Fluorenone dye-Zeolite L hybrid: a novel optical material

A major challenge facing humanity is developing renewable source of energy. Following the biological blueprint of the natural photosynthesis is possible design synthetic systems for converting light into stored energy: the so called artificial antenna systems. The encapsulation of ordered chromophore molecules into one dimensional zeolite channel systems results in host-guest compounds suitable for the development of novel optical materials such as lenses, infrared light-emitting diodes (used in telecommunications) or dye nanostructured materials for optical data storage [1]. X-ray powder diffraction study of zeolite K-L loaded with 0.5, 1, 1.5, 2 fluorenone-dye (FL) molecules per unit cell (ZL/FL hybrid) [2], was carried out to understand the functionality of these host-guest systems from the structural point of view. These data evidenced a significant change of the unit cell parameters due to the embedding of FL into the ZL 12-membered channels. The Rietveld refinements revealed that the maximum loading is 1.5 FL molecules per unit cell. A strong interaction between FL carbonyl group and two extraframework potassium cations is proved by the short bond distances which make this composite very stable

Compressibility behavior and pressure-induced over-hydration of zeolite K-AlSi-L

This 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

Potentially Toxic Elements in Ultramafic Soils: A Study from Metamorphic Ophiolites of the Voltri Massif (Western Alps, Italy)

Ultramafic soils are characterized by severe edaphic conditions induced by a low content of essential nutrients, an adverse Ca/Mg ratio, a low water-holding capacity, and high contents of geogenic potentially toxic elements (PTEs), in particular Cr, Ni, and Co. These metals commonly exceed the content limits set by environmental agencies and governments, representing serious environmental risks for ecosystems and human health. In alpine environments, ultramafic soils are characterized by modest thickness and poor horizon differentiation. Several studies on ultramafic soils have shown that their properties may be directly related to the characteristics of the parent rocks, but most of these studies deal with soil chemistry, metal availability, isotopic composition, and pedological characterization. The aim of this research is to investigate how much the geotectonic characteristics of ultramafic bedrocks, such as the degree of serpentinization, metamorphic imprint, and deformation, may affect the mineralogical and chemical variations of ultramafic soils, including the occurrence and potential mobility of the PTEs. Using a multiscale and multi-analytical approach, we fully characterize the properties and mineralogical composition of soil profiles with different ultramafic parent rocks, i.e., partially serpentinized peridotite, massive serpentinites, and foliated serpentinites, sampled within the Voltri Massif High Pressure\u2013 Low Temperature (HP\u2013LT) metaophiolite (Western Alps, Italy). Our results, related to soils located at comparable latitude, altitude, landscape position, and pedological environment, outline that the degree of serpentinization, the metamorphic imprint, and the deformation history of the ultramafic parent rocks are key factors influencing soil evolution, mineralogy, and chemistry, as well as PTEs distribution and mobility. Moreover, this study shows that the high content of Cr, Ni, and Co in the studied ultramafic soils has to be considered of geogenic origin and highlights the need for new approaches and methods to obtain indications on the potential contamination of natural or anthropogenic soils

Primary and authigenic minerals in serpentine soils under temperate climate conditions: source or trap for potentially toxic elements (PTEs)

In this study, we have analysed the mineralogy and the crystal chemistry of serpentine soils from ultramafic rocks of the metaophiolitic Voltri Massif (Liguria, Italy), in order to determine the primary and authigenic mineral species controlling the distribution and the mobility of PTEs during pedogenic processes. These serpentine soils were characterised by PTEs contents commonly exceeding the concentration limits laid down by environmental agencies, particularly for Cr (1200-2500 mg/kg) and Ni (1000-4200 mg/kg). With these hazardous PTEs concentrations, the knowledge of the distribution of PTEs-bearing minerals is of paramount importance for understanding their origin and their fate during the development of serpentine soil profiles and can allow to evaluate their effective bioavailability. All the studied soil profiles were restricted in depth (10-50 cm) and showed a low degree of maturity with weakly developed A-C horizons. Soil samples were subdivided into three aliquots in order to separate the soil skeleton (2 mm-63 \u3bc m) from the silt (63-2 \u3bc m) and clay fraction (<2 \u3bc m). Quantitative mineralogical analyses were performed in all aliquots by using XRPD data collected with synchrotron sources at the MCX beamline (ELETTRA - Synchrotron, Trieste, Italy) and refined with EXP-GUI GSAS software. Trace metals were determined with energy and wavelength electron microscopy. The mineralogy of the coarse and silty fractions was closely related to bedrock mineralogy. The following minerals were detected in decreasing order of abundance: antigorite, chlorite, tremolite, magnetite, Cr-rich spinel, chrysotile, ilmenite, clinopyroxenes, olivine. Allochthonous quartz and albite were always present as minor to trace constituents. The clay fraction was mainly composed by Fe-oxides and -oxyhydroxides (mainly hematite and goethite) with subordinate amounts of mixed-layer clay minerals (chlorite-smectite, chlorite-vermiculite). These authigenic secondary minerals were characterised by poor crystallinity, intimate intergrowths, and fine-scale heterogeneities. PTEs were hosted mainly in the residual primary minerals deriving from the underlying parent material and subordinately in secondary authigenic phases. Cr was mainly contained within spinels (magnetite, Cr-magnetite, ferrichromite, picotite, and hercynite), antigorite, diopside and augite. Nonnegligible amounts of Cr was also present in authigenic hematite (up to 0.1 wt%) and goethite (up to 0.15 wt%). The main Ni-bearing minerals were olivine and antigorite but significant Ni concentration was also detected in authigenic hematite (up to 2.8 wt%) and goethite (up to 4.2 wt%) which thus represented effective traps for Ni leached through mineral weathering to the soils solution. These results are the preliminary step for the evaluation of the role of mineral species in controlling the PTEs mobility during the evolution of serpentine soil profiles. Quantitative mineralogical data will be further used to perform mass balance calculations as well as to interpret and model the results of batch leaching experiments that will be conducted on the different soil fractions

Supramolecular organization of water–ethanol solution in ferrierite under pressure

Turning disorder into organization is a key issue in science. In particular, supramolecular organization induced by external stimuli has opened new paths for the bottom-up fabrication of nanostructures. By using a combined strategy based on the synergy of X-ray powder diffraction experiments and modeling studies [1], we showed that high pressure - in combination with the shape and space constraints of a hydrophobic all-silica zeolite - separate an ethanol–water liquid mixture into ethanol dimer wires and water tetramer squares (Figure 1). Separation of ethanol from water was accomplished in an all-silica ferrierite (Si-FER), by using as pressure transmitting medium a mixture of (1:3) ethanol and water in the 0.20 to 1.34 GPa pressure range. The system was studied in situ by high-pressure synchrotron X-ray powder diffraction at BM01 beamline at ESRF and refined via first principles modeling. Upon separation, the confined supramolecular blocks alternate in a binary two-dimensional architecture that remains stable upon complete pressure release. This unique architecture might rationalize the high selectivity of Si-FER in the separation of alcohol–water mixtures, a key issue in biofuel production. Moreover, as ferrierite is an exceptionally selective catalyst for biofuel synthesis in its hydrophilic Brønsted acid form, while only its pore entrances are actually exploited, we suggest that pressure could also be beneficial for the catalytic performance by enforcing the intrusion of reactants. These results support the combined use of high pressures and porous networks as a viable strategy for driving the organization of molecules or nano-objects towards complex, pre-defined patterns relevant for the realization of novel functional nanocomposites. [1] Arletti, R., Fois, E., Gigli, L., Vezzalini, G., Quartieri, S., Tabacchi, G. (2017) Angewandte Chemie, DOI: 10.1002/anie.20170021

Unravelling the High-Pressure Behaviour of Dye-Zeolite L Hybrid Materials

Self-assembly of chromophores nanoconfined in porous materials such as zeolite L has led to technologically relevant host-guest systems exploited in solar energy harvesting, photonics, nanodiagnostics and information technology. The response of these hybrid materials to compression, which would be crucial to enhance their application range, has never been explored to date. By a joint high-pressure in situ synchrotron X-ray powder diffraction and ab initio molecular dynamics approach, herein we unravel the high-pressure behaviour of hybrid composites of zeolite L with fluorenone dye. High-pressure experiments were performed up to 6 GPa using non-penetrating pressure transmitting media to study the effect of dye loading on the structural properties of the materials under compression. Computational modelling provided molecular-level insight on the response to compression of the confined dye assemblies, evidencing a pressure-induced strengthening of the interaction between the fluorenone carbonyl group and zeolite L potassium cations. Our results reveal an impressive stability of the fluorenone-zeolite L composites at GPa pressures. The remarkable resilience of the supramolecular organization of dye molecules hyperconfined in zeolite L channels may open the way to the realization of optical devices able to maintain their functionality under extreme conditions