Awards, prizes, publications

The ability to tune the energy gap in bilayer graphene makes it the perfect playground for the study of the effects of internal electric fields, such as the crystalline field, which are developed when other layered materials are deposited on top of it. Here, we introduce a novel device architecture allowing simultaneous control over the applied displacement field and the crystalline alignment between two materials. Our experimental and numerical results confirm that the crystal field and electrostatic doping due to the interface reflect the 120° symmetry of the bilayer graphene/BN heterostructure and are highly affected by the commensurate state. These results provide unique insight into the role of twist angle in the development of internal crystal fields and intrinsic electrostatic doping in heterostructures. Our results highlight the importance of layer alignment, beyond the existence of a moiré superlattice, to understand the intrinsic properties of a heterostructure.

Flat bands in moiré systems are exciting new playgrounds for the generation and study of exotic many-body physics phenomena in low-dimensional materials. Such physics is attributed to the vanishing kinetic energy and strong spatial localization of the flat-band states. Here, we use numerical simulations to examine the electronic transport properties of such flat bands in magic-angle twisted bilayer graphene in the presence of disorder. We find that while a conventional downscaling of the mean free path with increasing disorder strength occurs at higher energies, in the flat bands the mean free path can actually increase with increasing disorder strength. This phenomenon is also captured by the disorder-dependent quantum metric, which is directly linked to the ground state localization. This disorder-induced delocalization suggests that weak disorder may have a strong impact on the exotic physics of magic-angle bilayer graphene and other related moiré systems.

L’UCLouvain a l’honneur d’accueillir Jean-Marie Lehn, prix Nobel de chimie en 1987, pour une conférence exceptionnelle. Ce grand scientifique, pionnier de la chimie supramoléculaire, échangera avec les chercheur·euses et étudiant·es sur l'impact de ses découvertes et les défis futurs de la discipline.

Morpholines are prevalent in medicinal chemistry due to their favorable pharmacokinetic properties and widespread presence in FDA-approved drugs. Existing methods for morpholine synthesis often require prefunctionalized or protected reagents, limiting their versatility and efficiency. Here, we present a photocatalytic, diastereoselective annulation strategy for the synthesis of morpholines directly from readily available starting materials. This method employs a visible-light-activated photocatalyst, Lewis acid, and Brønsted acid to achieve high yields and stereoselectivity. It also provides access to diverse substitution patterns, including challenging tri- and tetra-substituted morpholines. Mechanistic studies reveal that the reaction proceeds through the formation of a radical cation intermediate, with triflic acid playing critical roles in protonating the substrate, preserving the photocatalyst, and preventing product oxidation. Beyond morpholines, this strategy is extended to piperidines, pyrrolidines, and other privileged nitrogen heterocycles. Our findings provide a modular approach for constructing complex, medicinally valuable scaffolds, advancing both synthetic and medicinal chemistry.

Open metal sites (OMSs) represent a distinctive feature of metal-organic frameworks (MOFs), intertwined with guest accommodation and energy transfer within nanosized pores. Fine-tuning OMSs provide an effective approach to regulating MOF’s responsiveness and binding affinity towards guests, allowing for the construction of luminescent sensors for specific analytes. Such a strategy remains unexplored due to the inherent complexity of the systems and sensing mechanisms. Herein, we delicately regulated the OMSs in PCN-700 through multiple synthetic methodologies, including direct synthesis, linker installation, and linker exchange. The resultant MOFs consist of Zr6-clusters featuring various coordination numbers. Notably, PCN-700-8u with unsaturated 8-coordinated Zr-clusters exhibited the highest sensitivity in detecting a toxic pesticide pentachloronitrobenzene (PCNB) due to the presence of strong coordination interaction, as validated through single crystal X-ray diffraction directly. PCN-700-10u/12u bearing unsaturated 10/12-coordinated clusters perform lower quenching efficiencies than PCN-700-8u, but higher than PCN-700-12s with saturated clusters. In contrast, all these MOFs exhibit similar quenching efficiencies towards hexachlorobenzene for the absence of coordination interaction. This study not only develops a cost-effective and easily attainable material for PCNB detection, but also illuminates the pivotal importance of OMSs in customizing MOF-based sensors for practical applications.

Particle exchange heat engines are a novel class of cyclic heat engines that are all-electrical, contain no moving parts and can therefore be scaled down to nanometer size. At the center of their operation is the manipulation of a particle flow between a hot and a cold reservoir through energy filtering mechanisms, where their efficiency depends primarily on the sharpness of the energy filter. In this study, we investigate the efficiency enhancement of such engines by utilizing ultra-sharp transmission resonances formed by magnetic impurities interacting with superconductors, known as Yu-Shiba-Rusinov bound states. To this end, we couple a neutral and stable diradical molecule to superconducting break-junction electrodes, and study its thermoelectric properties at ultra-low temperatures. By driving the molecular heat engine through a phase transition from a Kondo state into the Yu-Shiba-Rusinov regime, we observe a five fold increase in the thermoelectric power factor. This observation could pave the way for practical applications such as cryogenic waste heat recovery and efficient spot-cooling for future quantum computing architectures.

Trifluoromethylation is a key transformation in drug and agrochemical synthesis, yet current reagents often suffer from high cost, low atom economy, and low scalability. [Discover more...]

Iron photosensitizers represent a holy grail in photochemistry, but their widespread implementation is limited by their short excited-state lifetimes and poor cage escape yields.

The swelling of a polymer matrix by ionic liquids and additional lithium salts may lead to the formation of ionogel electrolytes. However, the introduction of additional ions usually results in a decreased lithium-ion transference number, because of the trapping of the lithium ions in clusters and polymer-ion complexes. [Discover more...]

Integrating magnetic skyrmions into neuromorphic computing could help improve hardware efficiency and computational power. However, developing a scalable implementation of the weighted sum of neuron signals - a core operation in neural networks - has remained a challenge. [Discover more...]