TEM image in Figure 1c shows the representative ZrP nanosheets exfoliated by TBA.…”

“…From the very beginning, we wanted to ensure the attachment of adamantyl groups onto the α-ZrP nanosheets. Because exfoliation of α-ZrP could be achieved with TXA [36], which are all quaternary ammonium hydroxides, it is natural to assume that TriMAA, with a similar structure and basicity, has the potential to exfoliate α-ZrP. However, after mixing TriMAA and α-ZrP, intercalation occurred, according to the peak from the XRD pattern (4.87 • /18.1 Å) being significantly sharper than the restacked exfoliated α-ZrP nanosheets using propylamine (6.02 • /14.7 Å) or TBA (4.85 • /18.2 Å), as shown in Figure 2a.…”

“…This structure, with abundant hydroxyl groups, endows α-ZrP with a high ion exchange capacity of 6.64 meq/g [27,28], which also facilitates the intercalation of α-ZrP [29][30][31][32][33]. Bulk crystalline α-ZrP can be exfoliated by amines [34][35][36][37][38][39] into single-layer nanosheets with a thickness of below 1 nm but a diameter of several micrometers [16,21,[40][41][42] to further expose the hydroxyl groups. The resultant exfoliated α-ZrP nanosheets, therefore, could be utilized as nanofillers for nanocomposites [43][44][45][46][47] and templates for creating abundant host-guest interactions for gels [48][49][50].…”

A Cationic Ru(II) Complex Intercalated into Zirconium Phosphate Layers Catalyzes Selective Hydrogenation via Heterolytic Hydrogen Activation

“…[59] It could be seen that a new peak at 5.9°emerged in the patterns of ex-ZrP_ 0.2 and ex-ZrP_0.4 samples while the peak at 11.7°remained but became weak. The appearance of the new peak (5.9°, 15.0 Å) revealed the partial exfoliation state, [60] which was due to intercalation of single layer of TBA into α-ZrP nanosheets in line with a slight increase of BET surface area (Table 1). Moreover, as the molar ratio of TBAOH to α-ZrP were raised from 0.2 to 0.4, the exfoliated ZrP catalysts offered a weaker peak at 5.9°(15.0 Å), as compared with that of α-ZrP, which meant higher extent of exfoliation degree for ex-ZrP_0.4 sample (Figure 1a).…”

Nanolayered Metal Phosphates as Biocompatible Reservoirs for Antimicrobial Silver Nanoparticles

“…Among these methods, the hydrothermal method has the advantage of resulting in highly crystalline layered α-ZrP structures with a narrow particle size distribution and controlled morphology [9]. α-ZrP has gained a considerable interest owing to the ease of controlling its structure and facile exfoliation into few or single-layered entities with all the consequent possibilities of enhancing its intercalation capacity and increasing tremendously its surface area to mass ratio [10][11][12][13][14][15][16].…”