Influence of the sacrificial polystyrene removal pathway on the TiO₂ nanocapsule structure

This study demonstrates the significant influence of the polystyrene removal pathway on the TiO₂ nanocapsules obtained from PS@TiO₂ core-shell particles. In a first step, the polystyrene spheres were coated with titanium oxide via hydrolysis and condensation of the titanium precursor to form PS@TiO₂ core-shell particles. Then, the creation of the empty cavity to form TiO₂ nanocapsules was achieved by removing the polystyrene template by i) thermal decomposition of the polystyrene or ii) dissolution of the polystyrene using Soxhlet extractor followed by a thermal procedure. These pathways to remove the polystyrene were investigated by thermogravimetric studies, IR spectroscopy, transmission and scanning electron microscopy and powder X-ray diffraction. The final TiO₂ nanocapsule structure strongly depends on the sacrificial polystyrene removal pathway. The preservation of the TiO₂ nanocapsules was obtained essentially when the polystyrene was dissolved before the crystallization of the TiO₂

Threading salen-type Cu- and Ni-complexes into one-dimensional coordination polymers: solution versus solid state and the size effect of the alkali metal ion

Compartmentalization of metal ions is crucial in biology as well as in materials science. For the synthesis of single source precursors, the preorganization of different metal ions is of particular interest for the low-temperature generation of mixed metal oxides. On the basis of a potentially Ω-shaped salen-type ligand providing an N2O2 as well as an O2O2 coordination site, mixed metal coordination compounds with Cu(II) or Ni(II) and alkali metal ions have been studied for their structural and optical properties. UV–vis and 1H NMR titrations show that the obtained compounds adopt partially different structures in solution compared to the solid state. In the latter case, the coordination geometry is mainly governed by the size of the alkali metal ion as well as the transition metal ion used

Ag Nanoencapsulation for Antimicrobial Applications

Biomaterial-related infections remain a significant challenge in medicine. Antimicrobial materials on the basis of Ag nanoparticles represent a promising solution for this issue. Therefore several Ag-containing nanocontainers and nanorattles have been synthesized and characterized that exhibit remarkable control over the release of Ag+ as antimicrobial active species. Their biological evaluation against prokaryotic as well as eukaryotic cells reveals that they fulfill the prerequisites for applications as antimicrobial implant coatings

Sequential multiple-target sensor: In3+, Fe2+, and Fe3+ discrimination by an anthracene-based probe

Indium is a nonphysiological toxic metal widely used in industry. While misunderstood, its toxicity is proposed to be linked to a perturbation of Fe3+ homeostasis through the binding of In3+ ions to essential iron metalloproteins such as transferrins. Therefore, the monitoring of In3+ and Fe3+ in biological environments is of prime interest for both basic research and diagnosis. Here we report the design of a salen-type anthracene- based probe able to selectively sense and discriminate In3+ and Fe2+/3+ ions by fluoro-colorimetry

Controlled preparation of supported Pt-Rh bimetallic catalysts

Les catalyseurs Pt-Rh supportés ont montré des propriétés intéressantes en ouverture sélective des naphtènes. Les performances catalytiques de ces catalyseurs dépendent, entre autres, de l'interaction entre le rhodium et le platine. L'objectif de ces travaux portait sur l'étude de l'influence de la méthode de préparation sur les interactions Pt-Rh. Dans ce but, plusieurs voies reposant sur des stratégies de synthèse différentes ont été sélectionnées, des plus classiques, comme l'imprégnation, aux plus sophistiquées, comme la modification d'un catalyseur monométallique parent par ajout d'un second métal par réaction de surface, la formation des particules Pt-Rh au sein de microémulsion ou de microsuspension ou encore la réduction des précurseurs métalliques assistée par radiolyse. Les catalyseurs ont été caractérisés par diverses techniques telles que la chimisorption d'hydrogène, la microscopie électronique en transmission, la réduction en température programmée, l'adsorption de molécules sondes (CO ou NO puis CO) suivie par infrarouge ou encore par réactions modèles. Ces caractérisations ont permis de mettre en évidence que (i) les imprégnations classiques ou assistées par radiolyse mènent à un mélange de particules monométalliques et bimétalliques, (ii) les méthodes de modification de surface permettent le dépôt du second métal sur les sites spécifiques des particules métalliques préformées, (iii) la synthèse des particules métalliques en microsuspension ou microémulsion permet également l'obtention de particules bimétalliques, mais avec la présence d'alliages Pt-Rh de surface.Pt-Rh supported catalysts have demonstrated interesting properties in selective ring opening of naphthenic molecules. Their catalytic performances depend on several properties like platinum-rhodium interaction. The aim of this work was to study the influence of the preparation method on Pt-Rh interactions. For this purpose, several preparation ways were selected, from the most classical ones, such as impregnation, to more sophisticated ways such as (1) surface modification of monometallic catalyst by addition of a second metal (surface reactions), (2) formation of Pt-Rh particles in microemulsion or in microsuspension, or (3) impregnation assisted by radiolysis. Catalysts were characterized by various techniques such as hydrogen chemisorption, transmission electron microscopy, temperature programmed reduction, adsorption of probe molecules (CO or NO then CO) followed by infrared spectroscopy, or model reactions.These characterizations allowed demonstrating that (i) the classical impregnation or the one assisted by radiolysis leads to monometallic and bimetallic particles, (ii) metal deposition on specific sites of preformed metallic particles can be obtained by surface modification of monometallic catalysts, (iii) the synthesis of metallic particles in microemulsion or microsuspension yields bimetallic entities with Pt-Rh alloy at the particle surface

Bimetallic salen-based compounds and their potential applications

The new bimetallic coordination compounds [LNiAg(NO3)], [LCuMn(NO3)2], [LCuCu(NO3)2], [LCuZn(NO3)2], and [{LCuBi(NO3)3}(ACN)] have been synthesized from a salen-type ligand L containing two distinct coordination sites to accommodate (different) metal ions M1 and M2. In the solid state, the formation of 1:1 compounds (LCu:M2) is always observed, but interactions between the compounds lead to differences in packing. For example, a head-to-tail arrangement along the crystallographic b-axis is observed in the case of the LCuBi compound, and the LNiAg compound is polymeric, while its Cu homologue LCuAg forms a discrete dimer. Given the inherent potential of the preorganizing, two metal ions using L could be used to synthesize nanoscale copper–bismuth and −manganese mixed metal oxides as a function of the temperature. The combination of different bioactive metal ions within one ligand system was furthermore explored for antimicrobial efficiency

Controlled preparation and characterization of Pt-Rh/Al 2 O 3 bimetallic catalysts for reactions in reducing conditions

Pt-Rh bimetallic catalysts on alumina support were prepared according to three different techniques, one leading to random deposition of the two metals at the support’s surface, the two others, namely the organometallic grafting and the colloidal route, favoring the formation of bimetallic particles with strong Pt-Rh interactions. Catalysts were characterized by ICP, H2 chemisorption, TPR, FTIR of chemisorbed CO and NO-CO. Then they were evaluated in cyclohexane dehydrogenation and methylcyclopentane hydrogenolysis reactions. Strong interaction between Pt and Rh was demonstrated for catalysts prepared by controlled preparation method, which leads to a strong synergetic effect for methylcyclopentane ring-opening, in terms of activity and selectivity, whereas these interactions do not play a role in cyclohexane dehydrogenation.Fil: Hérault, Nelly. Université de Poitiers; FranciaFil: Olivet, Lilian. Université de Poitiers; FranciaFil: Pirault Roy, Laurence. Université de Poitiers; FranciaFil: Especel, Catherine. Université de Poitiers; FranciaFil: Vicerich, Maria Ana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Pieck, Carlos Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Epron, Florence. Université de Poitiers; Franci

Silver-containing titanium dioxide nanocapsules for combating multidrug-resistant bacteria

Background: Joint arthroplasty has improved the quality of life of patients worldwide, but infections of the prosthesis are frequent and cause significant morbidity. Antimicrobial coatings for implants promise to prevent these infections. Methods: We have synthesized nanocapsules of titanium dioxide in amorphous or anatase form containing silver as antibacterial agent and tested their impact on bacterial growth. Furthermore, we explored the possible effect of the nanocapsules on the immune system. First, we studied their uptake into macrophages using a combination of electron microscopy and energy- dispersive spectroscopy. Second, we exposed immune cells to the nanocapsules and checked their activation state by flow cytometry and enzyme- linked immunosorbent assay. Results: Silver-containing titanium dioxide nanocapsules show strong antimicrobial activity against both E. coli and S. aureus and even against a multidrug-resistant strain of S. aureus. We could demonstrate the presence of the nanocapsules in macrophages, but, importantly, the nanocapsules did not affect cell viability and did not activate proinflammatory responses at doses up to 20 μg/mL. Conclusion: Our bactericidal silver-containing titanium dioxide nanocapsules fulfill important prerequisites for biomedical use and represent a promising material for the coating of artificial implants