1,721,003 research outputs found
Layered double hydroxides are still out in the bloom: Syntheses, applications and advantages of three-dimensional flower-like structures
No full textIncorporation of active nano-hybrids into poly(ε-caprolactone) for local controlled release: Antifibrinolytic drug
No full textOxidative stability of long-chain fatty acids with different unsaturation degrees into layered double hydroxides
No full textNowadays, there is increasing evidence that the intake of essential fatty acids (FAs) and oleic acid has high nutritional importance. However, the vulnerability of these FAs to oxidation deserves special attention. FA oxidation may be avoided or delayed by intercalation of its anionic form in inorganic matrices as layered double hydroxides (LDH). Thus, the aim of the study was to evaluate the protective effects of MgAl LDH towards oleate (O), linoleate (L) and α-linolenate (Ln) degradation. The incorporation and the loading of different FAs in anionic form in LDH was determined by X-ray diffraction and thermogravimetric analysis (TGA), respectively. In order to study the selectivity of LDH towards the FA, the inorganic solid was equilibrated with a mixture of O, L and Ln (1:1:1). TGA and gas chromatography showed that Ln was preferentially intercalated. Free FA (FFA) and intercalated FA (IFA) were heated at 40◦C in the dark and then analyzed weekly for a maximum of 42 days. Their oxidative stability was evaluated by monitoring the primary and secondary oxidative compounds. The volatile compounds were determined by solid-phase microextraction, coupled with gas chromatography–mass spectrometry. Peroxide values were higher in FFA samples than in IFA samples, such as hexanal and trans,trans-2,4-heptadienal % contents. The results showed the potential of LDH intercalation for FA preservation from oxidative modification
Preparation and characterization of hydrotalcite/carboxy-adamantane intercalation compounds as fillers of polymeric nanocomposites.
No full textMercaptoalkyl Groups Anchored on the Layer Surface of New α-Zirconium Phosphate Phosphonates for the Stabilization of Gold Nanoparticles
No full textLayered zirconium phosphate mercaptoalkylphosphonates, with general composition Zr(O3POH)2-x(O3P(CH2)11SH)x, where x=0.4-1.4, are prepared according to two procedures: direct reaction between a zirconyl salt and a mixture of phosphoric/phosphonic acid in propanol, or topotactic ion exchange reaction of phosphate groups of nanocrystalline & alpha;-Zr(O3POH)2 with mercaptoundecylphosphonate groups. FT-IR analysis and XPS proves the presence of the mercapto groups and, according to X-Ray diffraction analysis, they result randomly distributed on the layer surface. The solids are used as supports for gold nanoparticles synthesized according to three different methods: reaction of HAuCl4 with NaBH4, added after 24 hours (Procedure A), or concomitantly (Procedure B) to the addition of the Au(III) salt to the solid suspension, or by mixing the solid suspension with a colloidal dispersion of gold nanoparticles prepared according to the Turkevich method (Procedure C). The best results were obtained with Procedure B, that provided composites with gold nanoparticles having an average size of (6 & PLUSMN;2) nm.Layered zirconium phosphate mercaptoundecylphosphonates were prepared and employed as supports for gold nanoparticles. According to the procedure, different gold species are stabilized by the support: Au ionic species and/or small gold clusters, Au(0) nanoparticles with an average size of 6 nm, or larger Au(0) nanoparticles with an average size of 20 nm.imag
Alginate Microbeads Containing Halloysite and Layered Double Hydroxide as Efficient Carriers of Natural Antimicrobials
No full textThe present paper describes the preparation and characterization of novel microbeads from alginate filled with nanoclay such as halloysite nanotubes (HNTs). HNTs were used as support for the growth of layered double hydroxide (LDH) crystals producing a flower-like structure (HNT@LDH). Such nanofiller was loaded with grapefruit seed oil (GO), an active compound with antimicrobial activity, up to 50% wt. For comparison, the beads were also loaded with HNT and LDH separately, and filled with the same amount of GO. The characterization of the filler was performed using XRD and ATR spectroscopy. The beads were analyzed through XRD, TGA, ATR and SEM. The functional properties of the beads, as nanocarriers of the active compound, were investigated using UV-vis spectroscopy. The release kinetics were recorded and modelled as a function of the structural characteristics of the nanofiller
Solid state photoreduction of silver on mesoporous silica to enhance antifungal activity
Full text linkA solid-state Ultraviolet-photoreduction process of silver cations to produce Ag0 nanostructures on a mesoporous silica is presented as an innovative method for the preparation of efficient environmental anti-fouling agents. Mesoporous silica powder, contacted with AgNO3, is irradiated at 366 nm, where silica surface defects absorb. The detailed characterization of the materials enables us to document the silica assisted photo-reduction. The appearance of a Visible (Vis) band centered at 470 nm in the extinction spectra, due to the surface plasmon resonance of Ag0 nanostructures, and the morphology changes observed in transmission electron microscopy (TEM) images, associated with the increase of Ag/O ratio in energy dispersive X-ray (EDX) analysis, indicate the photo-induced formation of Ag0. The data demonstrate that the photo-induced reduction of silver cation occurs in the solid state and takes place through the activation of silica defects. The activation of the materials after UV-processing is then tested, evaluating their antimicrobial activity using an environmental filamentous fungus, Aspergillus niger. The treatment doubled inhibitory capacity in terms of minimal inhibitory concentration (MIC) and biofilm growth. The antimicrobial properties of silver–silica nanocomposites are investigated when dispersed in a commercial sealant; the nanocomposites show excellent dispersion in the silicon and improve its anti-fouling capacity
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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