1998 — 2002 |
Wasielewski, Michael |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Ultrafast Molecular Optical Switches: Design, Preparation, and Function @ Northwestern University
This award is recommended by the Advanced Materials Program in the Chemistry Division in support of the research of Dr. Michael Wasielewski at Northwestern University. The theme of the research is the design, synthesis and function of ultrafast molecular switches based on ultrafast optical gating of electron transfer in extended arrays of organic and organometallic donor-acceptor molecules. These switches will make use of high quantum yield and picosecond electron transfer processes to control the movement of electrons within the molecules. Three approaches to a molecular switch will be explored; first, the use of photogenerated electric fields to control electron transfer rates, second, the use of two sequential light pulses to generate radical anions or cations and then transfer them to an adjacent acceptor or donor, and third, excitation of bridging chromophores to control the lifetimes of photogenerated charge-separated states. The successful development of of new molecule-sized electronics promises to yield dramatic improvements in component density, response speed and energy efficiency. The impact of the research is broad and includes potential applications such as information storage, solar energy conversion and optical signal processing.
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0.915 |
2001 — 2004 |
Wasielewski, Michael |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Nanostructured Organic Materials For Ultrafast Optoelectronics @ Northwestern University
The Advanced Materials Program in the Chemistry Division supports this award to Northwestern University to design, synthesize and develop novel multifunctional fluorophores that combine fast unidirectional internal photoinduced electron transfer with efficient fluorescence from the charge-separated species. With this award, Professor Michael Wasielewski will study molecular structural features to tailor optical and electronic properties of these materials as desired. Molecular design incorporating perylene derivatives will be used to design molecular switches for potential applications in molecular devices. Graduate students will greatly benefit from training and research opportunities provided by this award in materials chemistry and in photophysical property characterization of materials.
With this award, ultra fast optical gating of electrons in synthetic molecular entities will be studied using photoexcitation. Molecules will be designed, synthesized and derivatives incorporated, and these molecules will be characterized by time-resolved femtosecond laser spectroscopic methods. Design of molecular switches with potential application in molecular devices will be one of the out come of these studies. Students will greatly benefit from training and research opportunities provided by this award in materials chemistry, and in characterization of photophysical properties of materials.
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0.915 |
2002 — 2005 |
Godwin, Hilary Hoffman, Brian (co-PI) [⬀] Hupp, Joseph (co-PI) [⬀] Lewis, Frederick (co-PI) [⬀] Wasielewski, Michael |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Acquisition of a Pulsed Fourier Transform Electron Paramagnetic Resonance Spectrometer @ Northwestern University
With this award from the Chemistry Research Instrumentation and Facilities (CRIF) Program, the Department of Chemistry at Northwestern University will acquire a Pulsed Fourier Transform Electron Paramagnetic Resonance (EPR) Spectrometer. The new instrument will support research in the following areas: a) mapping electronic coupling within photogenerated radical ion pairs at fixed distances using time-resolved EPR spectroscopy (Wasielewski); b) direct observation of guanine cation radical in duplex DNA (Lewis); c) time-resolved applications in energy conversion chemistry: finding and identifying electron traps at photo-active interfaces (Hupp); d) time-resolved EPR of electron transfer within protein complexes (Hoffman); e) EPR studies on cobalt (II)-substituted zinc-binding domains (Godwin); and f) EPR studies of monoamine oxidase (Silverman).
An electron paramagnetic resonance (EPR) spectrometer is an instrument used to obtain information about the molecular and electronic structure of molecules. It may also be used to obtain information about the lifetimes of free radicals which are often essential for the initiation of tumor growth and/or a variety of chemical reactions. These studies will have an impact in a number of areas, in particular the chemistry of photofunctional materials and biophysical chemistry.
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0.915 |
2004 — 2007 |
Wasielewski, Michael |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Dynamic Control of Spin-Selective Electron Transfer in Donor-Acceptor Arrays @ Northwestern University
With this renewal award, the Organic and Macromolecular Chemistry Program continues its support of the work of Professor Michael R. Wasielewski of the Department of Chemistry, Northwestern University, Evanston, IL. The research will extend the PI's research on the design and synthesis of novel molecular materials with the capability of undergoing light induced electron transfer to generate radical ion pairs. Taking advantage of the fact that the properties of radical pairs are affected by magnetic fields, an internal magnetic field in the form of a stable free radical will be incorporated. The effect of the additional unpaired spin and the ability to turn this spin on and off on electron and spin transfer will be investigated. These studies will provide fundamental knowledge concerning intramolecular interactions among unpaired electron spins that will aid in the design of systems for harvesting solar energy and for use in molecular optoelectronics. The project will provide important training for undergraduate and graduate students with an emphasis on women and underrepresented minorities.
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0.915 |
2006 — 2012 |
Lewis, Frederick [⬀] Schatz, George (co-PI) [⬀] Wasielewski, Michael |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Crc: Dna Photonics @ Northwestern University
Frederick D. Lewis, George C. Schatz, Michael R. Wasielewski (all at Northwestern University), Torsten Fiebig (Boston College) and Alexander L. Burin (Tulane University) are jointly supported for research into the electronic structure of DNA. More specific objectives include the investigation of the nuclear and electronic structure of short, well-defined duplex base pair domains in both the ground and electronically excited states; and investigation of the structural and electronic changes which occur upon the oxidation or reduction of duplex domains. The team will study short stable base pair domains in custom-designed hairpin and dumbbell structures. A wide range of state-of-the-art time-resolved spectroscopic, computational, and structural techniques will be used to probe how the structural changes within DNA are coupled to the properties of excited and ion states within it. Experimental approaches include molecular design and synthesis, spectroscopy, time-resolved transient absorption spectroscopy, time-resolved EPR spectroscopy, molecular dynamics, time-resolved circular dichroism, and electronic structure calculations. David Tiede (Argonne National Laboratory) will also collaborate with the team and bring expertise in time-resolved diffraction techniques.
The structural and functional integrity of DNA is critical to its role in biology, so that this project will provide fundamental information on how light and chemical agents introduce reactive sites within DNA, which change its structure and potentially alter its function. The anticipated outcomes of this collaboration include elucidation of the properties of neutral and ionized short DNA base-pair domains, training of undergraduate and graduate students in an important interdisciplinary area, and providing a model for interlocking collaboration among investigators with varying experience and in different research environments. This project is supported by the Collaborative Research in Chemistry Program.
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0.915 |
2007 — 2010 |
Wasielewski, Michael |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Photon-Controlled Organic Molecular Spintronics @ Northwestern University
With this award, the Organic and Macromolecular Chemistry Program supports the work of Professor Michael R. Wasielewski of Northwestern University. This research will involve development of a fundamental understanding of how to control charge and spin transport through organic molecules which is critical to the development of new approaches to electronics, computers, energy production and in the construction of spintronic devices. Rapid, laser-driven formation of molecular excited states leading to the production of correlated spins combined with modern pulsed electron paramagnetic resonance techniques will be used to generate and manipulate multi-spin systems. For example, photoinitiated electron transfer within covalently-linked organic donor-acceptor molecules having specific donor-acceptor distances and orientations results in formation of highly spin-polarized radical pairs in which the initial spin state is well defined. These organic radical ion pairs display coherent spin motion for microseconds at room temperature and longer at low temperatures, which makes it possible that this coherence can provide the basis for new organic information processing devices.
The broader impacts of this research involve the training of young scientists, including undergraduates and women, in a combination of synthetic methodology, to make complex molecules, quantum chemistry and high resolution spectroscopy, to study the synthesized compounds. This will enable these students to become proficient in a broad interdisciplinary area of chemistry which will allow them to become independent scientists and learn to work in a team, so necessary in today's marketplace. In addition, the results of this work will impact the fields of charge transport, solar energy, nanotechnology and device fabrication, and organic magnetism.
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0.915 |
2009 — 2014 |
Marks, Tobin (co-PI) [⬀] Ratner, Mark (co-PI) [⬀] Chang, Robert [⬀] Wasielewski, Michael Warner, Isiah (co-PI) [⬀] |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
International Materials Institute For Solar Energy Conversion @ Northwestern University
This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
With this award Northwestern University will establish an International Materials Institute (IMI) for Solar Energy Conversion. Although conventional silicon and other semiconductor solar cells have achieved high efficiency for solar energy conversion, their production costs remain high. Organic photovoltaic cells (OPVC) might yield cost-effective green energy for a wide variety of applications. The efforts of this IMI are focused on theory-guided fundamental research on OPVC - new materials design, processing, and device fabrication to understand physical processes and limitations to efficient conversion and storage of solar energy. Northwestern University, Louisiana State University and Argonne National Laboratory along with Tsinghua University in China will form the core partnership to lead the efforts of the IMI. Researchers from 35 more institutions worldwide including USA, China, Australia, Germany, Japan, South Africa, and Taiwan will participate as standing partners. IMI activities include exchange visits of faculty, postdoctoral scholars, and students among core partners, annual symposia and workshops for all partners to exchange research findings and development of a global cyber-based network for year-around communication of solar energy research. The IMI will integrate research and education with a strong focus on global leadership development for graduate students, undergraduate courses on energy conversion topics, teaching modules on solar energy topics for K-12, and inform the public about solar energy conversion and its role in energy conservation via museum and media presentations. A Leadership Council consisting of the lead researchers from core partner institutions will provide oversight and internal assessment of the research and education programs of the IMI. Guidance and external evaluation will be provided by a rotating Technical Advisory Board consisting of representatives from academia, industry and government laboratories.
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0.915 |
2009 — 2012 |
Marks, Tobin [⬀] Mirkin, Chad (co-PI) [⬀] Wasielewski, Michael Thomson, Regan (co-PI) [⬀] Stoddart, J Fraser (co-PI) [⬀] |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Mri: Acquisition of a Time-of-Flight Gc-Mass Spectrometer @ Northwestern University
This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
With this award from the Major Research Instrumentation (MRI) program, the Chemistry Department at Northwestern University will acquire a gas chromatograph time-of-flight (GC-TOF) mass spectrometer for use in teaching and research. A variety of research projects will be investigated including: 1) Organo-f-Element Chemistry - Integrated Synthetic, Mechanistic, Catalytic, and Thermochemical Studies; 2) Enzyme Mimics Based on Supramolecular Coordination Assembly; 3) Reticular Networks Forged for Dynamic Processes; 4) Unlocking the Synthetic Potential of N-Allylhydrazones; and, 5) Molecular Spintronics.
Mass spectrometry (MS) is used to identify the chemical composition of a sample and determine its purity by measuring the mass of the molecular constituents in the sample after they are ionized and detected by the mass spectrometer. Chromatography is an isolation technique that precedes the mass spectrometry analysis. It separates a mixture into its constituent chemicals which are then analyzed by the mass spectrometer. These are analytical techniques widely used to characterize the chemical composition of a sample. The mass spectrometer will be used by undergraduate and graduate research students and in undergraduate laboratory classes.
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0.915 |
2010 — 2013 |
Wasielewski, Michael |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Multi-Spin Interactions and Dynamics For Organic Spintronics @ Northwestern University
With this Renewal Award, the Chemical Structure, Dynamics, and Mechanisms Program continues to support Michael R. Wasielewski of Northwestern University in a project involving investigations of the factors controlling spin interactions and dynamics in organic multi-spin systems. In these studies, photoexcitation of organic radicals will be used to generate multi-spin systems which will be manipulated by optical and microwave pulse techniques to study their spin dynamics. The properties of these multi-spin systems in tailored covalent organic structures will be investigated to determine if their spin dynamics can be used to control spin polarization transport. These experiments, aimed at controlling the spin dynamics in multi-spin systems, will contribute to an understanding of the fundamental factors affecting electronic communication in organic molecules.
These investigations have the potential to make major contributions in light harvesting technology, energy storage and the development of quantum computers. The project will train students in modern spectroscopic and synthetic techniques. Collaboration with Professor Mark P. Niemczyk of Wheaton College will allow undergraduate students from that institution to participate in the project.
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0.915 |
2011 — 2014 |
Wasielewski, Michael |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Spin Coherences in Photosystem I Reaction Center Proteins and Model Systems @ Northwestern University
This award in the Chemistry of Life Processes (CLP) program supports work by Professor Michael R. Wasielewski at Northwestern University to carry out fundamental studies on the nature of multiple pathways for light-induced charge separation in one of the key light transduction proteins in green plants, the Photosystem I (PSI) reaction center (RC), which is responsible for providing the chemical potential necessary to reduce carbon dioxide to carbohydrates. The PSI RC in oxygenic organisms is unique because it is the only RC for which there is evidence that both sets of redundant cofactors engage in electron transport. The electron transfer cofactors in the PSI RC protein are arranged in two symmetric pathways, A and B, which results in charge transport to a common electron acceptor, and suggests the possibility that the PSI protein may function as an interferometer in which electrons traversing the two pathways are in a quantum superposition state. This project will address two key questions regarding the role of quantum superposition in PSI function: 1) Does charge transport within PSI involve independent spin-coherent radical ion pairs using either the A and B pathways or a quantum superposition state involving both pathways simultaneously? 2) Does the inherent quantum coherent nature of the dual-pathway charge separation sense and control excess excitation energy dissipation in the PSI RC? Time-resolved electron paramagnetic resonance spectroscopy will be used to probe these mechanisms, while theory and synthetic donor-acceptor systems will be used to model this behavior.
Understanding excess energy dissipation in photosynthetic organisms is critical to ensuring the viability and sustainability of photosynthetic energy transduction in nature, a process essential to life on Earth. Improved knowledge of this process provides an important conceptual basis for the design of artificial photosynthetic systems for solar energy conversion. The results of this research will be communicated to the public through the extensive outreach network of the Northwestern-funded Initiative for Sustainability and Energy at Northwestern (ISEN).
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0.915 |
2013 — 2016 |
Wasielewski, Michael |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Manipulating Multi-Spin Dynamics in Systems Targeting Organic Spintronics @ Northwestern University
The Chemical Structure, Dynamics and Mechanism B (CSDM-B) program supports Professor Michael R. Wasielewski of Northwestern University to carry out fundamental studies on controlling the spin dynamics of complex multi-spin molecular systems that target spintronics and quantum information processing. Fast photo-initiated electron transfer within covalently-linked organic donor-acceptor molecules having specific donor-acceptor (D-A) distances and orientations results in the formation of spin-entangled electron-hole pairs (i.e. spin-correlated radical ion pairs, SCRPs) having well-defined initial spin configurations and magnetic spin-spin interactions. The project focuses on the demanding task of controlling spin coherence within organic molecular arrays using SCRPs in tailored covalent structures. The specific goals are to investigate: 1) What is the scope of spin coherence transfer by optical excitation of an SCRP? 2) What factors determine coherence dephasing in SCRPs? 3) Can coherent spin states be transported ("teleported") over long distances using SCRPs? 4) Can nuclear spins be used to store and retrieve coherent electron spin states produced by an SCRP?
Developing a fundamental understanding of how to control charge and spin transport through organized arrays of organic molecules is critical to the development of new electronics and spintronics especially with regard to their potential impact on computers and information processing. Taking advantage of the quantum nature of electron spin may lead to advanced computer technologies with broad applications throughout society. The use of organic materials and bio-inspired approaches to these problems offers the possibility of developing solutions that are not only versatile, but are cost effective and environmentally benign as well.
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0.915 |
2016 — 2017 |
Wasielewski, Michael Aspuru-Guzik, Alan |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Quantum Information and Quantum Computation For Chemistry: Challenges and Opportunities @ Northwestern University
The Division of Chemistry is sponsoring this workshop entitled "Quantum Information and Quantum Computation for Chemistry: Challenges and Opportunities" to be held on November 14-15, 2016 in Arlington, Virginia. Since the early contributions by Richard Feynman in 1982, quantum information science and technology has become one of the most dynamic and promising fields of scientific endeavor. The possibility of accessing new forms of cryptography, communication, and computation has led to new intellectual frameworks for understanding our physical reality as well as to the understanding of the complexity of different tasks such as the simulation of quantum systems. The field of chemistry, with its core at the quantum realm has several points of contact with quantum information science and computation. The physical implementation of quantum information processors is poised to benefit from chemistry-related advances starting from surface science, nanoscale control and spectroscopy. The understanding of chemistry, on the other hand, benefits from the promise of scalable, efficient quantum simulation of chemical systems enabled by quantum simulators and full-blown quantum computers.
Professors Michael Wasielewski (Northwestern University) and Alan Aspuru-Guzik (Harvard University) are organizing a workshop that brings together a representative sample of the leading researchers working on the topic of quantum information and quantum computing. Through a series of discussions, the workshop participants develop deep perspectives on the challenges and opportunities for Chemistry in the field of quantum information science and technology in a timescale of five to ten years. The participating researchers are a mixture of theoreticians and experimentalists with a variety of backgrounds. The long term goal of this workshop is to develop a new subfield of chemistry at the interface of the core of the discipline with the emerging fields of quantum information and quantum computation. The outcomes of the workshop will be disseminated to the scientific community via a workshop report.
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0.915 |
2016 — 2019 |
Wasielewski, Michael |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Spin Dynamics of Photogenerated Multi-Spin Systems @ Northwestern University
In this project, funded by the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Professor Michael R. Wasielewski of the Department of Chemistry at Northwestern University is developing new molecules with controllable spin transport properties. These molecules target new information processing strategies and take advantage of the quantum nature of electron spin. This work may lead to advanced computer technologies with broad applications throughout society. The use of organic materials and bio-inspired approaches to achieve this goal offers the possibility of developing new structures that are not only versatile, but are cost effective and environmentally benign as well. The group has an ongoing relationship with local middle and high schools through a partnership with the Office of STEM Education Partnership (OSEP) at Northwestern University. Working with OSEP, they are developing educational materials useful in teaching and for incorporating research into learning and education. Additionally, regular 1-2 day professional development workshops are held and week-long job shadowing experiences for teachers are implemented to provide a multiplier effect in connecting students to the rich learning resources at Northwestern University.
Fast photo-initiated electron transfer within covalently-linked organic donor-acceptor molecules having specific donor-acceptor distances and orientations results in the formation of spin-correlated radical pairs (SCRPs) having well-defined initial spin configurations and magnetic interactions. Time-resolved electron paramagnetic resonance (EPR) and pulse-EPR spectroscopy are used to manipulate, control, and observe these coherent spin states. This new research investigates how spin sharing over multiple radical sites influences coherence dephasing in SCRPs; how electron transfer from a photo-excited stable radical to a distant site affects spin coherence; how coherent spin states can be propagated over long intramolecular distances using SCRPs; and how a photo-generated SCRP can produce transient spin frustration and propagate spin coherence within a three-fold symmetric molecular system. The project lies at the interface of organic, physical, and materials chemistry, and is therefore well suited to the education of scientists at all levels. This group is also well-positioned to provide the highest level of education and training for students underrepresented in science. Outreach activities involving K-12 students and their teachers are part of the project.
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0.915 |
2017 — 2020 |
Wasielewski, Michael Young, Ryan (co-PI) [⬀] |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Quantum Interference and Coherence Effects On Charge Transport in Organic Semiconductors @ Northwestern University
Nontechnical description: This project addresses preparation and investigation of new materials made of organic molecules possessing electronic properties that enhance the performance of semiconductors. These electronic properties determine how electrons flow along multiple possible pathways in the semiconductor, and therefore are anticipated to affect the material's behavior. Optical probe techniques utilizing ultra-fast lasers are implemented to understand the details of electronic charge transport in semiconductors comprising these new organic molecules. Such semiconductors may be utilized to significantly enhance the performance of ultra-fast optical or electronic devices that are at the core of communications and information technologies. These inexpensive materials, while attractive for implementing improvements to device performance, may therefore also have major impact on the economy. This project encompasses a wide variety of disciplines in materials science, offering training opportunities to scientists at all academic levels. Outreach plans further include ongoing efforts at Northwestern University to integrate students in grades K-12 in educational activities.
Technical description: Photo-initiated charge transfer events in organic semiconductors can occur over a very large range of timescales. However, the uniquely quantum mechanical aspect of electronic coherence generally persists for only 10s to 100s of femtoseconds (fs). This project designs and synthesizes new organic semiconductors to more easily detect and exploit these electronic coherences, and to investigate how the consequences of coherent charge transfer can be used to enhance charge generation and transport in organic semiconductors. Femtosecond time-resolved spectroscopies are used to study the charge transport dynamics at the earliest stages, where the influence of electronic coherences is manifest. More specifically, this project is investigating how coherent charge transfer from a donor to two or more electron acceptors occurs within molecular building blocks of organic semiconductors. Separately, the project investigates coherent charge transfer in thin solid films of organic semiconductors. Additionally, the influence of quantum interference in multi-path charge transfer processes on the rate and efficiency of electron-hole pair production in organic semiconductors is addressed. The ability to tailor the design and performance of organic semiconductors via quantum coherence effects is anticipated to enhance semiconductor device performance, therefore impacting electronic and photonic devices commonly used in modern communications and information technologies.
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0.915 |
2019 — 2022 |
Wasielewski, Michael |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Hyperpolarized Multi-Spin Systems as Qubits For Quantum Information Science @ Northwestern University
In this project, funded by the Chemical Structure, Dynamics, and Mechanisms-B Program of the Chemistry Division, Professor Michael R. Wasielewski of the Department of Chemistry at Northwestern University is developing a fundamental understanding of how to control charge and spin transport through organic molecules. Such control is critical to the future of electronics, computers, and quantum information science (QIS). The degree of control over molecular structure and properties afforded by this research makes it possible to develop molecules and materials that take advantage of electron spin changes to implement new strategies for computer of the future that may have speeds and encryption technologies far beyond the current models. The Wasielewski research group volunteers in the Science In The Classroom program (SITC), with 3rd/4th-graders at an elementary school in an historically under-served and diverse community in Chicago. Approximately one third of the classes served by SITC are multilingual, and learn English as a second language alongside the regular curriculum. By volunteering with the same class of students for the academic year, Northwestern students mentor and inspire young scientists. The research team also participates in the program "Letters to a Pre-Scientist" which focuses on creating personal connections between middle school students from underprivileged schools and scientists to encourage the younger students to consider science as a career by writing letters as a pen pals.
Photogenerated molecular excited states and electron transfer reactions are playing an increasing role in quantum information science (QIS). This project will address several goals based on what are known in the QIS field as the DiVincenzo criteria, which are essential for exploiting multi-radical assemblies as spin qubits that target QIS applications. Professor Wasielewski and his group use two spin-selective photophysical processes to hyperpolarize electron spins to generate well-defined initial quantum states of spin qubits and determine the dephasing mechanisms of the spin qubits. The team then manipulates and addresses specific spin qubits to demonstrate quantum gates and uses both microwave and visible photon pulses to move (teleport) spin coherences between two sites. Finally, the team establishes strategies for scalable spin qubit arrays based on DNA hairpin structures. They use laser excitation to generate the initial hyperpolarized spin qubits and time-resolved pulse electron paramagnetic resonance (pulse-EPR) spectroscopy to observe, manipulate and control the coherent spin states of these qubits.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
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0.915 |
2020 — 2023 |
Wasielewski, Michael Young, Ryan (co-PI) [⬀] |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Quantum Coherence Effects On Charge Generation in Organic Semiconductors @ Northwestern University
A fundamental understanding of energy and charge transfer processes in organic semiconductors is critical to the development of versatile next-generation photonic and electronic technologies, such as light-emitting diodes, photovoltaics, and sensors. Coherence is a phenomenon resulting from the quantum nature of semiconductors that plays an important role in determining energy and charge migration pathways within these materials and thus influences device performance. However, the role of coherence in charge transfer remains underexplored. This project is investigating how coherences involving molecular vibrations assist charge generation following light absorption by organic semiconductors. The graduate student participants in this project are being educated using an integrated approach that trains them to be problem solvers. The students are being taught to prepare complex materials and at the same time are learning the physical techniques necessary to answer the questions addressed by their research. This approach is very effective in developing the kind of intellectual flexibility necessary to meet the rapidly changing roles of scientists in society. This project also engages the broader community through outreach to elementary schools through to the collegiate level to educate and inspire the next generation of scientists.
Organic semiconductors suitable for photonic device applications must be designed for ultrafast photo-driven electron-hole pair formation and subsequent rapid charge transport over long distances. Many such materials are based on electron donor-acceptor molecular components, such that optimizing the performance of organic semiconductors requires a fundamental understanding of the microscopic aspects of charge transfer in donor-acceptor systems at the quantum mechanical level. The primary goal of this project is to investigate whether vibrational and/or vibronic coherences assist symmetry-breaking charge generation following photoexcitation of organic semiconductors. The secondary goals of the project are to investigate 1) whether higher-order polygonal structures in solids, i.e. tilings and tessellations, lead to coherences that assist charge separation in organic semiconductors, and 2) whether excitonic coherences resulting from energy transfer processes in organic semiconductors influence subsequent charge transfer within them. While charge transfer is inherently quantum mechanical, many of the salient features of electron transfer kinetics have been treated classically. However, these treatments largely ignore the role of quantum coherences between states as they are typically very short lived (~10-100 fs for electronic states, up to several ps for vibrational/vibronic states) and as such are assumed to have decayed prior to electron transfer. However, with increasingly advanced spectroscopic techniques and improvements in time resolution, it is now possible to probe these processes on the requisite timescales and observe these coherences and their effects directly, which will aid in the design of high-performance organic semiconductors.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
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0.915 |