Search results for "porous material"
showing 10 items of 361 documents
Cyclic metal(oid) clusters control platinum-catalysed hydrosilylation reactions : from soluble to zeolite and MOF catalysts
2020
The Pt-catalysed addition of silanes to functional groups such as alkenes, alkynes, carbonyls and alcohols, i.e. the hydrosilylation reaction, is a fundamental transformation in industrial and academic chemistry, often claimed as the most important application of Pt catalysts in solution. However, the exact nature of the Pt active species and its mechanism of action is not well understood yet, particularly regarding regioselectivity. Here, experimental and computational studies together with an ad hoc graphical method show that the hydroaddition of alkynes proceeds through Pt-Si-H clusters of 3-5 atoms (metal(oid) association) in parts per million amounts (ppm), which decrease the energy of…
Enzyme-responsive intracellular-controlled release using silica mesoporous nanoparticles capped with ε-poly-L-lysine.
2014
The synthesis and characterization of two new capped silica mesoporous nanoparticles for controlled delivery purposes are described. Capped hybrid systems consist of MCM-41 nanoparticles functionalized on the outer surface with polymer epsilon-poly-L-lysine by two different anchoring strategies. In both cases, nanoparticles were loaded with model dye molecule [Ru(bipy)(3)](2+). An anchoring strategy involved the random formation of urea bonds by the treatment of propyl isocyanate-functionalized MCM-41 nanoparticles with the lysine amino groups located on the epsilon-poly-L-lysine backbone (solid Ru-rLys-S1). The second strategy involved a specific attachment through the carboxyl terminus of…
High Fluorescence of Thioflavin T Confined in Mesoporous Silica Xerogels
2013
Trapping of organic molecules and dyes within nanoporous matrices is of great interest for the potential creation of new materials with tailored features and, thus, different possible applications ranging from nanomedicine to material science. The understanding of the physical basis of entrapment and the spectral properties of the guest molecules within the host matrix is an essential prerequisite for the design and control of the properties of these materials. In this work, we show that a mesoporous silica xerogel can efficiently trap the dye thioflavin T (ThT, a molecule used as a marker of amyloid fibrils and with potential drug benefits), sequestering it from an aqueous solution and pro…
Control of the pore wall thickness and thermal stability in low-cost bimodal porous silicas
2019
Abstract A new hierarchical bimodal mesoporous silica, labelled as UVM-12 (acronym of University of Valencia Materials), has been prepared by using a solution of sodium silicate as low-cost silicon source. The final self-assembling between cationic micelles of CTAB and anionic inorganic Si-based oligomers occurs in a homogeneous aqueous medium. The reaction is carried out from low-sized building blocks through a bottom-up approach. The UVM-12 solids combine two mesopore systems according to N2 adsorption–desorption isotherms, what is corroborated by TEM micrographs and XRD patterns. This material has been inorganically modified by incorporation of Al or Ti (M-UVM-12, M = Al, Ti) without alt…
Interaction of Gold with Co-Condensed and Grafted HMS-SH Silica: A 29Si {1H} CP-MAS NMR Spectroscopy, XRD, XPS and Au LIII EXAFS Study
2010
Hexagonal mesoporous silica (HMS) is functionalised with mercaptopropyl groups by adopting two different procedures ; co-condensation and grafting. In both cases tetraethylorthosilicate (TEOS) and 3-mercaptopropyltriethoxysilane (3-MPTES) are used as the silicon and sulfur precursors, respectively. The obtained materials are analysed by several techniques such as N 2 sorption, TG-DTA, XRD, SAXS and-solid state 29 Si { 1 H} CP-MAS NMR spectroscopy. By taking advantage of the chemical interaction between gold and the -SH groups, the effect of the thiol addition procedure on the supporting capability of the functionalised silica is evaluated by depositing gold through the incipient wet impregn…
Protein delivery based on uncoated and chitosan-coated mesoporous silicon microparticles
2011
Mesoporous silicon is a biocompatible, biodegradable material that is receiving increased attention for pharmaceutical applications due to its extensive specific surface. This feature enables to load a variety of drugs in mesoporous silicon devices by simple adsorption-based procedures. In this work, we have addressed the fabrication and characterization of two new mesoporous silicon devices prepared by electrochemistry and intended for protein delivery, namely: (i) mesoporous silicon microparticles and (ii) chitosan-coated mesoporous silicon microparticles. Both carriers were investigated for their capacity to load a therapeutic protein (insulin) and a model antigen (bovine serum albumin) …
A highly stable and hierarchical tetrathiafulvalene-based metal organic framework with improved performance as a solid catalyst
2018
[EN] Herein we report the synthesis of a tetrathiafulvalene (TTF)-based MOF, namely MUV-2, which shows a non-interpenetrated hierarchical crystal structure with mesoporous one-dimensional channels of ca. 3 nm and orthogonal microporous channels of ca. 1 nm. This highly stable MOF (aqueous solution with pH values ranging from 2 to 11 and different organic solvents), which possesses the well-known [Fe3(¿3-O)(COO)6] secondary building unit, has proven to be an efficient catalyst for the aerobic oxidation of dibenzothiophenes.
Acid versus base peptization of mesoporous nanocrystalline TiO2 films: functional studies in dye sensitized solar cells
2005
We report an analysis of the influence of acid/base conditions employed in the synthesis of TiO2 nanoparticles upon the performance of dye sensitised photoelectrochemical solar cells fabricated from these particles. The functional properties of the TiO2 nanoparticles in these devices are investigated by potential step chronoamperometry, transient laser spectroscopy, and photovoltaic device characterisation. We find that base peptization conditions employed in the sol–gel fabrication of the TiO2 nanoparticles result in a reduction in film electron density under negative applied bias, correlated with slower interfacial recombination losses and a higher device open circuit voltage.
Heterometallic Titanium–Organic Frameworks by Metal-Induced Dynamic Topological Transformations
2020
Reticular chemistry has boosted the design of thousands of metal and covalent organic frameworks for unlimited chemical compositions, structures, and sizable porosities. The ability to generate porous materials at will on the basis of geometrical design concepts is responsible for the rapid growth of the field and the increasing number of applications derived. Despite their promising features, the synthesis of targeted homo- and heterometallic titanium–organic frameworks amenable to these principles is relentlessly limited by the high reactivity of this metal in solution that impedes the controlled assembly of titanium molecular clusters. We describe an unprecedented methodology for the syn…
Enhancing extraction performance of organophosphorus flame retardants in water samples using titanium hierarchical porous silica materials as sorbent…
2021
Abstract A sorbent for the extraction of organophosphorus flame retardants has been proposed, based on UVM-7 (University of Valencia Materials) mesoporous silica doped with titanium. Designed cartridges have been applied to the extraction and preconcentration of flame retardants in water samples, followed by gas chromatography coupled to a mass spectrometry detector. Firstly, UVM-7 materials with different contents of titanium were synthesized and characterized by several techniques, thus confirming the proper mesoporous architecture. The potential of these materials was assessed in comparison with their morphological properties, resulting Ti50-UVM-7 the best solid phase. Several extraction…