Seminar

perovskites are among the most promising materials for next-generation solar cells, offering exceptionalefficiency gains and driving major investment in large-scale production. Yet, as the technology moves toward realworlddeployment, corrosion has emerged as a critical but often overlooked challenge. It arises not only fromenvironmental exposure but also from the intrinsic reactivity of the perovskite itself, which can attack metalelectrodes such as gold through complex chemical pathways.This show highlights why corrosion in perovskite devices is both subtle and important. Light and heat can triggerchemical changes that produce reactive species, either directly corroding metals or transforming the perovskite intoa more aggressive state. By connecting principles from corrosion science and semiconductor physics, we revealhow these reactions originate and what must be done to control them at their source.

Hard coatings are integral to modern manufacturing, significantly impacting the optical properties, friction, hardness,corrosion resistance, and wear resistance of various surfaces. The global market for hard coatings is valued at $1.2 billion,with strong growth expected in the coming years, offering opportunities for the direct application of fundamentalresearch in industrial settings. One key challenge in this field is the low toughness of protective coatings, particularly innitrogen-based PVD/CVD hard coatings, where this issue is compounded by the low cohesive energy of grain boundaries.Due to their lack of ductility, nitrogen-based ceramic materials are prone to grain boundary cracking under mechanicalload, leading to the degradation of protective layers and reduced lifetime of coated parts. Our research focuses onunderstanding the structure-property relationships of these materials.Commercial coatings are typically a few micrometers thick, with microstructures consisting of grains ranging fromnanometers to micrometers, making them well-suited for study using modern electron microscopy. By combiningpicoindentors for in situ SEM and TEM with FIB-based manufacturing, we developed in situ testing approaches to assesskey mechanical properties such as Young's modulus, fracture stress, and fracture toughness, as well as to explore theunderlying fracture mechanisms. In this talk, I will present our findings on the design of grain boundaries, materialcomposition, and transformation toughening strategies, which have significantly enhanced the mechanical properties ofhard coatings.

In nature, sequence-specific biopolymers, such as peptides and nucleic acids, are essential to various biological systems and processes. These biopolymers are utilized in materials science to achieve precise property control. Typically, variations in amino acid sequences focus on functional regulation while nucleotides are used for structural control. This raises the question: How can we integrate peptide-based functionality with the spatial precision of DNA nanotechnology for innovative material design? Here, I will present examples illustrating the incredible properties of peptide self-assembly from my PhD, and the remarkable nanoarchitecture design achieved through DNA nanotechnology from my Postdoc. These two key elements establish a vision of utilizing and synergizing peptide functionality with structural control achieved by DNA nanotechnology.Specifically, I will show how subtle changes in the molecular environment influence the morphology and behavior of peptide assemblies such as diphenylalanine crystals and enable control over their growth and disassembly processes, revealing insights into peptide-based material manipulation (Nat. Commun., 2016). Another example is that of the amorphous assemblies of tri-tyrosine peptides, where we linked the molecular arrangement to unique mechanical and optical properties of glass-like peptide structures (Nature, 2024).Next, I will introduce the principles of DNA nanotechnology for advanced structural control. By designing DNA nano-frames capable of self-assembling into organized lattices, we created micron-scale 3D materials. We discovered that a minor modification in DNA linker length induces a crystalline phase transition, from simple cubic to face-centered cubic structures, altering lattice geometry. In addition, we established a method using acoustic waves to achieve scalable and morphologically controllable DNA assemblies at the millimetric scale (Nat. Commun., 2024). This approach highlights how DNA nanotechnology provides unparalleled spatial control, decoupling structural architecture from functional elements such as peptides and nanoparticles. Together, these projects illustrate how peptides and DNA nanotechnology can be potentially integrated to engineer novel materials and enhance our capacity to design materials with tailored properties across scales.

Electrocatalytically driven reactions that produce alternative fuels and chemicals are considered as a useful means to store renewable energy in the form of chemical bonds. in recent years there has been a significant increase in research efforts aiming to develop highly efficient electrocatalysts that are able to drive those reactions. Yet, despite having made significant progress in this field, there is still a need for developing new materials that could function both as active and selective electrocatalysts. In that respect, Metal–Organic Frameworks (MOFs), are an emerging class of hybrid materials with immense potential in electrochemical catalysis. Yet, to reach a further leap in our understanding of electrocatalytic MOF-based systems, one also needs to consider the welldefined structure and chemical modularity of MOFs as another important virtue for efficient electrocatalysis, as it can be used to fine-tune the immediate chemical environment of the active site, and thus affect its overall catalytic performance. Our group utilizes Metal-Organic Frameworks (MOFs) based materials as a platform for imposing molecular approaches to control and manipulate heterogenous electrocatalytic systems. In this talk, I will present our recent study on electrocatalytic schemes involving MOFs, acting as: a) electroactive unit that incorporates molecular electrocatalysts, or b) non-electroactive MOF-based membranes coated on solid heterogenous catalysts.

Innovative battery electrode materials are essential for unlocking the full potential of Li-ion batteries in various aspects of modern life. A primary focus is identifying novel materials with greater elemental diversity that offer improved stability, rapid charge capabilities, and high performance. Promising candidates, like early transition metal oxides, are earth-abundant and present opportunities for next-generation anode materials due to their redox voltage and more than a single stable oxidation state. Exploring fundamental design principles for improved de/lithiation mechanisms will influence battery functionality and advance energy storage capabilities. The first part will delve into the impact of the insulator-metal transition during lithiation, focusing on two distinctive Wadsley-Roth (WR) structures. Our findings underscore the critical role of disorder within these structures in determining kinetics and retained capacities for these anodes. The second part proposes a novel strategy leveraging the induction effect to reduce the operation voltage of Mo-oxide-based anodes. This reduction opens the door for Mo-based oxide anodes as an alternative to graphene. Understanding these key aspects can guide the search for alternatives to existing anodes for advancing the development of Li-ion batteries with enhanced performance in the energy storage field.

Noble metal thin films have attracted significant interest owing to their distinctive properties and structures, which make them ideal for applications in microelectronics, catalysis, energy, and photovoltaics. While several parameters influence the properties of these metals for such applications, the deposition process remains a critical factor. Atomic Layer Deposition (ALD) stands out as a prevalent deposition technique due to its surface-sensitive nature. The ALD process is characterized by its self-limiting surface reactions, promoting a layer-by-layer growth mechanism and allowing for precise control over film thickness and conformality. However, challenges arise in achieving continuous, pinhole-free noble metal ALD layers on oxide surfaces, often resulting in low film quality. These challenges can be traced back to the lack of adequate nucleation sites and the poor wettability of the low-surface energy substrates. The research studied the impact of substrate surface functionalization using organometallic molecules, such as trimethylaluminum (TMA) and diethylzinc (DEZ), on the nucleation and growth of Ru layers. The results reveal an enhancement in both nucleation density and the average diameter of the Ru nanoparticles deposited, and these improvements were attributed to an increase in both nucleation sites and elevated surface diffusivity. The latter effect is speculated to result from a reduction in the substrate's surface free energy. The study also examines the influence of substrate surface characteristics, including surface termination and crystallinity, on the nucleation and growth of Ru metal via ALD. The morphologies of the resulting Ru thin films are studied using scanning electron microscopy (SEM), atomic force microscopy (AFM), and grazing incidence small angle x-ray scattering (GISAXS). These analytical results are integrated with an experimental model to elucidate the differences in growth mechanisms observed across substrates. The findings underscore the importance of substrate choice in the ALD process and broaden our understanding of Ru metal growth. This research serves as an important step in optimizing the ALD process for various applications by tailoring substrate selection.

In recent years, covalently bound dimers of chromophores have attracted significant interest as singlet fission (SF) material because of better control of coupling of different electronic states to the gateway 1(TT) by means of intramolecular vibrational modes.1 It has been shown that charge transfer (CT) plays a crucial role in mediating the S1-1(TT) interaction and their influence can be conveniently tuned by solvent polarity. Motivated by the experimental and theoretical work of Alvertis et al.,1 we have investigated the electronic states relevant to the SF for the covalently bound tetracene dimer with the goal to provide a broader picture of the occurring photodynamical processes.2 For that purpose, the second-order algebraic diagrammatic construction (ADC(2)) method in combination with the conductor-like screening model (COSMO) has been used. Vertical excitations and potential energy curves for excitonic and CT states along low-frequency symmetric and antisymmetric normal modes have been computed. These results have been combined with those obtained by density functional theory/multireference configuration interaction (DFT/MRCI) calculations for the 1(TT) state since its doubly-excited wavefunction is not accessible to the ADC(2) method. In the second part of the talk, DFT/MRCI calculations on dimer and trimer TIPS-Pn will be presented with the goal of a first theoretical understanding of the photodynamics of the 1(TT) state monitored by time-resolved mid-IR absorption spectroscopy.3

Organic/printed electronics is a technology enabling the fabrication of mechanically flexible/stretchable electronic circuits and devices using low-temperature, possibly by additive, solution processing methodologies. In this presentation we report the development of novel materials, as well as thin-film processing and morphology engineering, for flexible and stretchable organic and inorganic thin film transistors, electrolyte gated transistors and circuits. On material development, we present that “soft” small-molecules and polymers can be synthesized by co-polymerizing naphthalenediimide (NDI) or diketopyrrolopyrrole (DPP) units with proper co-monomer building blocks or properly designed additives. Furthermore, we also report the fabrication of stretchable inorganic metal oxide fiber network by spry coating metal salts+thermally labile polymer formulations. New transistor architectures using semiconductor film porosity as the key element for enhancing mechanical flexibility and tune charge transport are also demonstrated. These films, combined with elastomeric pre-stretching, enables unprecedentedly stable current-output characteristic upon mechanical deformation, which are used for sensing analytes, strain, light, temperature and physiological parameters. Finally, we report our recent work on molecular n-doping of organic semiconductors using a novel strategy involving catalysts.

The development of sustainable methods for the closed-loop production and recycling of plastics is an important challenge of current times. Reactions based on catalytic (de)hydrogenation are atom-economic, and sustainable routes for organic transformations.1 Using the following examples, this lecture will discuss the application of homogeneous (de)hydrogenative catalysis for the synthesis and degradation of polymers to enable a circular economy: (a) synthesis of polyamides/nylons from the ruthenium catalysed dehydrogenative coupling of diamines and diols and its reverse reaction i.e. hydrogenative depolymerisation of nylons,2 (b) synthesis of polyureas from the ruthenium/manganese catalysed dehydrogenative coupling of diamines3,4 and methanol, and its reverse reaction, i.e. hydrogenative depolymerisation of polyureas (Figure 1B)5, (c) Synthesis of polyethyleneimines from manganese catalysed coupling of ethylene glycol and ethylenediamine or the self-coupling of ethanolamine,6 and (d) Synthesis of polyureas and polyurethanes from the dehydrogenative coupling of diformamides and diamines/diols and its reverse reaction i.e. hydrogenative depolymerisation of polyureas and polyurethanes to diformamides and diamines/diols.7 Some applications of some of the polymers made using dehydrogenative processes in the field of batteries will also be discussed.8

Click chemistry has revolutionized many facets of the molecular sciences, with the realization of reactions that are ‘‘modular, wide in scope, give very high yields, generate only inoffensive byproducts that can be removed by nonchromatographic methods and are stereospecific”. Yet surprisingly little attention has been given to the development of intrinsically chiral click reactions (potentially enantiospecific, rather than ‘only’ enantioselective due to chiral auxiliary groups), while the modularity of many click reactions is best compared to one-dimensional LEGO. Of course, much could be done within the constraints – hence forementioned revolution – but it drove attention towards an extension of available click chemistries. Kolb, H. C.; Finn, M.; Sharpless, K. B., Click chemistry: diverse chemical function from a few good reactions. Angew. Chem. Int. Ed. 2001, 40, 2004-2021. The talk will focus on the resulting investigations in the field of S(VI) exchange chemistry, with specific emphasis on two fields: a) the development of the intrinsically enantiospecific click reactions and their use to e.g. make synthetic polymers with 100% backbone chirality that combine stability & degradabbility, and b) the development of multimodular click chemistry and single-polymer studies by a combination of AFM, TEM, scanning Auger microscopy

Over years’ transition metal-catalyzed C-H activation has propelled the field of organic synthesis for the construction of structurally complex and diverse molecules in resource-economical fashion. In this context, non-directed C-H activation has gained unprecedented attention for attaining region-specific C-H functionalizations in a step-economic mode. Unlike traditional Fujiwara-Moritani reaction, this approach relies on ligand assistance and thus uses arene as the limiting reagent. However, all existing non-directed C-H functionalizations utilize high thermal energy to induce the functional group which eventually put the regioselectivity at stake. In addition, use of super stoichiometric costly silver salts to regenerate the catalyst produces unwanted metal waste. In aid of developing a more sustainable and environmentally benign approach, we have established a photoredox catalytic system by a merger of palladium/organo-photocatalyst(PC) which forges highly regeiospecific C-H olefination of diverse arenes and heteroarenes. Visible light nullifies the requirement of silver salts and thermal energy in executing “region-resolved” Fujiwara-Moritani reaction.

The major concerns about industrially used catalytic systems today are: i) the high cost of catalysts; ii) the toxicity of heavy transition metals; iii) difficulties in removing trace amounts of toxic-metal residues from the desired product; and, finally, iv) rare transition metal depletion, which does not meet the requirement of sustainable development. Developing environmentally friendly catalysts is an excellent option in this regard. Naturally, the most recent catalyst development trend heralded a new era of metal-free catalysis or catalysts based on earth-abundant, nontoxic, and low-cost metals. This talk will go over our recent advances [1-4] in using small molecules to systematically mimic transition metal-based catalysis. We designed electron transfer catalysis using the smallest polycyclic odd alternant hydrocarbon, phenalenyl (PLY)-based molecules, which was inspired by a completely different field of molecular spin materials [5]. This talk will focus on how to avoid transition metals when performing various cross-coupling catalysis.