Seminars arranged by CaSTL

Ultrafast extreme ultraviolet spectroscopy reveals short-lived states in transition metal complexes and organohalide perovskite semiconductors

Abstract: X-ray absorption near edge spectroscopy (XANES or NEXAFS) is a powerful technique for electronic structure determination.  However, widespread use of XANES is limited by the need for synchrotron light sources with tunable x-ray energy.

Probing Molecular-Scale Catalytic Interaction between Oxygen and Cobalt Phthalocyanine Using Tip-Enhanced Raman Spectroscopy

Ultrahigh vacuum tip-enhanced Raman spectroscopy (UHV-TERS) is used to investigate adsorption of molecular oxygen (O2) with cobalt (II) phthalocyanine (CoPc) supported on Ag(111) single crystal surfaces, which is the initial step for the oxygen reduction reaction (ORR) using metal Pc catalysts. Two adsorption configurations are primarily observed, assigned as O2/CoPc/Ag(111) and O/CoPc/Ag(111) based on scanning tunneling microscopy (STM) imaging, TERS, isotopologue substitution, and density functional theory (DFT) calculations.

Investigations of excited state structural dynamics using femtosecond time-resolved absorption and stimulated Raman scattering spectroscopic techniques

Investigation of molecular dynamics with sufficient time and spectral resolution is very crucial for understanding the mechanistic aspects of any photophysical and photochemical process. In this seminar, I will briefly discuss about the femtosecond transient absorption technique and then introduce with the ultrafast Raman loss spectroscopic (URLS) technique that is analogous to femtosecond stimulated Raman scattering (FSRS) spectroscopy. These spectroscopic techniques (URLS/FSRS) offer excellent frequency and time resolution to decipher molecular dynamics at ultrafast timescales.

Single-molecule Catalysis: from solar energy conversion to living polymerization

This presentation will describe our efforts in developing single-molecule approaches to study catalysis, focusing on two stories. The first story will be about our work in using redox-selective super-resolution reaction imaging and sub-particle photocurrent measurements to determine the relation between charge-carrier surface activity and water oxidation efficiency on a semiconductor photoanode during photoelectrochemical water oxidation.

Ultrafast x-ray probes

Intense laser-plasma interactions are a robust source of light which is both on the fastest timescales imaginable and capable of imaging down to single atoms. Experiments showcasing the use of short-pulse lasers to create bright soft x-rays with circular helicity, white-light spectrum radiation suitable for near edge x-ray absorption fine structure (NEXAFS) radiography, and next generation attosecond sources will be presented.
 

New strategies for inorganic molecular design with machine learning and automated simulation

Chemical space is vast, with best estimates suggesting we have as yet characterized less than 1 part in 10^50 of all possible compounds. The need for efficient discovery of new materials and catalysts mandates that we identify smart ways to map out and explore chemical space. Although virtual high throughput screening with first-principles simulation has emerged as a powerful tool for materials discovery, even more efficient methods such as machine learning models become essential to tackle this enormous combinatorial challenge.

A Study on Chemical Contribution to the Enhancement Mechanism of Surface-Enhanced Raman Spectroscopy

With advances in nanofabrication combined and increased understanding of plasmonic properties of nanomaterials, SERS has been transformed into a powerful analytic technique for determining structural properties about a system. Although SERS was discovered several decades ago, a complete picture of the enhancement mechanism is very active area of research. With the discovery of single molecule SERS which gives rise to the possibility of 10^10 enhancement factors or more.

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