Correlative cellular ptychography with functionalized nanoparticles at the Fe L-edge

Precise localization of nanoparticles within a cell is crucial to the understanding of cell-particle interactions and has broad applications in nanomedicine. Here, we report a proof-of-principle experiment for imaging individual functionalized nanoparticles within a mammalian cell by correlative microscopy. Using a chemically-fixed HeLa cell labeled with fluorescent core-shell nanoparticles as a model system, we implemented a graphene-oxide layer as a substrate to significantly reduce background scattering. We identified cellular features of interest by fluorescence microscopy, followed by scanning transmission X-ray tomography to localize the particles in 3D, and ptychographic coherent diffractive imaging of the fine features in the region at high resolution. By tuning the X-ray energy to the Fe L-edge, we demonstrated sensitive detection of nanoparticles composed of a 22 nm magnetic Fe$_3$O$_4$ core encased by a 25-nm-thick fluorescent silica (SiO$_2$) shell. These fluorescent core-shell nanoparticles act as landmarks and offer clarity in a cellular context. Our correlative microscopy results confirmed a subset of particles to be fully internalized, and high-contrast ptychographic images showed two oxidation states of individual nanoparticles with a resolution of ~16.5 nm. The ability to precisely localize individual fluorescent nanoparticles within mammalian cells will expand our understanding of the structure/function relationships for functionalized nanoparticles

Heterogeneous catalysts via non-hydrolytic sol/gel process

Les synthèses par sol-gel non-hydrolytique (SGNH) d'oxydes mixtes Re-Si-Al et Mo-Si-Al sont présentées comme une voie innovante pour la préparation en une étape de catalyseurs hétérogènes de métathèse. Les catalyseurs supportés à base d'oxyde de molybdène sont intéressants du fait de leur faible coût d'achat, de leur résistance mécanique et de leur bonne activité à température modérée. Les catalyseurs supportés à base d'oxyde de rhénium sont connus pour être très actifs et sélectifs même à température ambiante. Cependant ils sont chers et la sublimation de l'oxyde de rhénium pose problème lors de leur synthèse. La synthèse utilisée est basée sur la réaction en une étape des précurseurs chlorés (ReCl5 ou MoCl3, SiCl4, AlCl3) avec du diisopropyléther (iPr2O) à 110 °C dans le dichloromethane. Le faible coût des précurseurs, l'absence de modificateurs de réactivité et de templates ainsi que la simplicité de synthèse rendent le procédé SGNH particulièrement attractif. Les catalyseurs oxydes mixtes obtenus présentent des compositions bien contrôlées, des textures mésoporeuses et avec des densités en sites acides élevées. La caractérisation par DRX, XPS et ToF-SIMS montre que les catalyseurs peuvent être décrits comme une matrice silice-alumine amorphe avec des espèces de surface Mo et Re bien dispersées. Pour les catalyseurs à base de Re, dans les compositions riches en silice, des pertes de rhénium ont été observées durant la calcination. Cette perte de rhenium peut être évitée en augmentant le taux d'alumine dans la composition. De plus, nous avons montré que la sublimation de Re, au cours de la calcination dans les compositions riches en silice, n'a pas lieu quand toutes les étapes du procédé (synthèse, lavage, séchage et calcination) sont réalisées en l'absence d'humidité. Nous avons étudié l'influence de la composition sur la texture, la structure, l'acidité et les propriétés de surface, qui sont corrélées aux performances catalytiques. Les performances des catalyseurs Re-Si-Al et Mo-Si-Al ont été évaluées en métathèse du propène et en métathèse croisée de l'éthène et du trans-2-butène. Les catalyseurs SGNH sont comparés à des catalyseurs avec des compositions similaires préparés par d'autres méthodes (imprégnation, thermal spreading, flame spray pyrolysis). Les catalyseurs préparés par SGNH présentent une très bonne activité spécifique en métathèse.The non-hydrolytic sol-gel synthesis (NHSG) of Re-Si-Al and Mo-Si-Al mixed oxides was proposed as an innovative one step route to heterogeneous olefin metathesis catalysts. Supported molybdenum oxide catalysts are receiving much attention as a result of their relatively low price, robustness and good activity at low temperature. Supported rhenium oxide catalysts are known to be highly active and selective even at room temperature. However, they are expensive and moderately stable because of the sublimation of the rhenium oxide. The NHSG synthesis used in this work is based on the one pot reaction of chloride precursors (ReCl5 or MoCl3, SiCl4, AlCl3) with diisopropylether (iPr2O) at 110 °C in dichloromethane. The simplicity of NHSG makes it attractive: multi-step procedures, expensive precursors, or reactivity modifiers are not needed. The mixed oxide catalysts exhibited well-controlled compositions and mesoporous textures, with high acid site densities. XRD, XPS and ToF-SIMS showed that the catalysts could be described as an amorphous silica-alumina matrix with well-dispersed Re or Mo surface species. In the case of Re-based catalysts, rhenium losses by sublimation during calcination were observed for the silica-rich formulations. The loss of rhenium could however be avoided by increasing the Al content. More importantly we demonstrate that Re sublimation during calcination of silica-rich formulations is suppressed when the whole preparation procedure (synthesis, washing, drying and calcination) is carried out in the absence of water. Particular attention was devoted to the study of the influence of the composition on texture, structure, acidity and surface properties, which were correlated with the catalytic performances. The performance of selected Re-Si-Al and Mo-Si-Al catalysts was evaluated in the metathesis of propene and in the cross-metathesis of ethene and trans-2-butene. The NHSG catalysts were compared to catalysts of similar compositions prepared by other more methods (impregnation, thermal spreading, flame spray pyrolysis). The catalysts prepared by NHSG have a high specific activity in the metathesis reaction

Synthèse par procédé sol-gel non-hydrolytique de catalyseurs oxydes mixtes pour la métathèse d'oléfines

Les synthèses par sol-gel non-hydrolytique (SGNH) d'oxydes mixtes Re-Si-Al et Mo-Si-Al sont présentées comme une voie innovante pour la préparation en une étape de catalyseurs hétérogènes de métathèse. Les catalyseurs supportés à base d'oxyde de molybdène sont intéressants du fait de leur faible coût d'achat, de leur résistance mécanique et de leur bonne activité à température modérée. Les catalyseurs supportés à base d'oxyde de rhénium sont connus pour être très actifs et sélectifs même à température ambiante. Cependant ils sont chers et la sublimation de l'oxyde de rhénium pose problème lors de leur synthèse. La synthèse utilisée est basée sur la réaction en une étape des précurseurs chlorés (ReCl5 ou MoCl3, SiCl4, AlCl3) avec du diisopropyléther (iPr2O) à 110 C dans le dichloromethane. Le faible coût des précurseurs, l'absence de modificateurs de réactivité et de templates ainsi que la simplicité de synthèse rendent le procédé SGNH particulièrement attractif. Les catalyseurs oxydes mixtes obtenus présentent des compositions bien contrôlées, des textures mésoporeuses et avec des densités en sites acides élevées. La caractérisation par DRX, XPS et ToF-SIMS montre que les catalyseurs peuvent être décrits comme une matrice silice-alumine amorphe avec des espèces de surface Mo et Re bien dispersées. Pour les catalyseurs à base de Re, dans les compositions riches en silice, des pertes de rhénium ont été observées durant la calcination. Cette perte de rhenium peut être évitée en augmentant le taux d'alumine dans la composition. De plus, nous avons montré que la sublimation de Re, au cours de la calcination dans les compositions riches en silice, n'a pas lieu quand toutes les étapes du procédé (synthèse, lavage, séchage et calcination) sont réalisées en l'absence d'humidité. Nous avons étudié l'influence de la composition sur la texture, la structure, l'acidité et les propriétés de surface, qui sont corrélées aux performances catalytiques. Les performances des catalyseurs Re-Si-Al et Mo-Si-Al ont été évaluées en métathèse du propène et en métathèse croisée de l'éthène et du trans-2-butène. Les catalyseurs SGNH sont comparés à des catalyseurs avec des compositions similaires préparés par d'autres méthodes (imprégnation, thermal spreading, flame spray pyrolysis). Les catalyseurs préparés par SGNH présentent une très bonne activité spécifique en métathèse.The non-hydrolytic sol-gel synthesis (NHSG) of Re-Si-Al and Mo-Si-Al mixed oxides was proposed as an innovative one step route to heterogeneous olefin metathesis catalysts. Supported molybdenum oxide catalysts are receiving much attention as a result of their relatively low price, robustness and good activity at low temperature. Supported rhenium oxide catalysts are known to be highly active and selective even at room temperature. However, they are expensive and moderately stable because of the sublimation of the rhenium oxide. The NHSG synthesis used in this work is based on the one pot reaction of chloride precursors (ReCl5 or MoCl3, SiCl4, AlCl3) with diisopropylether (iPr2O) at 110 C in dichloromethane. The simplicity of NHSG makes it attractive: multi-step procedures, expensive precursors, or reactivity modifiers are not needed. The mixed oxide catalysts exhibited well-controlled compositions and mesoporous textures, with high acid site densities. XRD, XPS and ToF-SIMS showed that the catalysts could be described as an amorphous silica-alumina matrix with well-dispersed Re or Mo surface species. In the case of Re-based catalysts, rhenium losses by sublimation during calcination were observed for the silica-rich formulations. The loss of rhenium could however be avoided by increasing the Al content. More importantly we demonstrate that Re sublimation during calcination of silica-rich formulations is suppressed when the whole preparation procedure (synthesis, washing, drying and calcination) is carried out in the absence of water. Particular attention was devoted to the study of the influence of the composition on texture, structure, acidity and surface properties, which were correlated with the catalytic performances. The performance of selected Re-Si-Al and Mo-Si-Al catalysts was evaluated in the metathesis of propene and in the cross-metathesis of ethene and trans-2-butene. The NHSG catalysts were compared to catalysts of similar compositions prepared by other more methods (impregnation, thermal spreading, flame spray pyrolysis). The catalysts prepared by NHSG have a high specific activity in the metathesis reaction.MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Impact of Mesoporous Silica Functionalization Fine-Tuning on Antibiotic Uptake/Delivery and Bactericidal Activity.

peer reviewedThe mesoporous SBA-15 material was surface-functionalized with amino and carboxylic acid groups and used as a platform to investigate the interaction of these chemical groups with tetracycline, kanamycin, and ampicillin antibiotics. The interactions between the antibiotic and the functionalized surfaces were characterized using two-dimensional 1H-13C HETCOR CP MAS and FTIR spectroscopy and indicated that -COO- NH3 + bondings had been formed between chemical groups on the silica surface and drug molecules. The surface modification resulted in higher kanamycin and ampicillin loadings and a slow-release rate, and all synthesized systems showed antibacterial activity against susceptible Escherichia coli bacteria. Almost total death of bacteria was obtained using a few ppm of tetracycline- and kanamycin-loaded systems, whereas the ampicillin-loaded one showed lower bactericidal activity than free ampicillin

High-Surface-Area SiO2-ZrO2 Mixed Oxides as Catalysts for the Friedel-Crafts-Type Alkylation of Arenes with Alcohols and Tandem Cyclopropanation Reactions

International audienceThe catalytic activity of SiO2-ZrO2 mixed oxides was studied for the Friedel-Crafts-alkylation reaction between anisole and benzylic or allylic alcohols. In particular, the influence of Zr content on the catalytic activity was studied. The catalyst with the lowest Zr content (5 mol% ZrO2) showed the highest activity with high selectivity for the alkylated product and good recyclability. We used this catalyst in the reaction of 1-phenyl-1- ethanol with toluene and xylene. We also studied the possibility of a tandem process that involved a Friedel-Crafts alkylation and the subsequent trans-hydrogenation of trans-1,3-diphenyl- 2-propen-1-ol for the synthesis of substituted cyclopropanes

Molecular Assemblies from Imidazolyl-Containing Haloalkenes and Haloalkynes: Competition between Halogen and Hydrogen Bonding

International audience1-(3-Iodopropargyl)imidazole and 1-(2,3,3-triiodoallyl)imidazole self-assemble to give polymeric chains as a result of N...I halogen bonding. However, these interactions are not sufficiently strong to compete with hydrogen bonding. N-H...O and N-H...N interactions govern the molecular arrangement in the 1:1 cocrystal of 1-(2,3,3-triiodoallyl)imidazole and morpholinium iodide

Guanidinium Alkynesulfonates with Single-Layer Stacking Motif: Interlayer Hydrogen Bonding Between Sulfonate Anions Changes the Orientation of the Organosulfonate R Group from “Alternate Side” to “Same Side”

International audienceHydrolyses of HCCSO3SiMe3 (1) and CH3CCSO3SiMe3 (2) lead to the formation of acetylenic sulfonic acids HCCSO3H·2.33H2O (3) and CH3CCSO3H·1.88H2O (4). These acids were reacted with guanidinium carbonate to yield [+C(NH2)3][HCCSO3] (5) and [+C(NH2)3][CH3CCSO3] (6). Compounds 1–6 were characterized by spectroscopic methods, and the X-ray crystal structures of the guanidinium salts were determined. The X-ray results of 5 show that the guanidinium cations and organosulfonate anions associate into 1D ribbons through R22(8) dimer interactions, whereas association of these ions in 6 is achieved through R22(8) and R12(6) interactions. The ribbons in 5 associate into 2D sheets through R22(8) dimer interactions and R36(12) rings, whereas those in 6 are connected through R12(6) and R22(8) dimer interactions and R46(14) rings. Compound 6 exhibits a single-layer stacking motif similar to that found in guanidinium alkane- and arenesulfonates, that is, the alkynyl groups alternate orientation from one ribbon to the next. The stacking motif in 5 is also single-layer, but due to interlayer hydrogen bonding between sulfonate anions, the alkynyl groups of each sheet all point to the same side of the sheet

H-1, C-13, and N-15 Solid-State NMR Studies of Imidazole- and Morpholine-Based Model Compounds Possessing Halogen and Hydrogen Bonding Capabilities

The halogen and hydrogen bonding interactions present in solid 1-(2,3,3-triiodoallyl)imidazole (1), morpholinium iodide (2), the 1:1 cocrystal 1-(2,3,3-triiodoallyl)imidazole-morpholinium iodide (3), morpholine (4), imidazole (5), and 1-(3-iodopropargyl)imidazole (6) have been investigated by solid-state H-1, C-13, and N-15 NMR spectroscopies. Comparison of the N-15 CP MAS NMR spectrum of 3 with that of 2 indicates that protonated morpholine is present in solid 3, but this conclusion must be taken with caution as GIPAW calculations predict a N-15 chemical shift for morpholine similar to that of the morpholinium cation. Conclusive evidence for the presence of a morpholinium cation in crystalline 3 was obtained by recording the static N-15 NMR spectrum of this host-guest complex and comparing the morpholiniun/morpholine part of the spectrum with the static spectra of 3 and 4 as obtained from ab initio calculations of NMR parameters based on the X-ray structures of these compounds. Concerning the imidazolyl group, N-15 NMR spectroscopy has proven quite valuable to identify changes in the bonding situation of the C-N = C nitrogen on passing from 1 to 3. In addition, slight differences are observed between the N-15 chemical shifts of 1 and 6 that are ascribed to differences in halogen bond strengths between the two compounds. Attempts have also been made to study halogen bonding by C-13 NMR spectroscopy, but this method did not provide exploitable results as signals corresponding to the sp and sp(2) carbon atoms bonded to iodine could not be observed experimentally. H-1 NMR spectroscopy is a powerful tool to study hydrogen bonding interactions of moderate energies such as +NH2 center dot center dot center dot X (X = N, O, I). Indeed, we have found that the chemical shifts of the NH hydrogens were quite sensitive to the nature of X and to the N-H center dot center dot center dot X distance. This is demonstrated by the fact that the chemical shifts of the +NH2 protons of the morpholinium cation in 2 and 3 are noticeably different

Avoiding rhenium loss in non-hydrolytic synthesis of highly active Re-Si-Al olefin metathesis catalysts

International audienc

Hydrolytic vs. Nonhydrolytic Sol-Gel in Preparation of Mixed Oxide Silica-Alumina Catalysts for Esterification

International audienceThis article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC B