We have a variety of recent and ongoing research projects on topics ranging from crystallization to surface reactivity to structure-property-behavior relationships of nanoparticles. Much of our research involves the use of state-of-the-art synchrotron-based methods. Brief descriptions of our focus areas are described below with links to selected publications.
Mineral Growth by Nanoparticle Aggregation
The transformation of aqueous species into solids is perhaps the least understood process in low-temperature mineral formation under conditions typical of Earth’s surface (De Yoreo et al., 2015). This is particularly true for nanosized solids that are byproducts of weathering at near-surface Earth conditions. We are investigating formation of important nanominerals including ferrihydrite, goethite, and schwertmannite, many aluminum and manganese-(oxy)hydroxides, and aluminosilicate phases such as imogolite, allophane, and certain clays.
We have studied the decomposition of hydrogen peroxide (H2O2) to oxygen (O2) and water (H2O) by commercial platinum nanocatalysts used in hydrogen fuel cells. We determined both the reaction mechanism and rate-limiting step by studying the effect of different reaction conditions, nanoparticle size, and surface composition on the rates of H2O2 decomposition by three platinum nanocatalysts with average particle sizes of 3, 11, and 22 nm. Results to date have been published in the following papers:
Novel Devices for Geochemical Studies
Comparison of SLA 3D-printed reactor (right) to similar design fabricated by conventional machining (left)
Desktop 3D printing stereolithography (SLA) is a fabrication technique based on photopolymerization that can be used to efficiently create novel reaction devices for laboratory geochemistry with complex features (e.g. internal channels, small volumes) that are beyond the capabilities of traditional machining methods. We evaluated the stability of 3D printed parts in order to establish a baseline for their stability at low-temperature aqueous geochemical conditions. Results to date have been published in the following papers:
Nanoparticle Precipitation on Mineral Surfaces
Thousands of active and former mine sites worldwide are releasing contaminated acid mine drainage (AMD) that impacts water quality and ecosystem health. Neutralization of AMD by reaction with crushed limestone is a relatively simple and cost-effective treatment method. We are working to improve the efficiency of AMD passive treatment by studying the formation of iron oxide mineral coatings on the limestone substrate that limit the neutraliztaion potential. Following a recent paper (link below) by Palomino-Ore et al. (2019), our experiments use custom 3D-printed reactors to test how different minerals (e.g., calcite) react with simulated AMD to form nanomineral coatings.
Optical Properties of Natural Iridescent Minerals
Iron oxide and hydroxide minerals can exhibit exhibit brilliant rainbow-like colors. As part of a series of undergraduate research projects, we are using x-ray scattering methods and optical and electron microscopic methods to understand the mechanism of color in natural turgite samples.