1,721,022 research outputs found
Thermoreversibly crosslinked silica-rubber composite prepared via melt processing
No full textThis paper addresses the industrially viable and environmentally sustainable preparation of thermoreversibly crosslinked composite rubbers. A maleimide-functionalized silica (Sil-M) is prepared and used as a reinforcement filler and crosslinking agent via Diels-Alders (DA) reaction onto furan-grafted ethylene-propylene rubber (EPRgF). The preparation of composite rubbers is carried out by reactive melt blending to guarantee for industrial scalability and avoiding use of organic solvent. Mechanical properties of EPRgF/Sil-M is compared to unfunctionalized EPRgF/Sil to demonstrate the role of DA crosslinking on mechanical properties. Furthermore, the combination between Sil-M and bismaleimide as a conventional DA crosslinker was investigated, to optimize crosslinking degree and materials performances. Overall, results reported in this paper demonstrate the possibility to develop a new class of recyclable composite rubbers for the substitution of conventional rubbers, that are currently causing major problems in the management of rubber products at their end-of life
1H and 17O NMR relaxation studies of the Fe(III)-Tiron system
No full textRelaxometry is a very powerful technique for investigating the solution structural and dynamic properties of paramagnetic complexes. Due to their peculiar magnetic characteristics and their great success as diagnostic probes for applications in MRI, many studies have been carried out on Gd(III)- and Mn(II)-based systems. Surprisingly, very few investigations have been reported on Fe(III) complexes despite their considerable importance in various fields of chemistry, starting from bioinorganic chemistry. Fe(III), with five unpaired electrons in the d orbitals, a 6S configuration and a high magnetic moment, is very well suited to be studied with this technique. In particular, in this work we focused on well-defined type of catecholate complexes of iron(III), Fe-Tiron (Tiron® = disodium 4,5-dihydroxy-1,3-benzenedisulfonate). The formation constants should allow for independent study of these complexes by an appropriate choice of starting pH and Tiron concentration. We report for the first time the complete characterization of the various species through a combined 1H and 17O NMR relaxometric study. In particular we investigated [Fe(Tiron)(H2O)4]- (pH=2.3), [Fe(Tiron)2(H2O)2]5- (pH=4) and [Fe(Tiron)3]9- (pH=8). Through a simultaneous fit of 1H Nuclear Magnetic Resonance Dispersion profiles (from 0.01 up to 500 MHz), 17O transverse relaxation rates (R2) and shifts (Dw) (measured at 11.7 T as a function of temperature) we were able to obtain accurate value of the structural and dynamic parameters that adequately describe the behaviour of these paramagnetic complexes in aqueous solution
Polypropylene containing Ti- and Al-Polyhedral Oligomeric Silsesquioxanes: Crystallization Process and Thermal Properties
No full textThis paper deals with the preparation and characterization of isotactic polypropylene (PP) containing different metal-polyhedral oligomeric silsesquioxanes (M-POSS). Two M-POSS, Ti(IV)- and Al(III)-isobutyl-POSS, defined by a monomeric structure, were selected for dispersion, and particular attention was paid to the assessment of the morphology, crystallization process and thermal behavior of M-POSS/PP composites, using SEM and TEM microscopy, x-ray diffraction (XRD), FTIR and Raman spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and gas chromatography/mass spectrometry. The study of M-POSS/PP thermal degradation showed that Ti-POSS and Al-POSS induce different effects on the thermoxidative behavior of the polypropylene matrix, showing a clear specificity of the metal center on the PP degradation pathway. In particular, Ti-POSS showed a significant stabilization of PP when heating under air, whereas limited effects were observed with Al-POSS. Moreover, Ti-POSS was also found to affect PP crystallization, driving the crystallization process along specific crystallographic directions
THE CSF MYELIN BASIC PROTEIN: A RELIABLE MARKER OF ACTUAL CEREBRAL DAMAGE IN HYDROCEPHALUS
No full text
DTPA-Functionalized silica-based monoliths for the removal of transition and lanthanide ions from aqueous phase
Full text linkTransition and rare-earth metals are essential raw materials used in a wide range of technological applications; moreover, their consumption is often associated with high production of wastes. Therefore, their recycling and recovery from end-of-life products or metal-contaminated aqueous environments is of considerable importance from a circular economy perspective. In our study, synthetic mesoporous silica monoliths, obtained by sol-gel synthesis[1] and functionalized with chelating groups are used for the recovery of metal ions from aqueous matrices (MONO-DTPA). The monoliths were characterized using a multi-technique approach and were tested in the recovery of paramagnetic Gd3+, Cu2+ and Co2+ ions from aqueous solutions, using 1H-NMR relaxometry to evaluate their uptake performance in real time and in simple conditions[2]. Detailed information on the kinetics of the capture process was also extrapolated. Finally, the possibility to regenerate the solid sorbents was evaluated. The modified silica monoliths were able to recover an appreciable amount of both di- and trivalent metal ions. The best results were obtained in the case of Cu2+ after 24 hours of contact, with a recovered amount of 0.29 mmol/g corresponding to 18.48 mg/g (Fig. 1, A).
The capture performance of MONO-DTPA has been shown to be superior to that of natural or synthetic materials commonly used for metal ion removal (Fig 1, B).
[1] V. Miglio, C. Zaccone, C. Vittoni, I. Braschi, E. Buscaroli, G. Golemme, L. Marchese and C. Bisio, Molecules 2021, 26, 1316
[2] S. Marchesi, S. Nascimbene, M. Guidotti, C. Bisio and F. Carniato, Dalton Trans. 2022, 51, 4502–4509
Enhancement of the luminescence properties of Eu (III) containing paramagnetic saponite clays
Full text linkIn this study, 1,10-phenanthroline molecules were introduced in the interlayer space of a paramagnetic synthetic saponite clay containing both Eu3+ and Gd3+ ions in structural positions. Two samples with different loading of phenanthroline dye were prepared. The resulting hybrid materials possessed improved optical emission properties due to an efficient antenna effect from the phenanthroline to the Eu3+ centers; this effect was demonstrated to be higher than the metal-to-metal Gd3+-Eu3+ energy transfer previously studied. Insights on the relaxometric properties in aqueous solution of the solids after incorporation of the antenna groups were also obtained through NMR relaxometric analyses
Novel light-emitting clays with structural Tb3+and Eu3+for chromate anion detection
No full textTb3+ and Eu3+ ions were encapsulated for the first time in the inorganic layers of a synthetic saponite clay following a one-pot synthetic approach. The co-presence of the two metal ions led to tuneable light-emitting properties, promoted by an efficient Tb3+ → Eu3+ energy transfer and enhanced Stokes shift character. To our knowledge, the so-prepared luminescent material was tested for the first time as an optical sensor for the detection of chromate anions in water
On the use of Me-Isobutylsilsesquioxanes (Me=Ti, V) as additives for enhancing thermal stability of polypropylene
No full textIncorporation of Antimony Ions in Heptaisobutyl Polyhedral Oligomeric Silsesquioxanes
No full textThe direct incorporation of Sb(V) ions into a polycondensed silsesquioxane network based on heptaisobutyl POSS units (Sb(V)-POSSs) through a corner-capping reaction is reported for the first time in this work. As a reference sample, a completely condensed monomeric Sb(III)-POSS was prepared using a similar synthetic protocol. The chemical properties of both Sb-containing POSSs were investigated with different analytical and spectroscopic techniques. The analyses confirm the success of the corner-capping reaction for both samples and indicate that an Sb(V)-POSS sample is characterized by a heterogenous multimeric arrangement with an irregular organization of POSS cages linked to Sb(V) centers, and has a more complex structure with respect to the well-defined monomeric Sb(III)-POSS
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