Nanogeoscience Research Program
Below is an overview of current
research projects. Positions in the nanogeoscience
group are posted here.
Nanoparticulate iron oxyhydroxide controls
on aqueous redox chemistry and microbial species distribution and
activity in natural environments.
communities are likely to include organism types with the range of
genomic potential needed to profit from the expected suite of electron
accepting minerals encountered in their habitats. We predict that redox
potential is a mineral characteristic key to strain selection, and we
will experimentally adjust the redox potential of electrodes coated
with iron oxyhydroxide nanoparticles and test for reproducible patterns
of organism response. We hypothesize that we can drive selection for
the strain with cytochromes best optimized to use the available mineral
substrate. The biochemical basis for selection will be investigated
through identification of protein variants involved in energy
metabolism and protein-nanomaterial interactions.
For more information, contact Jill Banfield.
This project is supported by DOE BES (Geochemistry).
Structure and Reactivity of Nanoparticle and Bulk Mineral
Coupled Diffusion and Adsorption Processes
within Aggregates of Iron Oxyhydroxide Nanoparticles
water-mineral interface is the site for important chemical cycles in
the environment, including the adsorption of nutrients and
contaminants, surface hosted catalysis, and direct redox reactions
between minerals and aqueous ions. In many natural settings, particle
aggregation reduces the amount and the accessibility of potentially
reactive surfaces. Thus, the rates of geochemically relevant processes
are frequently controlled by the mobility of aqueous inorganic or
organic species within complex, nanoporous aggregates.
We are using small angle-x-ray scattering combined with computational
methods to generate 3D models of nanoparticle aggregates (see Figure).
We have found that aggregate morphology varies considerably with
aggregation pathway (such as pH variation, drying or freezing) and that
pore morphology exerts considerable influence on the extent and
kinetics of the adsorption and release of aqueous copper ions. We are
combining molecular dynamics and lattice Boltzmann simulation methods
to provide insight into the physical and chemical controls on
interfacial processes within nanoparticle aggregates.
For more information, contact Ben
Gilbert. This project is supported by DOE BES (Geochemistry).
Molecular Structure and Processes and
studies of hydrated mineral surfaces have indicated significant
deviations from the bulk-terminated structure often assumed in surface
models. Some of these differences are simple bond-length
but others reflect new degrees of surface protonation and organization
of overlying water molecules (goethite), or changes in surface site
occupations associated with altered chemical reactivity (hematite). In
the proposed studies we seek to extend our past work to additional
important natural mineral surfaces (goethite, diaspore), to surfaces
with sorbed inorganic and organic species of differing chemical and
physical properties, and to undersaturated conditions where
precipitation may be readily initiated.
For more information, contact Glenn Waychunas. This project is supported by DOE
Environmental and Human Health Impacts of Engineered
Evaluation of the environmental and human
health impacts of Silver Nanowires
is now recognized that the manufacture of nanomaterials may represent
unique risks to humans and the environment, the field of nanotoxicology
remains at a nascent state. Inorganic nanowires have received very
little attention but there is a growing expectation that these
materials may have a widespread technological use.
In collaboration with Chris Vulpe and
the Berkeley COINS
Center we are studying the environmental impacts and biological
toxicity of nanowires, initially focusing on silver nanowires.
For more information,
contact Benjamin Gilbert.
This project has been supported by the NIEHS and an NSF Supplement
grant to COINS.
Imaging Electronic and Atomic
Redistribution during Redox Reactions at Surfaces
Reactions that occur
on timescales of less than one millionth of a second are central to
biogeochemical processes that shape the Earth's surface. For example,
the cycles of redox active elements such as iron, sulfur, and oxygen
are tightly coupled to the carbon cycle in both marine and terrestrial
environments. Many of the pathways involve transfer of multiple
electrons between aqueous ions and solids, and thus occur at hydrated
mineral surfaces. However, the speed of the fundamental chemical steps
render them inaccessible to conventional study. We propose to develop a
suite of ultra-fast x-ray methods to visualize the coupled electronic
and molecular steps that occur during redox transformations at the
water-mineral interface and to quantify the rates of intrinsic steps.
We will focus first on the oxidation of pyrite (FeS2), a reaction
central to acid mine drainage formation and biohydrometallurgy, and the
reductive dissolution of iron oxide (Fe2O3), a process central to
bioremediation of radionuclide-contaminated sites.
We will image the time evolution of surface electron density
distributions, surface structure, and local chemical speciation as the
surfaces react. The experiments will make use of nanoparticles of
discreet sizes to determine the effect of particle size on reaction
rates and mechanisms. The results of this work will advance basic
understanding of how electrons are transferred into and out of solids
and may find application in both environmental remediation and
For more information, contact Glenn
Waychunas. This project is supported by the DOE Chemical Imaging.
of ferric iron-based molecular clusters and nanoparticles in chemically
complex acid mine drainage solutions.
This task will study
the growth of nanoparticles in neutralized metal-contaminated acid mine
drainage (AMD) solutions to describe, at the atomic level, the
processes by which nanoparticles form, identify the impacts of
impurities on the growth mechanisms, and determine how interacting and
competing processes determine the fate of contaminants. The research
objectives will be accomplished by integrating results of experiments,
molecular-scale characterization, and simulations.
more information, contact Jill Banfield.
This project is supported by DOE BES (Geochemistry).