Heterogeneous Nucleation and Growth of Nanoparticles at Environmental Interfaces

Abstract

Mineral nucleation is a phase transformation of aqueous components to solids with an accompanying creation of new surfaces. In this evolutional, yet elusive, process, nuclei often form at environmental interfaces, which provide remarkably reactive sites for heterogeneous nucleation and growth. Naturally occurring nucleation processes significantly contribute to the biogeochemical cycles of important components in the Earth's crust, such as iron and manganese oxide minerals and calcium carbonate. However, in recent decades, these cycles have been significantly altered by anthropogenic activities, which affect the aqueous chemistry and equilibrium of both surface and subsurface systems. These alterations can trigger the dissolution of existing minerals and formation of new nanoparticles (i.e., nucleation and growth) and consequently change the porosity and permeability of geomedia in subsurface environments. Newly formed nanoparticles can also actively interact with components in natural and engineered aquatic systems, including those posing a significant hazard such as arsenic. These interactions can bilaterally influence the fate and transport of both newly formed nanoparticles and aqueous components. Due to their importance in natural and engineered processes, heterogeneous nucleation at environmental interfaces has started to receive more attention. However, a lack of time-resolved in situ analyses makes the evaluation of heterogeneous nucleation challenging because the physicochemical properties of both the nuclei and surfaces significantly and dynamically change with time and aqueous chemistry. This Account reviews our in situ kinetic studies of the heterogeneous nucleation and growth behaviors of iron(III) (hydr)oxide, calcium carbonate, and manganese (hydr)oxide minerals in aqueous systems. In particular, we utilized simultaneous small-angle and grazing incidence small-angle X-ray scattering (SAXS/GISAXS) to investigate in situ and in real-time the effects of water chemistry and substrate identity on heterogeneously and homogeneously formed nanoscale precipitate size dimensions and total particle volume. Using this technique, we also provided a new platform for quantitatively comparing between heterogeneous and homogeneous nucleation and growth of nanoparticles and obtaining undiscovered interfacial energies between nuclei and surfaces. In addition, nanoscale surface characterization tools, such as in situ atomic force microscopy (AFM), were utilized to support and complement our findings. With these powerful nanoscale tools, we systematically evaluated the influences of environmentally abundant (oxy)anions and cations and the properties of environmental surfaces, such as surface charge and hydrophobicity. The findings, significantly enhanced by in situ observations, can lead to a more accurate prediction of the behaviors of nanoparticles in the environment and enable better control of the physicochemical properties of nanoparticles in engineered systems, such as catalytic reactions and energy storage.

The apparent activation energy and pre-exponential kinetic factor for heterogeneous calcium carbonate nucleation on quartz

“…IðqÞq 2 dq for q = 0.01-0.1 Å −1 (refs. 36,39 ). For a nucleation-dominant system where nucleus size does not change significantly, the invariant is proportional to the nucleus number, and can be treated as the total nucleus number with a relative unit comparable to all invariant values calculated in this study 48 .…”

“…For samples with relatively high signal-to-noise ratios, we fitted the GISAXS intensity according to 36,39,48,49…”

“…For example, Fernandez-Martinez et al 34 and Li et al 36 reported that the interfacial energies for nucleation of CaCO 3 on silicates were as low as 35-50 mJ m −2 . The overall system's interfacial energy can be affected appreciably by individual interfacial energies among nuclei, substrates, and solutions 13,33,35,36,[39][40][41] .…”

Graphene-like carbon sheet/Fe3O4 nanocomposites derived from soda papermaking black liquor for high performance lithium ion batteries

“…On inhomogeneity substrates, the degree of surface hydrophilicity controlled the rate of nucleation and growth, because increased hydrophilicity can decrease the interfacial energy between the nanoparticles and substrate and improve the nucleation and growth rate of nanoparticles [33]. Lignins with highly hydrophilic groups can provide remarkably reactive sites for heterogeneous nucleation and growth of iron nanoparticles.…”

In Situ Atomic Force Microscopy Studies on Nucleation and Self-Assembly of Biogenic and Bio-Inspired Materials

“…These recent reports will be categorized into three groups based on their subjects: soft (E < 10 GPa) biogenic materials, soft bio-inspired materials, and hard (E > 10 GPa) materials. Since many previous review articles [135][136][137][138][139][140][141][142][143][144] have summarized AFM applications in nucleation of hard materials, this review will focus on soft materials.…”