Halogen bonding in 1,2-dibromo-4,5-dimethoxybenzene and 1,2-diiodo-4,5-dimethoxybenzene

An interesting case of ‘halogen-bonding-promoted’ crystal structure architecture is presented. The two title compounds, C8H8Br2O2 and C8H8I2O2, have almost indistinguishable molecular structures but very different spatial organization, and this is mainly due to differences in the halogen-bonding interactions in which the different species present, i.e. Br and I, take part. The dibromo structure exhibits a Pi-bonded columnar array involving all four independent molecules in the asymmetric unit, with intercolumnar interactions governed by C—Br...Br—C links and with no C—Br...O/N interactions present. In the diiodo structure, instead, the C—I...O synthon prevails, de.ning linear chains, in turn interlinked by C—I...I—C interactions.8H8Br2O2 and C8H8I2O2, have almost indistinguishable molecular structures but very different spatial organization, and this is mainly due to differences in the halogen-bonding interactions in which the different species present, i.e. Br and I, take part. The dibromo structure exhibits a Pi-bonded columnar array involving all four independent molecules in the asymmetric unit, with intercolumnar interactions governed by C—Br...Br—C links and with no C—Br...O/N interactions present. In the diiodo structure, instead, the C—I...O synthon prevails, de.ning linear chains, in turn interlinked by C—I...I—C interactions.Fil: Cukiernik, Fabio Daniel. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de General Sarmiento. Instituto de Ciencias; ArgentinaFil: Zelcer, Andrés. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Garland, Maria Teresa. Universidad de Chile; ChileFil: Baggio, Ricardo Fortunato. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentin

Optical quality mesoporous alumina thin films

A robust method for the preparation of optical-quality mesoporous alumina thin films is presented, using evaporation induced self assembly of triblock copolymer surfactants. The use of lowly reactive aluminium chloride as a precursor and a tertiary alcohol as a novel chloride scavenger results in highly homogeneous and smooth films with consistent controllable thickness between 30 and 100 nm. The films show very low refractive index and high transparency from UV to NIR regions, providing a new building block for solution processing of devices requiring low-κ materials.Fil: Zelcer, Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; ArgentinaFil: Saleh Medina, Leila María. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; ArgentinaFil: Hoijemberg, Pablo Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; ArgentinaFil: Fuertes, Maria Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín. Instituto Sabato; Argentin

Nanoencapsulation of isotropic and anisotropic particles through a green chemistry aerosol method: a scalable approach for ad-hoc surface tuning

The interest in core–shell materials with chemically tunable mesoporous surfaces has significantly grown in recent years. The main limitation to obtain these systems through sequential precipitation is the tuning of the core and shell sol-gel chemistry, which usually implies low concentrations and leads to high-quality colloids although in small quantities after a lengthy and costly process. Aerosol approaches can lead to faster production and easier separation of functional materials with well-defined architectures. We present a “green chemistry” general method to coat sub-micron colloidal particles with a variety of mesoporous metal oxide nanofilms via an aerosol synthesis technique. Different types of particulate supports with isotropic and anisotropic shapes were dispersed into the precursor solutions in order to synthesize a mesoporous shell keeping the shape of the support. We chose the synthesis of TiO2 and TiSiO4 nanofilms on conventional Stöber SiO2 spherical particles, and on anisotropic micronized mica particles as a case study. We used the commercial surfactant Pluronic® F127 as a porogen. The structure and composition of the obtained nanofilms were characterized by electron microscopy, X-ray diffraction, focused ion beam coupled to SEM, and nitrogen adsorption/desorption isotherms. The TiO2 shells obtained (with an anatase-like structure) have pore diameters between 3.9–4.8 nm depending on the support with film thicknesses of ~100 nm, while amorphous TiSiO4 shells have larger diameters (9.5–16 nm) with film thicknesses of between 50 and 200 nm depending on the support used. The method presented shows high reproducibility and, unlike batch methods, allows the continuous production and straightforward recovery of the materials.Fil: Franceschini, Esteban Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Giménez, Gustavo. Instituto Nacional de Tecnologia Industrial. Gerencia Operativa de Desarrollo Tecnologico E Innovacion. Sub Gerencia Areas del Conocimiento. Direccion Tecnica de Micro y Nanotecnologias. Departamento Nanomateriales Funcionales.; ArgentinaFil: Lombardo, Maria Veronica. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes.; ArgentinaFil: Zelcer, Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; ArgentinaFil: Soler Illia, Galo Juan de Avila Arturo. Universidad Nacional de San Martin. Instituto de Nanosistemas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

One-pot synthesis of silica monoliths with hierarchically porous structure

Poly(furfuryl alcohol) (PFA) and block copolymer Pluronic F127 were used as pore templates to create mechanically robust silica monoliths with a hierarchical and interconnected macro?mesoporous network in an easy, reproducible bimodal scale templating process. Control over the morphology was obtained by varying the reactant ratios. Phase separation on the submicrometer scale occurred when furfuryl alcohol was cationically polymerized and therefore became immiscible with the solvent and the silica precursor. Upon a subsequent sol?gel reaction, a silica-F127 matrix formed around the PFA spheres, leading to macropore structures with mesoporous walls. Surface areas of the final structures ranged from 500 to 989 m2/g and a maximum pore volume of 4.5 mL/g was achieved. Under mildly acidic conditions, micelle-templated mesopores resulted. Interconnected macropores could be obtained by increasing the pH or the block copolymer concentration. The formation mechanism and the relationship between PFA, Pluronic F127 and acidity are discussed in detail.Fil: Drisko, Glenna L.. University of Melbourne; AustraliaFil: Zelcer, Andrés. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Caruso, Rachel A.. University of Melbourne; AustraliaFil: Soler Illia, Galo Juan de Avila Arturo. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentin

Synthesis and photocatalytic activity of titania monoliths prepared with controlled macro- and mesopore structure

Herein, we report a one-pot synthesis of crack-free titania monoliths with hierarchical macro-mesoporosity and crystalline anatase walls. Bimodal macroporosity is created through the polymer-induced phase separation of poly(furfuryl alcohol). The cationic polymerization of furfuryl alcohol is performed in situ and subsequently the polymer becomes immiscible with the aqueous phase, which includes titanic acid. Addition of template, Pluronic F127, increases the mesopore volume and diameter of the resulting titania, as the poly(ethylene glycol) block interacts with the titania precursor, leading to assisted assembly of the metal oxide framework. The hydrophobic poly(propylene glycol) micelle core could itself be swollen with monomeric and oligomeric furfuryl alcohol, allowing for mesopores as large as 18 nm. Variations in synthesis parameters affect porosity; for instance furfuryl alcohol content changes the size and texture of the macropores, water content changes the grain size of the titania and Pluronic F127 content changes the size and volume of the mesopore. Morphological manipulation improves the photocatalytic degradation of methylene blue. Light can penetrate several millimeters into the porous monolith, giving these materials possible application in commercial devices.Fil: Drisko, Glenna L.. University of Melbourne; AustraliaFil: Zelcer, Andrés. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; ArgentinaFil: Wang, Xingdong. Commonwealth Scientific And Industrial Research Organization; AustraliaFil: Caruso, Rachel A.. School Of Chemistry; Australia. Commonwealth Scientific And Industrial Research Organization; AustraliaFil: Soler Illia, Galo Juan de Avila Arturo. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

One-pot synthesis of hierarchically structured ceramic monoliths with adjustable porosity

Hierarchically porous oxides are used in a variety of applications within the energy sector (e.g., fuel cells, batteries), biology (e.g., scaffolds, biocatalysis), separations, and catalysis. This article describes a reproducible one-step method for the preparation of metal oxides with controllable hierarchical pore architectures. The preparation is demonstrated for a wide range of materials, specifically silica, titania, zirconia, aluminum titanium oxide, titanium zirconium oxide, and yttrium zirconium oxide monoliths. The samples were prepared by exploiting the polymerization and phase separation of furfuryl alcohol to produce a colloidal dispersion of poly(furfuryl alcohol) particles. The gelation in the sol-gel process occurred after the in situ formation of the template. The removal of the polymer template led to the formation of macropores, whereas inclusion of an amphiphilic block copolymer (Pluronic F127) assisted mesopore formation, either by templating or by stabilizing the inorganic building blocks. The macropore and mesopore morphology could be altered by varying the synthesis conditions. This control over the pore structure was demonstrated in the silica, titania, and titanium zirconium oxide materials.Fil: Drisko, Glenna L.. University of Melbourne; AustraliaFil: Zelcer, Andrés. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Luca, Vittorio. Comisión Nacional de Energía Atómica; ArgentinaFil: Caruso, Rachel A.. University of Melbourne; AustraliaFil: Soler Illia, Galo Juan de Avila Arturo. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Incorporation of porous protective layers as a strategy to improve mechanical stability of Tamm plasmon based detectors

Nanostructures supporting optical modes known as Tamm plasmon-polaritons are a new class of optical devices with promising characteristics for sensing applications. Their synthesis involves the deposition of a thin metallic layer on top of a distributed Bragg reflector. Unfortunately, this metallic layer can be easily detached or scratched during normal handling or under operating conditions. In this work, a new strategy to protect these devices from mechanical stress by adding a porous protective overlayer is presented. Three different mesoporous oxides prepared using a sol-gel process were chosen to cover the device: ZrO2 and Ti-Si mixed oxides functionalized with either vinyl or phenyl groups. The mechanical and tribological properties of each candidate were measured using nanoindentation and its ideal thickness was determined by simulation of the optical response. Finally, the devices were characterized mechanically, to test their stability, and their sensing capabilities were determined for both liquids and vapours. The results indicate that thin mesoporous films used as protective layers provide a clear improvement in the device's resistance towards mechanical stress without compromising the optical and sensing properties. The strategy of protection using a porous top layer presented in this work can be extended to other devices which require interaction with the environment through an exposed unstable surface.Fil: Morrone, Josefina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes.; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); ArgentinaFil: Ramallo, Juan Ignacio. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes.; Argentina. Universidad Nacional de San Martín. Instituto Sabato; ArgentinaFil: Lionello, Diego Fernando. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes.; Argentina. Universidad Nacional de San Martín. Instituto Sabato; ArgentinaFil: Zelcer, Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; ArgentinaFil: Auguie, Baptiste Maxime Raphael. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); Argentina. Victoria University of Wellington; Nueva ZelandaFil: Angelome, Paula Cecilia. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes.; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); ArgentinaFil: Fuertes, Maria Cecilia. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes.; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); Argentin

A liquid crystal derived from ruthenium(II,III) and a long-chain carboxylate

The title compound, catena-poly[[tetrakis(μ-decanoato-κ2O:O′)diruthenium(II,III)(Ru—Ru)]-μ-octanesulfonato-κ2O:O′], [Ru2(C10H19O2)4(C8H17O3S)], is an octane­sulfonate derivative of the mixed-valence complex diruthenium tetradecanoate. The equatorial carboxyl­ate ligands are bidentate, bridging two Ru atoms to form a dinuclear structure. Each of the two independent dinuclear metal complexes in the asymmetric unit is located at an inversion centre. The octane­sulfonate anion bridges the two dinuclear units through axial coordination. The alkyl chains of the carboxyl­ate and sulfonate ligands are arranged in a parallel manner. The global structure can be seen as infinite chains of polar moieties separated by a double layer of non-polar alkyl groups, without interdigitation of the alkyl chains.Facultad de Ciencias Exacta

Growth and Branching of Gold nanoparticles Through MesoporousSilica Thin Films

Composite materials made of mesoporous oxide thin films containing metallic nanoparticles are of high interest in various fields, including catalysis, biosensing and non-linear optics. We demonstrate in this work the fabrication of such composite materials containing a sub-monolayer of gold nanoparticles (GNPs) of various shapes covered with mesoporous silica thin films. Additionally, the shape of the GNPs (and thus their optical properties) can be modified in situ through seeded growth and branching. Such growth proceeds upon wetting with HAuCl 4 solution, a surfactant (cetyltrimethylammonium bromide, CTAB) and a mild reducing agent (ascorbic acid, AA). The effect of varying several reaction parameters (time and CTAB and AA concentrations) was evaluated, showing that more anisotropic particles are obtained at longer reaction times, lower CTAB concentration and higher AA concentration. The final shape of the GNPs was also found to depend on their initial shape and size, as well as the pore size of the mesoporous film covering them. Because the growth proceeds through the pores of the film, it may lead to shapes that are not easily obtained in solution, such as particles with branches on one side only. Finally, we have confirmed that no damage was induced to the mesoporous silica structure during the growth process and thus the final particles remain well covered by the thin film, which can eventually be used as a filter between the GNPs and the outer medium.Fil: Angelomé, Paula C.. Universidad de Vigo; EspañaFil: Pastoriza Santos, Isabel. Universidad de Vigo; EspañaFil: Pérez Juste, Jorge. Universidad de Vigo; EspañaFil: Rodríguez-González, Benito. Universidad de Vigo; EspañaFil: Zelcer, Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; ArgentinaFil: Soler Illia, Galo Juan de Avila Arturo. Universidad de Buenos Aires; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Liz Marzán, Luis M.. Universidad de Vigo; Españ

Liquid crystalline materials based on the hyrbid system Triphenylene-Siloxane

En este trabajo se desarrolla la síntesis, caracterización y estudio de las propiedades térmicas y estructurales de compuestos mesogénicos basados en una arquitectura híbrida trifenileno-siloxano-alcano, con el objetivo de obtener materiales que reúnan propiedades de los segmentos trifenileno, como la formación de mesofases columnares, y de los segmentos siloxano, como la baja viscosidad, la baja tendencia a cristalizar y la baja temperatura de transición vítrea. Se prepararon tres grupos de compuestos: monoméricos, oligoméricos y poliméricos. En cada uno de estos grupos la movilidad molecular se ve cada vez más restringida. Todos los compuestos estudiados presentaron mesofases columnares hexagonales, generalmente ordenadas, con temperaturas de fusión desde por debajo de temperatura ambiente hasta 78°C y de isotropización desde 52°C hasta 108°C. Salvo excepciones, no se produce la microsegregación de los distintos tipos de segmento sino que la repulsión estérica entre grupos siloxano los lleva a ubicarse en posiciones alejadas en el espacio. Esta repulsión lleva a efectos drásticos en el comportamiento térmico de isómeros con distinta geometría de sustitución sobre el núcleo aromático, y lleva a la formación de una superestructura en la mesofase de uno de los compuestos estudiados. Uno de los oligómeros sintetizados puede ser alineado mecánicamente, abriendo la posibilidad de obtener cristales líquidos columnares monodominio. Se propone un mecanismo de orientación en el que las interacciones atractivas entre centros trifenileno funcionan como enlaces entre distintos oligómeros, reforzando el comportamiento correlacionado de por sí ya presente en los cristales líquidos.In this work the synthesis, characterization and study of the termal and structural properties of mesogenic compounds base don an hybrid triphenylene-siloxane-alcane architecture are developed, aiming at the realization of materials that gather properties from the triphenylene moieties, like the induction of columnar mesophases, and from the siloxane moieties, like low viscosity, low tendency to crystallization and low glass transition temperatures. Three groups of compound were prepared: monomeric compounds, oligomeric compounds and polymers. In each of this groups the molecular movility is gradually more hindred. All the studied compounds show hexagonal columnar mesophases, usually ordered, with fusion temperatures ranging from under room temperature up to 78°C, and isotropization temperaturas ranging from 52°C up to 108°C. Except for one case, there is no microsegregation of the disctint molecular moieties, but a strong steric repulsion between siloxane groups, that forces them to stay away from each other. This repulsion has drastic effects on the thermal behaviour of isomers of different sustitution geometry, and induces the formation of a superstructure in one compound’s mesophase. One of the oligomers can be mechanically aligned, living the possibility of realizing monodomain columnar liquid crystals. A orientation mechanism is proposed, in which the atractive interactions betweem triphenylene centres act as bond between different oligomers, enhancing the collective behaviour already present in liquid crystalline materials.Fil: Zelcer, Andrés. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina