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Breaking the deep-red light absorption barrier of iridium( iii )-based photosensitizers
No full textInternational audienceActivating photosensitizers with long-wavelength excitation is an important parameter for effective photodynamic therapy due to the minimal toxicity of this light, its superior tissue penetration, and excellent spatial resolution. Unfortunately, most Ir(III) complexes suffer from limited absorption within the phototherapeutic window, rendering them ineffective against deep-seated and/or large tumors, which poses a significant barrier to their clinical application. To address this issue, several efforts have been recently made to shift the absorption of Ir(III) photosensitizers to the deep-red/near-infrared region by using different strategies: functionalization with organic fluorophores, including porphyrinoid compounds, and ligand design via π-extension and donor–acceptor interactions. In this Frontier, we highlight such new developments and the ongoing challenges in this field
Electronic interactions of a quatertiophene-based surfactant at the liquid/gas interface
No full textInternational audienceWe report the synthesis of a new functional molecule, a quater-tiophene based surfactant, which can both adsorb at the water / gas interface (surface active molecule) and aggregates through pi-pi stacking interactions. We assess then the ability of this molecule to create these functionalities at interfaces. This interfacial functional aggregation, characterized here in situ for the first time, is probed thanks to Langmuir trough experiments and spectrometric ellipsometry. These results open some new routes for the design of new water based opto-electronic devices
Benzo-12-crown-4-ether-mediated lithium transport in supercritical CO2: A preliminary study for recycling lithium-ion battery cathode materials
No full textInternational audienceThe design of metal-complexing copolymer architectures is essential to enable solvent-free recovery of critical metals, and of interest for a large number of applications. In this study, the lithium transport efficiency of benzo-12-crown-4-ether (B12C4) from various salts (LiNO3, LiOAc, Li2SO4 and Li2CO3) in supercritical carbon dioxide (scCO2) was investigated. Among these salts, only Li+ from LiNO3 was effectively complexed by B12C4 in scCO2. As both B12C4 and the [B12C4-Li]NO3 complex are poorly soluble in scCO2, a scCO2-philic gradient polymer, poly(B12C4 ethyl methacrylamide-grad-1,1,2,2-tetrahydroperfluorodecyl acrylate) [P(B12C4EMAAm-grad-FDA)] was synthesized by RAFT polymerization. In this copolymer, the FDA unit is CO2-philic, while B12C4EMAAm acts as a metal-complexing group. The solubility of the copolymer was determined by cloud point measurement and compared to that of a PFDA homopolymer. The lithium recovery yield from lithium nitrate, quantified by inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis, reached 83 % under supercritical conditions (40 °C and 250 bar) in the presence of a small amount of water (molar ratio [water]/[LiNO3]=7.6), whereas only 25 % was recovered under dry conditions. The Li+ transport efficiency of the copolymer was also evaluated in the presence of cobalt ions. Using a mixture of lithium nitrate and cobalt nitrate hexahydrate (molar ratio [B12C4EMAAm]:[Li]:[Co]=3.6:1:1), recovery yields of 46 % and 84 % for lithium and cobalt were obtained, respectively. Despite its lack of selectivity toward lithium, P(B12C4EMAAm-grad-FDA) demonstrates strong potential as a complexing ligand for both lithium and cobalt under scCO2 conditions
A microstructure-resolved model of sodium-ion battery hard carbon electrodes
No full textInternational audienceTo improve the design and accelerate the adoption of Sodium-Ion Batteries (SIBs), it is necessary to improve our understanding of the electrochemical behavior of Hard Carbon (HC) negative electrodes. We report here a novel electrochemical model that unravels the sodiation mechanism of HC electrodes. This model considers the explicit 3D-resolved HC electrode microstructure at the mesoscale, operating in a half cell versus sodium metal. We have parameterized and validated this model using structural (particle shape and size, skeletal density, and textural properties) and electrochemical (cycling protocol, experimental capacity, and discharge profile) characterizations of a specific HC material. Then, we used the model to investigate how manufacturing parameters (formulation and porosity) affect the 3D-resolved sodiation heterogeneities, impacting the electrochemical performance at different C-rates. Our model represents the first approach to create a flexible computational tool for researchers and engineers to assess the kinetic and transport limitations of their specific HC material. Furthermore, it can help them understand the underlying sodiation phenomena taking place in their material via direct comparison with their galvanostatic profiles, while considering the sodiation heterogeneities arising from the electrode's 3D microstructure, supporting the ramp-up in the production of SIBs
Investigation of nitrogen-vacancy centre creation and position control in thin single-crystal diamond films
No full textInternational audienceThe remarkable physical and chemical attributes of diamond have established it as a leading material for a wide array of applications. Its properties make it invaluable in areas such as optics, electronics, biomedicine, mechanics, and the rapidly evolving field of quantum technologies.A Distributed Antenna Array (DAA) microwave system (Fig. 1), comprising 16 plasma sources arranged in a 2D matrix, has been successfully used for the deposition of single-crystal diamond (SCD) layers using H2/CH4/CO2 and H2/CH4/O2 gas mixtures. Operating at low pressure (< 1 mbar), this system provides highly homogeneous plasma and low growth rates (< 100 nm.h⁻¹), ensuring precise control over layer thickness and defect positioning. Among these defects, colour centres, particularly nitrogen-vacancy (NV) centres, are of significant interest due to their promising applications in quantum technology. Precisely controlling their position within the diamond lattice is key for optimizing their performance in quantum devices.In this work, using this innovative reactor, we synthesized nitrogen-doped SCD films of approximately 100 nm in thickness by introducing N2 into the initial gas mixture. Our aim was to refine both growth and post-treatment processes to improve NV centre creation and spin properties. In particular, we explored a new growth procedure suitable for enhancing the efficiency of in situ NV formation while reducing reliance on post-growth treatments. We successfully reduced the thickness of this in situ nitrogen-doped layer down to 50 nm. NV⁻/NV⁰ photoluminescence intensities and spin coherence time (T2*) of the produced NVs were determined throughout the process, i.e. before and after SCD growth, and following post-treatments such as He implantation and annealing. This step-by-step approach enabled improved NV centre formation and properties, paving the way for more efficient quantum technologies and nanoscale sensing systems
Fabrication of correlated disordered structures in thin films to tune the visual appearance of surfaces
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A-Site Vacancy Engineering in KNbO 3 Perovskite for Enhanced Lithium Storage
No full textInternational audienceDesign of tailored materials using innovative approaches that allow faster charging/discharging processes could be the key for improvement of electric mobility. In this work, a strategy is developed to modify KNbO3 perovskite structure by partially substituting K+ with La3+ at the A-site of the structure, creating two cation vacancies per substitution in the lattice. Materials with the general formula K1-3x La x square 2x NbO3 (with 0 <= x <= 0.15; square is an A-site vacancy) have been synthesized by the sol-gel method. With La substitution and creation of artificial vacancies in the structure, KNbO3 became activated for Li+ insertion. The highly substituted K0.55La0.15 square 0.30NbO3 (30% atomic A-site vacancies) exhibited 164 mAh g-1 at 0.02 A g-1 in the 0.05-3.0 V vs Li+/Li potential window. Ex situ 7Li and 93Nb MAS NMR confirmed an increased Li+ insertion in relation to vacancies and corresponding changes in Nb5+ local environment, respectively. In situ X-ray diffraction (XRD) analysis revealed a solid-solution-type storage mechanism with a maximum volume change of only 1.3% upon Li+ insertion for highly substituted material. This accounts for the remarkable capacity retention obtained after 900 cycles at 0.1 Ag-1. Diverged from the classical design of insertion materials, this study presents an alternative approach of creating vacancies without sacrificing the pristine phase, with a possibility to use the not so common class of ABO3-type perovskites as the battery electrode
Heptafluorobutyronitrile (c4f7n), hydrolysis, a density functional theory (dft) investigation
No full textInternational audienceHeptafluorobutyronitrile (C3F7CN) has received much consideration as an effective substitute to sulfur hexafluoride (SF6) in the electrical industrial sector over the last decade. However, liability is the key to emerging technology, and the thermoelectric aging of the insulation gases may produce unavoidable consequences that raise concerns for the operator and human safety. Recently, numerous pieces of literature mentioned the production of crystals in the form of amide and dimer (ligand) generated from the aging of C4F7N with few ppm of water molecules. It was found that the hydrolysis of fluoronitrile chemical reactions initial with the production of amide (C4H2F7NO) and following, with the addition of C4F7N molecules, accelerates the reaction to produce dimer (C8H2F14N2O), trimer (C12H2F21N30), tetramer (C16H2F28N40), and finally a triazine (C12F21N3) molecule. Thermodynamically, Rc is the favorable chemical reaction with a 23 kcal/mol energy barrier that generates a dimer molecule. Furthermore, with the presence of copper (Cu) metal, these dimers make the Cu complex as violet crystals. Gibbs free energy at elevated temperature indicates the driving force is needed to accelerate the reaction except Rd, whose energy values throughout remain consistent. Theoretical calculations reveal the water acts as a strong catalytic that can abruptly reduce the energy barrier from 59 to 10 kcal and open the pathway to generate the byproducts
Assessment of Indium‐Free Transparent Conductive Oxide Back Contacts for High‐Efficiency Ultra‐Thin Cu (In,Ga)Se 2 Solar Cells Down to 250 nm
No full textInternational audienceABSTRACT This work examines the feasibility and performance impact of replacing the usual molybdenum back contact with indium‐free transparent conductive oxides (TCOs) like fluorine‐doped tin oxide (SnO 2 :F) and aluminum‐doped zinc oxide (ZnO:Al) for ultra‐thin Cu (In,Ga)Se 2 (CIGS) solar cells (250–450 nm). Motivated by indium scarcity and cost reduction, these TCOs are evaluated for their figure of merit, stability under Se atmosphere, Na diffusion permeability, and band alignment with CIGS absorbers. Using simulations, prototype fabrication, and comprehensive characterizations, the compatibility of these TCOs with CIGS absorbers is assessed. Solar cells with thicknesses of 450 and 250 nm are fabricated. Their performance was compared under both rear and front illumination, as well as with the use of reflectors. A record efficiency of 8.6% with front illumination is achieved for a 250‐nm CIGS absorber using a gold back reflector with SnO 2 :F, single‐step CIGS deposition, and no heavy alkalines doping. The best rear‐illuminated efficiencies are obtained with ZnO:Al back contacts, reaching 6% for a 250‐nm CIGS, with only a 9% loss in J sc compared to front illumination, confirming a lower surface recombination rate at the ZnO:Al/CIGS interface compared to Mo/CIGS or SnO 2 :F/CIGS interfaces
Novel approach to probe ionic species mobility in molten salts electrolyte for Thermal Batteries
No full textInternational audienceMolten salt electrolytes play a crucial role in thermal battery cells, offering excellent electrochemical performance and zero self-discharge at room temperature before melting. However, the transport properties of ionic species in these media are not well understood, and much remains unknown about the factors that determine the effectiveness of one electrolyte over another.This study investigates the mobility of ionic species, particularly lithium and fluorine, in eutectic molten salt mixtures like LiF-LiCl-LiBr, commonly used in thermal batteries. Using advanced in situ high-temperature techniques, including high-temperature nuclear magnetic resonance (HT-NMR), pulsed field gradients (PFG), and electrochemical impedance spectroscopy (EIS), we aim to understand the ionic motion processes. The research also examines the binding of these salts with an MgO powder and the effect of compaction on retention properties.The LiF-LiCl-LiBr eutectic shows superior ionic conductivity compared to systems like LiCl-KCl due to its higher lithium concentration and greater lithium mobility. Lithium diffuses faster than other ionic species, such as fluorine, but its high melting point of 440 • C limits its operational temperature range. The compaction rate of bound pellets is key to electrolyte performance, influencing ionic mobility. Higher compaction enhances lithium diffusion but may cause leakage above certain thresholds, depending on salt type and temperature.This innovative approach enables rapid testing of various electrolytic compositions and binders, helping assess performance and the impact of manufacturing processes.</div