Synthesis of Mesoporous Silica@Co–Al Layered Double Hydroxide Spheres: Layer-by-Layer Method and Their Effects on the Flame Retardancy of Epoxy Resins

Hierarchical mesoporous silica@Co–Al layered double hydroxide (m-SiO2@Co–Al LDH) spheres were prepared through a layer-by-layer assembly process, in order to integrate their excellent physical and chemical functionalities. TEM results depicted that, due to the electrostatic potential difference between m-SiO2 and Co–Al LDH, the synthetic m-SiO2@Co–Al LDH hybrids exhibited that m-SiO2 spheres were packaged by the Co–Al LDH nanosheets. Subsequently, the m-SiO2@Co–Al LDH spheres were incorporated into epoxy resin (EP) to prepare specimens for investigation of their flame-retardant performance. Cone results indicated that m-SiO2@Co–Al LDH incorporated obviously improved fire retardant of EP. A plausible mechanism of fire retardant was hypothesized based on the analyses of thermal conductivity, char residues, and pyrolysis fragments. Labyrinth effect of m-SiO2 and formation of graphitized carbon char catalyzed by Co–Al LDH play pivotal roles in the flame retardance enhancement

Molecular Clusters in Mesoporous Materials as Precursors to Nanoparticles of a New Lacunar Ternary Compound PdxMoyP

Bimetallic clusters of composition Pd2Mo2(g5-C5H5)2(l3-CO)2(l2-CO)4 (PR3)2 (R = ethyl or phenyl) were incorporated by impregnation from solution into two different silica matrices, amorphous xerogels and ordered SBA-15, and a study of their thermal decomposition under a reducing atmosphere is reported. With both matrices, a suitable thermal treatment afforded nanoparticles of a new bimetallic phosphide. Although nanoparticles of composition PdxMoyP, isostructural with Mo3P, were formed in both matrices, they were more uniformly distributed in the SBA-15 framework and showed a narrower size distribution. The samples have been characterized by powder XRD, chemical analysis, FT-IR spectroscopy, TEM and electron tomography (3D TEM)

Nanoscale Confinement and Fluorescence Effects of Bacterial Light Harvesting Complex LH2 in Mesoporous Silicas

Many key chemical and biochemical reactions, particularly in living cells, take place in confined space at the mesoscopic scale. Toward understanding of physicochemical nature of biomacromolecules confined in nanoscale space, in this work we have elucidated fluorescence effects of a light harvesting complex LH2 in nanoscale chemical environments. Mesoporous silicas (SBA-15 family) with different shapes and pore sizes were synthesized and used to create nanoscale biomimetic environments for molecular confinement of LH2. A combination of UV-vis absorption, wide-field fluorescence microscopy, and in situ ellipsometry supports that the LH2 complexes are located inside the silica nanopores. Systematic fluorescence effects were observed and depend on degree of space confinement. In particular, the temperature dependence of the steady-state fluorescence spectra was analyzed in detail using condensed matter band shape theories. Systematic electronic-vibrational coupling differences in the LH2 transitions between the free and confined states are found, most likely responsible for the fluorescence effects experimentally observed

Polymer Composites Containing Gated Mesoporous Materials for On-Command Controlled Release

Polyamidic nanofibrous membranes containing gated silica mesoporous particles, acting as carriers, are described as novel hybrid composite materials for encapsulation and on-command delivery of garlic extracts. The carrier system consists of MCM-41 solids functionalized in the outer surface, with linear polyamines (solid P1) and with hydrolyzed starch (solid P2), both acting as molecular gates. Those particles were adsorbed on electospun nylon-6 nanofibrous membranes yielding to composite materials M1 and M2. FE-SEM analysis confirmed the presence of particles incorporated on the nylon nanofibers. The release of the entrapped molecules (garlic extract) from the P1, P2, M1, and M2 materials was evaluated using cyclic voltammetry measurements. Electrochemical studies showed that at acidic pH P1 and M1 were unable to release their entrapped cargo (closed gate), whereas at neutral pH both materials release their loading (open gate). Dealing with P2 and M2 materials, in the absence of pancreatin a negligible release is observed (closed gate), whereas in the presence of enzyme the load is freely to diffuse to the solution. These newly developed composite nanomaterials, provide a homogeneous easy-to-handle system with controlled delivery and bioactive-protective features, having potential applications on pharmacology, medical and engineering fields.The authors wish to express their gratitude to the Generalitat Valenciana (Grisolia scholarship 2011/012, project PROM-ETEO/2009/016), Spanish Government (MINECO Projects AGL2012-39597-C02-01, AGL2012-39597-C02-02 and MAT2012-38429-C04-01) and the CIBER-BBN for their support. IILA thanks DISTAM and Universita degli di Milano for a specialization scholarship. We would also like to thank the Institut de Ciencia dels Materials (ICMUV) and to the Microscopy Service of the Universitat Politecnica de Valencia for technical support. We thank Roquette for the Glucidex samples.Acosta Romero, C.; Pérez Esteve, E.; Fuenmayor, CA.; Benedetti, S.; Cosio, MS.; Soto Camino, J.; Sancenón Galarza, F.... (2014). Polymer Composites Containing Gated Mesoporous Materials for On-Command Controlled Release. ACS Applied Materials and Interfaces. 6(9):6453-6460. https://doi.org/10.1021/am405939y645364606

Structure and Luminescence Properties of Eu3+-Doped Cubic Mesoporous Silica Thin Films

Eu3+ ions-doped cubic mesoporous silica thin films with a thickness of about 205 nm were prepared on silicon and glass substrates using triblock copolymer as a structure-directing agent using sol–gel spin-coating and calcination processes. X-ray diffraction and transmission electron microscopy analysis show that the mesoporous silica thin films have a highly ordered body-centered cubic mesoporous structure. High Eu3+ ion loading and high temperature calcination do not destroy the ordered cubic mesoporous structure of the mesoporous silica thin films. Photoluminescence spectra show two characteristic emission peaks corresponding to the transitions of5D0-7F1 and 5D0-7F2 of Eu3+ ions located in low symmetry sites in mesoporous silica thin films. With the Eu/Si molar ratio increasing to 3.41%, the luminescence intensity of the Eu3+ ions-doped mesoporous silica thin films increases linearly with increasing Eu3+ concentration

Delivery modulation in silica mesoporous supports via alkyl chain pore outlet decoration

This article focuses on the study of the release rate in a family of modified silica mesoporous supports. A collection of solids containing ethyl, butyl, hexyl, octyl, decyl, octadecyl, docosyl, and triacontyl groups anchored on the pore outlets of mesoporous MCM-41 has been prepared and characterized. Controlled release from pore voids has been studied through the delivery of the dye complex tris(2,2¿-bipyridyl)ruthenium(II). Delivery rates were found to be dependent on the alkyl chain length anchored on the pore outlets of the mesoporous scaffolding. Moreover, release rates follow a Higuchi diffusion model, and Higuchi constants for the different hybrid solids have been calculated. A decrease of the Higuchi constants was observed as the alkyl chain used to tune the release profile is longer, confirming the effect that the different alkyl chains anchored into the pore mouths exerted on the delivery of the cargo. Furthermore, to better understand the relation between pore outlets decoration and release rate, studies using molecular dynamics simulations employing force-field methods have been carried out. A good agreement between the calculations and the experimental observations was observed.Financial support from the Spanish Government (projects MAT2009-14564-C04-01 and MAT2009-14564-C04-04) and the Generalitat Valencia (project PROMETEO/2009/016) is gratefully acknowledged.Aznar Gimeno, E.; Sancenón Galarza, F.; Marcos Martínez, MD.; Martínez Mañez, R.; Stroeve, P.; Cano, J.; Amoros Del Toro, P. (2012). Delivery modulation in silica mesoporous supports via alkyl chain pore outlet decoration. Langmuir. 28:2986-2996. https://doi.org/10.1021/la204438jS298629962

Experimental evidence of the ferroelectric phase transition near the λ−\lambda-point in liquid water

We studied dielectric properties of nano-sized liquid water samples confined in polymerized silicates MCM-41 characterized by the porous sizes \sim 3-10nm. We report the direct measurements of the dielectric constant by the dielectric spectroscopy method at frequencies 25Hz-1MHz and demonstrate clear signatures of the second-order phase transition of ferroelectric nature at temperatures next to the \lambda- point in the bulk supercooled water. The presented results support the previously developed polar liquid phenomenology and hence establish its applicability to model actual phenomena in liquid water.Comment: 4 pages, single figur

Self-Assembly Fabrication of Hollow Mesoporous Silica@Co–Al Layered Double Hydroxide@Graphene and Application in Toxic Effluents Elimination

Here, we propose a self-assembly process to prepare hierarchical HM-SiO2@Co–Al LDH@graphene, with the purpose of combining their outstanding performance. Hollow mesoporous silica was first synthesized as the core, using a novel sonochemical method, followed by a controlled shell coating process and chemical reduction. As a result of the electrostatic potential difference among HM-SiO2, Co–Al LDH, and graphene oxide, the HM-SiO2 spheres were coated by Co–Al LDH and graphene. Subsequently, the HM-SiO2@Co–Al LDH@graphene spheres were introduced into an epoxy resin (EP) matrix for investigation of their toxic effluents capture and elimination effectiveness during combustion. The amount of toxic CO and volatile organic compounds from the epoxy resin decomposition significantly suppressed after incorporating the HM-SiO2@Co–Al LDH@graphene hybrids, implying a reduced toxicity