Noncovalent interactions (NCIs) in π-conjugated organic materials serve as tunable levers that influence molecular structure and intermolecular interactions in the condensed phase and, in turn, impact the electronic, optical and mechanical properties of these materials. NCIs include attractive dispersion, electrostatic and induction interactions as well as repulsive exchange interactions. 

How to design materials with NCI considerations, however, remains an open question across many fields. Here, we seek to provide an atomistic perspective on these interactions through multiscale simulations to aid materials design, processing, and performance optimization. In this study, we investigate NCIs and their effects across various systems and complexity scales. 

First, we explore intramolecular NCIs and their influence on molecular conformation and the resulting electronic and optical properties. We demonstrate how NCI can lead to various preferred molecular conformations that, in turn, modulate the intrinsic molecular properties. Then we turn to  NCIs in multicomponent organic systems to elucidate how intermolecular NCIs influence molecular association, nucleation and growth in the organic condensed phase. Particular emphasis is placed on π-conjugated organic semiconductors, where both backbone-backbone and side-chain-mediated interactions critically influence solid-state packing and crystal growth. 

Collectively, this study demonstrates how NCIs can be strategically leveraged to guide material design and processing to optimize functional materials for organic electronics applications.

Noncovalent interactions (NCIs) in π-conjugated organic materials serve as tunable levers that influence molecular structure and intermolecular interactions in the condensed phase and, in turn, impact the electronic, optical and mechanical properties of these materials. NCIs include attractive dispersion, electrostatic and induction interactions as well as repulsive exchange interactions. 

How to design materials with NCI considerations, however, remains an open question across many fields. Here, we seek to provide an atomistic perspective on these interactions through multiscale simulations to aid materials design, processing, and performance optimization. In this study, we investigate NCIs and their effects across various systems and complexity scales. 

First, we explore intramolecular NCIs and their influence on molecular conformation and the resulting electronic and optical properties. We demonstrate how NCI can lead to various preferred molecular conformations that, in turn, modulate the intrinsic molecular properties. Then we turn to  NCIs in multicomponent organic systems to elucidate how intermolecular NCIs influence molecular association, nucleation and growth in the organic condensed phase. Particular emphasis is placed on π-conjugated organic semiconductors, where both backbone-backbone and side-chain-mediated interactions critically influence solid-state packing and crystal growth. 

Collectively, this study demonstrates how NCIs can be strategically leveraged to guide material design and processing to optimize functional materials for organic electronics applications.

Conjugated polymers have attracted significant attention as active materials in organic electronics, including organic photovoltaics, light-emitting diodes and thin-film transistors. Their appeal lies in the combination of solution processability, tunable electronic properties and mechanical flexibility, which together enable applications not readily achievable with conventional inorganic semiconductors. The widespread adoption of these materials, however, is hindered by their limited long-term stability. Exposure to oxygen, moisture, light and thermal stress can initiate a variety of degradation pathways, leading to structural and electronic changes that compromise device performance. Understanding the molecular level processes underlying such degradation remains a critical challenge for advancing the durability of organic electronic technologies.

Spectroscopic techniques are essential for probing the electronic structure and chemical evolution of conjugated polymers under operational and accelerated aging conditions. Such conventional methods as ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS) reveal energy level alignment and chemical bonding, while device-based techniques like deep-level transient spectroscopy (DLTS), impedance spectroscopy and thermally stimulated current (TSC) measurements are used to identify trap or defect states. These approaches, however, often rely on device fabrication and can suffer from interface or contact artifacts. 

In contrast, Constant Final State Yield Spectroscopy (CFSYS) and Variable Energy Ultraviolet Photoelectron Spectroscopy (VE-UPS) offer a highly sensitive, device-free framework for mapping the occupied electronic structure of materials. CFSYS monitors electron emission at a fixed electron kinetic energy while sweeping the photon energy, providing energy references directly tied to the vacuum level and revealing defect state distributions intrinsic to the material. In contrast, VE-UPS varies the photon energy to obtain full UPS spectra at each excitation energy, offering detailed insight into the electronic structure beyond simple HOMO–LUMO transitions. Together, CFSYS and VE-UPS enhance sensitivity to subtle electronic variations and defect states that arise during degradation. 

Applying these complementary techniques to conjugated polymer degradation enables a direct correlation between spectroscopic signatures and performance loss, providing new insight into the molecular origins of instability and guiding the design of more durable conjugated systems for organic electronic applications.

The work encompasses the development, optimization and application of advanced photoemission spectroscopy techniques to probe the electronic structure and stability of organic and hybrid materials. The second chapter focuses on precise calibration and performance optimization of the PHOIBOS hemispherical analyzer, ensuring accurate and reproducible spectroscopic measurements across diverse material systems. The third chapter highlights the design, construction and implementation of the VE-UPS and CFSYS systems, developed to enhance sensitivity to defect states and quantify the change in defect states of doped systems. 

These techniques are applied in the fourth chapter to investigate defect evolution and stability in conjugated polymers under varying electrochemical doping levels, revealing how doping influences degradation and electronic structure. The final chapter extends these methods to Dion-Jacobson tin halide perovskites, demonstrating how variations in spacer cations modulate their structural, energetic, and optical properties. Together, these studies advance both the methodological capabilities and the fundamental understanding of material electronic behavior and stability.

Conjugated polymers have attracted significant attention as active materials in organic electronics, including organic photovoltaics, light-emitting diodes and thin-film transistors. Their appeal lies in the combination of solution processability, tunable electronic properties and mechanical flexibility, which together enable applications not readily achievable with conventional inorganic semiconductors. The widespread adoption of these materials, however, is hindered by their limited long-term stability. Exposure to oxygen, moisture, light and thermal stress can initiate a variety of degradation pathways, leading to structural and electronic changes that compromise device performance. Understanding the molecular level processes underlying such degradation remains a critical challenge for advancing the durability of organic electronic technologies.

Spectroscopic techniques are essential for probing the electronic structure and chemical evolution of conjugated polymers under operational and accelerated aging conditions. Such conventional methods as ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS) reveal energy level alignment and chemical bonding, while device-based techniques like deep-level transient spectroscopy (DLTS), impedance spectroscopy and thermally stimulated current (TSC) measurements are used to identify trap or defect states. These approaches, however, often rely on device fabrication and can suffer from interface or contact artifacts. 

In contrast, Constant Final State Yield Spectroscopy (CFSYS) and Variable Energy Ultraviolet Photoelectron Spectroscopy (VE-UPS) offer a highly sensitive, device-free framework for mapping the occupied electronic structure of materials. CFSYS monitors electron emission at a fixed electron kinetic energy while sweeping the photon energy, providing energy references directly tied to the vacuum level and revealing defect state distributions intrinsic to the material. In contrast, VE-UPS varies the photon energy to obtain full UPS spectra at each excitation energy, offering detailed insight into the electronic structure beyond simple HOMO–LUMO transitions. Together, CFSYS and VE-UPS enhance sensitivity to subtle electronic variations and defect states that arise during degradation. 

Applying these complementary techniques to conjugated polymer degradation enables a direct correlation between spectroscopic signatures and performance loss, providing new insight into the molecular origins of instability and guiding the design of more durable conjugated systems for organic electronic applications.

The work encompasses the development, optimization and application of advanced photoemission spectroscopy techniques to probe the electronic structure and stability of organic and hybrid materials. The second chapter focuses on precise calibration and performance optimization of the PHOIBOS hemispherical analyzer, ensuring accurate and reproducible spectroscopic measurements across diverse material systems. The third chapter highlights the design, construction and implementation of the VE-UPS and CFSYS systems, developed to enhance sensitivity to defect states and quantify the change in defect states of doped systems. 

These techniques are applied in the fourth chapter to investigate defect evolution and stability in conjugated polymers under varying electrochemical doping levels, revealing how doping influences degradation and electronic structure. The final chapter extends these methods to Dion-Jacobson tin halide perovskites, demonstrating how variations in spacer cations modulate their structural, energetic, and optical properties. Together, these studies advance both the methodological capabilities and the fundamental understanding of material electronic behavior and stability.

Abstract: The early drug discovery workflow relies heavily on high-throughput experimentation, both in terms of organic synthesis as well as analysis of complex biosamples. The identification of new biological targets through large-scale biospecimen studies, the generation of large sets of drug candidates and their rapid bioactivity screening, as well as the in vitro and cell-based confirmation of hits followed by lead optimization, all rely on high-throughput strategies that  are typically spread out across diverse technologies in specialized facilities. The efficiency of this workflow could benefit from the consolidation of these activities in a single closed-loop platform. Mass spectrometry (MS) is an attractive technique to achieve such consolidation due to the inherent speed of mass analysis; however, this advantage is rarely fully used due to the widespread use of sample purification approaches (e.g. chromatography) before MS. 

Here we describe an automated system that achieves the consolidation of the early drug discovery pipeline by leveraging the advantages of desorption electrospray ionization (DESI), an ambient ionization technique that allows for the rapid and direct analysis of complex samples, both in qualitative and quantitative manner, without any need for workup. This system results from the combination of custom and commercial software, robotics and analytical instrumentation and can achieve throughputs better than 1 Hz using high-density arrays (up to 6,144 samples per array) and 50-nL samples (<5 ng analyte). More significantly, the inherent reaction acceleration phenomenon that occurs in microdroplets, such as those generated intrinsically through the DESI process, allows reaction times to be reduced to just milliseconds, effectively providing an on-the-fly synthetic method that can be coupled with in operando MS analysis or nano-microgram scale product collection for bioactivity assessment. 

The general workflow of this platform involves:

• Automated sample preparation or manipulation using a fluid handling workstation. 
• Generation of microarrays using a pin-tool.
• Automated transfer and analysis of spotted slides using ultrahigh-throughput DESI-MS. 
• Real-time processing of the spectral data. 

This methodology has been extensively demonstrated for the screening of organic reactions for identification of optimal synthesis conditions and the selective late-stage functionalization of complex molecules as well as for label-free quantitative biological assays using purified targets (e.g. enzymes, receptors), cell cultures, microorganisms or tissue biopsies, all with no sample cleanup. Examples of all these capabilities will be provided and framed within the overall context of drug discovery showcasing a new-generation system built within the ASPIRE initiative of the US National Center for Advancing Translational Sciences as well as a historical recount of the development of this technology.

Bio: Nicolás Morato is a research assistant professor at the Purdue Institute for Cancer Research of Purdue University. He is a trained chemist and engineer, and most of his career has been focused on analytical chemistry, in particular mass spectrometry. He completed his undergraduate studies at Universidad de los Andes (Colombia), and later his Ph.D. and a postdoctoral fellowship at Purdue University under the mentorship of Graham Cooks. 

Overall, his research involves the development of strategies for the rapid analysis of complex samples using ambient ionization mass spectrometry. Most of this effort revolves around the development and application of desorption electrospray ionization mass spectrometry (DESI-MS) for high-throughput experimentation in biochemistry, organic synthesis, clinical diagnosis and biomarker discovery with the underlying objective of consolidating this technology as an efficient closed-loop automated platform for early drug discovery. His work in this area has been recognized by several honors including graduate fellowships by Eastman and the ACS Division of Analytical Chemistry as well as the Tomas B. Hirschfeld Scholar Award from FAACS and the Postgraduate Award from IMSF and JMS.

Abstract: This talk will describe fundamental measurements aimed at understanding the conductance of pi-conjugated molecules connected between metal electrodes. We explore conductance in two regimes: 

• The tunneling regime, applicable to short molecules. 
• The polaron hopping regime, which pertains to longer molecules. 

In the tunneling regime, quantitative analysis of current-voltage (I-V) characteristics is aided greatly by application of an analytical single level model, which allows extraction of the HOMO or LUMO offset from the electrode Fermi level e and the electrode-orbital coupling G. We show that the single level model applies extremely well to common molecular junctions and we are able to relate the junction parameters e and G to molecular structure and the nature of the metal-molecule contacts. 

Our experiments in the polaron hopping regime rely on high yield click-like chemistry to build pi-conjugated molecular wires up to 10 nm in length from metal substrates. We probe the conductance and I-V behavior as a function of wire length and we observe a clear crossover from tunneling to hopping near 4 nm. Transport for long wires > 4 nm is thermally activated and we have recently observed a very strong conductance isotope effect (CIE), which may allow us to understand transition states and polaron localization effects for intramolecular conductance along pi-conjugated chains. In general, there are many opportunities to understand charge transport kinetics in molecules in much the same way that reaction kinetics are explored in classical physical organic chemistry. 

Bio: C. Daniel Frisbie is Distinguished McKnight University Professor of Chemical Engineering and Materials Science (CEMS) at the University of Minnesota. He joined the faculty in 1994 and served as Head of CEMS from 2014-2024. A physical chemist by training, he obtained a Ph.D. from MIT in 1993 and was an NSF postdoctoral fellow in chemistry at Harvard. His research focuses on materials for printed electronics, including organic semiconductors and their applications in devices such as transistors and sensors. He also has a longstanding program in molecular electronics. Research themes include the characterization of novel organic semiconductors, structure-property relationships, device physics and the application of scanning probe techniques. Recent efforts also include manufacturing approaches for large area flexible electronics and strategies for electrocatalysis. 

Abstract: Atmospheric pollutants, ranging from traditional organic aerosols to emerging contaminants such as nanoplastics and per- and polyfluoroalkyl substances (PFAS), play critical roles in air quality, climate forcing and environmental health. Their sources, atmospheric transformations, transport pathways and impacts, however, remain poorly constrained.

My research integrates state-of-the-art laboratory experiments with innovative field campaigns, including deployment of a mobile laboratory equipped with real-time mass spectrometry, to develop approaches for detecting emerging pollutants, characterize their spatial and temporal distributions and quantify the multiphase processes that drive their evolution in the atmosphere. By bridging controlled laboratory studies with complex atmospheric environments, this work reveals the mechanisms linking molecular-level transformations of pollutants to their climate and health impacts.

Bio: Dr. Yue Zhang is an assistant professor in the Department of Atmospheric Sciences at Texas A&M University. His research integrates laboratory experiments and field studies to investigate the processes and climate impacts of atmospheric pollutants, including such emerging contaminants as nanoplastics and per- and polyfluoroalkyl substances (PFAS). He obtained Ph.D. in environmental science and engineering from Harvard University and became a U.S. NSF postdoctoral fellow, jointly working with the University of North Carolina Chapel Hill, Aerodyne Research and MIT. He joined Texas A&M as an assistant professor in 2021. To date, he has published nearly 60 peer-reviewed papers, including those in natural communications and natural geosciences and has been recognized with the Best Paper of the Year in Environmental Science & Technology Letters, UNC Chapel Hill Postdoc of Research Excellence, the Montague Teaching of Excellence Award at Texas A&M University and the NSF CAREER Award. He also served as committee chair and working group chair roles within the American Association for Aerosol Research. 

Abstract: Peptides represent a rapidly expanding class of therapeutics capable of targeting protein surfaces and interfaces inaccessible to conventional small molecules. Yet our ability to study their behavior in living systems remains limited by the tools available. Traditional fluorescent labels are often too bulky to be incorporated without disrupting peptide function and target engagement. My research program develops minimally perturbative vibrational imaging tools to visualize peptide dynamics in complex biological environments. By integrating precision peptide design, bioorthogonal Raman tags and advanced spectroscopic imaging, we create platforms that enable noninvasive, chemically specific mapping of therapeutics in cells and tissues.

Abstract: Peptides represent a rapidly expanding class of therapeutics capable of targeting protein surfaces and interfaces inaccessible to conventional small molecules. Yet our ability to study their behavior in living systems remains limited by the tools available. Traditional fluorescent labels are often too bulky to be incorporated without disrupting peptide function and target engagement. My research program develops minimally perturbative vibrational imaging tools to visualize peptide dynamics in complex biological environments. By integrating precision peptide design, bioorthogonal Raman tags and advanced spectroscopic imaging, we create platforms that enable noninvasive, chemically specific mapping of therapeutics in cells and tissues.

Abstract: The presenter's Ph.D. in chemistry (chemical biology path) focused on harnessing peptide chemistry with structural and biophysical approaches to uncover how subtle changes in peptide architecture can be used to reshape GPCR signaling and immune signaling in useful ways. 

For his postdoctoral work, he turned his focus to proteostasis by pursuing biological characterization of small-molecule activators of autophagy discovered via a high-throughput, imaging-based screen. This public seminar will highlight some of these research findings. In his future independent lab, Russ seeks to scrutinize and therapeutically harness GPCR and kinase networks to address novel questions at the interface of chemical biology, signal transduction and drug discovery.