75 research outputs found
Layered double hydroxide and zirconium phosphate as ion exchangers for the removal of ‘black crusts’ from the surface of ancient monuments
No full textTwo ion exchanger solids (LDH and ZrP) as an innovative tool to remove gypsum from ancient monuments.</p
Mercaptoalkyl 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
α-Zirconium Sulfophenylphosphonate as a Catalyst for the Synthesis of 3,4-Dihydropyrimidin-2(1H)-One Derivatives Under Solvent Free Conditions
No full text3,4-Dihydropyrimidin-2(1H)-one derivatives were synthesized using layered α-zirconium sulfophenylphosphonate as a recyclable heterogeneous catalyst. Several classes of reagents, such as functionalized aromatic and aliphatic aldehydes, β-dicarbonyl derivatives and 2-aminobenzimidazole, were used to synthesize different 3,4-dihydropyrimidin-2(1H)-one derivatives under solvent free conditions
Layered double hydroxides are still out in the bloom: Syntheses, applications and advantages of three-dimensional flower-like structures
No full text"HYDROTALCITES IN NANOBIOCOMPOSITES" in Multifunctional and Nanoreinforced Polymers for Food Packaging
No full textComposite Sodium Alginate-ion exchangers as cleaning systems for the removal of gypsum efflorescences
No full textFilm forming systems constituted of an MgAl layered double hydroxide (MgAlCl) and half sodic zirconium
phosphate (ZrPNaH) ion exchangers, sodium alginate (SA), polyvinylalcohol (PVA) and water (exchangers,
polyvinylalcohol, alginate: EPA) were investigated as a cleaning tool for the removal of gypsum efflorescences on
fresco paintings. The high water content in EPA assures the gypsum solubilization which also benefits from the
capture of calcium and sulphate ions by the exchangers. Moreover, calcium ions cause the SA reticulation thus
allowing an easy detachment of the mixture from the surface without leaving residues. PVA acts as medium to
disperse the inorganic exchangers in SA. Before formulating the EPA, the rheological properties of calcium
alginate were investigated as a function of the ZrPNaH content in order to assess the conditions leading to film
forming systems with suitable consistency and surface adhesion. To test EPA efficiency, gypsum efflorescences
were artificially generated on fresco mock-ups prepared using the distinctive fresco technique and painted with
five pigments (Hematite, Ultramarine Blue, Naples Yellow, Malachite and Manganese Black). The mock-ups were
treated with EPA and the efficiency of the treatment in the gypsum removal was investigated by several techniques including X ray diffraction (XRD), X ray Fluorescence (XRF), Infrared spectroscopy (MIR), Raman
spectroscopy, SEM-EDX and colorimetric analysis
Incorporation 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
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