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Layered materials exhibit unique charge and energy transfer characteristics, making them promising candidates for emerging photophysical and photochemical applications, and particularly in energy conversion and quantum information science. In two-dimensional systems, spatial confinement in a certain dimension causes reduced dielectric screening and enhanced Coulomb interaction compared to bulk materials. Upon light excitation, the relaxation processes of the charge and energy carriers, as well as their rearrangement in the lateral plane, allow for unique and structure-specific interaction dynamics of the electrons and holes in these systems and of their bound states - neutral and charged excitons. In particular, these dimensionality effects induce strong exciton-electron and exciton-hole interactions in doped or gated systems, where optical excitations coexist alongside electronic excitations. These interactions dominate the exciton decay and diffusion and introduce bound three-particle states in such systems. A many-particle theoretical picture of the formation and propagation of these states is crucial for proper tracking and understanding of the interaction pathways, crystal momentum effects, the involved particle-particle coupling and their relation to the underlying structure, dimensionality, and symmetry.

"Molecules in a Quantum-Optical Flask" When confined to small dimensions, the interaction between light and matter can be enhanced up to the point where it overcomes all the incoherent, dissipative processes. In this "strong coupling" regime the photons and the material start to behave as a single entity, having its own quantum states and energy levels. In this talk I will discuss how such cavity-QED effects can be used in order to control material properties and molecular processes. This includes, for example, modifying photochemical reactions [1], enhancing excitonic transport up to ballistic motion close to the light-speed [2-3] and potentially tailoring the mesoscopic properties of organic crystals, by hybridizing intermolecular vibrations with electromagnetic THz fields [4-5]. 1. J. A. Hutchison, T. Schwartz, C. Genet, E. Devaux, and T. W. Ebbesen, "Modifying Chemical Landscapes by Coupling to Vacuum Fields," Angew. Chemie Int. Ed. 51, 1592 (2012). 2. G. G. Rozenman, K. Akulov, A. Golombek, and T. Schwartz, "Long-Range Transport of Organic Exciton-Polaritons Revealed by Ultrafast Microscopy," ACS Photonics 5, 105 (2018). 3. M. Balasubrahmaniyam, A. Simkovich, A. Golombek, G. Ankonina, and T. Schwartz, "Unveiling the mixed nature of polaritonic transport: From enhanced diffusion to ballistic motion approaching the speed of light," arXiv:2205.06683 (2022). 4. R. Damari, O. Weinberg, D. Krotkov, N. Demina, K. Akulov, A. Golombek, T. Schwartz, and S. Fleischer, "Strong coupling of collective intermolecular vibrations in organic materials at terahertz frequencies," Nat. Commun. 10, 3248 (2019). 5. M. Kaeek, R. Damari, M. Roth, S. Fleischer, and T. Schwartz, "Strong Coupling in a Self-Coupled Terahertz Photonic Crystal," ACS Photonics 8, 1881 (2021).

Ice melts at 0 [˚C], however, water can be super-cooled homogeneously down to ~-40 [˚C] without freezing. The ability to control the temperature of freezing of super-cooled water is highly important in many scientific sub-fields. Freezing can be induced at higher temperatures by the application of electric fields (known as electro-freezing). Despite the importance of the process of electro-freezing, its mechanism at the molecular level is still not fully understood. Recently, icing experiments performed by our group have demonstrated that electro-freezing comprises of the interactions of an electric field with specific ions of trigonal planar configuration, creating arm-chair hexagons that mimic the hexagons of the crystal ice. In my research, I investigated the effect of electro-freezing of super-cooled water on silver and copper electrodes. I found that the mechanism of electro-freezing of super-cooled water as induced by the silver electrodes is very complex and irreproducible. In contrast, the high icing temperature (~-4 [˚C]) on the copper (111) face is induced primarily by a mechanism of epitaxy.

Self-assembly of inorganic nanoparticles (NPs) into ordered structures has led to a wide range of materials with unique optical, electronic, and catalytic properties. Various interactions have been employed to direct the crystallization of NPs, including van der Waals forces, hydrogen bonding, and magnetic dipolar interactions. Among them, Coulombic interactions have remained largely unexplored, owing to the rapid charge exchange between spherical NPs bearing high densities of opposite charges (superionic NPs). In this talk, I will describe a new method to assemble superionic NPs under conditions that preserve their native surface charge density. Our methodology was used to assemble oppositely charged NPs (“spherical polyelectrolytes”) into highly ordered assemblies exhibiting previously unknown morphologies.

Inorganic semiconductor nanomaterials have been under extensive research for the last few decades for their fascinating optical and electronic properties. Our group demonstrated the guided growth approach for planar semiconductor nanowires (NWs), by taking advantage of the epitaxial relations between the substrate and the inorganic overlayer. Epitaxy enables one to control crystallographic orientation, growth directions, and properties of the nanostructures. Among the inorganic semiconductors, the family of chiral inorganic semiconductor nanomaterials has recently become a focal point of many studies owing to their unique behavior in condensed matter physics and their potential in spintronics and circularly polarized optoelectronics for information technology. Despite the extensive studies on the enantioselective growth of chiral crystals induced by chiral molecules, “chiral epitaxy”, namely the enantioselective growth of chiral crystals by epitaxy on chiral crystal surfaces has not yet been demonstrated. Here, we explore the interaction between intrinsically chiral inorganic semiconductor nanomaterials and various chiral and asymmetric surfaces. In one chapter, we demonstrate the enantioselective guided growth of Te NWs on a chiral plane of ReSe2. In order to determine the handedness of the NWs and the substrate, we made special modifications to a known handedness-determination STEM method, which allowed us to analyze both Te and ReSe2 structures. To the best of our knowledge, this is not just the first guided growth of Te on ReSe2, but it is also the first demonstration of enantioselective crystallization of a chiral crystal induced by its epitaxial relations with a chiral surface of a different crystal. Namely, this is the first demonstration of chiral epitaxy. In the second chapter, we study the guided growth of the chiral wide-bandgap semiconductor α-TeO2 along the asymmetric nanogrooves of annealed M-plane sapphire (α-Al2O3). The NWs show both straight and helical morphologies depending on their crystallographic orientation. This is the first demonstration of the guided growth of TeO2 NWs. In addition, this system demonstrates the formation of helical nanostructures with coherent handedness, controlled by interaction with an asymmetric substrate. All the NWs were characterized with SEM, AFM, TEM, EDS, and Raman spectroscopy. Overall, this work presents a new approach for enantioselective growth of chiral nanocrystals based on epitaxy. This gas-phase process should be suitable for a wide range of inorganic nanomaterials, and compatible with fabrication processes for integration into functional devices.

The need for affordable large scale energy storage has risen dramatically with the increase in usage of renewable energy sources. In recent years, beyond Li batteries such as Na ion batteries (SIB), gained much interest due to limited Lithium resources. However, SIBs are still far from meeting the demands in terms of electrochemical performance, rendering research on SIBs very important. During battery cycling, chemical and electrochemical processes result in the formation of an interphase between the anode and electrolyte called the solid electrolyte interphase (SEI). The effect of the SEI on electrochemical performance cannot be overstated, as its composition and structure dictate interfacial ionic transport in the battery cell. Since the SEI is very thin (10-50 nm) and is composed of disordered, organic, and inorganic phases it is extremely difficult to characterize at the atomic-molecular level. In this seminar I will present methodology developed for probing the native SEI formed in SIBs by using nuclear magnetic resonance (NMR) and signal enhanced NMR by exogenous and endogenous dynamic nuclear polarization (DNP). Employing these techniques enabled us to gain information on the chemical composition of the SEI together with important insights into the SEI’s structural gradient formed with different Na electrolytes. Correlating the compositional and structural information acquired with the SEI’s function can assist in designing SIBs with improved performance and longer lifetime.

The two natural allotropes of carbon, diamond and graphite, are extended networks of sp3- and sp2- hybridized carbon atoms, respectively. By mixing different hybridizations and geometries of carbon, one could conceptually construct countless synthetic allotropes. In this talk, I will introduce graphullerene, a new two-dimensional superatomic allotrope of carbon combining three- and four-coordinate carbon atoms. The constituent subunits of graphullerene are C60 fullerenes that are covalently interconnected within a molecular layer, forming graphene-like hexagonal sheets. The most remarkable thing about the synthesis of graphullerene is that the solid-state reaction produces large polyhedral crystals (hundreds of micrometers in lateral dimensions), rather than an amorphous or microcrystalline powder as one would typically expect from polymerization chemistry. Similar to graphite, the crystals can be mechanically exfoliated to produce molecularly thin flakes with clean interfaces—a critical requirement for the creation of heterostructures and optoelectronic devices. We find that polymerizing the fullerenes leads to a large change in the electronic structure of C60 and the vibrational scattering mechanisms affecting thermal transport. Furthermore, imaging few-layer graphullerene flakes using transmission electron microscopy and near-field nano-photoluminescence spectroscopy reveals the existence of moiré-like superlattices. The discovery of a superatomic cousin of graphene demonstrates that there is an entire family of higher and lower dimensional forms of carbon that may be chemically prepared from molecular precursors.

Creation of reconfigurable and multi-functional materials can be achieved by incorporating architecture into material design. In our research, we design and fabricate three-dimensional (3D) nano-architected materials that can exhibit superior and often tunable thermal, photonic, electrochemical, biochemical, and mechanical properties at extremely low mass densities (lighter than aerogels), which renders them useful and enabling in technological applications. Dominant properties of such meta-materials are driven by their multi-scale nature: from characteristic material microstructure (atoms) to individual constituents (nanometers) to structural components (microns) to overall architectures (millimeters and above). Our research is focused on fabrication and synthesis of nano- and micro-architected materials using 3D lithography, nanofabrication, and additive manufacturing (AM) techniques, as well as on investigating their mechanical, biochemical, electrochemical, electromechanical, and thermal properties as a function of architecture, constituent materials, and microstructural detail. Additive manufacturing (AM) represents a set of processes that fabricate complex 3D structures using a layer-by-layer approach, with some advanced methods attaining nanometer resolution and the creation of unique, multifunctional materials and shapes derived from a photoinitiation-based chemical reaction of custom-synthesized resins and thermal post-processing. A type of AM, vat polymerization, has allowed for using hydrogels as precursors, and exploiting novel material properties, especially those that arise at the nano-scale and do not occur in conventional materials. The focus of this talk is on additive manufacturing via vat polymerization and function-containing chemical synthesis to create 3D nano- and micro-architected metals, ceramics, multifunctional metal oxides (nano-photonics, photocatalytic, piezoelectric, etc.), and metal-containing polymer complexes, etc., as well as demonstrate their potential in some real-use biomedical, protective, and sensing applications. I will describe how the choice of architecture, material, and external stimulus can elicit stimulus-responsive, reconfigurable, and multifunctional response

Accumulating work points out relevant genes and signaling pathways hampered in human disorders as potential candidates for therapeutics. Developing nucleic acid-based tools to manipulate gene expression, such as siRNAs, mRNA and genome editing strategies, open up opportunities for personalized medicine. Yet, although major progress was achieved in developing RNA targeted delivery carriers, mainly by utilizing monoclonal antibodies (mAbs) for targeting, their clinical translation has not occurred. In part because of massive development and production requirements and high batch-to-batch variability of current technologies, which relies on chemical conjugation. Here we present a self-assembled modular platform that enables to construct theoretically unlimited repertoire of RNA targeted carriers. The platform self-assembly is based on a membrane-anchored lipoprotein, incorporated into RNA-loaded novel, unique lipid nanoparticles that interact with the antibody Fc domain. We show that a simple switch of 8 different mAbs, redirects specific uptake of siRNAs by diverse leukocyte subsets in vivo. The platform therapeutic potential is demonstrated in an inflammatory bowel disease model, by targeting colon macrophages to reduce inflammatory symptoms, and in Mantle Cell Lymphoma xenograft model, by targeting cancer cells to induce cell death and improve survival. In addition, I will discuss novel approach for delivering modified mRNA to specific cell types in vivo utilizing this platform. I will also share some data on mRNA vaccines for COVID19 and Finally, I will share new data showing very high efficiency genome editing in glioma and metastatic ovarian cancer. This modular delivery platform can serve as a milestone in turning precision medicine feasible.

In this lecture, the theoretical and technical base for atomic imaging of defects in inorganic 2D materials in the low-voltage transmission electron microscope SALVE will be discussed. Atomic defects can significantly change the properties of the material: Using 2D-TMDs and 2D-TMPTs and corresponding heterostructures, this is shown experimentally and verified by corresponding quantum mechanical calculations. We also use the electron beam for the targeted formation of new phases in the inorganic 2D matrix. Since the interaction cross-sections of electron beam and organic 2D materials differ strongly from the inorganic case, we explore highest-resolution imaging conditions for 2D polymers and various 2D MOFs and show that there is a trend towards lower voltage TEM as well. We may conclude that low-voltage TEM and low-dimensional materials are just made for each other.

Electrostatic interactions between polyelectrolyte (PE) charges and dissociated counterions provide PEs with intriguing properties and significantly determine their conformation and dynamics. This research shows how weak PE chains form a global network when they are oppositely charged and how strong electric fields lead to orientational order. The development of controlled drug release and responsive structures is demonstrated by the use of ordered PE with tunable intermolecular interactions.

Neurodegenerative diseases are often clinically, genetically, and pathologically heterogeneous. The clinical impact of understanding heterogeneity is perhaps best observed in cancer, where subtype-specificity within diagnoses, prognoses, and treatments have had a critical impact on clinical decision making and patient outcomes. A better understanding of how mechanisms are related to or drive heterogeneity within diseases such as Amyotrophic Lateral Sclerosis (ALS), will have a direct impact on patient outcomes, with a conscious effort to move towards precision medicine and targeted therapeutics for patients, which are urgently needed. For this reason, neuroscientists and oncologists have long aspired to achieve an understanding of the mechanisms governing pathophysiology. Our interdisciplinary work integrates technologies across a wide range of fields to surpass the current barriers in understanding disease pathophysiology. This talk will highlight a series of optical and photoacoustic imaging tools as well as multi-omics analysis that have been developed and studied in Dr. Smith’s lab to address the urgent need for non-invasive cancer detection and the characterization of neurological disorders. Through this work, we aim to develop translational technologies and methodologies to better characterize, understand, and detect disease pathogenesis, beyond current capabilities.

High-Performance, Rechargeable Li-ion Batteries (LIBs) are key to the global transition from fossil fuels to renewable energy sources. LIBs utilizing lithium metal as the anode are particularly exciting due to their exceptional energy density and redox potential, yet their advancement is hindered by growth of metallic filaments and unstable surface layers. Efficient cationic transport, which is crucial for battery performance, largely depends on the heterogeneous and disordered interphase formed between the anode and the electrolyte during cycling. Directly observing this interphase as well as the dynamic processes involving it is a great challenge. Here we present an approach to elucidate these dynamic processes and correlate them with the corresponding interfacial chemistry, focusing on the first step of cationic transport: surface adsorption. Employing Dark State Exchange Saturation Transfer (DEST) by 7Li NMR, we were able to detect the exchange of Li-ions between the homogenous electrolyte and the heterogeneous surface layer, highlighting the hidden interface between the liquid and solid environments. This enabled determination of the kinetic and energetic binding properties of different surface chemistries, advancing our understanding of cationic transport mechanisms in Li-ion batteries. 

Neuromorphic computing designs have an important role in the modern ‘big data’ era, as they are suitable for processing large amount of information in short time, eliminating the von Neumann (VN) bottleneck. The neuromorphic hardware, taking its inspiration from the human brain, is designed to be used for artificial intelligence tasks via physical neural networks, such as speech or image recognition, bioinformatics, visual art processing and much more. The memristor (memory + resistor), is one of the promising building blocks for this hardware, as it mimics the behavior of a human synapse, and can be used as an analog non-volatile memory. The memristor has been proven as a viable memory element and has been used for constructing resistive random access memory (RRAM) as a replacement for current VN hardware. However, the mechanism of operation and the conducting bridge formation mechanisms in electrochemical metallization memristors still require further investigation. A planar single-nanowire (NW) based memristor is a good solution for elucidating the mechanism of operation, thanks to the high localization of switching events, allowing in-situ investigation as well as post-process analysis. Our group, which has developed the guided-growth approach to grow guided planar NWs on different substrates, has used this method to integrate guided epitaxial NWs into functional devices such as field-effect transistors (FETs), photodetectors and even address decoders. However, the guided-growth approach has not been used for creating memristors up to date. In this work, I successfully synthesized guided NWs of two metal-oxides on flat and faceted sapphire substrates – ZnO and β-Ga2O3 were successfully grown in the VLS mechanism as surface guided NWs. I successfully grew planar guided β-Ga2O3 NWs on six different sapphire substrates, for the first time as far as we know. We characterized the newly grown β-Ga2O3 NWs with SEM, TEM, EDS and Raman spectroscopy. The monoclinic NWs grew along surprising directions on the flat sapphire surfaces and I demonstrated a new mode of growth – epitaxy favored growth on a faceted surface, when graphoepitaxy is also possible. I created electrochemical metallization memristors with the obtained NWs and successfully demonstrated the effect of resistive switching for β-Ga2O3 guided NW based devices. With the abovementioned achievements, we expanded the guided-growth approach on flat and faceted sapphire surfaces, and opened the opportunity for creating surface guided-NW based neuromorphic hardware.

From a perovskite photovoltaic device standpoint, the Al2O3 ALD can be thought of as a thin film encapsulate to protect the underlined material from the extrinsic entities. However, as per the literature is concerned, the role of Al2O3 ALD in the perovskite photovoltaic devices is much beyond a mare passive component. This raises a severe ambiguity over the choice of surface (or interface) on which ALD needs to be done for optimized device performance, in terms of the device efficiency and stability. In my presentation, I would like to elucidate the characteristic differences between the surface limited and substrate enhanced ALD processes which is important to perovskite devices. The objective here is to discuss a unified correlation between the role of the Al2O3 ALD mechanism with the perovskite device performance by excluding popular overestimated assumption about the conformality on non-ideal surface, like perovskite or organic thin films. In addition, I would like to emphasize on the fact that how the ALD process can be used to passivate the buried interfacial defect and enhancing the VOC, PL and ELQE.

Not a day goes by when we don’t hear about the “climate crisis”; some effects are well documented, like the rise in the average global temperature and the shrinking of the polar ice caps. Undoubtedly, carbon dioxide levels in the atmosphere have been increasing, but what does “science” say about the potential consequences? The combination of the atmosphere, oceans, cryosphere and biosphere is the ultimate non-linear coupled complex system. How well do we understand what might happen? In the first part of my talk, I shall review my exploration of the original literature to try and separate out speculation, hypothesis, results of computational models, and most significantly actual observations. In the second part of my talk, I shall discuss what will actually work to reduce carbon dioxide emissions (complete elimination or Net Zero is an impossibility). Although it has become fashionable for governments to impose mandates enshrined in laws, the only laws that matter are the laws of thermodynamics and Ohm’s law.

Aromatic dichalcogenides exhibits a rich reductive and oxidative redox chemistry and the one and two electron reductions and oxidations of such Ar2Ch2 species appears at rather mild potentials. The successive 1e–-reductions often have very similar potentials as the one electron process results in the formation of an odd-electron bond, which stabilizes the radical anion, for example in hypothetical Ph2S2•− by about 30 kcal/mol. Inspired by the natural dithiol/disulfide 2H+/2e− couple, we investigated a 2,2′-bipyridine that is equipped with a disulfide/dithiolate unit in the backbone for storing multiple electrons and protons.[2] The synchronized transfer of electrons and protons is a critical step in many chemical and biological transformations. In particular, hydride and H atom transfer reactions are important in, for example, catalytic hydrogenation or small molecule activation reactions relevant to renewable energy storage. We examined in depth the fundamental 2e–, 2e–/2H+ and 1e–/H+ reactivity of the switch depending on the metalation. It appears that the Re compound overcomes the drawback of many metal-free hydride donors, which show a large gap between the first and second reduction process, and detrimental side reactions of the radical intermediate. Furthermore, we applied such Ar2Se2 in the anodic amination and esterification of nonactivated alkenes. Amination and esterfication reactions are of considerable importance since C–N and C–O bond motifs can be found in numerous organic compounds associated with biological, pharmaceutical, or material scientific applications. We developed versatile protocols for the electrochemical functionalization and a detailed kinetic and thermodynamic analysis gave valuable insights into the mechanism of the reaction as well as the impact of, e.g. solvent, additives, on the organocatalysis.

Somitogenesis, the segmentation of the antero-posterior axis in vertebrates, is thought to result from the interactions between a genetic oscillator and a posterior-moving determination wavefront. I will introduce the current state of knowledge of that important stage in the development of vertebrate embryos. Surprisingly while the oscillator period is very sensitive to temperature changes, the size of the segments is not. I shall describe our results pertaining to the importance of the decrease in time of the Fgf8 gradient on the propagation of the wavefront and the observation that the somitogenetic period, embryo growth rate, PSM shortening rate and Fgf8 decay rate all slow down as 1/(T-Tc) with Tc=14.4°C, suggesting that critical slowing may affect the embryo metabolism resulting in a natural compensation of thermal effects on somite size.

https://weizmann.zoom.us/j/97641167767?pwd=YURCbjI5VjdJZ2hmWXAwMTVCS1p3UT09 Nearly 100 years ago, Jones and Dole experimentally pointed out a puzzle associated with the incremental modification of the bulk viscosity of water induced by small concentrations of salt. The strange behavior relates to cation specificity. This puzzle remains unsolved. This talk will remind you about this problem and suggest a possible approach. I hope that I can engender some ideas from you.

The successes and failures of approximate density functionals are due to their connection with semiclassical expansions. In the semiclassical limit, relative errors in local density approximations vanish. Carefully derived corrections to that limit have been shown to be far more accurate than our usual DFT approximations. I will discuss important new results in our 20-year-long quest to derive density functional approximations as expansions in hbar. These include both a new correction to the expansion of the exchange energy of atoms and an orbital-free calculation with sub-milli-Hartree accuracy. [1] Semiclassical Origins of Density Functionals Elliott, Peter, Lee, Donghyung, Cangi, Attila and Kieron Burke, Phys. Rev. Lett. 100, 256406 (2008). [2] Leading correction to the local density approximation for exchange in large-Z atoms Nathan Argaman, Jeremy Redd, Antonio C. Cancio, and Kieron Burke, Phys. Rev. Lett. 129, 153001 (2022). [3] Orbital-free functional with sub-milliHartree accuracy, Pavel Okun and Kieron Burke, in preparation.

Heterostructures (HS) of two-dimensional materials offer unlimited possibilities to design new materials for applications to optoelectronics and photonics. In such HS the electronic structure of the individual layers is well retained because of the weak interlayer van der Waals coupling. Nevertheless, new physical properties and functionalities arise beyond those of their constituent blocks, depending on the type and the stacking sequence of layers. In this presentation we use high time resolution ultrafast transient absorption (TA) and two-dimensional electronic spectroscopy (2DES) to resolve the interlayer charge scattering processes in HS. We first study a WSe2/MoSe2 HS, which displays type II band alignment with a staggered gap, where the valence band maximum and the conduction band minimum are in the same layer. By two-colour pump-probe spectroscopy, we selectively photogenerate intralayer excitons in MoSe2 and observe hole injection in WSe2 on the sub-picosecond timescale, leading to the formation of interlayer excitons (ILX). The temperature dependence of the build-up and decay of interlayer excitons provide insights into the layer coupling mechanisms [1]. By tuning into the ILX emission band, we observe a signal which grows in on a 400 fs timescale, significantly slower than the interlayer charge transfer process. This suggests that photoexcited carriers are not instantaneously converted into the ILX following interlayer scattering, but that rather an intermediate scattering processes take place We then perform 2DES, a method with both high frequency and temporal resolution, on a large-area WS2/MoS2 HS where we unambiguously time resolve both interlayer hole and electron transfer with 34 ± 14 and 69 ± 9 fs time constants, respectively [2]. We simultaneously resolve additional optoelectronic processes including band gap renormalization and intralayer exciton coupling. Finally, we investigate a graphene/WS2 HS where, for excitation well below the bandgap of WS2, we observe the characteristic signal of the A and B excitons of WS2, indicating ultrafast charge transfer from graphene to the semiconductor [3]. The nonlinear excitation fluence dependence of the TA signal reveals that the underlying mechanism is hot electron/hole transfer, whereby a tail the hot Fermi-Dirac carrier distribution in graphene tunnels through the Schottky barrier. Hot electron transfer is promising for the development of broadband and efficient low-dimensional photodetectors. [1] Z. Wang et al., Nano Lett. 21, 2165–2173 (2021). [2] V. Policht et al., Nano Lett. 21, 4738–4743 (2021). [3] C. Trovatello et al., npj 2D Mater Appl 6, 24 (2022).

Canceled

Transition metal catalyzed carbonylation reactions of a wide range of organic compounds provide entry to some molecules of value to the pharmaceutical, commodity, and petrochemical industries. Examples to be presented include the preparation of indolizine derivatives by palladium-catalyzed oxidative alkoxycarbonylation, the synthesis of N-fused heterocycles via dearomatic carbonylation, the highly regioselective and chemoselective carbonylation of bifunctional organic reactants with haloarenes, styrenes, and alkynes. These transformations were successfully applied to the synthesis of natural products including Avenanthramide A

Catalysis is a general process that speeds up the reaction rate without altering the process thermodynamics. It is often essential to study the kinetics of the reaction to infer the mechanism of catalysis, an insight that can help in catalyst design. However, bulk catalysis, and specifically electrocatalysis, cannot capture the inherent heterogeneity of seemingly identical catalysts. This talk aims to provide basic principles behind electrocatalysis and introduce a new way to study electrocatalysts at the single entity level. Together, we will review the latest progress in the field and conclude with future directions that can be applied to the vast majority of catalysts ranging from organic, bio, and inorganic materials.

Functional materials are the main building blocks of advanced technologies based on energy storage and conversion systems essential for our modern life including batteries, solar cells, and heterogeneous catalysis. Improvements in materials performance and development of new materials rely on our ability to obtain structure-function correlation as well as understand degradation processes when the materials are integrated into a device. To this end, advanced analytical tools that can provide information at the atomic level are essential. Solid-state nuclear magnetic resonance (ssNMR) spectroscopy is well suited for this task, especially when equipped with high sensitivity by Magic Angle Spinning - Dynamic Nuclear Polarization (MAS-DNP). However, to date, the majority of materials studied by MAS-DNP were non-reactive and non-conductive materials with DNP from exogenous sources of polarization such as nitroxide radicals. This approach cannot be simply extended to functional materials as the properties that stem from the material’s functionality in the device, including electrical conductivity, chemical reactivity and defects, often pose challenges in the study of the materials by DNP. In this talk I will frame the challenges associated with the application of MAS-DNP to functional materials and describe approaches to address them. Results will be presented from three ubiquitous material systems spanning a range of applications: carbon allotropes, transition metal dichalcogenides (TMDs) and metallic microstructures. We systematically investigated the deleterious effect of materials’ conductivity and formulated means to reduce the effect. We explored the feasibility of utilizing inherent unpaired electrons for endogenous DNP and applied it to probe buried phases in all-solid-state lithium-metal battery and the surface chemistry in carbons. I will show that wealth of information achieved by DNP on various functional materials, can place DNP-NMR as a preferable tool for materials scientists. Our findings are expected to apply to many other systems where functional materials are dominant, making DNP a more general technique.

Colloidal nanocrystals possess high surface area-to-volume ratios; as a result, many nanocrystal properties are heavily influenced by their surfaces. At these surfaces exist a complex interface between the inorganic solid (governed by the crystal structure and particle morphology) and organic ligands. The organic ligands play a key role in controlling nucleation and growth, passivating under-coordinated surface sites, and providing steric stabilization for solvent dispersibility. Depending on the particular application of the nanocrystal, the native organic ligands may then need to be removed or exchanged. We use a complement of NMR spectroscopic techniques to understand the nature of the nanocrystal surface and ligand binding. Then, using principles of inorganic coordination chemistry, we rationally enact ligand exchange reactions on these surfaces to maximize nanocrystal functionality. This talk will briefly discuss the surface chemistry of three different platforms. (1) I will discuss how we experimentally developed an atomistic picture of perovskite nanocrystal surface termination, and then used that information to better understand how common surface treatments can “heal” halide perovskite nanocrystal surfaces. (2) I will discuss how different -donating, L-type ligands were installed on the surface of metal phosphide nanocrystals, and how they affected the hydrogen evolving ability of these electrocatalysts. (3) I will discuss a new strategy for thermally activating metal carbide nanocrystal CO2 reduction catalysts using labile ligands that decompose at significantly lower temperatures than the native ligands. This circumvents issues commonly encountered with high-temperature thermolysis (coking) or acid treatments (etching, poisoning) that are used to activate nanocrystal catalysts.

The development of advanced photovoltaic devices, including those that might overcome the single junction efficiency limit, as well as the development of new materials, all rely on advanced characterization methods. Among all the existing methods optically based ones are very well adapted to quantitatively probe optoelectronic properties at any stage. We here present the use of multidimensional imaging techniques that record spatially, spectrally and time resolved luminescence images. We will discuss the benefits (and challenges) of looking into energy conversion systems from high dimensions perspective and those of dimensional reduction for improved intelligibility through some examples, mostly drawn from halide perovskite materials and device. These examples will help visit questions related to efficient transport and conversion in solar cells, as well as questions related to chemical and operational stability of the devices.

This lecture presents an overview on major research work of the Fellow’s group in the areas of polymer nanoparticles for drug delivery, control of protein adsorption on materials surfaces and protein nanofibers. In addition, the new excellence graduate school (Research Training Group) RTG 2723: Materials‐Microbe‐Microenvironments: Antimicrobial biomaterials with tailored structures and properties (M‐M‐M) funded by the German Science Foundation will be introduced. Polymer nanoparticles (PNP) became recently exceedingly popular through novel vaccination technologies but have also major potential for fighting inflammation and cancer. These drug release properties of the PNP depend on their structure. Yet, the literature reports little about the structure and the properties of most PNPs, except the chemical composition. The PNP’s crystallinity, thermal and mechanical properties are frequently ignored, even though they may play a key role in the drug delivery properties of the PNPs. Protein adsorption on biomaterials is the first process after implantation and determines much of the fate of the biomaterial, such as cell adhesion, blood coagulation or infection at the implant site. Despite decades of research, only rules of thumb exist to predict protein adsorption behavior. We present nanotechnological approaches to control protein adsorption using nanostructured semicrystalline polymers and crystal facets of TiO2. Selfassembled protein nanofibers consisting of one or more proteins, potentially allow to tailor the properties of biomaterials interfaces and to create bone mimetic structures. Finally, the new DFG‐RTG 2723: Materials‐Microbe‐Microenvironments: Antimicrobial biomaterials with tailored structures and properties (M‐M‐M) in Jena will be introduced. The aim of the RTG is to provide excellent training for approximately 40 international doctoral researchers in antimicrobial biomaterials in interdisciplinary tandem projects, connecting materials science and medical science. The RTG pursues a new strategy by developing antibiotic free biomaterials, where the antimicrobial action is based mainly on physical principles. The new RTG offers ample opportunity for fruitful cooperation and exchange with leading research institutions in Israel.

This colloquium will be divided into two applications parts, dealing with synthesis of supported molecular catalysts and solid catalysts for photoprotection. In the first of these areas, we describe a mechanical approach for stabilizing supported weakly interacting active sites (i.e. those that interact non-covalently with the support) against aggregation and coalescence. We use silica as a prototypical example of a support, and an iridium pair-site catalyst incorporating bridging calixarene ligands as an active site. Atomic-resolution imaging of the Ir centers before and after ethylene-hydrogenation catalysis show the metals resisted aggregation and deactivation, remaining atomically dispersed and accessible for catalysis. When active sites are located at unconfined environments, the rate constants for ethylene hydrogenation are markedly lower compared with confining external-surface pockets [1], in line with prior observations of similar effects in olefin epoxidation catalysis [2,3]. Altogether, these examples represent new opportunities for enhancing reactivity on surfaces by synthetically controlling mechanical features of active site catalyst environments. In the second of these areas, reactive oxygen species (ROS) are associated with several human health pathologies and are invoked in the degradation of natural ecosystems as well as building materials that are used in modern infrastructure (e.g., paints and coatings, polymers, etc). Natural antioxidants such as vitamin E function as stoichiometric reductants (i.e. reaction with ROS synthesizes rancid oils). While enzymes such as superoxide dismutase working in tandem with catalase decompose decompose ROS to H2O and O2 through H2O2 as an intermediate, these enzymes are fragile and costly. Other non-stoichiometric commercial antioxidants that degrade ROS include hindered amine light stabilizers (HALS). Here, we demonstrate that cerium carbonate acts as a degradation catalyst for photogenerated ROS, and describe the performance and characterization of this new catalyst using X-ray photoelectron spectroscopy, and in comparison with HALS and stoichiometric reductants. Our results demonstrate catalytic antioxidant activity of cerium carbonate when dispersed in polymethylmethacrylate polymer. FTIR data demonstrate that a dispersion of 2 wt. % cerium carbonate within the polymer essentially stops degradation by photogenerated ROS, which otherwise cause oxidation of the polymer backbone, in the control polymer lacking cerium carbonate. Experiments with methylene blue dye in aqueous solution demonstrate that cerium carbonate decreases the rate of ROS degradation of dye, in the presence of UV irradiation and air by 16 fold. These effects become even more pronounced (over 600 fold decrease in rate of ROS dye degradation) when cerium carbonate is paired with a photoactive metal oxide. The mechanism involved in this latter case crudely mimics the enzyme tandem sequence referred to above. [1] C. Schöttle, E. Guan, A. Okrut, N. A. Grosso-Giordano, A. Palermo, A. Solovyov, B. C. Gates, A. Katz*, Journal of the American Chemical Society, J. Am. Chem. Soc. 2019, 141, 4010-4015. [2] N. A. Grosso-Giordano, C. Schroeder, A. Okrut, A. Solovyov, C. Schottle, W. Chasse, N. Marinkoyic, H. Koller, S. I. Zones, A. Katz, Journal of the American Chemical Society 2018, 140, 4956-4960. [3] N. A. Grosso-Giordano, A. S. Hoffman, A. Boubnov, D. W. Small, S. R. Bare, S. I. Zones, A. Katz, Journal of the American Chemical Society 2019, 141, 7090-7106. [4] M. K. Mishra, J. Callejas, M. Pacholski, J. Ciston, A. Okrut, A. Van Dyk, D. Barton, J. C. Bohling, A. Katz, ACS Applied Nano Materials 2021, 4, 11, 11590-11600.

https://weizmann.zoom.us/j/95467631640?pwd=MHZBNThNQlRUeU1CM29kQXZZcGxOdz09 password:864419 Solid oxide fuel cells (SOFCs), especially proton conducting (PC)-based, and electrolyzes (SOEs), operating above 250°C, demonstrate rapid electrode kinetics, but are limited in their long term stability due to thermal stresses related to on/off cycling. Thermal stress could be reduced dramatically, for PC-SOFCs devices operating in the temperature range of 150-250°C, which would still benefit from fast electrode kinetics and would not require Pt-containing catalytic electrodes. However, a proton-conducting ceramic electrolyte, operating below 250°C hasn’t been identified yet. In this work I investigated the synthesis, preparation protocols and properties of La(OH)_3 and La_2 Ce_2 O_7 (LCO50) powder and ceramics to explore their suitability as proton conductors. Preparation of appropriate pellet samples of La(OH)_3 from the synthesized powder requires (i) elimination of the presence of carbonate oxides followed by (ii) hydration of the remaining La2O3 in boiling deionized water. Room temperature compaction of these powders into solid pellet samples requires prolonged dwell uniaxial pressure. Although the primarily protonic conductivity of the compacted sample reached only 3·10-11 S/cm at 90°C and is insufficient for practical applications; the grain boundaries are apparently not blocking, making it attractive to look for dopants that may potentially enhance the low temperature conductivity. Nominally anhydrous LCO50 has an unexpectedly high conductivity 10-11 S/cm at 110 °C, which is probably due to oxygen vacancies. LCO50 undergoes hydration with a large lattice expansion, which combined with low hydration enthalpy (5.2 kJ/mol) restricted compact crack-free sample. Hydration of LCO50 by 7.5% of the maximum possible showed to have non-blocking grain boundaries, and increases the conductivity by an order of magnitude, which has to be attributed to protonic conduction. Findings describe in this work, point that both investigated materials are promising candidates for further studies as proton conductors.

Catalysis is a key technology, since it allows for increased levels of selectivity and efficacy of chemical transformations. While significant progress can be made by rational design or engineered step-by-step improvements, many pressing challenges in the field require the discovery of new and formerly unexpected results. Arguably, the question “How to discover?” is at the heart of the scientific process. In this talk, (smart) screening strategies for accelerated discovery and improved reproducibility will be presented, together with new photocatalytic transformations. In addition, two other exciting areas will be addressed: N-heterocyclic carbenes (NHCs) are powerful ligands in catalysis due to their strong electron-donating properties and their ability to form very stable bonds to transition metals. In addition, they can stabilize and modify nanoparticles or flat metals surfaces, outperforming established phosphine or thiol ligands regarding structural flexibility, electron-donating properties and stability. Current research is highly interdisciplinary and focusses on the basic understanding of the binding mode, mobility and the elucidation of the impact on the surface properties. Exciting applications in materials science, heterogeneous catalysts and beyond are within reach. Biological membranes and their constituents are some of the most important and fundamental building blocks of life. However, their exact role in many essential cellular processes as well as in the development of diseases such as cancer or Alzheimer's is still not very well understood. Thus, we design, synthesize and evaluate imidazolium-based lipid analogs that can integrate into biological membranes and can be used as probes for live cell imaging or to manipulate membranes.

Charge transfer and transport processes through molecular interfaces are ubiquitous and of a crucial role in determining functionality of biological systems and in enabling energy conversion applications. We study computationally such processes to understand structure-function relationships at the molecular level. We will discuss studies in the following two primary fields: (1) Photovoltaic and charge transfer properties of organic semiconductors materials. (2) Charge transport through voltage-biased molecular scale bridges. Importantly we establish predictive computational scheme that addresses key challenges. Our studies are employed in conjunction with experimental efforts to design materials and applications that control and tune relevant physical properties

Molecular crystals are supramolecules “par excellence"1 as they are macroscopic objects composed by millions of molecules periodically disposed and held together by non-covalent interactions with specific physico-chemical properties dictated by their architectures. This offers a vibrant solid-state chemistry playground to build organic solids with tailored functionalities, such as novel luminescent materials,2 solid-state molecular machines,3 and multicomponent crystals with complex topologies.4 The inherent dynamic nature of the weak intermolecular forces that are driving organic crystals self-assembly is also conferring adaptive responsiveness, e.g., mechanical reconfiguration and shape-memory effect, to this class of materials making them ideal building blocks for the design and synthesis of multifunctional crystalline systems that can be exploited as actuators, flexible single-crystalline optoelectronic devices, and self-healing materials.5

The studies of magnetic atoms adsorbed on non-magnetic surfaces provide a fundamental insights into the quantum many-body phenomena at the nanoscale. They imprint non-trivial signatures in STM measurements, and can serve as a prototype for potential applications in quantum information technology. Our work aims at the investigation of the electronic structure, spin and orbital magnetic character for the Co adatom on the top of Cu(100) surface. We make use of DFT combined with exact diagonalization of the multi-orbital Anderson impurity model, including the spin-orbit coupling. For the Co atom d-shell occupation nd=8, a singlet many-body ground state and Kondo resonance are found, when the spin-orbit coupling is included in the calculations. The differential conductance is evaluated in a good agreement with the STM measurements. This comparison is the most direct way to demonstrate the validity of our theoretical approximation. Our results illustrate the very essential role which the spin-orbit coupling is playing in a formation of Kondo singlet for the multi-orbital impurity in low dimensions.

Self-assembly and self-organization are two big challenges in the natural sciences. What are the rules governing the emergence of greater structures from unassuming elements? Does statistical-mechanics restrict their complexity? Biochemical processes can shape highly specific structures and function on the macro-scale using only molecular information. Although stereochemistry has been a central focus of molecular sciences since Pasteur, its synthetic province has been restricted to the nanometric scale. In my talk, I will describe how to propagate molecular information to self-assemble free-form architectures on the micron-scale and beyond. These architectures are a thousand times greater than their constituent molecules yet have a preprogrammed geometry and chirality. I will then show how to animate such synthetic microstructures into bacteria-like micro-swimmers. Previous artificial microswimmers relied on an external chemical fuel to drive their propulsion which restricted their operational concentration as they competed locally over fuel. I will demonstrate how to use material science and physical chemistry to self-assemble fuel-free micro-swimmers that are driven solely by light. The fuel independence allows the swimmers to stay active even at high densities, where they form turbulent flow structures (previously seen in living fluids), and cooperate to perform a greater task.

Zoom Link: https://weizmann.zoom.us/j/93495966390?pwd=T3hDNXY1WFh6bFpIbDh3OEFxZlcwZz09 The fibre-matrix interface plays a vital role in the overall mechanical behaviour of a fibre-reinforced composite, but the classical approach to improving the interface through chemical sizing is limited by material properties. Achieving a simultaneous improvement in strength and toughness in a composite is a particular challenge since these properties are mutually exclusive, and the chemical modification of the interface often results in one property being improved at the expense of the other. In contrast, the geometrical modification of the fibre-matrix interface to allow for mechanisms such as mechanical interlocking of components is a promising approach to resolving this challenge. This study explores a novel type of topographical obstacle – polymer droplets at the fibre-matrix interface. Discrete epoxy droplets are deposited onto glass fibres and embedded in an epoxy matrix to form model composites. The effect of the interfacial epoxy droplets is investigated using single fibre experiments.

Zoom Link: https://weizmann.zoom.us/j/99290579488?pwd=cUIyV05SMUQ0VDErNUtma1RTL3BIQT09 In the last decade, halide perovskites (HaPs) have developed as promising new materials for a wide range of optoelectronic applications, notably solar energy conversion. Although their technology has advanced rapidly towards high solar energy conversion efficiency and advantageous optoelectronic properties, many of their properties are still largely unknown from a basic scientific standpoint. Due to the highly dynamical nature of HaPs, one of the main avenues for basic science research is the use of molecular dynamics (MD) simulations, which provide a full atomistic picture of those materials. One of the main limiting factors for such analysis is the time scale of the MD simulation. Because of the complexity of the HaP system, classical force field approaches do not yield satisfactory results and the most widely used force calculation approach is based on first-principles, namely on density functional theory (DFT). In recent years, a new type of force calculation approach has emerged, which is machine learned force fields (MLFF). These methods are based on machine learning (ML) algorithms. Their wide spread use is enabled by the ever-increasing computational power and by the availability of large-scale shared repositories of scientific data. Here, we have applied one MLFF algorithm, known as domain machine learning (GDML). After training a MLFF based on the GDML model, we observed that the MLFF fails in a dynamical setting while still showing low testing error. This has been found to be due to lack of full coverage of the simulation phase space. To address this issue, we have suggested the hybrid temperature ensemble (HTE) approach, where we create rare events that are training samples on the edge of the phase space. We achieve this by combing MD trajectories from a range of temperatures to a single dataset. The MLFF model, trained on the HTE dataset, showed increasing accuracy during the training process, while being dynamically stable for a long duration of MD simulation. The trained MLFF model also exhibited high accuracy for long-term simulations, showing remaining errors of the same magnitude of inherent errors in DFT calculation.

Methodologies that rely on the addition and removal of molecular hydrogen from organic compounds are one of the most oft-employed transformations in modern organic chemistry, representing a highly relevant tactic in synthesis. Despite their overall simplicity, organic chemists are still pursuing sustainable and scalable processes for such transformations. In this regard, electrochemical techniques have long been heralded for their innate sustainability as efficient methods to perform redox reactions. In our first report, we discovered a new oxidative electrochemical process for the a,b-desaturation of carbonyl functionalities. The described desaturation method introduces a direct pathway to desaturated ketones, esters, lactams and aldehydes simply from the corresponding enol silanes/phosphates, and electricity as the primary reagent. This electrochemically driven desaturation exhibits high functional group tolerance, is easily scalable (1–100 g), and can be predictably implemented into synthetic pathways using experimentally or computationally derived NMR shifts. Our second report demonstrated the reductive electrochemical cobalt-hydride generation for synthetic organic applications inspired by the well-established cobalt-catalyzed hydrogen evolution chemistry. We have developed a silane- and peroxide-free electrochemical cobalthydride generation for formal hydrogen atom transfer reactions reliant on the combination of a simple proton source and electricity as the hydride surrogate. Thus, a versatile range of tunable reactivities involving alkenes and alkynes can be realized with unmatched efficiency and chemoselectivity, such as isomerization, selective E/Z alkyne reduction, hydroarylation, hydropyridination, strained ring expansion, and hydro-Giese.

Zoom Link: https://weizmann.zoom.us/j/95952232097?pwd=OW9SL2JlNkNYQVJ1cW5FT05HcEh2QT09 The optimally-tuned range separated hybrid (OT-RSH) functional is a non-empirical method within density functional theory, which is known to yield accurate fundamental gaps for a variety of systems. Here we extend its applicability to magnetic resonance parameters, enhance its accuracy by designing OT-RSH based double-hybrid functionals, and increase its precision for solid-state calculations by designing and generating RSH pseudopotentials.

Zoom Link: https://weizmann.zoom.us/j/97777492731?pwd=YXZDR0lqYUtMbHVidUlIWkl2TGxjdz09 Protein-metal interactions play an important regulatory role in the modulation of protein folding and in enabling the “correct” biological function. In material science, protein self-assembly and metal-protein interaction have been utilized for the generation of multifunctional supramolecular structures beneficial for bio-oriented applications, including biosensing, drug delivery, antibacterial activity, and many more. Even though, the nature and the mechanisms of metal-protein interaction have been extensively studied and utilized for the functionalization of protein-based materials, mainly with metal-based nanoparticles, our understanding of how metals shape protein folds, the inter-and intramolecular interactions, the associative behavior, and evolve material characteristics of protein constructs, is limited. To address these highly challenging scientific questions, I have explored the self-assembling behavior of silk fibroin protein and its’ interaction with metal nanoparticles for the formation of multifunctional composites. The central goal of my research was to explore the full potential of metal nanoparticles (NP), in particular, copper oxide (CuO) to modify the self-assembly pathway of fiber-forming protein- silk fibroin. CuO NP has been chosen as a candidate for this study, due to its versatile properties and bio-relevant functionalities applicable for sensing, antibacterial function, and capability to regulate cellular activity. Thus, to address this challenge I first focused on the understanding of metal NP-induced structural transformations in natively folded protein and on probing whether these structural changes can be artificially imposed on the assembled, β-sheet rich protein complexes. My experimental results showed that CuO NPs are indeed capable of template the assembly of natively folded silk fibroin, on the one hand, and on the other hand, exhibited variations in NPs-silk fiber interaction when added at the post-synthetic stage. Yet, the fundamental questions of how RSF-CuO NPs self-assembly occurs remain to be addressed. The exploration of biomaterial applications for silks is only a relatively recent advance; therefore, the future for this family of structural proteins appears promising.

Zoom: https://weizmann.zoom.us/j/95703489711?pwd=Tyt5cU1tV2YrMFhYUytBU001bm4yQT09 Viable, global-scale photoelectrochemical energy conversion of cheap, abundant resources such as water into chemical fuels (“solar fuels”) depends on the progress of semiconducting light-absorbers with good carrier transport properties, suitable band edge positions, and stability in direct-semiconductor/electrolyte junctions. Investigations concentrated mainly on metal-oxides that offer good chemical stability yet suffer from poor charge transport than non-oxide semiconductors (e.g., Si, GaAs). Fortunately, only a fraction of the possible ternary and quaternary combinations (together ~ 105 – 106 combinations) were studied, making it likely that the best materials are still awaiting discovery. Unfortunately, designing controlled synthesis routes of single-phase oxides with low defects concentration will become more difficult as the number of elements increases; and 2) there are currently no robust and proven strategies for identifying promising multi-elemental systems. These challenges demand initial focusing on synthesis parameters of novel non-equilibrium synthesis approaches rather than chemical composition parameters by high-throughput combinatorial investigations of synthesis-parameter spaces. This would open new avenues for stabilizing metastable materials, discovering new chemical spaces, and obtaining light-absorbers with enhanced properties to study their physical working mechanisms in photoelectrochemical energy conversion. I will introduce an approach to exploring non-equilibrium synthesis-parameter spaces by forming gradients in synthesis-parameters without modifying composition-parameters, utilizing two non-equilibrium synthesis components: pulsed laser deposition and rapid radiative-heating. Their combination enables reproducible, high-throughput combinatorial synthesis, resulting in high-resolution observation and analysis. Even minor changes in synthesis can impact significantly material properties, physical working mechanisms, and performances, as demonstrated by studies of the relationship between synthesis conditions, crystal structures of α-SnWO4, and properties over a range of thicknesses of CuBi2O4, both emerging light-absorbers for photoelectrochemical water-splitting that were used as model multinary oxides.

https://weizmann.zoom.us/j/97328767376?pwd=MkZoQ0hmbVVRank0bzkxbGpqSUdYUT09 passcode: 891716 Lithium-ion batteries with liquid electrolytes are commonly employed for powering portable electronic devices. To expand the range of applications where Li ions batteries can be used (e.g., electric transportation), solid electrolytes are considered as a safer alternative to the liquid electrolytes and they may enable use of lithium metal anodes. In this study we focused on composite solid electrolytes which are based on solid polymer (Polyethylene Oxide) and ceramic particles (Li1.5Al0.5Ge1.5P3O12, LAGP). Previous studies revealed that the highest ionic conduction path in the composites is through the interface polymer - ceramic interface. However, the chemical nature of the interface and the reason for its higher conductivity remains unclear. We aim to gain molecular - atomic level insight into the nature of the polymer - ceramic interface from solid state NMR spectroscopy. Here, I will present the development of a solid - state NMR approach that can potentially be used to selectively probe the interface. To gain sensitivity and selectivity Dynamic Nuclear Polarization (DNP), a process in which high polarization from unpaired electrons is transferred to surrounding nuclear spins will be employed. Several metal ion dopants were tested for their DNP performance in LAGP powder, and Mn2+ ions were further examined in their efficacy in the composite electrolyte. The approach was tested for selectively enhancing the NMR signal of the PEO - LAGP interface. Electrochemical characterization and in - depth solid state NMR studies provided insight into the performance of the composite and degradation processes in the composite.

Zoom Link: https://weizmann.zoom.us/j/96430042316?pwd=cjJwdFUrSEE5VnU4eVNuY08wZ1F3QT09 Raman spectroscopy is used as a primary non-destructive tool for characterization of strain in thin films. It is based on the concept of the mode Grüneisen parameter, which is the ratio between the relative change in the energy of a given vibrational mode and the relative change in the unit cell volume. It has been recently reported (Kraynis et al.) that under biaxial strain, doped CeO2-films exhibit values of the mode Grüneisen parameter, which are up to 40% smaller than the bulk literature value. Doped CeO2-films are strongly anelastic, posing a question on the relation between Raman scattering frequency and anelastic strain. This work describes the way to separate anelastic and elastic contributions to the Grüneisen parameter of doped ceria thin films and show that this concept remains applicable, if only the elastic part of the strain must be taken into account. As a reference, I deposited a purely elastic yittria thin film by sputter deposition and calculated its Grüneisen parameter in a similar way. The experimental and literature values of the yittria Grüneisen parameter were found compatible, confirming that for purely elastic strain, Grüneisen parameter concept is fully applicable.

With the growing complexity of functional materials and chemical systems, we often nd ourselves limited in our ability to fully represent the set of descriptors of a chemical system. In complex chemical systems, nding a complete crystallographic model that folds all the interatomic correlations using a small set of structural descriptors may not always be feasible or practical. Alternatively, one can take a data-driven approach and measure the relative changes in structural or chemical features (e.g, structural correlations, oxidation states). An experimental data-driven approach does not require complete models and enjoys the rapidly evolving machine-learning tool-set, which excel at classifying relational datasets and, if also labelled by an observed property, can provide predictive power that links system's descriptors with observed properties. I will focus on two types of complexities: (1) Hierarchical complexity, in which dierent types of structural or chemical correlations change change with the probed correlation length. For example, in ferroic materials dierent prop- erties (e.g., mechanical, dielectric, optoelectronic) may depend dierently on short- and long- range structural correlations. In multi-component alloys local chemical correlations (random- distribution, ordering, clustering) can aect corrosion and plasticity, but altogether show a single average structural phase. Since selected materials' properties depend on correlations at a specic hierarchical level, it is important to be able to isolate those from one another. (2) Evolutionary complexity, where the order changes over space and/or time. Nucleation, crys- tal growth, intercalation - are examples for processes that involve evolutionary complexity and can also be found in batteries, heterogeneous catalysis and photovoltaics. Isolating and track- ing order-related correlations in heterogeneous kinetically-stabilized or dynamically changing systems is, therefore, important for their more complete understanding, design and control. Total scattering and Pair Distribution Function (PDF) analysis are key methods for unfolding structural correlations at dierent correlation lengths. Using 4D-STEM to generate nm-resolution spatially-resolved electron-PDF data taken from hot-rolled Ni-laminated bulk-metallic-glass [1], I demonstrate how both hierarchical and evolutionary complexity can be uncovered and studied. Par- tially assisted with a machine-learning classication toolbox, we show how dierent aspects of the structural and chemical order, such as chemical-short-range-order, can be directly visualized as a function of position. In a dierent example [2] I show how an evolutionary complex systems can be manipulated to achieve a desired chemical state. In this example we demonstrate an active reaction control of Cu redox state from real-time feedback from in-situ synchrotron measurements. While complexity can lead to a lack of control over a chemical system, it is essentially adding tuning-knobs that, once isolated, understood and controlled, can unlock new materials with desired functionalities. [1] Y. Rakita, et al., Mapping Structural Heterogeneity at the Nanoscale with Scanning Nano-structure Electron Mi- croscopy (SNEM), arXiv:2110.03589 (2021). [2] Y. Rakita, et al., Active reaction control of Cu redox state based on real-time feedback from in situ synchrotron measurements, JACS 142, 18758 (2020). DOI: 10.1021/jacs.0c09418. 1

baradhn@is.mpg.de In the quest for improving sustainability of earth’s resources, discovery of new catalysts is a press-ing issue. There are several reasons for that, among which are: First, presently the most efficient and stable catalysts for the chemical processes that we use to transform raw resources into products with the desired functions (materials or energy type), contain expensive and non-abundant elements such as Pt, Ir, and Ru. This explains the efforts to find abundant, accessible, low-cost, stable alternatives that will yield functionality comparable to exist-ing catalysts. For example, for water splitting, many new materials with different compositions have shown promising results as catalysts. However, they are mostly prepared by wet chemical synthesis, which results in chemical waste and can be too slow for industrial use. Second, the morphology of the materials is important, because it affects their catalytic properties as higher surface areas yield more catalytic active sites, surface energetics change, leading to improved reaction rates, and other differences that affect catalytic activity. These reasons emphasize the motivation to accelerate the process of finding new materials with varying nanostructures and optimized functionality, by sys-tematic exploration of several parameter spaces. Glancing angle deposition (GLAD) is a physical vapor deposition (PVD) shadow growth technique where the substrate is positioned at an oblique angle to the vapor source and can be manipulated with regard to substrate tilt angle and rotation, during the deposition. The thin films obtained by GLAD have unique nano-structures, which depend on ballistic shadowing of the substrate, and are formed as nano-structured films, leading to 3D nano-fabrication. I will present the first original results I obtained of using GLAD to form different types of material compositions and nanostructures as functional catalysts for sustainable resources. Nano-scale mor-phology and material composition are varied simultaneously using an adapted shadow growth GLAD system,[1] which eliminates the commonly used wet chemical steps for nanostructure synthe-sis. In a well-controlled one-step growth, I quickly and directly attain a large number of different nano-columnar structures, including nanorods, nano-barcodes, and nano-zigzags, with varying ma-terial compositions, on a single large-area substrate. GLAD also serves to form nanoporous ultra-thin mesh structures, in a novel dry synthesis method.[2] Both nanostructure types were studied for their electrocatalytic performance in the O2 evolution as well as CH3OH oxidation reactions and show high activity and stability. The insights I gained, show a dependence of catalytic activity on composition and nanostructuring, which the standard experimental techniques cannot achieve or explore, thus illustrating the importance and impact that GLAD has, and will have, on developing sustainable catalysts. [1] H.-N. Barad, M. Alarcón-Correa, G. Salinas, E. Oren, F. Peter, A. Kuhn, P. Fischer, Mater. To-day 2021, In Press, DOI 10.1016/j.mattod.2021.06.001. [2] H. Kwon, H.-N. Barad, A. R. S. Olaya, M. Alarcon-Correa, K. Hahn, G. Richter, G. Wittstock, P. Fischer, ArXiv211105608 Phys. 2021.

Zoom Link: https://weizmann.zoom.us/j/91582672181?pwd=WFR1NVhKZGtra2w1WG9CcGFLSGU0Zz09 Non-stoichiometric oxides are a group of materials that are extremely popular in the energy storage and conversion industry. Their functionality relies heavily on point defects and their various properties show significant dependency on point defect type and concentration. This work deals with three such properties: mechanical, electromechanical and electro-chemo-mechanical while looking into two case study materials: 1. Acceptor-doped proton conducting BaZrO3, a promising electrolyte for protonic ceramic fuel cells as it combines high bulk proton conductivity with good chemical stability. The protonic conductivity is achieved by dissociative water incorporation into oxygen vacancies formed by acceptor dopants on Zr4+ sites. Doping was found to cause linear decrease in elastic modulus with increasing dopant concentration while the size of the dopant was proved to be a key factor. Water incorporation into the vacancies decreases the moduli even further. An unexpectedly large strain electrostriction coefficient of ≈ 5·10-16 m2/V2 was observed which makes BaZrO3 the first non-classical electrostrictor with a perovskite structure. The electromechanical response was observed to follow elastic moduli trend with respect to dopant size, giving a clear indication that electrostrictive response is related to point defect induced lattice distortions. 2. Acceptor doped oxygen conducting CeO2. The first known all solid-state electro-chemo-mechanical actuators operating at room temperature were demonstrated. These devices are based on nanocrystalline (Ti-oxide/Ce0.8Gd0.2O1.9) and (V-oxide/Ce0.8Gd0.2O1.9) composite layers. Under applied bias these composites undergo an electrochemical reaction generating change in specific volume and, thereby, mechanical work. The nanocrystalline composites are the key part of these devices and they are specifically designed to provide the fastest oxygen ion diffusion coefficient observed in a solid at room temperature. This achievement paves a way to a new field of studies: all solid-state chemotronics. The findings presented in this work link together three properties of non-stoichiometric ion conducting oxides: elastic deformation, electromechanical response and solid-state electrochemistry.

Single layers of transition metal dichalcogenides are semiconducting 2D materials which present unique electronic, excitonic and spin properties. Heterostructures composed of these materials show highly intriguing excited-state phenomena, along with a large degree of atomistic and structural tunability stemming from the underlying quantum selection rules dominating these phenomena. A predictive understanding of the effect of structural complexity on the nature of excited-state properties and interaction dynamics is crucial in order to design efficient devices for various applications, within the fields of photovoltaics, photocatalytics, optoelectronics, spintronics, and material-based quantum computing. In this research, we propose a study of the electronic and excitonic properties in heterostructures based on layered transition metal dichalcogenides and the role of structural complexities in their time-resolved relaxation mechanisms. For this, we will analyze decay processes induced by excitonic interactions with lattice vibrations, as well as other excitons and charged particles in the crystals. We will utilize predictive, Green’s-function based ab-initio methods implemented through advanced software and apply highly advanced computations using high-performance computing clusters worldwide. We will develop computational models based on these predictive approaches and on our findings to study the underlying mechanisms dominating the involved excitation processes and the light-matter interactions leading to them. Our research will be constantly driven and validated by collaborations with relevant experimental research.

Zoom Link: https://weizmann.zoom.us/j/95894806650?pwd=c21JSFRhcUZaalROaUlBWnh4T25yZz09 Low-dimensional materials, such as 2D monolayers, 1D nanowires, and 0D quantum dots and molecules, are rich with new phenomena. The reduced dimensionality, strong interactions, and topological effects lead to new emergent degrees of freedom of fundamental interest and promise for future applications, such as energy-efficient computation and quantum information. Thermal transport, which is sensitive to all energy-carrying degrees of freedom and their interactions, provides a discriminating probe to study these materials and identify their emergent excitations. However, thermal measurement in low dimensions is dominated by the lattice, requiring an approach to isolate the electronic contribution. In this talk, I will discuss how the measurement of nonlocal voltage fluctuations in a multiterminal device can reveal the electronic heat transported across a low-dimensional bridge. We use 2D graphene as an electronic noise thermometer, demonstrating quantitative electronic thermal conductance measurement over a wide temperature range in an array of dimensionalities: 2D graphene, 1D nanotubes, 0D localized electron chains, and 3D, microscale bulk materials. I will discuss ongoing work revealing electron hydrodynamics, interaction-mediated plasmon hopping, spin waves in a magnetic insulator, and a crossover from phonon to spin transport in a bulk spin liquid candidate material.

London dispersion (LD) interactions, the attractive part of the van-der-Waals interaction1,2 hold somewhat of a unique position in the chemical world. Although their role in influencing macroscopic phenomena (such as the higher boiling points of larger alkanes) is well recognized, they are usually overlooked when discussing molecular phenomena. Substituents in reactions are generally considered as a source of “steric hindrance” and not as “steric attractors”, better termed dispersion energy donors (DEDs). As such, their influence on reaction outcomes was quantified and presented by classic steric factors such as the A-value. We have shown, using computational quantum mechanical tools, that these well recognized steric factors have also an attractive LD component that balance part of the steric repulsion. By focusing on the LD component we can explain various non-intuitive trends between substituents, such as the inconsistency between the size of the halogens and their A-values.3 In addition, a systematic analysis of both the steric and dispersion interactions of the same molecules allows us to quantify the relative weights of the two effects and form a new DED scale.4 Such corrected steric and LD factors could later be applied to explore the role of LD interactions also in other reactions. Our computations show that LD interactions have a significant influence on the overall relative stabilities and energetics in cyclohexane chair conformers, and also in related concerted reactions, and must not be ignored in reaction design.    Bibliography (1) Eisenschitz, R.; London, F. Z. Phys. 1930, 60, 491–527. (2) London, F. Trans. Faraday Soc. 1937, 33, 8–26. (3) Solel, E.; Ruth, M.; Schreiner, P. R. London Dispersion Helps Refine Steric A-Values: The Halogens. J. Org. Chem. 2021, 86 (11), 7701–7713. (4) Solel, E.; Ruth, M.; Schreiner, P. R. London Dispersion Helps Refine Steric A‑Values: Dispersion Energy Donor Scales. J. Am. Chem. Soc. 2021, Accepted.

Metal halide perovskites (MHPs) have re-emerged as exceptional semiconductor materials for photovoltaics and optoelectronics, gaining tremendous attention in the fields of materials and energy harvesting over the past decade. Their unique properties, alongside their relatively cheap and easy production, make them excellent candidates as materials for the next-generation optoelectronic technologies. Besides their technological advantage, their soft ionic lattice and anharmonic potential, that are part of the underlying reasons for their unusual and outstanding performance, challenge the well-established models of classical semiconductor physics and provoke many scientific research opportunities and questions. In order to intrinsically study these outstanding behaviors, a simple system is requires, diminishing complexities that can arise when examining the popularly studied polycrystalline thin films that contain multiple defects, mainly grain boundaries. Over the past decade, our group has been developing and mastering the surface-guided growth of horizontal semiconductor NWs, which can be employed to grow arrays of epitaxial single crystal MHP NWs. These NWs offer a unique opportunity as a simple model-system for investigating the intrinsic properties of MHPs, due to their single crystal nature and quasi one-dimensional structure. These are especially suitable for the investigation of how lattice strain affects the materials’ properties, considering their inherent heteroepitaxial strain. The aim of this PhD work was to gain insight on the growth of surface-guided CsPbBr3 NWs, as a representative of the MHP family, and study the effect of epitaxial strain on their structure and properties. To achieve this goal, we first developed the crystal growth of the surface-guided CsPbBr3 NWs on sapphire, by a few different vapor-phase methods. We inspected their growth in situ using simple optical microscopy to try to learn how these unique materials grow. These were followed by integration of the NWs into nanodevices in order to examine their optoelectronic properties, with a special emphasis on the influence of strain on their performance. We finally exemplified a high-throughput study using an automated optical system that can probe many NWs in a short amount of time, to develop a charge-carrier behavior model based on a large amount of data. Studying the epitaxially strained surface-guided CsPbBr3 NWs provides important insight into the crystal growth and optoelectronic properties of MHPs

The fact that many crystals are not in equilibrium is quite obvious and not very surprising. Yet, this often complicates our attempts to understand some of their most fundamental properties, such as for instance, their overall morphology. To further add to this complexity, non-equilibrium properties are nowadays studied in crystals made out of building blocks that consume energy and actively propel (i.e., active matter). Despite some complications that exist when trying to make analogies between the behavior of bulk crystals and their nanoscale analogs, the latter offer many advantages when studying kinetic aspects of crystal formation, in both “conventional” as well as “active” crystals. In my talk I will present two different cases where nanocrystals are used in order to shed light on some of these aspects. The first story dates all the way back to the 19th century and the seminal work by Louis Pasteur on crystals that exhibit chiral macroscopic shapes when made out of chiral building blocks. Using a model system of tellurium nanocrystals, I was able to show that the reason for chiral shape formation in crystals composed of chiral building blocks might not always be as trivial as expected. In the second part of the talk, I will present the first steps I took on an ongoing journey to understand the diffusion of extremely small (sub 10 nm) chemically propelled nanocrystals. This is meant to pave the way to ultimately use them as building blocks for non-equilibrium active crystalline matter.

Phosphine carboxylate, H2PCO2-, was prepared and isolated for the first time. This heavier analogue of carbamate was found to be a carbon dioxide adduct on the edge of stability. The mechanism of phosphine carboxylate formation was found to proceed by a chain reaction that alternates between the acidified HPCO and the newly found cyclic hemi-acidified H(PCO)2-. This mechanism sheds light on the electrophilic reactivity of PCO- and similar molecules as well as their acid-base reactivity. Acidification of phosphine carboxylate forms phosphine carboxylic acid, an analogue of carbamic and carbonic acids that has surprising kinetic stability. Nucleophilic reactivity of phosphine carboxylate forms stabilized organic-soluble esters that may be used as building blocks in organic synthesis

Zoom Link: https://weizmann.zoom.us/j/96221353497?pwd=OWppT1ExY1Ewcm8zSGt4MzcvNWNiUT09 The central aim of the research is to understand how the molecular and nanoscale interactions between two natural biopolymers, fiber-forming protein-silk and conductive polysaccharide-pectin, shaping the physical properties of macro-scale composite material.

Zoom Lecture: https://weizmann.zoom.us/j/98819686427?pwd=algvMEJUNHdvaFppNS9xVzlTUkhYQT09 Passcode: 551107 Many functions of RNA depend on rearrangements in secondary structure that are triggered by external factors, such as protein or small molecule binding. These transitions can feature on one hand localized structural changes in base-pairs or can be presented by a change in chemical identity of e.g. a nucleo-base tautomer. We use and develop R1ρ-relaxation-dispersion NMR methods for characterizing transient structures of RNA that exist in low abundance (populations

Zoom Link: https://weizmann.zoom.us/j/97324532197?pwd=MGoxSGhJODNWQ2ZGT1p4elJjMG9lZz09 Cell-cell communication is essential for growth, development and function. Cells can communicate mechanically by responding to mechanical deformations generated by their neighbors in the extracellular matrix (ECM). The ECM is a non-linear viscoelastic material and therefore mechanical communication is expected to be frequency-dependent. In my talk, I will describe our work on the characteristics and implications of mechanical communication over the ECM.

Zoom LInk: https://weizmann.zoom.us/j/95962123886?pwd=ZWV6WkwxKzlNU00zRU1ER3JIWkg4Zz09 In this talk I will describe cutting-edge bio and nanotechnologies for engineering functional tissues and organs, focusing on the design of new biomaterials mimicking the natural microenvironment, or releasing biofactors to promote stem cell recruitment and tissue protection. In addition, I will discuss the development of patient-specific materials and 3D-printing of personalized vascularized tissues and organs. Finally, I will show a new direction in tissue engineering, where, micro and nanoelectronics are integrated within engineered tissues to form cyborg tissues and bionic organs.

Zoom LInk: https://weizmann.zoom.us/j/97917323609?pwd=OGpCVzNKWGlCSS9lbTIyS0FtN1lHUT09 Recent experiments have demonstrated that rapid rupture fronts, akin to earthquakes, mediate the transition to frictional motion. Moreover, once these dynamic rupture fronts ("laboratory earthquakes" ) are created, their singular form, dynamics and arrest are well-described by fracture mechanics. Ruptures, however, need to be created within initially rough frictional interfaces, before they are able to propagate. This is the reason that ``static friction coefficients” are not well-defined; frictional ruptures can nucleate for a wide range of applied forces. A critical open question is, therefore, how the nucleation of rupture fronts actually takes place. We experimentally demonstrate that rupture front nucleation is prefaced by slow nucleation fronts. These nucleation fronts, which are self-similar, are not described by fracture mechanics. They emerge from initially rough frictional interfaces at a well-defined stress threshold, evolve at characteristic velocity and time scales governed by stress levels, and propagate within a frictional interface to form the initial rupture from which fracture mechanics take over. These results are of fundamental importance to questions ranging from earthquake nucleation and prediction to processes governing material failure.

Zoom link: https://weizmann.zoom.us/j/94322871667?pwd=NXkvODRXWVZlbW9hSEtScHN1M0F4dz09 passcode: 870711 Neuroimaging has allowed us to map the correlations between brain activation, and external stimuli or behaviour. Yet these correlations can only hint at the function of the brain regions involved. In order to more casually investigate these relationships between brain and behaviour, we must perturb the brain, and see what changes this brings about in behaviour. I will provide a framework for doing so through covert neurofeedback. This technique allows us to perturb brain networks by reinforcing desired network states directly, through a reward orthogonal to the networks being trained. Yet a prerequisite for such a test of function and causality, is a strong hypothesis regarding the purported link between a specific network and behaviour. We must therefore also develop better behavioural tools, in order to establish such links.

Zoom Link: https://weizmann.zoom.us/j/92668474661?pwd=d01aQVZkWnhiT0NRQlFkVE5XeWRjdz09 Caveolae, the flask-shaped pits covered by caveolin-cavin coats, are abundant features of the plasma membrane of many cells. Besides appearing as single membrane indentations, caveolae are organized as superstructures in the form of rosette-like clusters. Here we propose that clustering of caveolae is driven by forces originating from the elastic energy of membrane bending deformations and membrane tension. We substantiate this mechanism by computational modeling, which recovers the unique shapes observed for the most ubiquitous caveolar clusters consisting of two, three, four and five caveolae.

Zoom Link: Zoom: https://weizmann.zoom.us/j/91742036303?pwd=cWJuOFBEZUpYU3p6bHBjUEduRllxdz09 Passcode: 771770 Electron and nuclear spins in diamond have long coherence and relaxation times at room temperature, making them a promising platform for applications such as biomedical and molecular imaging and nanoscale magnetic field sensing. While the optically-active nitrogen-vacancy (NV) defect has received a great deal of attention, the substitutional nitrogen (or P1) center also exhibits long coherence and relaxation times. These P1 centers are typically present at significantly larger concentrations (about an order magnitude larger) than NVs, allowing us to explore the role of P1-P1 interactions in mediating DNP. The system can, in principle, show DNP via the solid effect (SE), cross effect (CE) and Overhauser effect (OE) depending on the P1 concentration and the field. Here, we show enhancement of natural abundance 13C nuclei found within the diamond, using the unpaired electron of the P1 center (concentration 110-130 ppm) in particles with a 15-25 μm diameter, under static conditions at room temperature and 3.4 T. We discuss the DNP spectrum, the active DNP mechanisms and what we can learn about the diamond powder from DNP.

Zoom Link: https://weizmann.zoom.us/j/92088510918?pwd=bW11Rk1TKzEzeFdES3NJS1VCaTE4Zz09

Zoom Link: https://weizmann.zoom.us/j/94661424796?pwd=U0Z1YjdsbGUrV29STEZlMVhweUtXUT09 All our cells contain the same genetic information, encoded in the sequence of nucleotides that compose our DNA. The identity of different cells, and their response to different stimuli, is therefore controlled by processes regulating which subset of genes is “expressed” at a specific cell and a specific time. The first step in gene expression regulation is the binding of a special family of proteins, called transcription factors, to specific sequences in regulatory regions in the DNA. Packaging of the DNA into the dense structure of chromatin, and chemical modifications of the DNA, provide the cell with the possibility of dynamically modulating expression but add additional layers of complexity to the process in ways that are not fully understood. In my talk, I will report on our work using single-molecule optical tweezers assays to study how the thermodynamics and kinetics of transcription factor binding are modulated by these different layers of information. .

Zoom Link: https://weizmann.zoom.us/j/97142508810?pwd=S2Voc3BMYnh6RmFTYUxLbUFjQXRGZz09 Until recently, computational studies of chemical reactivity were exclusively dealt with using quantum mechanical approaches, which severely limited the system's size and accessible time scales for simulation. To bypass the need to solve Schrodinger's equation, and facilitate large-scale simulations for up to millions of atoms, both accurate and efficient models of the chemical bond have to be constructed. I will present recent advances in the field of modeling chemical reactions in large-scale, complex systems (i.e. "dirty chemistry"), with a particular focus on ReaxFF reactive molecular dynamics. Prominent applications from recent years will be highlighted, including: (a) discovery of the underlying operation principles of a novel laser-based mass-spectrometry technique, and (b) prediction of the surprising chemistry that leads to the formation of several key precursors to biomolecules of life upon the collapse of a "primordial bubble". Finally, I will present a new ReaxFF formulation that opens exciting new avenues for orders of magnitude more accurate simulations for long time scales.

Zoom Link: https://weizmann.zoom.us/j/91657907719?pwd=M2F2WlRKWGRuUHlxN0tNWFhZVUVzZz09 The genetic material of live organisms is packed and stored within the nucleus. It contains DNA wrapped around the nucleosomes, which then organized into chromatin fibers that partition into distinct compartments, which eventually fill the entire nucleus. Chromatin three dimensional topology is essential for proper accessibility of transcription factors, which control tissue-specific gene expression programs. Whereas chromatin partition into specific domains has been described in cells in culture conditions, information regarding chromatin 3 dimensional distribution in tissues within live organisms is still missing. We have imaged the chromatin in muscle fibers of live, intact Drosophila larvae, and revealed its 3 dimensional structure. Our results demonstrate novel 3 dimensional architecture of the chromatin which is evolutionary conserved, and has important implications on the regulation of gene expression.

Zoom: Link: https://weizmann.zoom.us/j/98957854014?pwd=ZTEyazd6cThxUE90L3ZJbkdkbkFWQT09 passcode: 159170 Magnetic Resonance Imaging (MRI) is a non-ionizing, non-invasive imaging modality that has become key in modern medicine. Its high value resides in a broad range of soft tissue contrasts or biomarkers that can be tuned to enable the identification and follow-up of many pathophysiological or metabolic processes. Such developments were made possible thanks to almost forty years of hardware and software development, yet access to MRI nowadays remains exclusive, bound to radiology suites in hospitals, and restricted to less than half of the world population. This limited accessibility is mostly due to its one-fits-all design and its prerequisites for intense magnetic field strength that impact cost, siting infrastructure, and clinical compatibility. One way to improve accessibility in MRI is to lower the magnetic field strength that will naturally influence cost, siting, and compatibility. Further, lowering the field strength can translate in smaller footprint designs which geometry and contrast could purposely be tuned to certain targeted applications. Indeed, relaxation mechanisms are known to change with the surrounding magnetic field, with larger T1 dispersion at low field that have for the most part been unexplored. Although very promising, many challenges arise linked to the lower intrinsic nuclear spin polarization inherent to low field technologies, calling for original and innovative approaches to reach clinical relevance. During this seminar, Prof. Najat Salameh will describe those challenges and possible solutions by presenting the current landscape of low field imaging and recent progress made at the Center for Adaptable MRI Technology, Basel University.

Zoom: https://weizmann.zoom.us/j/96278790117?pwd=T1ZjaHlxQjlEQkFIbE12UDJCazNwZz09 Two-dimensional layered (van-der-Waals) heterostructures, made by stacking different monolayers of semiconducting transition-metal dichalcogenides, have been drawing much attention as versatile platforms for studying fundamental solid-state phenomena and for designing opto-electronic devices. Interlayer excitons, electron-hole pairs that bind to each other across the interlayer spacing in these heterostructures, hold promise as key tools for probing the interlayer interface structure, and for exploring many-body interactions(1). With long lifetimes, spin polarization, and electric tunability, interlayer excitons are also promising as flexible information carriers(2, 3). However, they were mostly studied through the scope of their visible light emission, missing essential properties such as their momentum-space image or their absorption strength, necessary for rigorous study of their many-body interactions and potential applications. In this talk I will present our recent studies aimed at measuring such unknown interlayer exciton properties and their dependence on the heterostructure. I will show a new interlayer exciton in WSe2/MoS2 heterostructures which we discovered based on its light emission in infra-red wavelengths, rather than in the visible range(4). I will demonstrate its properties as inferred from its optical interrogation. Then, I will present the quantitative measurement of the elusive optical absorption spectrum of interlayer excitons using electric-field modulation spectroscopy, essential for coherent coupling of light to those excitons(5). Finally, I will reveal how time- and angle-resolved photoemission spectroscopy is used to image the interlayer exciton in momentum-space, yielding its size and binding energy, so far inaccessible through optics(5).

Zoom Link: https://weizmann.zoom.us/j/92447973616?pwd=UWJkRWdraGFVQjdPb3ByWis1bDk2Zz09 Development of targeted nanoparticle for personalized cancer therapeutics often requires complex synthetic schemes involving both supramolecular self-assembly and multiple chemical modifications. These processes are generally difficult to predict, execute, and control. I will describe a new method to accurately and quantitatively predict self-assembly of kinase inhibitors drug molecules into nanoparticles based on their molecular structures. The drugs assemble with the aid of new kind of excipient comprised of highly conjugated sulfated molecule into particles with ultra-high drug loadings of up to 90%. Using quantitative structure-nanoparticle assembly prediction (QSNAP) calculations and machine learning, a new algorithm was developed as highly predictive indicators of both nano-self assembly and nanoparticle size with unprecedented accuracy.

Link: https://weizmann.zoom.us/j/96046369379?pwd=emp0U0wwcmpNQlhsMisrNmp0bjRDdz09 Passcode: 693143 The molecular mechanisms and associated structures and dynamics of liquid-liquid phase separation (LLPS) proteins that form membrane-less organelles in cells have attracted considerable interest in recent years. EPR spectroscopy along with site directed spin labelling (SDSL) using nitroxide spin labels is a well-established technique to study dynamics of proteins. In this seminar I will discuss the dynamic properties of the spin labelled low complexity N-terminal domain of cytoplasmic polyadenylation element binding-4 protein (CPEB4NTD) in its LLPS and non-LLPS states. We found the coexistence of three CPEB4NTD populations with distinct spin label rotational correlation times before and after LLPS. We identified population I as the predominant protein species in the dilute phase, with fast motions that agree with expected dynamic properties of monomeric CPEB4NTD. We assigned population III to a compact ensemble that undergo slow motions, and population II to a looser ensemble experiencing intermediate motions. LLPS, which took place with increasing temperature is associated with increased population of II at the expense of III, while population I remains constant. At the end based on these findings, I will present a three-component equilibrium model that postulates the existence of LLPS-competent CPEB4NTD species (II and III) prior to macroscopic phase separation.

https://weizmann.zoom.us/j/93597285944?pwd=S0FJdHJ6eVpFTGJ3dHJHa3c1amJyUT09 Abstract: A long-standing challenge within density functional theory (DFT) is the development of functionals that accurately predict the band gap and electronic structure of crystalline solids. A promising candidate for this task is the screened range-separated hybrid (SRSH) functional, which has been shown to yield accurate results for finite systems when one of the parameters in the functional, the range-separation parameter, is selected a priori. In the bulk limit, however, this parameter cannot be selected non-empirically based on the ionization potential theorem, owing to the delocalized electronic orbitals. Recently, we have developed a new method for the non-empirical tuning of the range-separation parameter, that is based on the removal of an electron in a state that corresponds to a Wannier function. We have applied the method to a set of systems ranging from narrow band gap semiconductors to large band gap insulators, obtaining fundamental band gaps in excellent agreement with experiment.

Zoom Link: https://weizmann.zoom.us/j/98521602060?pwd=T1B1TEJqcXEwUW50QzBEaXd3RS9XZz09 SARS-CoV-2 outbreak of the coronavirus disease (COVID-19) has underlined the acute need for extremely sensitive, accurate, fast, point-of-care mRNA quantification sensors. Here I will show how solid-state nanopores can be used to digitally count target mRNA molecules from both biological and clinical Covid-19 samples surpassing the accuracy and gold-standard” RT-qPCR. Additionally, we applied our method for the sensing of cancer metastatic mRNA biomarkers MACC1 and S100A4 at early stage of the diseases, suggesting a potential use of the method in early precision medicine diagnostics. Moving beyond nucleic acids, I will discuss our on-going efforts towards the use of plasmonic nanopore devices for the single protein molecules identification based on partial labelling of only two or three amino acids. This research opens up vast directions for single-cell proteomics of even rarely expressed proteins.

Abstract: The present seminar will review our work in 1H LF NMR energy relaxation time technology and its application in chemical and morphological characterization and monitoring of oxidation of polyunsaturated fatty acids (PUFA) found in many important commercial products such as edible oils, foods, and biological systems. PUFA’s aggregates are related simultaneously with material’s functionality and degradation. The multiple double bonds and allylic carbons characteristics of the PUFA’s molecular structure are responsible for its oxidation susceptibility and can result in the degrade of the product’s functionality and formation of toxic substances. Wherein individual PUFA molecules have specific structures their material functionality and stability against oxidation are strongly depended on their aggregate structures such as in oils or within aqueous emulsions and specific arrangements within these structures with other components such as antioxidants is an important material parameter. The oxidation degree of PUFA’s rich materials can be measured via different methods such as volumetric, spectroscopic and chromatographic technologies. The traditional technologies based on titrimetric techniques have many drawbacks. These methods need strict time regimes during individual stages of analyzes, control of the intensity of the agitation and control of reaction components including light and atmospheric oxygen exposure. Other disadvantage of these traditional methodologies is the requirement of a large amount of solvents, being environmental unfriendly. In order to overcome the disadvantages of the traditional technologies used to monitor oxidation we are suggesting the use 1H LF NMR relaxation. This technology does not require organic solvents, complex samples preparation and the sample is preserved after analysis. The 1H LF NMR generates 2D T1 (spin-lattice) vs. T2 (spin-spin) energy relaxation time domain that is able together with self-diffusion test to characterize chemical and morphologically complex aggregate materials such as PUFA in liquid or solid assembly or in presence of interfacial forces of water. In addition, these spectra can efficiently monitor oxidation and assess antioxidants efficacy. We demonstrate the work we have done to date on the 1H LF NMR data processing optimization and the application of this technology in the characterization and monitoring of oxidation on oils on fatty acids saturated, monounsaturated and polyunsaturated. This sensor application is of relevant contributions for diverse fields such as food industries, pharmaceuticals, cosmetics and biofuels. The seminar is divided into three parts: a) Optimization of the ILT data processing technology of 1H LF NMR energy relaxation time. This study showed the efficiency of the regularization parameters for data reconstruction, and a relative high accuracy of the primal dual convex objectives (PDCO) solutions in comparison to the graphic results of real data. b) Developing of intelligent NMR relaxation sensor applications of fatty acids (FA) with saturated chains, MUFA and PUFA-rich oils for their chemical and physical/morphological characterization and monitoring of their autoxidation. Detailed fingerprinting chemical and morphological maps were generated for saturated FAs, MUFAs, PUFAs and their oxidation polymerized final products. It was possible to propose peak assignments to the various spin-lattice (T1) and spin –spin (T2) energy relaxation time proton populations (TD) based on the molecular segmental motions of the different fatty acids chemical and structural segments (e.g., glycerol; double bonds; aliphatic chains; and tails) to generate an explicatory dictionary of T1 and T2 values with chemical and physical/morphological structures and their changes due to oxidation. c) Developing of intelligent 1H LF NMR energy relaxation time domain sensor application for PUFA-rich oil-in-water emulsions characterization and monitoring autoxidation. Emulsions based on linseeds, very rich in α-linolenic acid PUFA (18:3) and structural oleosin protein and other emulsification agents naturally producing nano-scale oxidation stable oil bodies, were formed from linseed in water. The linseed emulsions enriched with PUFA-rich fish oil were analyzed under thermal oxidation conditions, using 1H LF NMR T1-T2 energy relaxation time reconstruction for determining the oil bodies composition and structure and oxidative stability.

Zoom Link: https://weizmann.zoom.us/j/98510631069?pwd=QzVFbzNxMHZETWwrM0xjbVBmV3FDdz09 Biofilms are aggregates of cells that form on surfaces and interfaces. A major characteristic of biofilms is the self-secretion of an extracellular matrix, that is composed of biopolymers, mainly proteins, polysaccharides, and nucleic acids. Using a variety of biophysical methods, we study the basic interactions between matrix components that lead to the formation of a 3D network. In this talk I will describe our recent findings, going all the way from peptides through full-length proteins to whole biofilms.

Zoom Link: https://weizmann.zoom.us/j/95267372668?pwd=dEhvRlA3SGtvVTQ1QnVmZ3JJdTZEQT09 Thermosensitive microgels are widely studied hybrid systems combining properties of polymers and colloidal particles uniquely. This study explores the frequency-dependent linear viscoelastic properties of dense suspensions of micron-sized microgels in conjunction with an analysis of the local particle structure and morphology-based on superresolution microscopy. By identifying the dominating mechanisms that control the elastic and dissipative response, we can explain these widely studied soft particle assemblies' rheology. Interestingly, our results suggest that the polymer brush-like corona's lubrification reduces friction between the microgel contacts.

https://weizmann.zoom.us/j/99592122461?pwd=MjM4ZDN0ZDFVeGZOYkdqQi9CUy9uUT09 Semiconductor nanowires (NWs) are quasi 1D nanostructures, exhibiting distinctive physical properties suitable for efficient bottom-up design of nanodevices. A challenging limiting step of their integration into planar functional systems is the difficulty to align them on horizontal surfaces. One simple and elegant way to avoid post growth assembly of NWs is to grow them horizontally in the first place. Over the past decade, our group has established the surface guided growth of horizontal semiconductor NWs aligned by crystalline substrates with controlled crystallographic orientations, directions and position. As the NWs are comprised of different semiconductors, they are optically active is different spectral regimes including the UV and visible range. However, optical activity in the pivotal infrared (IR) regime is not yet exhibited for guided NWs and a systematic exploration of it can pave the way for effective devices for telecommunication and night vision technologies. CdTe, a narrow band-gap II-VI semiconductor (~1.5 eV), is an attractive candidate owing to its promising optical and electrical properties, making it an attractive material for solar cells and near IR (NIR) photodetectors. Its alloys with mercury, known as MCT (HgxCd1-xTe) are already central components of efficient IR photodetectors due to continuous bandgap narrowing with growing percentage of mercury. In this work, we present the vapor-liquid-solid (VLS) growth and self-alignment of surface guided CdTe NWs with a wurtzite crystal structure on flat and faceted sapphire substrate (α-Al2O3). The NWs were integrated into fast IR photodetectors showing high on/off ratio of up to ~104 and, to the best of our knowledge, the shortest response times (~100 ms) to IR irradiation with respect to other CdTe based photodetectors. Attempts to create HgxCd1-xTe through cation exchange show initial conversion (~2%) of the crystal, though with significant bandgap narrowing of ~ 55 meV. These findings pave the way for simple and elegant fabrication of CdTe NWs’ based NIR nano-photodetectors, which can be expended to a wide range of Mid-IR and Far-IR photodetectors with small size through bandgap engineering.

We model intrinsically disordered proteins (IDPs) as associative polymers (APs). We study the kinetics of gelation in solutions of amphiphilic polymers that contain strongly associating stickers connected by long soluble chain segments. We explore the relation between primary sequence and droplet morphology in APs in poor solvent. We find that gelation of APs can be suppressed by grafting them to surfaces, a possible way to control aggregation of IDPs. Zoom Link: https://weizmann.zoom.us/j/99868477151?pwd=U3hFTWhjZ05nT3Ryd1ZHOXJ6Z3Y1Zz09

Zoom Link: https://weizmann.zoom.us/j/93181739182?pwd=YTd0K1drTmZSdnB0bElFZVI4K0NXdz09

Some fundamental concepts of catalysis are as of yet not fully explained but are of paramount importance for the development of improved supported metal catalysts for chemical industries and environmental remediation. Structure (in)sensitivity is such a fundamental physical concept in catalysis, which relates the rate of a catalytic reaction per unit surface area to the size of a nanoparticle. If this rate per unit surface area changes with catalyst particle size, a reaction is termed structure sensitive. Conversely if it does not - a reaction is termed structure insensitive. Historically, many fundamental physical concepts explaining the behavior of metal nanoparticular catalysts have been formulated by studying single crystal facets with surface science techniques which has left a considerable gap in our basic knowledge of catalysts at work. By using and developing state-of-the-art operando (micro)spectroscopic techniques, inter alia operando high-temperature high-pressure FT-IR, in-situ high-resolution STEM, and quick-X-ray absorption spectroscopy (quick-XAS) with millisecond time resolution, over the last few years I have been exploring the fundamental physical concepts behind fundamental structure-activity relationships of catalytic reactions by studying non-model catalysts at work. For example, by applying these methods to study a structure sensitive reaction (carbon dioxide hydrogenation) to a structure insensitive one (ethene hydrogenation) we show that the same geometric and electronic effects that we find to explain structure sensitivity make it unlikely for structure insensitivity to exist (while we do observe it empirically). However, interestingly, in the case of the structure insensitive ethene hydrogenation reaction, such size-dependent nanoparticle restructuring effects as the decrease of the reversibility of adsorbate-induced restructuring and the increase of carbon diffusion with increasing particle size are observed by quick-XAS (see Figure 1). While for the structure sensitive CO2 hydrogenation no such perturbation was observed. We further show that this particle size dependent restructuring induced by ethene hydrogenation can make a structure sensitive reaction structure insensitive. Hence, we may postulate that structure insensitive reactions should rather be termed apparently structure insensitive, which changes our fundamental understanding of the age-old empirical observation of structure insensitivity.

One of the key advantages in using light-sensitive hydrogel biomaterials is the ability to spatially structure cell scaffolds with three-dimensional mechanical cues that guide cellular morphogenesis. However, this has proven difficult because of the high toxicity associated with the cross-linking interactions. To overcome this challenge, we developed a new paradigm in micro-patterning using a reversible temperature-induced phase transition from liquid to solid vis-à-vis lower critical solubility temperature (LCST). This facilitates reduced transport kinetics of the polymer chains in solution, thus enabling crosslinking that is truly compatible with cell-laden 3D culture. Cellularized constructs were patterned to reveal a difference in morphogenesis between chemically crosslinked “stiffer” and physically crosslinked “softer” regions. Emphasizing the importance of mechanical heterogeneity in cellular morphogenesis, the results validate cutting-edge technology that can provide scientists with a robust set of tools for engineering cell and tissue growth in three dimensions.

Zoom Lecture: https://weizmann.zoom.us/j/95418425823 Deposition and attachment are key steps in colonization and fouling of surfaces by bacteria and other microorganisms, undesired in most applications. Soft hydrophilic surfaces are attractive as potential low-fouling coatings, however, deposition on such surfaces open questions regarding microscopic mechanism of attachment and its relation to deposition kinetics, not addressed in the current picture. In the talk, I will highlight our effort to understand deposition and attachment of bacteria and microparticles on low-fouling surfaces and develop appropriate characterization techniques and models.

Zoom Lecture: : https://weizmann.zoom.us/j/91487772614 Structural superlubricity may provide a viable route to the reduction of friction and wear. In this talk I will present results of fully atomistic numerical simulations of static and dynamical properties of graphite/hexagonal boron nitride (h-BN) heterojunctions, performed adopting a recently developed inter-layer potential. We found that structural superlubricity at interfaces between graphite and h-BN persists even for the aligned contacts sustaining external loads. A negative friction coefficient, where friction is reduced upon increasing normal load, is predicted. It is demonstrated that further control over the physical properties of 2D layered materials can be gained via tuning the aspect-ratio of nanoribbons. The sliding dynamics of the edge-pulled nanoribbons is found to be determined by the interplay between in-plane ribbon elasticity and interfacial lattice mismatch. Our results are expected to be of general nature and should be applicable to other van der Waals heterostructures.

Zoom lecture https://weizmann.zoom.us/j/96236417861 Mechanical sensing in cell fate decision making: from nuclei to embryos. Cells constantly probe extracellular mechanics by assessing the resistance to applied forces via adhesion, cytoskeletal, and nuclear mechanotransducers and the emerging signals direct cell-fate decisions during development and regenerative processes. The conversion of forces into biochemical cues depends on the rheological properties of subcellular elements and multicellular systems, which have been optimized during metazoan evolution. In my talk, I will present micropipette nuclear aspiration measurements of cells that express or lack the expression of different combinations of A- and B-type lamin proteins. By evaluating the mechanical contributions of assembled and disassembled lamin filamentous, and the interactions with stabilized condensed chromatin, we propose a nuclear viscoelastic model that supports a shockabsorbing response for protecting the genetic material from instantaneousimpact and a viscoelastic regime that permits slow dissipation under constant load. In a living organism, the genetic material is also protected by a physical decoupling mechanisms of the cell nucleus, which is affected by nuclear stiffening during ageing. If time permits, I will also discuss the development in situ rheological systems for performing non-invasive measurements of oocytes and embryos during preimplantation development. We combine rheology of the whole oocyte and the internal cytoplasmic mass. These stress-strain relationships are correlated with oocyte fertilization capacity, where negative outcome is underlined by impaired cytoskeletal organization.

This seminar consists of two parts. The first part is related to the investigation of mechanism of tunable domain wall (DW) conductivity in the ferroelectric LiNbO3 thin films with sub-µm thickness, Using a combination of scanning transmission electron microscopy (STEM) and local probe techniques we generate and delineate the electrically-charged 180º DWs and test their conducting behavior using local probe spectroscopy and imaging under electrical bias. More importantly, electrical tunability of DW conductivity by sub-coercive voltage is realized through the changes in DW conformity. The obtained results provide tangible evidence that the charged DWs can be used as multilevel logic elements in analog computing devices. The second part discusses the dynamic switching behavior in the HfO2-based films investigated by a combination of local probe microscopy and pulse switching techniques. Application of HfO2-based materials to ferroelectric memory and logic devices has generated considerable interest as they allow overcoming significant problems associated with poor compatibility of perovskite ferroelectrics with CMOS processing. High-resolution studies of the time- and field-dependent evolution of the domain structure in La:HfO2 thin film capacitors provides an insight into the mechanism of imprint - one of the main degradation effects hindering integration of ferroelectric HfO2 into CMOS-compatible memory technology.

Engineering vascularized constructs represents a key challenge in tissue engineering. Sufficient vascularization in engineered tissues can be achieved through coordinated application of improved biomaterial systems with proper cell types. We have shown that vessel network maturity levels and morphology are highly regulated by matrix composition and analyzed the vasculogenic dynamics within the constructs. We also explored the effect of mechanical forces on vessels organization and demonstrated that morphogenesis of 3D vascular networks is regulated by tensile forces. Revealing the cues controlling vascular network properties and morphology can enhance tissue vascularization and improve graft integration prospects.

Much has been written of the potential of ultra-high field MR scanners, such as 7 tesla, due to their inherently higher signal-to-noise ratio (SNR). This native boost is of great use in making techniques that operate in a low SNR regime, such as spectroscopy, more viable. Application of spectroscopic techniques at 7 tesla also come with a secondary, yet perhaps more important benefit in increased spectral resolution. This can allow for the quantitative investigation of metabolites that are difficult to resolve and measure reliably at lower field strengths. This seminar will relate early experiences in spectroscopy from the Siemens Terra 7T system at the University of Glasgow. This will include the optimisation of single voxel techniques for clinical studies, such as the measurement of glutamate in neuroinflammatory conditions, as well as an update on development work, such as a spectral 2D correlated spectroscopy (COSY) acquisition for investigation of glioma tumours, including a focus on 2-hydorxyglutarate. It will also cover the development of a novel MR spectroscopic imaging (MRSI) technique based on the EPSI sequence, which will allow for high resolution, full spectral bandwidth 7T acquisitions in a clinically viable time, by application of compressed sensing methods

Spatial and temporal control are critical properties to advance functional macromolecular materials in order to mimic key features of living systems. In my lecture, I will discuss our methodology in developing multicomponent supramolecular polymerization strategies in water. Using peptide-polymer conjugates we are able to address non-equilibrium states in the preparation of thermoresponsive hydrogel materials. Here, we make use of charge regulated ß–sheet selfassembly of oligopeptides and introduce reactive oxygen species (ROS) responsive subdomains to tune the time-domain of supramolecular polymerization. Using multicomponent assembly protocols, we currently explore the co-presentation of different epitopes and immunostimulating agents at the surface of supramolecular polymers. I will briefly discuss this modular supramolecular platform for immunotherapy applications and the development of multifunctional antitumor vaccines.

For the past two years we have been involved in the synthesis and characterization of new Uranium-based endohedral fullerenes and have obtained X-Ray crystal structures for several of these compounds. Some are mono-uranium species, U@C2n, while some are di-uranium compounds (see structure at the left), U2@C2n.1 Very recently we isolated two new mono-uranium compounds that violate the Isolated Pentagon Rule (IPR) with a C76 and a C80 cage possessing fused five-membered rings (pentalenes) on their surfaces.2 Still other endohedral structures are much more interesting and totally unanticipated, with formula U2X@C2n, where X= C, O, S or N and 2n= 72, 78 or 80, which reveal interesting metal-cage interactions and totally unprecedented clusters trapped inside. Some of the carbide compounds have been crystallized and the encapsulated U2C cluster (in U=C=U@C80) exhibits unprecedented bonding with totally unanticipated properties (see structure to the right).3 Finally, we have found that bis-porphyrin capsules exhibit exquisitely selective supramolecular binding for several of these uranium-based endohedral fullerene compounds.4 The synthesis, purification and characterization of these interesting endohedral fullerenes will be presented and discussed, along with very recent results about uranium-based endohedrals. References 1. Zhang, X.; Wang, Y.; Morales-Martínez, R.; Zhong, J.; de Graaf, C.; Rodríguez-Fortea, A.; Poblet, J. M.; Echegoyen, L.; Feng, L.; Chen, N., J. Am. Chem. Soc. 2018, 140 (11), 3907-3915. 2. Cai, W.; Abella, L.; Zhuang, J.; Zhang, X.; Feng, L.; Wang, Y.; Morales-Martínez, R.; Esper, R.; Boero, M.; Metta-Magaña, A.; Rodríguez-Fortea, A.; Poblet, J. M.; Echegoyen, L.; Chen, N., J. Am. Chem. Soc. 2018, 140 (51), 18039-18050. 3. Zhang, X.; Li, W.; Feng, L.; Chen, X.; Hansen, A.; Grimme, S.; Fortier, S.; Sergentu, D.-C.; Duignan, T. J.; Autschbach, J.; Wang, S.; Wang, Y.; Velkos, G.; Popov, A. A.; Aghdassi, N.; Duhm, S.; Li, X.; Li, J.; Echegoyen, L.; Schwarz, W. H. E.; Chen, N., Nature Comm. 2018, 9 (1), 2753. 4. Fuertes-Espinosa, C.; Gómez-Torres, A.; Morales-Martínez, R.; Rodríguez-Fortea, A.; García-Simón, C.; Gándara, F.; Imaz, I.; Juanhuix, J.; Maspoch, D.; Poblet, J. M.; Echegoyen, L.; Ribas, X., Angew. Chem. Int. Ed. 2018, 57 (35), 11294-11299.

The control/elimination of microorganisms, viruses and micropollutants is relevant in many water treatment systems. We developed Laser-induced graphene (LIG), a three-dimensional, porous, electrically conductive graphene material generated by irradiation of polymer substrates composites, which have strong antifouling and antimicrobial properties. This method to “laser-print” electrically conductive antifouling graphene coatings on membranes holds promise for advanced water treatment and purification

Halide perovskites (ABX3) attracted much of attention in the last years due to their excellent photovoltaic activity. They are unique in the sense that they exhibit long carrier lifetime despite having many apparent structural defects. Recent studies in our group concluded that this unique behavior is due to strong coupling between the electronic band structure and the strongly anharmonic motion of the atoms within the crystal. Therefore, it is imperative to understand the source of anharmonic atomic motion in this class of materials. Studies have indicated the B-cation lone pair to be a possible source for strong anharmonic behavior in the perovskite crystals. In order to understand the anharmonic behavior and its origin, I investigated a series of perovskites with different lone pair stereoactivity. Using low frequency Raman spectroscopy, I quantified the level of anharmonicity and determined the influence of the B-cation lone pair on the structural dynamics.

Abstract: In recent years, Van der Waals (2D) materials, have attracted increasing attention due to their distinctive physical properties. As layered materials, they have been considered for flexible electronics as they can sustain strain higher than 10% without breaking down, although they are only 1-3 atom thick. Their superior mechanical properties led to a renewed interest in the mechanics of thin membranes linked to condensed matter physics. In this talk we will show how we can apply non-uniform strain to a suspended Van der Waals material (WS2) and alter the dynamics of excitons and trions. Surprisingly, we find that as we increase the non-uniformity of the strain, we are able to convert the excitons into trions with almost 100% efficiency without any electrostatic gating. Our results explain inconsistencies in previous experiments and pave the way towards new types of optoelectronic devices.

Planarity plays a crucial role in determining the electronic and optical properties of π-conjugated backbones. Here I will discuss two examples of non-planar and planar systems: twisted acenes and planar furan-based macrocycles. In the first part, I will demonstrate how twisting affects the electronic, optical and chiroptical properties of acenes. We have introduced a series of twisted acenes, having an anthracene backbone diagonally tethered by an n-alkyl bridge, which induces different degrees of twisting. This helically-locked system allows us to systematically monitor the effect of twisting on electronic and optical properties of anthracene. The effect of twisting on chiroptical properties, charge delocalization and π-conjugation will also be demonstrated. In the second part, I will present bifuranimide as a stable furan containing analog, which resulted in the introduction of the first macrocyclic furans. These π-conjugated macrocycles were found to be completely planar, in contrast with thiophene macrocycles which are highly-twisted. The prospects of macrocyclic furans as π-conjugated analogs of crown-ethers and synthons for cycloarenes by multiple Diels–Alder cycloadditions will be discussed.

Following our recent observations of contraction waves in the primitive epithelium of Placozoa, we develop a model of tissues as sheets of contractile cells. The simple model assumes only a strain-threshold for contraction, and explains/predicts a variety of unique and surprising phenomena, e.g.: contraction waves in response to external stress, spontaneously-compressed steady-state, emerged limit-cycles, mechanical frustration and active resistance to rupture. In the talk I will present both the experimental observations and the model results. This model of “active cohesion” may be relevant to any epithelial tissue, to manufacturing of synthetic active materials, and to models of evolution of multicellularity.