1,721,233 research outputs found
High-pressure-induced structural changes, amorphization and molecule penetration in MFI microporous materials: a review
No full textThis is a comparative study on the high-pressure behavior of
microporous materials with an MFI framework type (i.e.
natural mutinaite, ZSM-5 and the all-silica phase silicalite-1),
based on in-situ experiments in which penetrating and nonpenetrating
pressure-transmitting media were used. Different
pressure-induced phenomena and deformation mechanisms
(e.g. pressure-induced over-hydration, pressure-induced amorphization)
are discussed. The influence of framework and
extra-framework composition and of the presence of silanol
defects on the response to the high pressure of MFI-type
zeolites is discussed
Unraveling the Molecular Structure of Zeolite–Octyl Methoxycinnamate Hybrid UV Filters: A Combined Spectroscopic and Computational Approach
Full text linkIn this contribution, we tried to shed light on the molecular structure of octyl methoxycinnamate (octinoxate, OMC) adsorbed in NaX zeolite, which represents a promising hybrid UV filter system. The combination of infrared spectroscopy and density functional theory modeling was crucial to identify all the complex host-guest interactions and to unveil that, although slightly thermodynamically unfavored, OMC is dominantly present in the trans-form inside the NaX framework. We also showed that the interaction between the zeolite Na cations and the OMC molecule is the key feature that determines the stability and efficacy of these hybrid UV filters. These findings confirm that cationic zeolites are promising materials for the encapsulation of UV filters to decrease their negative impact on the environment and their photochemical instability
Compressibility behavior and pressure-induced over-hydration of zeolite K-AlSi-L
Full text linkThis paper reports a study, performed by in-situ synchrotron X-ray powder diffraction, of the high-pressure
behavior of zeolite L. The experiments were performed using both penetrating (methanol: ethanol: water mixture,
m.e.w.) and non-penetrating (silicon oil, s.o.) pressure transmitting media (PTM) to study the compressibility
and the possible pressure-induced hydration (PIH) of this synthetic zeolite, technologically relevant as
host-guest system exploited in numerous application fields. The experiments were performed from Pamb to 6.2
and 6.3 GPa in s.o. and m.e.w., respectively. The crystal structure refinements were performed up to 6.3 GPa and
3.1 GPa for the patterns collected in m.e.w. and s.o., respectively, while the unit cell parameters were determined
in the whole pressure range for both media. A strong PIH effect is evident when zeolite L is compressed
in m.e.w. and the over-hydration is essentially ascribable to the filling of most the H2O sites, to the appearance of
a new H2O site and to the partially filling of the K sites. The over-hydration starts at a very low pressure
(0.5 GPa) and the maximum H2O content can be estimated in 31.1 H2O molecules, against the original value of
18. The PIH is completely reversible upon P release. The main difference between the compression behavior of
zeolite L in the two media is the higher compressibility in the non-penetrating one, evidenced by ΔV=− 6.3%
and −9.9% in m.e.w. and s.o, respectively. Our data are consistent with the general behavior of zeolites
compressed with penetrating media, when the intrusion of H2O molecules hinders the effects of the applied
pressure. The results of this work are compared with those obtained on a K-gallosilicate with LTL topology,
where PIH induces the formation of H2O nanotubes inside the zeolite channel
Zeofilters for potentially innovative sunscreen products: formulation, stability and spectroscopic studies
No full textExposure to both UVA and UVB radiation from the sun stands as the primary cause of skin cancers, contributing to the escalating yearly count of diagnosed cases. Sunscreen products, (i.e. organic and inorganic UV filters) have become ubiquitous in personal-care products, packaging, plastics, dyes, and many other sectors. Ideal UV filters should be photostable and dissipate the absorbed energy efficiently. However, most organic UV filters are photolabile upon protracted UV exposure, leading to the formation of photoproducts of unknown toxicity for human health and environment. The chemical environment surrounding UV filters may strongly affect their behaviour: the interaction with other components of sunscreen formulations may enhance their degradation. Particularly, the interaction between photochemically incompatible ingredients must be avoided. Therefore, much effort has been invested in developing more effective and safe sunscreens. Our team recently focused on the preparation and characterization of hybrid UVfs obtained by the encapsulation of organic UV filters into various zeolites differing for topology. The zeolite most efficient for the encapsulation of organic UV filters, in term of stability and efficiency in radiation filtration, resulted to be LTL zeolite. Here, hybrid materials realized after the encapsulation of octinoxate (OMC) and avobenzone (AVO) in LTL zeolite were tested in terms of skin permeation profiles, cytotoxicity and photostability once the materials are dispersed in cream formulations, so to mimicking the real condition of use. The results show that the hybrids were successfully incorporated into oil-in-water emulsions and the skin permeation tests displayed a very low UV filter permeation through pig skin and no UV filter accumulation in dermis layer. The photostability of the hybrid-based emulsions were compared with that of emulsions containing a mixture of bare OMC and AVO, highlighting a reduced decrease in UV screening efficiency upon irradiation for the samples containing the hybrid materials with respect to the free filters. This evidence confirms that the encapsulation in the zeolite frameworks prevents some of the photodegradation reactions. The result of this paper highlights that zeolite encapsulation is increasingly establishing as a viable way to stabilize UV filters and other photoactive molecules
Different glassmaking technologies in the production of Iron Age black glass from Italy and Slovakia
Full text linkThis study presents the results of an archaeometrical investigation performed on 75 black glass beads dated to the ninth–fifth century BC coming from Bologna, Cumae, and Pozzuoli (Italy), and Chotin (Slovakia). The analyses of the major, minor, and trace elements—as well as that of Sr and Nd isotopes performed on a selection of samples coming from Bologna—provided evidence for two different production technologies in Iron Age black glass found in Italy (natron glass, probably produced in Egypt) and Slovakia (wood ash glass, probably produced in Europe). In both cases, the glasses derive their black colouration from the high presence of iron (around 12 % FeO), introduced into the glass batches through the intentional choice of dark sands. The production model appears to be small-scale and experimental, characterised by the use of non-sorted raw materials and poorly defined formulae, producing glass with a high chemical variability. The wood ash technology appears to have dropped out of use in Europe until the Medieval period, while natron production spread quickly, becoming predominant throughout the Mediterranean.status: Publishe
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