Student Thesis Prize Awards
2018-2019 CALL FOR NOMINATION IS NOW CLOSED
Notification of Decision: Between mid-October and mid-November.
The Kavli ENSI Thesis Prize Committee is pleased to announce the recipients of the best Thesis Prize.
2018-2019 Dr. Christian Dierks
Advisor: Professor Omar Yaghi, Department of Chemistry
Covalent organic frameworks (COFs) are porous crystalline extended structures comprised of molecular building blocks and stitched together through directional covalent bonds. This allows for the design and construction of 2D and 3D framework structures with atomic precision. In his dissertation, Christian Diercks has devised protocols for pre- and post synthetic functionalization of such frameworks to tailor them for electronic applications as electrocatalysts, heterojunctions, and solid state conductors. In particular, he has funcitonalized layered 2D COFs with cobalt porphyrin active sites for the electrocatalytic reduction of carbon dioxide into value-added carbon products. To optimize the performance of these catalysts he investigated structural parameters (pore size and number of active sites), electronic parameters (framework conductivity, overpotential), as well as the influence of the morphology of the catalyst. The optimized framework electrocatalysts display high turnover frequencies and high current density at low overpotential, high faradaic efficiency for product formation over competitive off-pathway reduction, and long-term stability and cyclability.
2017 - 2018 Dr. Dohyung Kim
Advisor: Professor Peidong Yang, Department of Chemistry, Materials science and Engineering
Electrochemical or photochemical conversion of carbon dioxide to value-added products has the potential to fundamentally change our traditional ways of harvesting energy and manufacturing chemical products. Kim's thesis focuses on the use of nanoparticles as catalusts for CO2 conversion and their structural factors affecting catalytic properties are discussed. The shift in the electrocatalytic behavior of gold-copper nanoparticles by the change of compostion and atomic orderedness has been studied to illustrate the catalytic importance of structural precision down to the atomic level. The ways of interfacing nanoparticle electrocatalysts to light absorbing platforms were explored for CO2 valorization using renewable energy sources. NAnoparticles can alos be integrated with other materials such as the metal-organic frameworks or molecular complexes for the creation of a CO2 catalytic system. Mor eimportantly, the dynamic restructuring of nanoparticles was utilized to induce favorable electrocatalytic properties for CO2 to conversion multicarbon products. Overall, the works covered in the thesis not only illustrate the structural complexity of nanoscale catalytic systems but emphasize the need og having a comprehensive understanding of all facots for the development of CO2 catalysis.
2016 - 2017 Dr. Felipe H. da Jornada
Advisor: Professor Steven G. Louie, Department of Physics
Since the experimental isolation of graphene in 2004, there has been tremendous interest in studying quasi-2D systems. These materials are atomically thin, and display many fascinating properties not found in regular bulk materials. Their high carrier mobility, high optical absorption, and tunable electronic properties make these quasi-2D materials ideal building blocks for next-generation chips and solar-cell devices. My dissertation seeks to explain, from a fundamental physics perspective, why these quasi-2D materials behave like this. In order to give unbiased predictions of how these systems behave, we use theoretical frameworks that do not rely on experimental fitting parameters, and use supercomputers to perform calculations. We show that many of these interesting electronic and optical properties stem from the weak electronic screening in these materials, which a result of their reduced dimensionality and which often cannot be accounted for with simpler models. We also introduce new computational approaches to make these calculations much faster and more realistic, and we show, for instance, that even the substrate that holds these materials in experiments can dramatically influence the measured properties.
2016 - 2017 Dr. Yingbo Zhao
Advisor: Professor Omar Yaghi, Department of Chemistry
Zhao’s dissertation focuses on the development of reticular chemistry, where molecular building blocks are linked into extended frameworks using strong bonds, in the context of nanomaterial design. Specifically, the dissertation advances the frontier of reticular chemistry is three aspects: (a) bringing metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), the products of reticular chemistry, into nanometer size regime and integrating them into mesoscopic constructs; (b) developing reticular chemistry beyond crystalline materials and synthesizing glassy form of MOFs; (c) Designing woven frameworks where interlacing molecular threads form crystalline three-dimensional frameworks. These developments not only provide a series of porous building blocks for nanomaterial design, but also lead to energy related applications such as electrochemical carbon dioxide reduction.
2015 - 2016 Dr. Kelsey Sakimoto
Advisor: Professor Peidong Yang, Department of Chemistry
Converting sunlight to chemicals in an efficient, reliable, and inexpensive manner is a grand challenge of the century. My thesis sheds some light on a potential approach, combining high efficiency semiconductor based light harvesters, and higher performance biological catalysis for CO2 fixation. This work covers the design of a bacterium that synthesizes and uses inorganic nanoparticles for photosynthesis, enabling self-replicating solar-to-chemical production. I also begin the exploration of the mechanism behind the new form of charge transfer between semiconductor and bacterium, driving the future investigations of how these new forms of life tick. These insights guide our work as we embark on version 2.0
2014 - 2015 Dr. Noah Bronstein
Advisor: Professor Paul Alivisatos, Department of Chemistry
Bronstein's dissertation highlights a path to achieve high photovoltaic conversion efficiency in luminescent solar concentrators, devices which absorb sunlight with a luminescent dye and then re-emit it into a waveguide where it is ultimately collected by a photovoltaic cell. Luminescent concentrators have been studied for more than three decades as potential low-cost but not high efficiency photovoltaics. Astute application of the black body radiation law indicates that photonic design is necessary to achieve high efficiency: a reflective filter must be used to trap luminescence at all angles while allowing higher energy photons to pass through. In addition, recent advances in the synthesis of colloidal nanomaterials have created the possibility for lumophores with broad adsoption spectra, narrow-bandwidth emission, high luminescence quantum yield, tunable Stokes shifts and tunable Stokes ratios. Together , these factors allow luminescent solar concentrators to achieve the optical characteristics necessary for high efficiency. The first generation of these devices was fabricated and tested. The devices achieved the highest luminescent concentration factors yet recorded in literature while maintaining high photon collection efficiency.
2014 - 2015 Dr. Daniel Goldman
Advisor: Professor Carlos Bustamante, Department of Chemistry
During translation, the ribosome reads the genetic code of the messenger RNA, adding one amino acid at a time to the nascent polypeptide. In order to carry out it's biological function, the polypeptide must fold to the native state, and the folding process can begin before translation is complete. Goldman's thesis work has focused on ribosome-nascent chain interactions that affect both the folding process and the activity of the ribosome. Using a novel optical tweezers assay, we observed folding transitions of single ribosome-bound nascent polypeptides. We found that the ribosome can modulate the kinetics of folding, guiding the protein to the native state.
2013 - 2014 Dr. Long Ju
Advisor: Professor Feng Wang, Department of Physics
Ju's thesis describes the use of optical spectroscopy in studying the physical properties of two dimensional nano materials like graphene and hexogonal boron nitride. Compared to bulk materials, atomically thin two dimensional materials are unique in that both electronic band structure and chemical potential can be tuned in situ by electric field. Therefore optical studies in such systems greatly benefit from modern micro-facbrication technique and electric control of the material properties. This thesis demonstrated a few examples of new possibilities in material science by combining opticap spectroscopy with other experimental techniques, such as electric transport and STM measurements. These experiments are driven by important problems in 2D materials but are generally beyond the reach of each individual technique.
2013 - 2014 Dr. Ziliang Ye
Advisor: Professor Xiang Zhang, Department of Mechanical Engineering
Ye's dissertation is devoted to study the range of fascinating optical 'dark' effects that emerge in the nanoscale and usually cannot be probed by the linear optical spectroscopy or imaging in the far field zone. The studied systems are consisted of two parts: artificlal plasmonic antennas and natural two dimensional transiiton metal dichalcogenides (TMCDs). With plasmonic antennas, I realize the classical analog of a few intriguing quantum mechanical effects, including electromagnetic induced transparency, anti-Hermitian coupling induced super-radiance, and spin Hall effect for photon. Because most of these effects only occur in the subdiffractional scale, I develop a nearfield scanning tunneling microscopy with a super-resolution to observe these 'dark' effects. In the study of 2D TMDC, I discover several excitonic states are originated from a very large exciton binding energy in the unique 2D semiconducting material. Using another nonlinear optical probe, second harmonic generation spectroscopy, I further identify an edge response at the domain boundary of a continuous TMDC crystal synthesized by the chemical vapor deposition technique. Finally, a TMDC exciton based light emitting device is demonstrated as a practical application.