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Department Seminar: Graduate Research Initiative Program

Graduate Student Practice Talks for upcoming AIChE Annual Meeting
Thursday, October 26, 2017, 11:30 am
130 Koffolt Lab, CBEC
151 W Woodruff Ave
Columbus, OH 43210

Abhilasha Dehankar

Dynamic Control of Gold Nanoparticle-Conjugated DNA Origami Templates

Abhilasha Dehankar1, Joshua A. Johnson2, Carlos E. Castro2,3 Jessica O. Winter1,2,4

1Department of Chemical and Biomolecular Engineering, 2Interdisciplinary Biophysics Graduate Program, 3Department of Mechanical and Aerospace Engineering, 4Department of Biomedical Engineering, The Ohio State University, Columbus OH, 43210, USA

Fabrication of nano-sized electronic and photonic devices through lithographic techniques is becoming increasingly challenging and energy intensive. Additionally, these methods are primarily confined to 2D surfaces and often do not include dynamic components that can reconfigure in response to external stimuli. Bio-inspired assembly through molecular recognition, such as base pairing interactions between deoxyribonucleic acid (DNA) strands, can be exploited to create dynamic, as well as robust, 3-D platforms for the organization of nanoparticles (NPs). DNA origami platforms can be used to organize NPs in precise orientations and spacings in 2D and 3D, yielding tailored plasmonic interactions. In some cases, these templates can be dynamic, adopting new conformations in response to external stimulus and altering these interactions. However, using the gold standard strand invasion approach that relies on de/hybridization kinetics, the inherent actuation time scale for these structures ranges from minutes to hours. Heating can increase response kinetics; however, use of external energy input is limited by bulk heat transfer. Therefore, localized energy input is desired as a means to potentially provide faster dynamics. Properties of NPs, such as surface plasmon resonance, can be explored as a localized energy source. Current research is focused on a fundamental understanding of the impact of NPs on dynamics and conformations of DNA origami structures actuated using the energy responsive NPs.


Our present study employs DNA origami hinges with single stranded DNA overhangs on the hinge arms as a model system. The sequence of these overhangs is complementary to that of single stranded (ss)-DNA on modified gold NP (AuNP) surfaces. A comparative study was conducted between the conformations of a closed hinge with varying locations of ss-DNA on the hinge arm in the presence and absence of AuNPs and analyzed by Transmission Electron microscopy (TEM) to determine the free energy landscape. Additionally, actuation kinetics of two different actuation pathways, strand displacement and bulk heating, were compared.   Kinetics was studied in the bulk phase using fluorescence spectroscopy to analyze a Forster Resonance Energy Transfer (FRET) reporter system that indicated both NP binding and hinge closure. These results provided a comprehensive understanding of mechanical energy stored in NP-DNA origami composites. Preliminary experiments were performed for a third actuation scheme, localized actuation of composites using laser excitation to plasmonically heat AuNPs. Future experiments are investigating kinetics of structures undergoing local, plasmonic heating utilizing an in-house two source fluorometer instrument with separate excitation and modulation sources. This research could lead to higher order NP-DNA origami composites, that can store and release energy in response to light, with potential applications in nanophotonics.

Frank Kong

Thermodynamic Simulations and Techno-Economic Analysis on the Utilization of CO2 and a Novel Modularization Strategy for Chemical Looping Based Gtl Processes

Authors: Mandar Kate, Peter Sandvik, Charlie Fryer, Frank Kong, Abbey Empfiled, Liang-Shih Fan


The utilization of carbon dioxide (CO2) as a feedstock in a chemical looping process that converts methane to syngas and a variety of downstream products has the ability to be impactful in the field of carbon capture, utilization, and sequestration (CCUS). The Ohio State University Chemical Looping methane to syngas (MTS) process’ novelty comes from the coupling of carbon capture and utilization strategy, which captures and utilizes CO2 to create a synergy atypical to many processes that are designed to deal with the challenges of carbon constraints. CO2utilization allows for increased flexibility of H2:CO molar ratios that may be required for variations in the downstream processing while producing a comparable quantity of syngas with reduced natural gas input. In this study, thermodynamic models for chemical looping reactor systems are examined using ASPEN Plus. The chemical looping reducer reactor considered employs steam, natural gas and CO2 as feedstock along with metal oxide oxygen carriers. This presentation will initially present system optimization based on thermodynamic Gibbs free energy minimization for the desired syngas composition required for downstream gas to liquid (GTL) processes. With CO2co-injection in the MTS process, the thermodynamic optimization indicates a natural gas savings of more than 20% over that of the baseline partial oxidation processes for GTL applications. Experimental verification using Thermo-gravimetric analyzer and bench-scale moving bed reactor that compared well with the thermodynamic model simulations will also be presented. A comprehensive techno-economic analysis on an energy, balanced (water balance, steam balance, heat and electricity balance) thermodynamic performance model of the MTS process with and without CO2 utilization & modularization strategy was developed.

Tags: Seminar