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Chemical Analysis of Nanodomains

We seek to understand the basic principles that underlie energy-relevant chemical separations; develop analytical methods to improve the sensitivity, reliability, and productivity of analytical determinations; and to develop new approaches to analysis. Our research emphasizes instrumentation and technique development highly relevant to the main focus areas of the Separation and Analysis activities of the Division of Chemical Science, Geoscience and Biosciences within the DOE Office of Basic Energy Sciences.

The goal of this research is to develop the next generation of imaging tools and methodologies for the analysis of phenomena that occur at nanometer length scales and picosecond time scales. The developed instrumentation and methodology will be applied to model systems of interest to the DOE mission, where fundamental insight can be gained with the high spatial and temporal resolution afforded by our developed methods: chemical reactions in heterogeneous silica supported catalysts; the organization and dynamics of mixed model lipid bilayers and cell membranes; chromatographic interactions; and heterogeneous enzyme reactions. The methods we propose to develop are:

  1. High resolution total internal reflection (TIR) Raman microspectroscopy and imaging
  2. Sub-diffraction limited imaging, including differential interference contrast (DIC) microscopy, variable-angle evanescent-field (EFM) microscopy, and time-resolved stimulated emission depletion (STED) microscopy
  3. Novel single molecule spectroscopies

This research is supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences through the Ames Laboratory.  The Ames Laboratory is operated for the U.S. Department of Energy by Iowa State University under Contract No. DE-AC02-07CH11358

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  • Researchers have overcome the extreme challenge of directly observing the dynamics of how light excites electrons and generates electricity in solar cell and photovoltaic technologies.  The formation and dissociation of bound electron and hole pairs, known as excitons, were studied using a combination of broadband terahertz pulses (a trillion cycles per second) and selective laser pumping to reveal the light-induced excitation dynamics and charge transport mechanism within perovskites.  Perovskites are a class of materials that show promise as industrial solar energy materials.

  • Temperature programmed surface reaction profiles of 2-propanol on CeO2 and Ce-Na for m/z=58.

    Researchers have discovered that sodium modification of ceria leads to boost in ceria catalytic activity for the formation of hydrogen from an alcohol that can be derived from renewable resources, isopropanol.  Infiltrating sodium carbonates into ceria disrupts its structure resulting in an increase in the number of surface oxygen vacancies.

  • BiI3 forms molecular complexes in solvents such as tetrahydrofuran or dimethylformamide, enabling solution-based deposition of thin films. Annealing BiI3 thin films in different solvents can dramatically change the morphology.  By annealing in dimethylformamide dense, large-grained films were produce that resulted in higher photocurrent and power conversion efficiency in proof-of-concept solar cells.

    Using inexpensive, solution-based processing, bismuth—halide (BiI3) thin films were produced and found to have optical properties that are suitable for solar energy harvesting.  While lead (Pb)-based halide perovskites have enormous promise for photovoltaic solar cells because of their low cost and high solar-to-electric power conversion efficiency, they also have poor stability and there are environmental and health concerns related to the high Pb content.

  • Using 207Pb solid-state NMR, UV-Vis, and XRD, researchers showed that semi-crystalline phases and non-stoichiometric impurities permeate samples made in solution. Solid-phase synthesis avoids the former, but not the latter.

    How you make perovskite materials matters. Lead (Pb) halide (e.g. chloride) perovskites are promising semiconducting materials for photovoltaic solar cells, because of their low cost and their high efficiency for converting sunlight into electricity.  Semi-crystalline phases and compositional imperfections were found to permeate these materials when made by solution phase synthesis, even after heat treatment.

  • Researchers discovered semiconducting nanocrystals that not only function as stellar light-to-energy converters but also as stable light emitters.  Scientists synthesized a series of perovskite nanocrystals with different morphologies i.e., dots, rods, wires, plates, and sheets.  Perovskite materials such as CH3NH3PbX3 (X = I, Br) are known to display many intriguing electronic light and chemical properties.

  • Thanks to a groundbreaking new method, scientists have created the first 3D super-resolution maps of catalytic activity on an individual catalytic nanoparticle while reactions are occurring.  Catalysts are used in manufacturing everything from stain remover to rocket fuel; they make production more efficient by facilitating chemical reactions.  Each catalyst being studied is only about 200 nanometers in diameter (it would take a chain of approximately 500 nanocatalysts to equal the thickness of a single sheet of paper).

  • For the first time, researchers can keep multiple nanoparticles in focus while tracking their 3D orientations on a surface with unprecedented angular resolution.  The new technique can accurately track anisotropic gold particles that are tilted out of the horizontal plane and has the advantage of not relying on particle interactions with the surface to keep track of them.

  • A new technique makes it possible to track not only the location of moving particles to within 10 nanometers, but also their rotation and orientation.   This is like watching a football game from the ionosphere and knowing where the football is at anytime within 1.5 inches, how the ball is spinning, and what direction it is moving.

  • Researchers have developed a new way to track gold nanorods as they move around and re-orient themselves on metal surfaces, with significantly improved spatial resolution and speed compared with existing methods.

  • A new technique simultaneously illuminates the location, orientation and rotation in 3D of individual gold nanorods. Gold nanorods have been used as orientation probes in optical imaging because of their shape-induced anisotropic optical properties and now we can do this even better. Gold nanorods have the benefits of being biocompatible and having optical properties that depend on their orientation. This new development provides full 360° rotational information about these nanorods without sacrificing spatial and time resolution.