Addressable transition metal complexes as models for quantum bits and logic gates
The project concerns the design, development and study of spin dynamics in binuclear transition metal complexes
as models for quantum logic gates. The first part focuses on Cu(II) complexes. The second part explores Fe(II)-
based complexes that can be optically addressed in the visible range. The complexes will first be characterized by
continuous-mode electron paramagnetic resonance (EPR) spectroscopy to highlight the quantum bit behavior of
the mononuclear complexes used to form the binuclear species. Detailed studies of spin-lattice relaxation time (T1)
and spin-spin relaxation time (coherence time, T2) will then be carried out using pulsed EPR. Studies on
addressable complexes (mononuclear and possibly binuclear) will determine the impact of the presence of one
paramagnetic center on the coherence time of another within the binuclear entity, enabling the robustness of
quantum logic gates manipulatable by visible light to be assessed.
Silver nanowires synthesized from end-of-life solar panels for CO2 reduction and transparent electrodes
Silver nanowires (AgNW) networks are remarkable materials with both the highest electrical and thermal conductivity at ambient temperature, and a good chemical stability. They are used in transparent electrodes, for instance in organic solar cells, heating films or electrochromic devices. Their synthesis has been upscaled at the industrial level with high yield and reproducibility. More recently, they also found promising applications in low-emissivity layers on windows, and in catalysis of CO2 reduction at ambient temperature as a selective electrocatalyst.
In this PhD project, we will turn to recycled sources of silver from dismantled end-of-life silicon solar panels for the synthesis of AgNWs, in a “green chemistry” approach. The quality of the nanomaterial will be checked directly in two relevant devices, namely IR-low-emissivity films for reduction of heat loss, and electroreduction of CO2 for the production of e-fuels. The project will focus on understanding the fundamental basis of the impact of impurities on the synthesis of AgNWs, the physical properties of the AgNW networks, their stability under electrical stress or chemical wear, and their performance as active material in the devices.
The work will take place in Grenoble, the second scientific hub in France. The PhD student will be hired by CEA, a major French research institution with a high focus on alternative energies. He/she will join the fundamental research lab SyMMES, expert in nanomaterial design and energy devices such as solar cells, batteries and electrolyzers. She/he will work in co-supervision in the partner lab LMGP expert in materials science, synthesis and implementation at Grenoble INP. SYMMES and LMGP belong to University Grenoble Alpes and host widely international teams. The project will be actively supported by a local industrial recycling company.
Applicants should hold a Master 2 degree in chemistry, physics or materials science with skills in nanomaterials, electrochemistry or physical chemistry and in basic science for energy. Good English proficiency and a strong interest for innovation and collaborative work are expected.
Optimizing cryogenic super-resolution microscopy for integrated structural biology
Super-resolution fluorescence microscopy (“nanoscopy”) enables biological imaging at the nanoscale. This technique has already revolutionized cell biology, and today it enters the field of structural biology. One major evolution concerns the development of nanoscopy at cryogenic temperature (“cryo-nanoscopy”). Cryo-nanoscopy offers several key advantages, notably the prospect of an extremely precise correlation with cryo-electron tomography (cryo-ET) data. However, cryo-nanoscopy has not provided super-resolved images of sufficiently high quality yet. This PhD project will focus on the optimization of cryo-nanoscopy using the Single Molecule Localization Microscopy (SMLM) method with fluorescent proteins (FPs) as markers. Our goal is to significantly improve the quality of achievable cryo-SMLM images by (i) engineering and better understanding the photophysical properties of various FPs at cryogenic temperature, (ii) modifying a cryo-SMLM microscope to collect better data and (iii) developing the nuclear pore complex (NPC) as a metrology tool to quantitatively evaluate cryo-SMLM performance. These developments will foster cryo- correlative (cryo-CLEM) studies linking cryo-nanoscopy and cryo-FIB-SEM-based electron tomography.
In vitro reconstitution of microtubule network polarization.
Microtubules, biological polymers present in all eukaryotic cells, serve as a support for intracellular transport via molecular motors, thus defining cellular polarity. Contrary to the dogma establishing the centrosome as the determinant of this polarity, research from the CytoMorpho Lab reveals that microtubules can self-organize without an organizing center. In vitro experiments have demonstrated that microtubules actively separate molecular motors of opposite polarities into distinct domains, creating a new mechanism of active phase separation. Such partitioning of space by microtubules and motors constitutes a new mechanism of morphogenesis. The doctoral project aims to encapsulate this system in lipid vesicles of controlled size to study how relative dimensions enable efficient polarization. This approach will require the development of a microfluidic device and optimization of biochemical conditions for anchoring motors in the lipid bilayer. The perspectives include the creation of "artificial cells" capable of polarization and the reevaluation of cellular polarization models, particularly for T lymphocytes and other differentiated cells.
Study of the thermomechanical properties of solid hydrogen flows
IRIG's Department of Low Temperature Systems (DSBT) is developing several research themes around cryogenic solid hydrogen and its isotopes. The applications of this research range from the production of renewable micrometre-sized solid hydrogen targets for the generation of high-energy protons for laser-plasma acceleration, to the formation and injection of millimetre- or centimetre-sized hydrogen ice cubes for the supply and control of plasma in fusion reactors using magnetic or inertial confinement. A cross-cutting issue in these applications is the need for a detailed understanding of the mechanical properties of solid hydrogen, in order to gain a better understanding of the physics of extrusion and target production, as well as the formation and acceleration of icicles for injection into fusion plasmas.
The subject of this thesis focuses on the study of solid hydrogen extrusion under pressure. Using this technology, the DSBT has been developing several cryostats for over 10 years, enabling the production of ribbons of solid hydrogen, ranging in size from a few millimetres to a few tens of micrometres, extruded at speeds of a few millimetres per second.
The main objective of the research is to gain a better understanding of extrusion mechanisms to enable the development of numerical predictive tools for extrusion system design. This experimental thesis will be based on cryogenic rheometry using a capillary rheometer and/or a duvet experiment developed during a previous thesis. This study will be carried out in collaboration with the Laboratoire de Rhéologie et Procédés at Grenoble Alpes University.
INVESTIGATION OF CONFORMATIONAL HETEROGENEITY AND DYNAMICS IN FLUORESCENCE ACTIVATING AND ABSORPTION-SHIFTING TAGS (FAST)
Fluorescent proteins, particularly Reversibly Switchable Fluorescent Proteins (RSFPs), have revolutionized advanced fluorescence imaging, paving the way for applications such as super-resolution microscopy. Among emerging alternatives, fluorogen-based reporters, such as the FAST (Fluorescence Activating and Absorption Shifting Tag) system, stand out dur to their enhanced photostability and versatility. FAST operates via non-covalent binding of a small engineered protein to an organic fluorogen, which induces fluorescence and allowing real-time monitoring without chromophore maturation. However, challenges remain in optimizing these systems due to limited mechanistic understanding of fluorogen-protein interactions, binding dynamics, and photophysical behavior under illumination. This PhD project aims to characterize the binding modes of FAST systems at atomic resolution using multidimensional NMR spectroscopy, X-ray crystallography, and UV-visible spectroscopy. Recent findings suggest that fluorogens can adopt multiple binding modes, and that slight chemical modifications impact binding kinetics and fluorescence brightness. By integrating laser-based illumination in NMR investigations, we will further probe how light absorption affects fluorogen conformation and dynamics. The insights gained from this study will enable the rational design of optimized FAST variants, enhancing their performance for specific microscopy applications and advancing the field of fluorescence imaging.
Molecular dynamics and disorder in the viral replication machinery of SARS CoV 2
The nucleocapsid protein (N) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is essential for genome replication, encapsidating the viral genome and regulating gene transcription. The protein is highly disordered, comprising two disordered termini and a central disordered domain that are essential to its function. The central domain contains a number of important mutations that are responsible for enhanced viral fitness, and comprises a region that is hyperphosphorylated during the viral cycle. NMR spectroscopy is the tool of choice for studying the conformational behaviour of intrinsically disordered proteins, an abundant class of proteins that are functional in their disordered form. They represent 40% of the proteome and are too dynamic to be studied by crystallography or electron microscopy. The host lab has developed a large number of unique NMR-based tools to help understand the function of this class of proteins at atomic resolution. We will use NMR, paramagnetic NMR, small angle scattering, single molecule FRET and electron microscopy, in combination with molecular dynamics simulation, to describe the interactions of N with viral partner proteins and viral RNA to describe the process of encapsidation of the viral genome by the nucleocapsid protein, as well as the impact of mutations present in variants of concern. The results will be correlated with light and electron microscopy, carried out in collaboration.
Chiral Superconductors and Thermal Transport
In this PhD project, we intend to probe two well-known unconventional superconductors with thermal transport, through an original approach combining macroscopic and microscopic probes. These superconductors are UPt3 and UTe2, chosen because they address two issues currently under hot debate in the international community, that could strongly benefit from this new approach. UPt3 addresses the question of topological superconductivity, while UTe2 requires a clear identification of its spin-triplet superconducting order parameter.
Topological superconductivity is an active subject on the theoretical side and because of its potential interest in the field of quantum engineering. However, unambiguous experimental results are scarce, and we intend to focus here on UPt3, the first ever superconductor demonstrating the existence of transitions between superconducting phases, together with convincing evidences for chiral superconductivity. The goal is to probe predictions on the existence of an anomalous (zero field) thermal Hall effect, which would arise from the chiral edge currents.
A new approach is proposed, combining a newly designed set-up for the macroscopic measurement of thermal conductivity and thermal Hall effect, together with a microscopic probe realizing Scanning Thermal Spectroscopy. This will be realized thanks to a collaboration between two labratories in Grenoble: a team Pheliqs, mastering high quality crystal growth of these systems together with low temperature thermal transport measurements, and two teams in Néel, experts in Scanning SQUID microscopy and microscopic thermal measurements down to sub-Kelvin temperatures.
With this project, the PhD student will acquire very broad skills, ranging from sample preparation, low temperature instrumentation, and major actual issues in the field of quantum materials.
Control of two-dimensional magnetism by structural and chemical engineering of van der Waals interfaces
2D materials exhibit tunable interlayer interactions due to weak van der Waals bonding, which influences magnetic ordering in 2D magnets. The stacking sequence and internal chemistry impact ferromagnetic (FM) or antiferromagnetic (AFM) ordering, as seen in materials like CrBr3, CrI3, and Fe5GeTe2, where doping with Co raises the Curie temperature and alters magnetic phases. Chemical disorder also affects magnetic properties, with Mn/Sb substitution promoting FM ordering in Mn(Bi,Sb)2Te4. However, understanding how the atomic structure affects macroscopic magnetic properties remains limited due to the coexistence of metastable configurations. Precise control over stacking and chemical order is needed to harness 2D materials' magnetic and quantum properties. Transmission electron microscopy (TEM), especially aberration-corrected STEM, is today one of the most powerful techniques, enabling atomic-scale imaging and spectroscopy, for studying structural and chemical properties of 2D materials. This PhD project aims to study the relationship between atomic structure, chemistry, and magnetic properties in epitaxial 2D layers like (Fe,Co)5GeTe2, combining growth via molecular beam epitaxy (MBE) with STEM-based structural and chemical analysis.
Unraveling the mechanism of enzymatic carbon fixation
The Synchrotron Group at the Institut de Biologie Structurale in Grenoble is currently developing an innovative method called TR-FOX (Time-Resolved Functional Oscillation Crystallography). This technique aims to elucidate, firstly, the global dynamics of biological macromolecules in action and, secondly, their fine catalytic mechanism. It relies on the use of an injector capable of depositing onto the crystal, during the course of the X-ray diffraction data collection, a nanoliter droplet containing the substrate and cofactor of the studied reaction. This triggers the enzymatic reaction within the crystal. The approach can be combined with UV-Visible absorption spectroscopy to characterize the reaction kinetics more precisely. The goal is to obtain a series of structures during the catalytic cycle in order to make a molecular movie depicting the functioning of the enzyme. This thesis has two objectives: (i) improve and validate the TR-FOX method and, (ii) study the catalytic mechanism of two enzymes involved in carbon fixation either by capture or conversion of CO2.