Physical Chemistry Seminar: Professor Wei Xiong, University of California, San Diego
About the Seminar
Shedding Infrared Light on Molecules: From Molecular Polaritons to Hyperspectral Imaging
Mid-Infrared (MIR) light can interact with molecules by selectively exciting molecular vibrational modes. On one hand, in combination with photonic structures, MIR can target specific vibrational states of molecular to influence chemical reactions; on the other hand, IR spectroscopy has long been used as a molecular sensing tool. In this talk, I will discuss recent advancement in my lab, focusing on these two key topics.
In the first topic, I will explain how photonic environments can modify molecular dynamics through strong light-matter coupling. This strong coupling leads to the molecular vibrational polaritons – a hybrid quasiparticle between light and matter. Using two-dimensional infrared (2D IR) spectroscopy, we have demonstrated that strong coupling to photonic environments can efficiently promote energy transfer within or between molecules, subsequently slowing down competing reaction pathways. This research provide insights into designing photonic structures to modify chemical landscapes and influence reaction pathways.
In the second topic, I will present the latest development in fast-scanning vibrational sum frequency generation (VSFG) microscopy, tailored to differentiate collagen tissues in healthy and tumorous conditions. We revealed distinct spectral signatures between healthy and tumorous tissues, which arise from the coherent nature of VSFG signals – akin of a microscopic Young’s double slit experiment. VSFG’s unique power to resolve varying alignments of collagen fibrils empowers it as a distinctive label-free technique for tumor identification in the future.
About the Speaker
Professor Wei Xiong is a Full Professor and Kent Wilson Faculty Scholar in the Department of Chemistry and Biochemistry at the University of California, San Diego. Wei received his B.S. degree from Peking University, China, in 2006. He then joined Prof. Martin Zanni’s group at the University of Wisconsin, Madison, and completed his Ph.D. degree in 2011. At Madison, Wei focused on developing novel 2D vibrational spectroscopy (transient 2D IR and heterodyne 2D SFG spectroscopy) to study molecules on solid-state material surfaces. Wei then moved to the University of Colorado, Boulder, in 2011, where he worked with Prof. Margaret Murnane and Henry Kapteyn to develop the table-top XUV source for ultrafast measurements and time-resolved photoelectron spectroscopy for nanoparticles. He joined the faculty at the University of California San Diego in 2014. At UCSD, Wei’s research focuses on using and developing ultrafast nonlinear spectroscopic and imaging tools to reveal molecular structures and dynamics of materials, including ultrafast dynamics of polaritonic systems, guest molecule adsorptions in self-assembled materials, femtosecond charge transfer dynamics on organic material interfaces. Wei is a fellow of the American Association of the Advancement of Science, a recipient of Sloan Research Fellow, Coblentz Award, National Brown Investigator Award, and Journal of Physical Chemistry C Lectureship, and a finalist of the Blavatnik National Awards for Young Scientists.