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Time: 1pm
Sina Hamian
Postdoctoral Scholar
UC Irvine (Wickramasinghe Group)
Title: Towards stimulated tip-enhanced Raman spectroscopy using heterodyne scheme
Abstract: Despite the success of spontaneous Raman spectroscopy with strong field enhancement such as tip/surface-enhanced Raman spectroscopy (TERS/SERS), stimulated Raman spectroscopy (SRS) is demanded for practical applications requiring fast acquisition rates. In order to achieve high signal-to-noise ratio in SRS, we developed a heterodyne scheme using a home-built shot-noise-limited photodetector, which is designed to resonate at the modulation frequency of a reference beam. The SRS setup is comprised of a HeNe pump and a tunable external cavity diode (ECDL) probe laser (680±10 nm). The reference beam is extracted and shifted by 80 MHz to completely avoid the 1/f noise. We will discuss some data from experiments performed on 1,2-bis-(4-pyridyl) ethylene (BPE) molecules attached to 100 nm gold nano dimers encapsulated in porous silica shells, then we discuss possible ways to improve the set.
Bio: Sina Hamian is a postdoctoral scholar at the Center for Chemistry at the Space-Time Limit (CaSTL) at the University of California, Irvine (UCI), working under supervision of Professor Kumar Wickramasinghe. He earned his Ph.D. from University of Utah in 2017, working on nanoscale energy transport on an AFM platform under Professor Keunhan Park’s supervisory. He accomplished his Master and undergraduate studies at Sharif University of Technology and K.N.Toosi University of Technology, respectively during which he worked on heat transfer in nanofuilds. His work is published in multiple peer-reviewed journal papers. He is now focused on stimulated Raman spectroscopy (SRS).
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Time: 1:30pm
Hui Wang, Postdoctoral Scholar
UC Irvine, Wu group
Title: Density functional theory study of single molecule or single atom catalysts on different substrates
Abstract: Density functional theory calculations are employed to study the C-H bond broken in Azulene adsorbed on metal surfaces. Combined experimental and DFT study, we found photons can couple to the C-H bond activation of specific hydrocarbons through a resonant photo-assisted tunneling process. As another project, we also identify how the local molecular environment on graphene can be used to stabilize a single platinum adatom and provide favorable activity for a benchmark reaction, CO oxidation. Graphene is modified via defects and dopants specifically single vacancy and pyridinic N-doping so that we can see how the electronic structure and chemical activity of Pt atoms are affected.
Bio: Hui Wang obtained his PhD in materials physics chemistry from Chinese Academy of Sciences, and now is a postdoctoral researcher of Prof Wu group. His current research interests involve the electronic structure, vibration spectroscopy and manipulation of single molecule or single-atom catalysts on different substrates.
