Solubilité du CO2 dans les carbonates fondus à haut température

This thesis deals with the structural and transport properties study of different mixtures of molten carbonates used for the capture and valorisation of CO2. Different spectroscopic techniques (NMR, PFGNMR, NMR MAS, electrical impedancemetry, Raman) were used to study eutectic compositions Li2CO3/Na2CO3 (52:48 mol%), Li2CO3/K2CO3 (40:60 mol%), Li2CO3/K2CO3 (62:38 mol%) Li2CO3/Na2CO3/ K2CO3 (43.5:31.5:25 mol%), Na2CO3/ K2CO3 (59:41 mol%) and two binary systems : Li2CO3/Na2CO3 and Li2CO3/K2CO3 at high temperature. We also have studied the glass synthetized at highs temperature and pressure from the mixture K2CO3/MgCO3 (50:50 mol%). The NMR and Raman measurements confirmed only the presence of anionic species CO2-3. These result was confirmed by the study of glass obtained by quenching of liquid under high pressure. No effect of composition or temperature on speciation was detected. From the measurements of electrical conductivity and self-diffusion coefficients, we have shown that the electrical conductivity of carbonates doesn’t only depend on the radius of the cations, but also it depends on the electrostatic interaction between the ions. With the addition of K2CO3 to the mixture, the interaction between the charge carriers present in the liquid increases and results in a reduction of the electrical conductivity. Also we have shown that the high solubility of CO2 in compositions with high lithium carbonate content is associated with a high mobility of Li+ cations.Cette thèse porte sur l’étude structurale et sur les propriétés de transport de mélanges de carbonates fondus utilisés pour le captage et la valorisation du CO2. Différentes techniques spectroscopiques (RMN, RMN PFG, RMN MAS, impédancemétrie électrique, Raman) ont été utilisées pour étudier les compositions eutectiques Li2CO3/Na2CO3 (52:48 mol%), Li2CO3/K2CO3 (40:60 mol%), Li2CO3/K2CO3 (62:38 mol%) Li2CO3/Na2CO3/ K2CO3 (43.5:31.5:25 mol%), Na2CO3/ K2CO3 (59:41 mol%) ainsi que deux systèmes binaires : Li2CO3/Na2CO3 et Li2CO3/K2CO3 à haute température. Nous avons aussi étudié le verre synthétisé à haute pression à partir du mélange K2CO3/MgCO3 (50:50 mol%). Les mesures RMN et Raman n’ont pas mis en évidence la présence d’espèces anioniques autres que CO32-, résultat confirmé par l'étude du verre obtenu par trempe du liquide à haute pression. Aucun effet de la composition ni de la température sur la spéciation n’a été détecté. A partir des mesures de conductivité électrique et de coefficients d’autodiffusion, nous avons montré que la conductivité électrique des carbonates ne dépend pas seulement du rayon des cations, mais également de l’interaction électrostatique entre les ions. Avec l’ajout de K2CO3 au mélange, l’interaction entre les porteurs de charge présents dans le liquide augmente ce qui a pour effet de réduire la conductivité électrique. Enfin, nous avons montré que la haute solubilité du CO2 dans les compositions à haute teneur en carbonate de lithium est associée à une mobilité élevée des cations Li+

Solubility of CO2 in molten carbonates at high temperature

Cette thèse porte sur l’étude structurale et sur les propriétés de transport de mélanges de carbonates fondus utilisés pour le captage et la valorisation du CO2. Différentes techniques spectroscopiques (RMN, RMN PFG, RMN MAS, impédancemétrie électrique, Raman) ont été utilisées pour étudier les compositions eutectiques Li2CO3/Na2CO3 (52:48 mol%), Li2CO3/K2CO3 (40:60 mol%), Li2CO3/K2CO3 (62:38 mol%) Li2CO3/Na2CO3/ K2CO3 (43.5:31.5:25 mol%), Na2CO3/ K2CO3 (59:41 mol%) ainsi que deux systèmes binaires : Li2CO3/Na2CO3 et Li2CO3/K2CO3 à haute température. Nous avons aussi étudié le verre synthétisé à haute pression à partir du mélange K2CO3/MgCO3 (50:50 mol%). Les mesures RMN et Raman n’ont pas mis en évidence la présence d’espèces anioniques autres que CO32-, résultat confirmé par l'étude du verre obtenu par trempe du liquide à haute pression. Aucun effet de la composition ni de la température sur la spéciation n’a été détecté. A partir des mesures de conductivité électrique et de coefficients d’autodiffusion, nous avons montré que la conductivité électrique des carbonates ne dépend pas seulement du rayon des cations, mais également de l’interaction électrostatique entre les ions. Avec l’ajout de K2CO3 au mélange, l’interaction entre les porteurs de charge présents dans le liquide augmente ce qui a pour effet de réduire la conductivité électrique. Enfin, nous avons montré que la haute solubilité du CO2 dans les compositions à haute teneur en carbonate de lithium est associée à une mobilité élevée des cations Li+.This thesis deals with the structural and transport properties study of different mixtures of molten carbonates used for the capture and valorisation of CO2. Different spectroscopic techniques (NMR, PFGNMR, NMR MAS, electrical impedancemetry, Raman) were used to study eutectic compositions Li2CO3/Na2CO3 (52:48 mol%), Li2CO3/K2CO3 (40:60 mol%), Li2CO3/K2CO3 (62:38 mol%) Li2CO3/Na2CO3/ K2CO3 (43.5:31.5:25 mol%), Na2CO3/ K2CO3 (59:41 mol%) and two binary systems : Li2CO3/Na2CO3 and Li2CO3/K2CO3 at high temperature. We also have studied the glass synthetized at highs temperature and pressure from the mixture K2CO3/MgCO3 (50:50 mol%). The NMR and Raman measurements confirmed only the presence of anionic species CO2-3. These result was confirmed by the study of glass obtained by quenching of liquid under high pressure. No effect of composition or temperature on speciation was detected. From the measurements of electrical conductivity and self-diffusion coefficients, we have shown that the electrical conductivity of carbonates doesn’t only depend on the radius of the cations, but also it depends on the electrostatic interaction between the ions. With the addition of K2CO3 to the mixture, the interaction between the charge carriers present in the liquid increases and results in a reduction of the electrical conductivity. Also we have shown that the high solubility of CO2 in compositions with high lithium carbonate content is associated with a high mobility of Li+ cations

Understanding the bactericidal mechanism of Cu(OH)2 nanorods in water through Mg-substitution: high production of toxic hydroxyl radicals by non-soluble particles

International audienceTo date, there is still a lack of definite knowledge regarding the toxicity of Cu(OH)2 nanoparticles towards bacteria. This study was aimed at shedding light on the role played by released cupric ions in the toxicity of nanoparticles. To address this issue, the bactericidal activity of Cu(OH)2 was at first evaluated in sterile water, a medium in which particles are not soluble. In parallel, an isovalent substitution of cupric ions by Mg2+ was attempted in the crystal structure of Cu(OH)2 nanoparticles to increase their solubility and determine the impact on the bactericidal activity. For the first time, mixed Cu1xMgx(OH)2 nanorods (x ≤ 0.1) of about 15 nm in diameter and a few hundred nanometers in length were successfully prepared by a simple co-precipitation at room temperature in mixed alkaline (NaOH/Na2CO3) medium. For E. coli, 100% reduction of one million CFU per mL (6 log10) occurs after only 180 min on contact with both Cu(OH)2 and Cu0.9Mg0.1(OH)2 nanorods. The entire initial inoculum of S. aureus is also killed by Cu(OH)2 after 180 min (100% or 6 log10 reduction), while 0.01% of these bacteria stay alive on contact with Cu0.9Mg0.1(OH)2 (99.99% or 4 log10 reduction). The bactericidal performances of Cu(OH)2 and the magnesium-substituted counterparts (i.e. Cu1xMgx(OH)2) are not linked to cupric ions they release in water since their mass concentrations after 180 min are much lower than minimal concentrations inhibiting the growth of E. coli and S. aureus. Finally, an EPR spin trapping study reveals how these nanorods kill bacteria in water: only the presence of hydrogen peroxide, a by-product of the normal metabolism of oxygen in aerobic bacteria, allows the Cu(OH)2 and its magnesium-substituted counterparts to produce a lethal amount of free radicals, the majority of which are the highly toxic HO•

Flexible and luminescent fibers of a 1D Au( i )–thiophenolate coordination polymer and formation of gold nanoparticle-based composite materials for SERS

International audienceShaping of functional materials is of tremendous importance for applications. Among coordination polymer compounds, one of the challenges is to get fibers that can be self-standing and flexible, while maintaining their crystallinity and properties. Here, the synthesis and characterization of free-standing fibers of a Au(I)-based coordination polymer (CP) are reported. The flexible fibers of the 1D gold(I)–thiophenolate [Au(SPh)]n CP have an average diameter of 270 nm and length of a few micrometers. They are hydrophobic because of the presence of phenyl rings and exhibit high chemical stability in harshly acidic and basic conditions due to the strong Au(I)–S interactions. These fibers are red-emissive at room temperature because of the presence of aurophilic interactions. In addition, a composite material can be easily obtained through calcination, resulting in the formation of gold nanoparticles (AuNPs) on the CP fiber surface. Owing to the plasmonic resonance of AuNPs, this composite material exhibits good sensitivity towards the detection of molecules as observed through surface enhanced Raman scattering (SERS)

Revisiting Mg solubility in CuO nanorods: limit probed by neutron diffraction and effect on the particle toxicity towards bacteria in water

International audienceBoth nanometer-sized CuO and MgO particles exhibit bactericidal activities against Staphylococcus aureus and Escherichia coli, two bacteria causing healthcare-associated infections. The solid solution Cu1−xMgxO is potentially interesting for biomedical applications as one of the compositions could have a much higher bactericidal activity than the parent CuO and MgO oxides considered separately. But, to date, no Vegard’s law proves the real existence of such a solid solution. This study was aimed at shedding light on the solubility of Mg2+ ions in CuO nanoparticles and its impact on the free oxygen radicals they produce, the quantity of which determines their bactericidal performance. The solid solution Cu1−xMgxO does exist and particles were synthesized as nanorods of 50–60 nm length by thermally decomposing at 400 °C the single source precursors Cu1−xMgx(OH)2. Vegard’s laws exist only in the compositional range 0 ≤ x ≤ 0.1, due to the low capacity of the distorted NaCl-type structure to accommodate regular coordination [MgO6] octahedra. Only neutron diffraction allowed the detection of the small amount of MgO nanoparticles present as impurity in a 10 g sample beyond the solubility limit of x = 0.1. In this series, CuO nanorods remain the most active against E. coli and S. aureus with reduction in viability of 99.998% and 98.7% after 180 min in water, respectively. Our synthesis route has significantly increased the activity of pure CuO nanoparticles beyond the values reported so far, especially against E. coli. The bactericidal performances of CuO and the magnesium-substituted counterparts (i.e. Cu1−xMgxO) are not linked to cupric ions they release in water since their mass concentrations after 180 min are much lower than minimal concentrations inhibiting the growth of E. coli and S. aureus. TheseCuO nanorods kill bacteria in water because they produce a large quantity of free oxygen radicals in the presence of H2O2 only, the majority of which are highly toxic HO• radicals. Mg2+ ions have a detrimental effect on this production, thus explaining the lowest bactericidal performance of Cu1−xMgxO nanorods. Definitive knowledge of the toxicity of Cu1−xMgxO nanoparticles towards bacteria in water is now available

Transparent and luminescent glasses of gold thiolate coordination polymers

International audienceObtaining transparent glasses made of functional coordination polymers (CPs) represents a tremendous opportunity for optical applications. In this context, the first transparent and red-emissive glasses of gold thiolate CPs have been obtained by simply applying mechanical pressure to amorphous powders of CPs. The three gold-based CP glasses are composed of either thiophenolate [Au(SPh)]n, phenylmethanethiolate [Au(SMePh)]n or phenylethanethiolate [Au(SEtPh)]n. The presence of a longer alkyl chain between the thiolate and the phenyl ring led to the formation of glass with higher transparency. The glass transitions, measured by thermomechanical analysis (TMA), occurred at lower temperature for CPs with longer alkyl chains. In addition, all three gold thiolate glasses exhibit red emission at 93 K and one of them, [Au(SMePh)]n, remains luminescent even at room temperature. An in-depth structural study of the amorphous gold thiolates by XRD, PDF and EXAFS analysis showed that they are formed of disordered doubly interpenetrated helical chains. These d10 metal-based compounds represent the first examples of transparent and luminescent CP glasses