Past Seminars & Events

Professor Xavier Roy
Department of Chemistry
Columbia University
Abstract

Next level quantum materials

Over the past 15 years, two-dimensional (2D) materials have garnered significant attention due to their exceptional physical, mechanical, and chemical properties, as well as our ability to seamlessly incorporate them into various devices. In this seminar, I will present our recent advancements in the development of the next generation of 2D materials. To begin, I will discuss our efforts to assemble atomically defined clusters of atoms, which we refer to as “superatoms,” into hierarchical 2D structures. These superatoms mimic the role of atoms in conventional 2D “atomic” solids, resulting in remarkable material properties. I will highlight recent synthetic breakthroughs and explore the distinctive transport behaviors that emerge due to the atomic precision of the 2D lattice and the specific interactions between these building blocks. In the second part of the presentation, I will introduce novel atomic 2D materials that have been developed in our laboratories in recent years. Specifically, I will delve into how magnetic order strongly influences optical transitions in the 2D magnetic semiconductor CrSBr. Additionally, I will provide insights into the synthesis and characterization of CeSiI, the first f-electron-based heavy fermion metal, which also falls under the category of 2D van der Waals (vdW) materials. Conceptually, our synthetic design takes a traditional 3D intermetallic heavy fermion compound and slices it into atomically thin vdW sheets by incorporating iodine into the structure. The resulting material is cleavable and effectively 2D electronically, even in bulk crystals.

Xavier Roy

Professor Xavier Roy received a B.Eng. (2002) and a Master of Applied Science (2005) in Chemical Engineering from Ecole Polytechnique of Montreal, performing research under the guidance of Prof. Basil Favis. He earned his Ph.D. in Chemistry with Prof. Mark MacLachlan at the University of British Columbia in 2011, working as an NSERC Alexander Graham Bell Scholar. He went on to do postdoctoral research as a Canada NSERC Postdoctoral Fellow with Prof. Colin Nuckolls at Columbia University from 2011 to 2013. He joined the Columbia University Faculty in 2013 as an Assistant Professor of Chemistry, and was promoted in 2018 to the rank of Associate Professor and received tenure in 2020.

Hosted by Professor Gwendolyn Bailey

Laura McCaslin
Sandia National Laboratories
Abstract

A Bottom-Up Approach to Rational Design of Molecular Materials

Organic donor-acceptor (D-A) co-crystals are a promising class of molecular materials for next-generation optoelectronic devices. High-throughput screening and machine learning methods employ structure-function relationships to predict combinations of donor and acceptor molecules with desired properties. However, optical properties of materials are particularly difficult to predict due to the computational expense of performing electronically excited state calculations. Furthermore, calculations of a molecular material’s radiative and non-radiative lifetimes cannot be straightforwardly computed from D-A cluster models, as orbital energy differences, couplings, and oscillator strengths differ substantially between the molecular dimer and a crystalline material. In this talk I present a novel approach to predicting radiative and non-radiative lifetimes in D-A co-crystals based on orbital structure-function relationships. The basis for this approach is the striking similarity of orbital character between the D-A dimer and D-A co- crystal, especially in the ground and first excited states. Furthermore, these orbital characteristics are related to the degree of charge transfer in different electronic states, which are key quantities for predicting radiative and non-radiative lifetimes. Here I present a novel metric for predicting the degree of charge transfer in the S1 (HOMO → LUMO) electronic state using ground state orbital analysis alone, enabling low cost predictions of radiative and non-radiative lifetimes in D-A co-crystals for future high-throughput screening approaches. We use this metric to correlate S1 charge transfer with internal conversion and intersystem crossing timescales in D-A co-crystals, measured with UV pump, UV-Vis probe ultrafast transient absorption spectroscopy (TAS). Non-adiabatic mixed quantum-classical dynamics (NA-MQC) calculations of D-A dimer models enable characterization of the ultrafast TAS signatures to unravel the complex physics underlying long exciton lifetimes in D-A co-crystals.

Laura McCaslin

Dr. Laura McCaslin is a staff scientist in theoretical chemical physics at Sandia National Laboratories in Livermore, CA. Her research program specializes in studying the electronic structure, photochemistry, and dynamics of molecular systems. During her undergraduate studies at the University of California Berkeley, McCaslin performed research under the advisement of Prof. Martin Head- Gordon on the electronic structure of microsolvated ions. After completing a BS in Chemical Biology in Spring 2012, she began her PhD studies at the University of Texas Austin in Fall 2012. McCaslin performed research on the electronic and vibrational structure of small molecules under the advisement of Prof. John Stanton, completing her PhD in Fall 2016. She began a postdoc position at the Hebrew University of Jerusalem in January 2017 under the advisement of Prof. R. Benny Gerber, where she employed molecular dynamics calculations to study reactions at atmospheric aerosol interfaces. She began her independent research program at Sandia National Labs in Spring 2020, where her research in electronic structure and molecular dynamics has spanned many fields, including atmospheric chemistry, materials discovery and characterization, quantum control, and photodynamics.

Hosted by Professor Ilja Siepmann

Professor Alexandra Velian
Department of Chemistry
University of Washington
Abstract

Molecular Catalysts Go Nano: Installing Active Sites on Clusters and Nanosheets

A central research goal in the Velian group is to create next-generation single atom catalysts poised to harness the cooperativity between the active site and chemically non-innocent supports. To emulate defect sites in inorganic heterogeneous catalysts in a controlled fashion, we embed well-defined active sites on the surface of clusters and 2D nanosheets. 

The first part of this seminar will introduce a class of atomically precise nanoclusters distinguished by the presence of discrete active sites that engage dynamically with the non-innocent metal chalcogenide cluster support, and with substrates. Together with their scalable syntheses, solution processability and their ease of characterization using molecular methods, this family of nanoclusters provide atom level insights into the metal/support interface, and how the ensuing cooperativity can be harnessed to dramatically alter catalytic activity. 

The second part of the talk will introduce an orthogonal approach to catalyst engineering, in which the basic principles of organometallic- phosphine chemistry are harnessed to anchor single site active sites on the surface of two-dimensional black phosphorus nanosheets. Molecular synthetic and characterization strategies are leveraged to probe the bonding and functionality of the modified nanosheets.

Alexandra Velian

Professor Velian began her independent career at the University of Washington in 2017. A central goal in the group is to create next-generation catalysts geared to turn green- house gases like methane and carbon dioxide into value added products. Her approach is to use molecular strategies to synthesize single-site catalysts that harness metal-support interactions, and shine light on processes that govern the substrate/active sites/ support interactions. 

Professor Velian’s scientific and academic contributions have been recognized with several awards and distinctions, including the Inorganic Chemistry Lectureship Award (2023), the Camille Dreyfus Teacher Scholar Award (2023), the Marion Milligan Mason AAAS Award (2023), the C&EN Talented 12 distinction (2022), a Cottrell Scholar Fellowship (2020), the NSF Career Award (2019), the Young Investigator Award – ACS Division of Inorganic Chemistry (2016) and the Alan Davison Prize for the Best Thesis in Inorganic Chemistry at MIT (2015). Professor Velian completed her undergraduate studies in chemistry at Caltech, where she conducted research primarily with Professor Theodor Agapie. As the first member of his group, she developed the synthesis of low-valent mono- and bimetallic complexes supported by a terphenyl diphosphine framework. 

She received her Ph.D. under the direction of Professor Christopher C. Cummins at MIT, where she developed the synthesis of anthracene and niobium- supported precursors to reactive phosphorus fragments and studied their behavior using chemical, spectroscopic, and computational methods. Notably, this work gave rise to the synthesis of the 6π all-inorganic aromatic anion heterocycle P2N3−, produced in the “click” reaction of P2 with the azide ion. 

Following her PhD, Alexandra was a Materials Research Science & Engineering Center postdoctoral fellow with Professor Colin Nuckolls at Columbia University, where she worked on creating well-defined functional nanostructures by linking atomically precise metal chalcogenide clusters. 

Professor Velian was born in Tulcea, Romania, and currently lives in Seattle with her husband, daughter and two cats. Outside chemistry, she loves the outdoors and ballroom dancing.

Hosted by Professor Gwendolyn Bailey

Professor Kathryn Riley
Department of Chemistry
Swarthmore College
Abstract

Embodying DEI in Teaching, Research, and Outreach

In this talk, I will discuss the challenges and triumphs in my journey as a black woman in chemistry. I will also share how my personal experiences have shaped my current approaches to DEI work. Specifically, I will outline how I have designed my courses for inclusivity, how I have built and sustained a diverse research team, how my research enables the participation of diverse scholars in nanomaterials research, and the work I am doing to improve K-12 education in underserved communities.

Kathryn Riley

Dr. Kathryn Riley is an Assistant Professor in the Department of Chemistry and Biochemistry at Swarthmore College. She received her Ph.D. from Wake Forest University in 2014 and was a National Research Council (NRC) postdoctoral fellow at the National Institute of Standards and Technology (NIST) from 2015-2016. Before her current appointment, she was a Consortium for Faculty Diversity (CFD) postdoctoral fellow at Swarthmore from 2016-2018. Dr. Riley’s research involves the development of analytical techniques for the characterization of nanomaterials (NMs) and their dynamic physical and chemical transformations in biological and environmental matrices. Her research group specifically aims to broaden participation in the field by developing techniques that provide new quantitative insights in less time and at a reduced cost when compared to more commonly employed methods. Projects in her group span the analysis of engineered NMs (metal and metal oxide NMs, DNA nanostructures) and incidental NMs (nano and microplastics).

Hosted by Alexander Umanzor

Professor Kathryn Riley
Department of Chemistry
Swarthmore College
Abstract

Chemistry in Context: Re-envisioning Introductory Chemistry to Serve DEI Goals

In the Fall of 2022, the introductory chemistry course at Swarthmore (Chem 010) underwent significant revision to address several curricular priorities, including improved accessibility, engagement, and persistence for learners from diverse backgrounds. In this talk, I will discuss the process through which Swarthmore chemistry faculty revised Chem 010 to its present form. I will begin by discussing the national landscape of chemistry education, its relation to the previous version of Chem 010, and its role in motivating our curricular changes. Then, I will discuss the departmental and course level planning needed to reform our curriculum. Finally, I will present our new model for the course and outcomes from our first semester of implementation.

Kathryn Riley

Dr. Kathryn Riley is an Assistant Professor in the Department of Chemistry and Biochemistry at Swarthmore College. She received her Ph.D. from Wake Forest University in 2014 and was a National Research Council (NRC) postdoctoral fellow at the National Institute of Standards and Technology (NIST) from 2015-2016. Before her current appointment, she was a Consortium for Faculty Diversity (CFD) postdoctoral fellow at Swarthmore from 2016-2018. Dr. Riley’s research involves the development of analytical techniques for the characterization of nanomaterials (NMs) and their dynamic physical and chemical transformations in biological and environmental matrices. Her research group specifically aims to broaden participation in the field by developing techniques that provide new quantitative insights in less time and at a reduced cost when compared to more commonly employed methods. Projects in her group span the analysis of engineered NMs (metal and metal oxide NMs, DNA nanostructures) and incidental NMs (nano and microplastics).

Hosted by Alexander Umanzor

Professor Kathryn Riley
Department of Chemistry
Swarthmore College
Abstract

On the march towards environmental relevance: Advancing analytical methods to probe the nano-bio interface

The unique properties of engineered nanomaterials (ENMs) have enabled their increased use for a range of environmental, medical, and commercial applications. Owing to their unique antibacterial and antimicrobial properties, silver nanoparticles (AgNPs) are one of the most widely used ENMs, leading to their release into the environment during production, use, and disposal. Upon encountering environmental systems, AgNPs form eco-coronas that can lead to subsequent physicochemical transformations (e.g., aggregation, dissolution, oxidation, sulfidation, etc.) and that ultimately affect the environmental fate, transport, and toxicity of AgNPs. The complex composition of eco-coronas, which includes biomolecules, organic molecules, inorganic ions, and more, poses a significant analytical challenge, including both the availability of suitable measurement techniques and the development of laboratory model systems that mimic the complexity of “real-world” conditions. Work in our group aims to address these shortcomings. Specifically, we have developed a suite of electrochemical and electrokinetic separation techniques to probe the nano- bio interface. More recently, we have developed an environmentally relevant model system using the bacterium Caulobacter crescentus from which we derive complex eco-coronas. This talk will present the application of our analysis techniques to measure the effect of eco-coronas on AgNP reactivity, including preliminary data related to the environmental reactivity of AgNPs based on the C. crescentus model system.

Kathryn Riley

Dr. Kathryn Riley is an Assistant Professor in the Department of Chemistry and Biochemistry at Swarthmore College. She received her Ph.D. from Wake Forest University in 2014 and was a National Research Council (NRC) postdoctoral fellow at the National Institute of Standards and Technology (NIST) from 2015-2016. Before her current appointment, she was a Consortium for Faculty Diversity (CFD) postdoctoral fellow at Swarthmore from 2016-2018. Dr. Riley’s research involves the development of analytical techniques for the characterization of nanomaterials (NMs) and their dynamic physical and chemical transformations in biological and environmental matrices. Her research group specifically aims to broaden participation in the field by developing techniques that provide new quantitative insights in less time and at a reduced cost when compared to more commonly employed methods. Projects in her group span the analysis of engineered NMs (metal and metal oxide NMs, DNA nanostructures) and incidental NMs (nano and microplastics).

Hosted by Professor Christy Haynes

Professor Garnet Chan
Bren Professor in Chemistry
California Institute of Technology
Abstract

Simulating the quantum world on a classical computer

Dirac wrote that the laws that govern ordinary matter were known, but that the resulting equations of quantum many-particle systems were too complicated to be soluble. I will describe how, a century later, the situation has very much changed in the classical simulation of molecules and materials.

I will use examples from recent work in our group in simulations of small molecule spectroscopy as well as of the ground-states of high-temperature superconductors.

Garnet Chan

Garnet Chan is the Bren Professor of Chemistry at Caltech. A native of HK and the UK, he held positions at Cornell University and Princeton University before assuming his position at Caltech.

Hosted by Professor Don Truhlar

Professor Philip G. Jessop
Department of Chemistry
Queens University
Kingston, Canada
Abstract

CO₂-Switchable Materials

Stimuli-responsive materials can switch back and forth between two forms, upon application or removal of a trigger. This flexibility makes it possible to reduce energy and materials consumption in industrial processes. While it’s now well known that CO₂ can act as an inexpensive trigger for stimuli-responsive materials, 1 the extent of the utility of this concept is only now being realized. CO₂-switchable materials have applications in catalysis, 2 adhesives, particle formation, paints, and many other products and processes. This presentation will focus on new ways in which CO₂-switchable materials can contribute to chemical separations and coatings, potentially lowering their economic and environmental costs.

Philip G. Jessop

Dr. Philip Jessop is the Canada Research Chair of Green Chemistry at Queen’s University in Canada and the Executive Research Director of Forward Water Technologies Inc. His research interests include green solvents, biomass conversion and CO 2 -responsive materials. Distinctions include the NSERC Polanyi Award (2008), Canadian Green Chemistry & Engineering Award (2012), the Eni Award (2013), NSERC Brockhouse Prize (2019), and Fellowships in the Royal Society of Canada, the Royal Society of Chemistry, and the American Chemical Society. He served as the Chair of the Editorial Board for the journal Green Chemistry (2017-2022), has chaired three major international conferences and helped create two spin-off companies and GreenCentre Canada, a centre for the commercialization of green chemistry technologies. His Tiktok video series “Jessop’s Which Is Greener?” has reached tens of thousands of viewers.

Hosted by Nathan Rackstraw

Professor Edith (Phoebe) Glazer
Department of Chemistry
North Carolina State University
Abstract

Targeting Cytochrome P450s - From Biophysics to Selective Inhibitors

Cytochrome P450s (CYPs) are a superfamily of enzymes that perform challenging reactions in all life forms. In humans, these amazing enzymes are responsible for the metabolism of xenobiotics, as well as the biosynthesis of several essential signaling molecules. Thus, CYPs play an integral protective role via degradation, in addition to aiding in the regulation of growth, development, and homeostasis via (bio)synthesis. Notably, these two processes have opposite requirements for selectivity, with the drug metabolizing CYP enzymes of the liver exhibiting extreme promiscuity while the biosynthetic CPYs of other tissues performing chemistry with exquisite regio- and stereo-control. We are working towards an understanding of P450 structural flexibility and dynamics that can be exploited for the development of drugs selective for specific P450 enzymes that play a role in cancer initiation, progression, and resistance to treatment. Our current focus is on CYP1B1, which is absent or expressed at very low levels in the liver and healthy tissues while being overexpressed in tumors, giving it the title of “universal tumor antigen”. Evidence from basic science, clinical, and epidemiological studies demonstrate that CYP1B1 creates DNA mutagens, facilitates malignant progression, and then causes resistance to the majority of common chemotherapeutics, regardless of their mechanism of action. I will detail our development of cell-based assays for CYP1B1 and related family members, and will present our approach to the development of highly potent and selective CYP1B1 inhibitors. This work was supported by the National Institutes of Health (R01 138882).

Edith (Phoebe) Glazer

Professor Edith (Phoebe) Glazer is a Professor of Chemistry at North Carolina State University (NCSU). Following a formative education at Williams College, she received her PhD in Chemistry and Biochemistry at the University of California, San Diego with Yitzhak Tor, and then performed an NIH postdoctoral fellowship between the Scripps Research Institute, in the laboratory of David Goodin, and Caltech, with Harry Gray. Her doctoral and postdoctoral contributions included new synthetic approaches to extended aromatic ligands and multimetallic arrays, compounds that exhibited so-called “dual emission”, and probes for electron and energy transfer in heme proteins, including cytochrome P450s and Nitric Oxide Synthase. She began her independent career at the University of Kentucky in 2009, and moved to NCSU in 2023. The Glazer Group is focused on using light to control biological processes through the creation of reactive metal complexes. Other research projects include targeting medically important heme proteins, and developing research tool compounds to elucidate cell biology.

Hosted by Professor Ambika Bhagi-Damodaran

Professor Mario Barbatti
Aix Marseille University, CNRS, ICR, Marseille, France
Institut Universitaire de France, Paris, France
Abstract

Perspectives in Mixed Quantum-Classical Dynamics for Modeling Molecular Photoprocesses

Molecular excited electronic states are central to diverse fields, including biology, health, and technology. Upon photoexcitation, these molecules are unequilibrated systems with multiple competing reaction pathways and time evolution from a few picoseconds to microseconds, depending on the processes involved. Moreover, they present highly complex electronic densities and often visit geometric conformations with multireference characters. Mixed quantum-classical nonadiabatic dynamics help characterize these systems by providing insights into the physical-chemical phenomenon, delivering information for the deconvolution of experimental time-resolved data, and predicting properties before and after synthesis. However, these methods face challenges, including developing new functionalities, reliable research protocols, efficient computational methods, integration with experimental analysis, and a balanced description of the electronic correlation between states with different characters. In recent years, my research group has proposed mixed quantum-classical nonadiabatic dynamics methods for treating open quantum systems, systems excited by incoherent light, and zero-point-energy leakage. We also created methodologies for propagating dynamics computing nonadiabatic couplings without wave functions and estimating the temperature of microcanonical quantum systems. I will overview some of these new approaches in this lecture. I will also discuss case studies showing these methods in action.

Mario Barbatti

Mario Barbatti is a professor of theoretical chemistry at the Aix Marseille University in Marseille, France, and a senior member of the Institute Universitaire de France. He is an expert on developing and applying mixed quantum-classical dynamics to study molecular excited states and the leading developer of the Newton-X software platform. Among his main contributions, Barbatti delivered the first comprehensive map of the internal conversion channels of isolated nucleobases, explained how UV irradiation can generate nucleobases out of inorganic components, and discovered a new internal conversion mechanism involving solvent chromophore interactions. Barbatti held a chair of excellence A*Midex at the Aix Marseille University between 2015 and 2019. In 2019, he was awarded a European Research Council advanced grant; in 2021, he was elected a member of the European Academy of Sciences.

Hosted by Professor Don Truhlar