Balanced homodyne detection in second-harmonic generation microscopy

We demonstrate the association of two-photon nonlinear microscopy with balanced homodyne detection for investigating second harmonic radiation properties at nanoscale dimensions. Variation of the relative phase between second-harmonic and fundamental beams is retrieved, as a function of the absolute orientation of the nonlinear emitters. Sensitivity down to approximately 3.2 photon/s in the spatio-temporal mode of the local oscillator is obtained. This value is high enough to efficiently detect the coherent second-harmonic emission from a single KTiOPO4 crystal of sub-wavelength size.Comment: 9 pages to appear in Applied Physics Letter

Chemistry related to the [Fe]-Hydrogenases

The work in this thesis is focused on the synthesis, reactivity and electrochemistry of chemical models of the active site structures found in [Fe]-hydrogenase, an enzyme that catalyses the reversible reduction of protons to dihydrogen. This enzyme possesses an unusual active site, the “H-cluster”, which is comprised of an {Fe4S4}-cubane linked by a cysteinyl bridge to a di-iron organometallic subsite which is ligated by dithiolate, CO and CN groups.Chapter I gives a general overview of the biology and chemistry of iron-sulfur proteins and chemical models of their prosthetic groups, with emphasis on the [Fe]-hydrogenase.Chapter II describes the synthesis, structures and spectroscopic features of 6 new {2Fe3S}-subsite model complexes with a range of functional groups together with X-ray crystallographic structures for all of these.Chapter III reports and discusses the electrochemical properties of the new {2Fe3S}-complexes. Studies on electrocatalytic hydrogen evolution by these systems are also described.Chapter IV reports the first synthesis of a free-standing “H-cluster” model complex in which an {Fe4S4}-cubane cluster is coupled to an {2Fe3S}-subsite as in [Fe]-hydrogenase. Spectroscopic, electrochemical and DFT calculations provide an insight into the electronic properties of the synthetic assembly and this is placed in the context of the natural system.Chapter V describes some early results on the incorporation of synthetic di-iron subsites into electropolymers to provide solid-state electrocatalysts together with the prospects for future work in the area.La synthèse de modèles du site actif de l'hydrogénase à fer, responsable de la catalyse réversible de la réduction des protons en dihydrogène, est un enjeu crucial dans l'optique d'une meilleure compréhension du fonctionnement du système enzymatique et du développement de nouveaux types de catalyseurs à base de clusters fer-soufre. Durant cette thèse ont été abordés les aspects synthétiques (ligands soufrés et complexes fer-carbonyle) aussi bien que les études spectroscopiques et électrochimiques

Transferts couplés electron proton : relais, coupures et catalyse

HD

Proton-Coupled Electron Transfer in Azobenzene/Hydrazobenzene Couples with Pendant Acid–Base Functions. Hydrogen-Bonding and Structural Effects

International audienc

Attempts To Catalyze the Electrochemical CO 2 -to-Methanol Conversion by Biomimetic 2e – + 2H + Transferring Molecules

International audienc

Ligand “noninnocence” in coordination complexes vs. kinetic, mechanistic, and selectivity issues in electrochemical catalysis

International audienc

A Pioneering Career in Electrochemistry: Jean-Michel Savéant

International audienceProf. Jean-Michel Savéant sadly passed on August 16 2020. We would like to honor his memory, his tremendous contribution to electrochemistry and its use for a general understanding of the laws of physical chemistry. In this review, we highlight his decisive role in the foundation of molecular electrochemistry. We also present his major achievements in the field of molecular and biomolecular catalysis. Finally, we review his unique contribution to dissociative electron transfers and to the electrochemical approach of proton-coupled electron transfers. This shows how various concepts rigorously established and experimentally validated assemble to each other to enlighten complex systems

pH-dependence on HER electrocatalytic activity of iron sulfide pyrite nanoparticles

Iron sulfide pyrite (FeS2) nanoparticles are investigated for the electrocatalysis of hydrogen evolution reaction (HER) at pH values ranging from 0.3 to 13. It is evidenced that HER can be performed at any pH, showing remarkable robustness and stability for more than 24 h. The catalytic mechanism for HER by pyrite nanoparticles changes over the pH range, with a pH-dependent behavior below pH 5 and a pH-independent behavior above pH 5. Keywords: Hydrogen evolution reaction, Pyrite, Iron sulfide, Electrocatalytic film

Offshore CO₂ Capture and Utilization Using Floating Wind/PV Systems: Site Assessment and Efficiency Analysis in the Mediterranean

A methanol island, powered by solar or wind energy, indirectly captures atmospheric CO2 through the ocean and combines it with hydrogen gas to produce a synthetic fuel. The island components include a carbon dioxide extractor, a desalinator, an electrolyzer, and a carbon dioxide-hydrogen reactor to complete this process. In this study, the optimal locations to place such a device in the Mediterranean Sea were determined, based on three main constraints: power availability, environmental risk, and methanol production capability. The island was numerically simulated with a purpose built python package pyseafuel. Data from 20 years of ocean and atmospheric simulation data were used to “force” the simulated methanol island. The optimal locations were found to strongly depend on the power availability constraint, with most optimal locations providing the most solar and/or wind power, due to the limited effect the ocean surface variability had on the power requirements of methanol island. Within this context, optimal locations were found to be the Alboran, Cretan, and Levantine Sea due to the availability of insolation for the Alboran and Levantine Sea and availability of wind power for the Cretan Sea. These locations were also not co-located with areas with larger maximum significant wave heights, thereby avoiding areas with higher environmental risk. When we simulate the production at these locations, a 10 L s−1 seawater inflow rate produced 494.21, 495.84, and 484.70 mL m−2 of methanol over the course of a year, respectively. Island communities in these regions could benefit from the energy resource diversification and independence these systems could provide. However, the environmental impact of such systems is poorly understood and requires further investigation

Inserting a Hydrogen-Bond Relay between Proton Exchanging Sites in Proton-Coupled Electron Transfers

International audienc