Student Research: VIPER Class of '16

Eric Lu: This summer, Eric's research in Prof. Igor Bargatin’s lab addressed the phenomenon that at the nanoscale, solids emit more energy to their surroundings than predicted by the Stefan-Boltzmann law, which applies for larger distance scales. Consequently, a device can switch from insulating itself to capturing "near field" radiation by moving just a few microns towards a heat source. Eric has been engineering a structure which permits adjustments to the device–heat-source separation while preventing arbitrary rotation. In the face of design challenges from working on tiny devices, work continues with the hope of developing a passive, highly efficient heat management system.

David Lim: This summer, David worked under Prof. Andrew M. Rappe in the Department of Chemistry.  David performed quantum mechanical calculations using DFT (density functional theory) methods to explore structural, magnetic, and electronic properties of multiferroic quadruple-perovskite material CaMn7012. The material undergoes metal-insulator transition accompanied by charge-ordering below 440 K, which can potentially be utilized to improve the energetic efficiencies of electronic devices. Furthermore, the material exhibits the largest improper ferroelectric polarization measured up to date below 90 K. Unlike conventional displacive ferroelectrics, the polarization is induced largely by noncollinear magnetism (type-II multiferroic), which would allow an efficient magnetoelectric coupling. One of the main goals of the research has been to propose microscopic mechanisms of the observed experimental noncollinear spin configuration and how the polarization arises as a result. The results so far have provided insights into the correlations among computational and physical parameters.

Alan Dai: In Prof. Eric Schelter’s Group, Alan is working on a synthetic inorganic chemistry project with the end goal of facilitating the separation and purification of rare earths, critical elements for many clean energy applications. He utilized organic synthesis techniques to create novel ligands designed to coordinate with various rare earth metals and stabilize higher than normal metal oxidation states. He then characterized Ce complexes containing these ligands for their electronic, thermodynamic, and structural properties. Currently, Alan is seeking to expand the scope of his complexes to include better stabilizing ligands and other rare earth elements.

Julia Fordham: This summer, Julia researched the photovoltaic capabilities of lead chalcogenide nanocrystals. While working in Prof. Christopher B. Murray lab, she synthesized the nanocrystals, created films on glass substrates, performed solid ligand exchange, and tested the electronic properties of the samples. She investigated different size nanocrystals and several ligands to determine the best combinations that can be used in photovoltaic devices.

Connor Lippincott: Connor spent his summer working on a synthetic organometallic chemistry project under the mentorship of Prof. Eric Schelter and Ph.D. candidate Justin Bogart. He focused on rare earth separations, an important field due to the unstable economy surrounding the rare earth metals. These metals are important in many energy applications, ranging from magnets in wind turbines to important catalysts in fuel cells. He worked on the synthesis of a tripodal nitroxide ligand (an organic structure with three coordinating N-O groups) for the purpose of coordinating it to the rare earth metals, affecting their solubility for separation purposes. The tripodal structure of the ligand, when coordinated to metals, presents an open coordination site with which to do novel chemistry. One of Connor’s primary goals is the synthesis of the first Ce(IV) compound with a coordinated alkyl group.

Albert Xiao: In the summer following his freshman year at Penn, Albert explored the issue of inexpensive efficient solar energy conversion in the context of quantum dot sensitized solar cells. As part of Prof. Christopher B. Murray’s Group, Albert investigated electron transfer rates in CdSe quantum dot sensitized solar cells. Albert fabricated solar cells with different sized quantum dots, using electrophoretic deposition, and studied the conversion efficiency of and the electron transfer rates in the cells before and after applying ligand exchange techniques. The data show that the ligand exchange increases charge transfer rate itself as well as the size-dependency of the charge transfer rates. In the future, these data should allow scientists and engineers to better optimize quantum dot size for maximum efficiency solar cells.

More recently, in the summer of 2014, Albert conducted research on nanostructured thermoelectric materials in the Molecular Foundry at the Lawrence Berkeley National Lab, as part of the Department of Energy's Science Undergraduate Laboratory Internship (S.U.L.I.) program. Albert worked as a member of Jeffrey Urban's group in the Materials Sciences Division at Berkeley lab. His research focused on the coupling of photo and thermo-electric phenomena in a few specific materials. The goal of the research is to control and improve the energy conversion efficiency of thermoelectric materials.