A size-dependent phase map of nanometric iron(III) oxide (γàεàα pathway) based on the TEM observations. Blue dots: the maximum size of γ-Fe2O3 crystals, dark brown dots: the maximum size of twinned ε-Fe2O3 crystals, and brown circles: the maximum size of ε-Fe2O3 single crystals (Lee and Xu, 2016).

Nanosystems, such as nanocrystals and nanopores are ubiquitous in geological environments, especially in the critical zone where fluids meet the solid earth. Geochemical reactions and processes in nano-systems are greatly different from those in macroscopic bulk systems. Two department Faculty are involved in research that deals with nanosystems.

Current research in Huifang Xu’s program includes studies of the relationship among morphology, size, reactivity and stability of nano-crystals; chemical reactions (with focus on sorption, desorption, precipitation, dissolution, and replacement reactions) in nanoporous environments; self-assembled nano-structures in the earth systems; and nano-structured materials for environmental management, such as removals of U, Tc, As, perchlorate, and dyes. Xu’s group also studies catalytic roles of biomolecules and polymers in mediating formations of sedimentary dolomite and other carbonate minerals. A combination of experimental and modeling techniques are used, including aqueous analytical methods, calorimetry, FTIR and NMR spectroscopy, SQUID magnetometer, atomic force microscopy, electron microprobe and Scanning/transmission electron microscopy, density functional theory and molecular dynamics simulations.

Current research in Eric Roden’s program includes studies of enzymatic reductive dissolution of nanoparticulate Fe(III) oxide phases; reductive precipitation of nanoparticulate uranium and other trace/contaminant metals; and enzymatic oxidation and phase conversion of ferrous iron-bearing minerals. Studies are conducted in both mineralogically defined systems as well as physically and chemically heterogeneous natural soil and sediment materials.