Search results for "Dame"
showing 10 items of 1466 documents
Heteropolyacid-Based Heterogeneous Photocatalysts for Environmental Application
2015
Polyoxometalates (POMs) are a wide class of discrete nanosized transition metal–oxygen clusters. The synthesis of POMs has received great interest not only because they present intriguing architectures but also because they have potential applications in catalysis, medicine, electrochemistry, materials design or models for self-assembling nanoscale systems. Recently, POMs have also been studied as green and cheap photocatalysts. The potentialities of POMs are attributed to their unique structural features; indeed, POMs are photostable and non-toxic, have oxygen-rich surfaces and excellent redox properties and possess photochemical characteristics similar to those of the semiconductor photoc…
E-beam irradiation and UV photocrosslinking of microemulsion-laden poly(N-vinyl-2-pyrrolidone) hydrogels for ‘‘in situ’’ encapsulation of volatile hy…
2011
Gelled microemulsions are the subject of considerable scientific and commercial interest. Many efforts are currently devoted to improving their toxicological profile and functioning as biocompatible diffusion barrier for the controlled delivery of hydrophobic compounds. In the present investigation, a non-ionic polymeric surfactant was chosen to generate an oil-in-water microemulsion of a model fragrance in the presence of poly(N-vinyl-2-pyrrolidone) (PVP). The microemulsion was then subjected to either electron-beam or UV-irradiation to induce free-radical crosslinking of PVP at low temperature and in the absence of crosslinking agents, catalysts and initiators. Irradiation conditions with…
Hydrogel films engineered in a mesoscopically ordered structure and responsive to ethanol vapors
2014
Abstract Responsive hydrogels filling the interstitial spaces of photonic crystals can form mesoscopically structured materials, which exhibit reversible shifts in the Bragg diffracted light as a response of environmental changes. These materials can be used to generate chemical or biochemical sensors. The present work reports on the synthesis and characterization of ethanol responsive hydrogels that can be used in the design of novel breathalyzers. The dynamic mechanical behavior of the macroscopic hydrogels and their swelling features in the presence of different liquids or vapors have been investigated to orientate the choice of the best responsive material and curing process. The swelli…
Smart hydrogels for novel optical functions
2007
Nanocomposites of inherently conductive polyaniline (PANT) within a highly hydrophilic polyvinyl alcohol (PVA) based hydrogel have been produced by coupling a conventional dispersion chemical oxidative polymerization to a subsequent high energy irradiation step, in order to convert the polymer stabilizing the aqueous dispersion, namely the PVA, into a highly water swollen hydrogel incorporating the PANT particles. The incorporation of the electroactive and "pH-sensitive" polymer into a transparent and highly permeable hydrogel matrix has been pursued as a route to the development of a novel class of potentially biocompatible, smart hydrogels that can respond to changes of the surrounding en…
Inherently fluorescent polyaniline nanoparticles in a dynamic landscape
2012
Abstract In this paper we report for the first time on the emissive behavior of two polyaniline (PANI) nanoparticle systems produced via oxidative chemical polymerization in the presence of either poly(vinyl alcohol) (PVA) or chitosan as polymeric stabilizers in water. The emission from PANI nanoparticles is irreversibly quenched by an increase of pH of the suspending medium from acid to neutral (chitosan–PANI) or alkaline (PVA–PANI). Conversely, PANI nanorods synthesized in the same conditions of the above, but in presence of poly(N-vinyl pyrrolidone), is not emissive at any pH. The role of the polymeric surfactant as a soft template is key in controlling the morphology and the properties …
Micro- to Nanoscale Bio-Hybrid Hydrogels Engineered by Ionizing Radiation
2021
Bio-hybrid hydrogels consist of a water-swollen hydrophilic polymer network encapsulating or conjugating single biomolecules, or larger and more complex biological constructs like whole cells. By modulating at least one dimension of the hydrogel system at the micro- or nanoscale, the activity of the biological component can be extremely upgraded with clear advantages for the development of therapeutic or diagnostic micro- and nano-devices. Gamma or e-beam irradiation of polymers allow a good control of the chemistry at the micro-/nanoscale with minimal recourse to toxic reactants and solvents. Another potential advantage is to obtain simultaneous sterilization when the absorbed doses are wi…
Co3O4 particles grown over nanocrystalline CeO2: influence of precipitation agents and calcination temperature on the catalytic activity for methane …
2015
Crystalline cobalt oxides were prepared by a precipitation method using three different precipitation agents, (NH4)(2)CO3, Na2CO3 and CO(NH2)(2). Cobalt oxide nanoparticles corresponding to a Co3O4 loading of 30 wt% were also deposited over high-surface area nanocrystalline ceria by the same precipitation agents. The effect of calcination temperature, 350 or 650 degrees C, on the morphological and structural properties was evaluated. Characterization by BET, XRD, SEM, TEM, Raman spectroscopy, H-2-TPR, XPS and NH3-TPD was performed and the catalytic properties were explored in the methane oxidation reaction. The nature of the precipitation agent strongly influenced the textural properties of…
Photocatalytic CO2 reduction in gas–solid regime in the presence of H2O by using GaP/TiO2 composite as photocatalyst under simulated solar light
2014
GaP/TiO2 composites exhibited a remarkable photocatalytic activity for CO2 reduction in the presence of water vapor producing methane. By decreasing the GaP:TiO2 mass ratio an increase in the photocatalytic activity of the composite was observed for up to a 1:10 mass ratio. The photocatalytic activity of the composite can be attributed to the band structures of the solids as well as to the efficient charge transfer between GaP and TiO2 heterojunction.
Experimental dynamic analysis of elastic-plastic shear frames with secondary structures
2003
Various experimental models are developed to study the influence of lightweight secondary structures on the dynamic response of elastic and elastic-plastic shear frames. Small-scale two-story model frames, with an elastic single-degree-of-freedom secondary structure attached, are considered for sinusoidal and random in-plane support excitation. Both elastic and elastic-plastic responses are recorded by varying the material properties of the columns of a distinguished floor. Parametric studies are performed by varying the secondary structure's fundamental frequency and damping. Experimental results are compared with those obtained by computational simulations. Experimental and numerical resu…
Structure-property relationships in aromatic thioethers featuring aggregation-induced emission : Solid-state structures and theoretical analysis
2019
We describe in this paper a structure–property relationship study of aromatic thioethers with aggregation-induced emission (AIE) properties. We combine a structural analysis based on geometrical consideration with an in-depth analysis of the crystalline packing supported by quantum mechanical calculations. Our results allow us to correlate the enhanced fluorescence quantum yields with the significant increase of C–H⋯π and the decrease of π⋯π interactions in the solid state – a result which supports the well-accepted AIE mechanism quantitatively.