Materials science, chemistry, medicine

— I am passionate about using scientific knowledge and tools to address important problems.


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Charge-transfer ferroelectrics

Ferroelectricity is considered the electronic analogue of ferromagnets: an electronic polarization can be manipulated with an external electric field.  This property has been studied in organic charge-transfer complexes for more than four decades, however, only manifests at < 81 K.  In collaboration with Sir Fraser Stoddart, we developed a new supramolecular design for organic charge-transfer complexes that are capable of spontaneously forming hydrogen bonded networks.  These structures demonstrate ferroelectricity at room temperature and above .   (Tayi et al. Nature  2012) 

(w/ Alex Shveyd, Andrew Sue, and Dennis Cao) 


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Optical materials

As we studied the versatility of our supramolecular design, we stumbled upon a new architecture for charge-transfer complexes.  Historically, CT complexes form two architectures in a one-to-one ratio: a mixed stack lattice (alternating donors and acceptors) or segregated stacks (a stack of donors neighboring a stack of acceptors).  By incorporating supramolecular recognition sites,  we developed a class of CT complexes that assembles into a two-dimensional architecture  with bidirectional charge-transfer ferroelectricity in two dimensions.  (Tayi et al. submitted  ).

 (w/ Alex Shveyd, Andrew Sue, Dennis Cao, and Ashwin Narayanan)


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Nanofiber, nanoparticle fabrication

Another type of hydrogen-bonded network is a peptide amphiphile (PA).  PAs are molecules with three specific segments: a biepitope, β-sheet-forming segment, and a hydrophobic tail.  When solubilized in water, these molecules self-assemble into filamentous, one-dimensional nanostructures that are bioactive.  Using techniques like electrospinning and electrospray, we can create large-area thin films of peptide amphiphile microfibers with control over the bioactivity and mesostructure.  (Tayi et al. submitted )

(w/ Tommy Pashuck) 


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Adaptive composites

My interest in composites came from examining the shortcomings of conventional composites, like rebar-reinforced concrete and fiber-reinforced composites.  For example, once cast, these materials are difficult to change; once broken, they are expensive to repair.  We have developed a new concept for composite materials: systems that are adapt to their environment and are reconfigurable in shape and strength.  Such properties were realized by exploiting dynamic non-covalent interactions.

 (w/ Ju-Hee So, George Whitesides)

 


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Non-equilibrium chemistry

The earth is getting warmer - grappling with the extensive production of carbon dioxide is an important scientific problem.  Conventional approaches to dealing with carbon dioxide involve carbon sequestration: compress the gas and bury it in the ground.  To date, this approach is not cost competitive.  Instead of taking a physical approach, we intend to take a chemical one.  Our approach converts carbon dioxide into a more reactive form that is highly reactive; by mixing this form of carbon dioxide with another compound, we can hope to produce a new chemical that has economic value.  Therefore, capturing carbon dioxide and selling the chemical product could make such a "carbon conversion" process more cost effective.

(w/ Mostafa Baghbanzadeh, George Whitesides)