Formation and Aggregation of ZrO₂ Nanoparticles on Muscovite (001)

Abstract

The aggregation of nanoparticles is a key step in the formation of solid phases and a controlling factor for the behavior of suspended nanoparticles in solution. Using a charged mineral surface [muscovite (001)], we apply the surface X-ray diffraction techniques crystal truncation rod (CTR) measurements and resonant anomalous X-ray reflectivity (RAXR) to investigate the aggregation process of Zr nanoparticles at the sub-nanometer scale. The aggregation process was studied as a function of ionic strength (0, 1, 10, and 100 mM NaCl), and the interfacial particles were characterized by CTR/RAXR and AFM. The observations are consistent with an aggregation process that follows a multistep mechanism, which starts with the 3D aggregation of primary building units to form nanosheets. These sheets continue to grow through addition of building units to their reactive edges at higher ionic strength. Once the size and concentration of aggregates are sufficient, "faceto-face" stacking of nanosheets becomes the preferred aggregation mechanism as this minimizes the electrostatic repulsion of the charge that accumulates along nanosheet edges.

Competitive Adsorption of ZrO2 Nanoparticle and Alkali Cations (Li+–Cs+) on Muscovite (001)

“…Here, we can assume that the particles' size distribution is mainly representative of their aggregation behavior in solution. 18 Such a "nonselective" adsorption of ZrO 2 nanoparticles in both Li + and Na + solutions is also inferred by the weak correlation between the Zr surface coverage and the associated hydration energies of coexisting ions (Li + and Na + ), as shown in Figure 5. The interfacial exchange reaction is independent of the ions' hydration energies because the desorption reaction does not involve changes in their hydration spheres but is rather a substitution reaction between two types of "OS"-bound chemical entities.…”

“…17 The adsorption of ZrO 2 nanoparticles seems to occur in a pseudo-"outer sphere"binding mode, where the surface of the nanoparticles is formed by (protonated) O rather than Zr. 18 We will have to consider several energetic contributions to the exchange reaction: (a) the energy required to desorb an adsorbed alkali ion (ΔG des ), (b) the energy gained by adsorption of the ZrNP together with the energy gained by the rehydration of the surface site vacated by an IS complex (ΔG ads_NP ), and (c) the energy gained by the rehydration of IS-bound cations (ΔG hyd_i ).…”

“…In this study, we chose ZrO 2 as a model nanoparticle to study its sorption behavior on the muscovite (001) surface in solutions containing different alkali ions. We have recently studied the aggregation mechanisms of such nanoparticles in solutions of a fixed pH of 2.5 and increasing ionic strength, 18 which points to a stepwise formation of nanoparticles containing a plateletlike morphology (i.e., larger lateral than vertical dimension). The surface net positive charge, accumulating at the nanoparticle edges, drives the adsorption of nanoparticles on the mica surface through electrostatic attraction.…”

Interaction between Amorphous Zirconia Nanoparticles and Graphite: Electrochemical Applications for Gallic Acid Sensing Using Carbon Paste Electrodes in Wine

“…(2) formation of thicker oligomers prior to interfacial attachment; (3) lateral growth of nanosheets via the addition of building units to edges; and (4) formation of vertical nanosheet stacks accompanied by lateral addition of building units [41]. However, when they are presented as discrete particles, on analysis by the Zetasizer, the sizes range averagely from 20 nm to about 470 nm.…”

“…The particles did not appear consistently as discrete particles, but as small aggregations with average sizes ranging from 10 µm to 100 µm. The increased particle sizes observed in the SEM images could be attributed to any of these aggregation steps: (1) adsorption and aggregation of primary building units, small oligomer; (2) formation of thicker oligomers prior to interfacial attachment; (3) lateral growth of nanosheets via the addition of building units to edges; and (4) formation of vertical nanosheet stacks accompanied by lateral addition of building units [41]. However, when they are presented as discrete particles, on analysis by the Zetasizer, the sizes range averagely from 20 nm to about 470 nm.…”