LaCNS Seminars Fall 2017

  

Jared Delcamp photo1) Tuesday, September 12, 12:30 pm, 215 Williams Hall (joint LaCNS – Organic Chemistry seminar)

Prof. Jared Delcamp (Dept. of Chemistry & Biochemistry, University of Mississippi), host Donghui Zhang

“Photon Management in NIR and SSM Dye-Sensitized Solar Cells”

Abstract:  Recently, dye-sensitized solar cells (DSCs) were shown to be the highest power conversion efficiency technology of any solar cell technology when using photons from the beginning of the solar spectrum until 700 nm. Two key directions are apparent in further elevating this technology: (1) broadening the spectral window used, and (2) efficiently subdividing the spectrum further for multijunction devices which can be used in combination with many solar cell technologies. Progress toward designing optimal panchromatic organic sensitizers to use NIR photons based on physical organic concepts such as proaromaticity and cross conjugation will be discussed. Additionally, the design and realization of a series sequential multijunction dye-sensitized solar cell (SSM-DSC) system for effective photon management will be discussed. Ongoing research to optimize this system based on transition metal redox shuttle design and high voltage organic dye design will be analyzed. The SSM-DSC system coupled with electrocatalysts as solar-to-fuel systems has been shown to power water splitting and CO2 reduction coupled with water oxidation from a single illuminated area without external bias.

 

 Ken Jordan photo2) Monday, November 13, 3:00 pm, 1008B Digital Media Center

Prof. Kenneth Jordan (Richard King Mellon Professor and Distinguished Professor of Computational Chemistry, Department of Chemistry, Univ. of Pittsburgh), host Revati Kumar

“Model Hamiltonians for Characterizing Excess Electrons Interacting with Fullerenes and Polyaromatic Hydrocarbons”

Abstract:  It is well known that certain metals and graphene support Rydberg-type series of excess electron states, where the binding of the electron is due to the interaction with its image potential.  Sufficiently, polarizable molecules and clusters possess very-extended non-valence anion stats that can be viewed as finite system analogs to image potential states.  In this talk, I discuss the development of one electron Hamiltonians for describing these excess electron species.  These are generated by coupling the excess electron to a many-body polarizable force field.

 

 Norman Wagner photo3) Monday, November 20, 3:00 pm, 1008B Digital Media Center

Prof. Norman Wagner (Robert L. Pigford Chaired Professor of Chemical & Biomolecular Engineering, University of Delaware, Newark), host Bhuvnesh Bharti

"The micromechanics of shear thickening fluids and their application as protective materials for medical professionals, first responders, football players, astronauts and spacecraft"

Abstract: Shear thickening colloidal and/or nanoparticle suspensions are commonly encountered in chemical and materials processing, and are also the basis of a technology platform for advanced, field responsive nanocomposites. In this presentation, I will review some of the experimental methods and key results concerning the micromechanics of colloidal suspension rheology. Micromechanics is the ability to predict the properties of complex systems from a colloidal or microscopic level description of the structure and forces. A fundamental understanding of colloidal suspension rheology and in particular, shear thickening, has been achieved through a combination of model system synthesis, rheological, rheo-optical and rheo-small angle neutron scattering (SANS) measurements, as well as simulation and theory (Colloidal Suspension Rheology, Mewis and Wagner, Cambridge Univ. Press, 2012).

Shear thickening fluids (STFs) are novel field-responsive materials that can be engineered to be useful nanocomposites for enhanced ballistic and impact protection, puncture resistant medical gloves, energy absorbing materials for mitigating impacts and concussions, as well as in systems for mitigating micrometeoroid and orbital debris threats in space applications.  The development of commercial applications of STFs will be discussed. The rheological investigations and micromechanical modeling serve as a framework for the rational design of STF-based materials to meet specific performance requirements not easily achieved with more conventional materials (Phys. Today, Oct. 2009, p. 27-32). I will illustrate some technological applications of STFs under commercial development, including use in astronaut protection and possible application in the manned mission to Mars.

 

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