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Research

Expertise

  • Interfacial phenomena
  • Development of beam-sensitive imaging and correlative approaches to materials characterization 
  • Nanomaterials synthesis and template-mediated reaction pathways

Research Interests

  • Interfacial phenomena probed with techniques afforded by the advanced analytical electron microscopy
  • Geo-inspired separation of rare earth elements
  • Template-mediated nucleation of inorganic materials: biomineral crystal formation, evolution, and maturation. Using the principles of biomineralization to visualize the low-contrast nanostructures: metallization of DNA origami probed with advanced analytical electron microscopy techniques in situ.

Current Research Projects:

1) Geo-inspired separation of rare earth elements: 

(in collaboration with Pacific Northwest National Laboratory and University of Alabama).

Rare earth elements occupy a special place on the periodic table - due to their unique properties, they’ve become key ingredients in multiple vital applications, including data storage and clean energy technologies. The ever-increasing demand and supply chain disruptions have prompted science and industries to seek alternative sources, find new ways of extracting and refining rare earths from all sources, and develop novel, more efficient separation methods. This research project provides a unique understanding of the spatio-chemical environment, binding, clustering, and kinetics of rare earths in ionic adsorption clays and uses this knowledge to develop novel geologically-inspired approaches to separation of rare earth elements.  

2) Mapping of electrostatic potentials and magnetic fields in liquid phase using electron holography: 

(in collaboration with Pacific Northwest National Laboratory and with Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich).

It is important to know how individual nanoparticles interact with each in liquid phase. Off-axis electron holography, a transmission electron microscopy technique, was used to measure the magnetic induction of bacterial magnetite nanocrystals in a liquid environment. The liquid layer presents plenty of challenges. We are working to expand this technique to mapping of electrostatic potentials in liquid phase and for studying a variety of interfacial phenomena in liquids, with nanometer spatial resolution.

3) Application of biomineralization to materials synthesis and characterization:

  • 1) Biomineralization, biomineral crystal formation, evolution, and maturation
  • 2) Interfacial phenomena
  • 3) Metallization of macromolecular templates 

Nature is replete with examples of biominerals formed by the living organisms with complex architectures and advanced functionalities. Microbes and plants can also synthesize a wide variety of new nanomaterials  and incorporate elements not commonly found in living organisms. My ongoing work involves understanding the role of biomineralization proteins in nucleation, growth, evolution and functional properties of resulting biominerals, within multidisciplinary research framework. I am involved in development of advanced analytical techniques for characterization of biomineral formation and growth. These include  electron microscopy in liquid phase, correlative technique for characterization of organic-inorganic interfaces using combination of high-resolution electron microscopy and atom probe tomography (in collaboration with the group of Prof. Alberto Perez-Huerta at University of Alabama, Tuscaloosa). Some examples include:

  •  Liquid phase EM imaging of colloidal, soft, and biological materials:

The findings obtaining with using magnetotactic bacteria as model system lend themselves naturally to the investigation of many real-world samples. Our current in situ liquid phase electron microscopy effort is focused on imaging of a variety of  biological, soft, and colloidal materials. The systems of interest span from characterization of colloidal suspensions and gel-based nanocomposites, to probing the interactions of living cells with engineered nanomaterials and monitoring biomass degradation.

  • Colloidal systems and gel-based nanocomposites: 

Alumina nanoparticles are often used as model colloidal system. In aqueous solutions, these nanoparticles aggregate to form hydrated clusters with varying aspect ratio that are significantly larger than the primary particle. Such clusters with the surrounding hydration cloud increase the effective solids content of the suspensions and effectively decrease the available free liquid carrier, resulting in exceptionally high suspension viscosity. 

Structural characterization of aqueous polymeric gels is usually addressed by using Small Angle Scattering techniques, as the very nature of these sample limits direct imaging of the polymeric assembly to bright field cryo-TEM of thin sections of either freeze-dried or vitrified samples. We use fluid cell S/TEM to image nanoparticles as small as ~6 nm in thick polymeric gel-based nanocomposites. While every gel is different, our HAADF-STEM approach to nanoparticle imaging is robust.

  • DNA origami:  

DNA origami triangle
Top, Left: DNA origami triangles imaged with electron microscopy; Right: Fine structural details are revealed by high-resolution imaging.
Bottom, Left: Class-average image from a subset of images above; Right: histogram identifying nine helices along the side of the triangle.

 

For many practical uses, DNA origami nanostructures need to be metallized, yet the very nature of DNA-templated nanoparticle nucleation remains elusive.

Our current work with DNA origami is focused on elucidating of mechanism of metallization. But first, we must visualize the DNA origami nanostructures themselves. We use advanced electron microscopy to probe the structure and spatio-chemical properties of DNA origami.