Singh Seminar Series: Lucas Barreto and Neha Srikumar

Probing Electronic and Structural Properties of Materials via Photoemission-Based Techniques

Speaker: Lucas Barreto

Abstract: The properties of a material are directly related to its atomic and electronic structures. Combining structural and electronic characterizations is essential to understanding and tuning materials’ properties. In this talk, I will discuss examples of photoemission-based techniques used to investigate materials electronically and structurally. Mainly, I will focus on examples of topological insulators and graphene investigated by Angle-resolved Photoemission Spectroscopy (ARPES), X-ray Photoelectron Spectroscopy (XPS), and Photoelectron Diffraction (PhD). Also, the determination of transport properties by combining ARPES and conductivity measurements will be shown.

About the Speaker: Lucas Barreto is a Principal Scientist at the Singh Center for Nanotechnology, where he assists users with process development at the Quattrone Nanofabrication Facility. He has a background in surface science, focusing on the electronic and structural properties of quantum materials and thin films. He earned his Ph.D. in Physics from Aarhus University in Denmark (2014). Before joining the Singh Center for Nanotechnology, he worked as a Laboratory Manager at Drexel University, an assistant professor at the Federal University of ABC (Brazil), and a postdoctoral fellow at the University of Campinas Brazil).

Microsecond biochemical reactions via an integrated ESI-MS silicon and glass device

Speaker: Neha Srikumar

Abstract: Limitations in current microfluidic mixing technology typically allow for the sampling of protein hydrogen deuterium (H/D) exchanges only on millisecond to hour time scales. However, it has been well documented that select side chains and post-translational modifications on proteins undergo H/D exchanges on the microsecond scale. We have thus produced a microfluidic device capable of 1 𝜇s reagent mixing and 10 𝜇s to 1 ms post mix reaction times to study amino acids and peptides with fast exchanging sites. To account for back-exchange of deuterium for hydrogen in solution, we have also fabricated an in-built electrospray orifice to rapidly transition peptides to a gaseous, ionized state, thus preventing further reactions past specified exchange times and allowing for subsequent analysis via mass spectrometry.

About the Speaker: Neha Srikumar is a PhD candidate in the biochemistry, biophysics and chemical biology (BBCB) program here at the University of Pennsylvania, mentored by David Issadore and Benjamin Garcia (now at Washington University in St. Louis). Her past work prior to beginning her PhD has involved developing instrumentation and software for mass spectrometer based analysis of protein as well as tissue engineering work and microfluidics for organ-on-a-chip applications. For her PhD, she aimed to work at the intersection of microfluidics and proteomics to better sample preparation for structural proteomics assays. Separate from her thesis work, she has taken the time to teach and mentor students, training students in the Singh Center QNF cleanroom, as a teaching assistant, and helping out her lab mates doing interdisciplinary work. She hopes to expand her work in the future, using microfluidics to better improve other structural and dynamic proteomics techniques and has been awarded with a structural biophysics training grant fellowship and analytical chemistry fellowship for her work so far.