Séminaire AXE 1 – Sciences et Matériaux Quantiquesprésenté par : Alexina Ollier

Speaker: Alexina Ollier, Center for Quantum Nanoscience (QNS), Institute for Basic Science (IBS), Seoul, South Korea

Here, we report on imaging the spin texture of triple-Q magnetic order of Co1/3TaS2. The sample
was measured with a low temperature STM (T=6K) under ultra-high vacuum with normal
and spin-polarized tips. The STM images with the normal tip show the triangular lattice of the
sample. The spin-polarized (SP) tip shows an additional symmetry related to the triple-Q
ordering. In addition to that, the SP STM images revealed different spin textures with respect
to the tip-spin orientation. The analysis suggests the presence of a phase difference between the
tip and the triple-Q ordering of the sample. This work gives a new insight into the exploration of
chiral magnetic ordering with topological Hall effect using scanning probe microscopy.

Séminaire de l’Axe 2 “Nanosciences pour le Vivant” présenté par : Thomas PONS

Thomas PONS (Laboratoire de Physique et d’Etudes des Matériaux, ESPCI, Sorbonne Université, Paris (LPME))

Fluorescent biodetection assays using pairs of fluorescent donors and acceptors interacting via Förster Resonant Energy Transfer (FRET) are appealing thanks to their ease of use, versatility and specificity. They are however limited in sensitivity due in particular to their limited distance range. We are currently developing a novel type of biodetection assay based on energy transfer using Whispering Gallery Modes (WGM) from optical microcavities excited by fluorescent quantum dots as donors and polymeric dye-loaded nanoparticles (dyeNP) as acceptors. The high quality factor of the microcavities enables a strong enhancement of energy transfer to dyeNP acceptors placed within their evanescent field. In particular, we have studied their interactions in a model system using streptavidin-coated microcavities and biotinylated dyeNPs. Upon their specific biomolecular interaction, the dyeNP bind to the microcavity surface, leading to efficient energy transfer, with a typical sensitivity in the fM range, 4-6 orders of magnitude more sensitive than typical FRET assays. We further demonstrate the ultrasensitive detection of DNA oligonucleotides.

Contact :Damien MERTZ  damien.mertz@ipcms.unistra.fr

Séminaire IPCMS présenté par : Cécilia Ménard-Moyon

Dr. Cécilia Ménard-Moyon  (CNRS, Immunology, Immunopathology and Therapeutic Chemistry, UPR 3572, University of Strasbourg)

Résumé :

The relatively low-cost production of graphene oxide (GO) and its dispersibility in various solvents,
including water, combined with its tunable surface chemistry, make GO an attractive building block to
design multifunctional materials. There are many applications for which it is fundamental to preserve
the intrinsic properties of GO, for instance in the biomedical field. As a consequence, the derivatization
of GO to impart novel properties has to be well controlled and the characterization of the functionalized
samples thoroughly done. Despite the great progress in the functionalization of GO, its chemistry is not
always well controlled and not fully understood.[1] In this context, I will explain some strategies for the
functionalization of GO through the selective derivatization of the epoxides and hydroxyl groups without
alteration of its properties and with biomedical perspectives for anticancer therapy.[2,3] I will also
present how the incorporation of carbon nanomaterials, such as carbon nanotubes and GO, in hydrogels
formed by the self-assembly of aromatic amino acid derivatives can control drug release.[4,5]
[1] Guo S, Garaj S, Bianco A, Ménard-Moyon C, Nat. Rev. Phys., 4 (2022) 247.
[2] Guo S, Nishina Y, Bianco A, Ménard-Moyon C, Angew. Chem. Int. Ed. Engl., 59 (2020) 1542.
[3] Guo S, Song Z, Ji DK, Reina G, Fauny JD, Nishina Y, Ménard-Moyon C, Bianco A, Pharmaceutics, 14 (2022) 1365.
[4] Guilbaud-Chéreau C, Dinesh B, Schurhammer R, Collin D, Bianco A, Ménard-Moyon C, ACS Appl. Mater.
Interfaces, 11 (2019) 13147.
[5] Xiang S, Guilbaud-Chéreau C, Hoschtettler P, Stefan L, Bianco A, Ménard-Moyon C, Int. J. Biol. Macromol., 255
(2024) 127919.

Séminaire Axe 1- “Sciences et Matériaux Quantiques” présenté par : Cosimo Gorini

Charge currents may be generated by pure spin injection via the spin galvanic effect, also
referred to as “inverse Rashba – Edelstein effect”, and/or the inverse spin Hall effect. In a
typical spin pumping setup consisting of a injector, e.g. a driven magnetic electrode, and a
converter, a metallic spin-orbit coupled system, both effects contribute to the conversion. If
however the converter is 2D only the spin galvanic channel is available. This is notably the
relevant scenario for 2D dimensional electron gases at oxide interfaces.
Recent experiments at such interfaces show strongly anisotropic spin- (and orbit-) to charge
conversion [1], which I will explain in terms of the “tunneling anisotropic spin galvanic effect”
[2]. I will also show how intrinsic time scales heavily affect such conversion in the ultrafast
regime [3].

References
[1] El Hamdi et al., Nat. Phys. 19, 1855 (2023)
[2] Fleury et al., Phys. Rev. B 108, L081402 (2023)
[3] El Hamdi et al., Phys. Rev. B 110, 054412 (2024)

Contact: Arnaud GLOPPE (arnaud.gloppe@ipcms.unistra.fr) – Guillaume SCHULL (schull@unistra.fr)

Séminaire IPCMS présenté par : Rupert Huber

Orateur : Rupert Huber (Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN)
University of Regensburg)


Résumé : The carrier wave of light can drive electrons through solids on time scales faster than a cycle of light. This ‘lightwave electronics’ concept opens a fascinating coherent quantum world full of promise for future quantum technologies. We will discuss prominent examples of lightwave-driven dynamics in solid-state quantum materials, ranging from Bloch oscillations via topologically non-trivial electron trajectories to optical band-structure engineering and attoclocking of Bloch electrons. We also take slow-motion movies of single molecules and atomic defects and observe the quantum flow of electrons with the first all-optical subcycle microscope reaching atomic resolution. Our results offer a radically new way of watching and controlling elementary dynamics in nature or steer chemical reactions, on their intrinsic spatio-temporal scales.


Séminaire DSI présenté par Aram Yoon

Aram Yoon (Shell Energy Transition Center, Amsterdam)

Résumé : Electrocatalysis plays a pivotal role in various energy conversion and storage applications, including fuel cells, electrolyzers, and batteries. It facilitates the conversion of chemicals from one form to another, making it essential for clean and sustainable energy technologies. Transition metal oxides show great promise in this regard, as they are abundant on Earth and can modify their electrical and chemical properties by adjusting their oxidation state through surface and interface engineering. To effectively harness these materials in energy conversion devices, it is imperative to gain insights into how catalysts’ structures behave in working environments, as this significantly influences chemical conversions and the catalysts’ own chemical status. However, investigating the structure and chemistry of electrocatalysts under electrochemical reaction conditions is a challenging endeavor. Electrochemical systems involve reactions and transformations occurring at multiphase boundaries, including solid-solid and solid-liquid interfaces. This complexity necessitates the use of diverse techniques to probe these interfaces, further complicated by the need to maintain the electrolyte and applied potential.

In my presentation, I will delve into the behavior of Cu2O catalysts under dynamic reaction conditions, employing a multimodal approach centered on in situ Electrochemical Cell Transmission Electron Microscopy (EC-TEM). This approach will focus on two conversion reactions involving Cu2O catalysts: electrochemical CO2 reduction and nitrate reduction. Through this investigation, I will demonstrate structural changes of Cu2O catalysts during redox reactions. The primary emphasis will be on correlating various operando techniques, such as X-ray absorption microscopy and spectroscopy, with electrochemical characterization to gain a comprehensive understanding of how structural heterogeneity impacts catalysis.

Pour tout contact : Maria Letizia De Marco (0388107028 – maria-letizia.demarco@ipcms.unistra.fr)