Aldehyde-containing clays: a sustainable approach against the olive tree pest, Bactrocera oleae.

A set of organic/inorganic layered materials was obtained by functionalizing a montmorillonite-containing bentonite natural clay with linear aliphatic C6 or C7 aldehydes through a cost-effective and technologically simple incipient-wetness deposition method. The solids were investigated by means of a multi-technique approach (X-ray powder diffraction, XRPD, scanning electron microscopy, SEM, Fourier-transform infrared spectroscopy, FT-IR, thermogravimetric analysis, TGA, elemental analysis and solid-state nuclear magnetic resonance, ssNMR) to clarify the nature of the deposited organic species and the mode of interaction between the aldehyde and the clay. Since both natural clays and short-chain linear aldehydes find application as alternative strategies in the control of the olive fruit fly, Bactrocera oleae, the hybrid layered materials were tested under real-life conditions and their insect-inhibiting capability was evaluated in open-field trials on olive tree orchards in Tuscany, Central Italy. Specific tests were conducted to evaluate the resistance of the solids to weathering and their capability to provide a constant and long-lasting release of the bioactive ingredient. Aldehyde-containing bentonite clays have shown promising performance in controlling B. oleae infestation (with up to 86-95% reduction of affected olive fruits) in open-field trials across two years in two locations with different pedological and meteo-climatic characteristics.

Silica-based monoliths functionalized with DTPA for the removal of transition and lanthanide ions from aqueous solutions.

Transition and rare earth metals serve as indispensable raw materials across a broad spectrum of technological applications. However, their utilization is frequently linked to substantial waste production. Consequently, the recycling and recovery of these metals from end-of-life products or metal-contaminated aqueous environments hold significant importance within the framework of a circular economy. In our investigation, we employed synthetic mesoporous silica monoliths, synthesized via the sol-gel method and functionalized with chelating groups, for the efficient recovery of metal ions from aqueous matrices. 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 under simple conditions. Detailed information on the kinetics of the capture process was also highlighted. Finally, the possibility to regenerate the solid sorbents was evaluated.

Immobilization of Alendronate on Zirconium Phosphate Nanoplatelets.

Different amounts of sodium-alendronate (ALN) were loaded into layered zirconium phosphates of alpha and gamma type (αZP and γZP) by means of topotactic exchange reactions of phosphate with ALN. In order to extend the exchange process to the less accessible interlayer regions, ALN solutions were contacted with colloidal dispersions of the layered solids previously exfoliated in single sheets by means of intercalation reaction of propylamine (for αZP) or acetone (for γZP). The ALN loading degree was determined by liquid P-nuclear magnetic resonance (NMR) and inductively coupled plasma (ICP), and it was reported as ALN/Zr molar ratios (Rs). The maximum R obtained for γZP was 0.34, while αZP was able to load a higher amount of ALN, reaching Rs equal to 1. The synthesized compounds were characterized by X-ray powder diffractometry, scanning electron microscopy (SEM), solid-state NMR, and infrared spectroscopy. The way the grafted organo-phosphonate groups were bonded to the layers of the host structure was suggested. The effect of ZP derivatives was assessed on cell proliferation, and the results showed that after 7 days of incubation, none of the samples showed a decrease in cell proliferation.

Eu3+ and Tb3+ @ PSQ: Dual Luminescent Polyhedral Oligomeric Polysilsesquioxanes.

The synthesis and characterization of novel luminescent amorphous POSS-based polysilsesquioxanes (PSQs) with Tb3+ and Eu3+ ions directly integrated in the polysilsesquioxane matrix is presented. Two different Tb3+/Eu3+ molar ratios were applied, with the aim of disclosing the relationships between the nature and loading of the ions and the luminescence properties. Particular attention was given to the investigation of site geometry and hydration state of the metal centers in the inorganic framework, and of the effect of the Tb3+ → Eu3+ energy transfer on the overall optical properties of the co-doped materials. The obtained materials were characterized by high photostability and colors of the emitted light ranging from orange to deep red, as a function of both the Tb3+/Eu3+ molar ratio and the chosen excitation wavelength. A good energy transfer was observed, with higher efficiency displayed when donor/sensitizer concentration was lower than the acceptor/activator concentration. The easiness of preparation and the possibility to finely tune the photoluminescence properties make these materials valid candidates for several applications, including bioimaging, sensors, ratiometric luminescence-based thermometers, and optical components in inorganic or hybrid light-emitting devices.

The Control of the Coordination Chemistry for the Genesis of Heterogeneous Catalytically Active Sites in Oxidation Reactions.

This Review provides a summary of the use and the role of coordination complexes as precursors for the generation of heterogeneous catalysts for oxidation reactions of interest for fine chemical synthesis. Specific attention is paid to the comprehension of phenomena explaining the formation of active sites in heterogeneous catalysts. Different families of coordination precursors are considered. For each example, a brief critical description of the synthesis, characterization, and catalytic performance is reported. Special attention is paid to the chemical environment of the first coordination sphere of the active metal centre. The catalysts obtained by heterogenization, grafting, or anchoring of homogeneous catalysts can therefore exhibit enhanced catalytic performance by merging advantages of both homogeneous and heterogeneous systems. The deposition of coordination complexes over a preformed support is indeed a conceptually versatile strategy to design novel catalysts with tuned and controlled properties.

Application of NMR relaxometry for real-time monitoring of the removal of metal ions from water by synthetic clays.

The removal of paramagnetic metal ions with different charges and ionic radii (i.e. Gd3+, Cu2+, and Co2+) from aqueous solutions was carried out by using a Na+-exchanged synthetic saponite clay. Saponite, composed of sub-micrometer particles and characterized by high cation-exchange capacity, was prepared through a classical low-cost hydrothermal approach. The metal ion uptake tests were performed in water at pH = 5.5 and 3.0, and the capture process was monitored in real time by 1H-NMR relaxometry. The experimental data were confirmed by the conventional ICP-OES technique. Details of the uptake process kinetics were extrapolated from the NMR analyses as well. Saponite showed good sorption capacity for all selected metal ions. The regeneration of the solid sorbent after metal uptake was also analysed, obtaining encouraging results.

Hyper Cross-Linked Polymers as Additives for Preventing Aging of PIM-1 Membranes.

Mixed-matrix membranes (MMMs) are membranes that are composed of polymers embedded with inorganic particles. By combining the polymers with the inorganic fillers, improvements can be made to the permeability compared to the pure polymer membranes due to new pathways for gas transport. However, the fillers, such as hyper cross-linked polymers (HCP), can also help to reduce the physical aging of the MMMs composed of a glassy polymer matrix. Here we report the synthesis of two novel HCP fillers, based on the Friedel-Crafts reaction between a tetraphenyl methane monomer and a bromomethyl benzene monomer. According to the temperature and the solvent used during the reaction (dichloromethane (DCM) or dichloroethane (DCE)), two different particle sizes have been obtained, 498 nm with DCM and 120 nm with DCE. The change in the reaction process also induces a change in the surface area and pore volumes. Several MMMs have been developed with PIM-1 as matrix and HCPs as fillers at 3% and 10wt % loading. Their permeation performances have been studied over the course of two years in order to explore physical aging effects over time. Without filler, PIM-1 exhibits the classical aging behavior of polymers of intrinsic microporosity, namely, a progressive decline in gas permeation, up to 90% for CO2 permeability. On the contrary, with HCPs, the physical aging at longer terms in PIM-1 is moderated with a decrease of 60% for CO2 permeability. 13C spin-lattice relaxation times (T1) indicates that this slowdown is related to the interactions between HCPs and PIM-1.

Bifunctional Paramagnetic and Luminescent Clays Obtained by Incorporation of Gd3+ and Eu3+ Ions in the Saponite Framework.

A novel bifunctional saponite clay incorporating gadolinium (Gd3+) and europium (Eu3+) in the inorganic framework was prepared by one-pot hydrothermal synthesis. The material exhibited interesting luminescent and paramagnetic features derived from the co-presence of the lanthanide ions in equivalent structural positions. Relaxometry and photoluminescence spectroscopy shed light on the chemical environment surrounding the metal sites, the emission properties of Eu3+, and the dynamics of interactions between Gd3+ and the inner-sphere water placed in the saponite gallery. The optical and paramagnetic properties of this solid make it an attractive nanoplatform for bimodal diagnostic applications.

Silica Monolith for the Removal of Pollutants from Gas and Aqueous Phases.

This study focused on the application of mesoporous silica monoliths for the removal of organic pollutants. The physico-chemical textural and surface properties of the monoliths were investigated. The homogeneity of the textural properties along the entire length of the monoliths was assessed, as well as the reproducibility of the synthesis method. The adsorption properties of the monoliths for gaseous toluene, as a model of Volatile Organic Compounds (VOCs), were evaluated and compared to those of a reference meso-structured silica powder (MCM-41) of commercial origin. Silica monoliths adsorbed comparable amounts of toluene with respect to MCM-41, with better performances at low pressure. Finally, considering their potential application in water phase, the adsorption properties of monoliths toward Rhodamine B, selected as a model molecule of water soluble pollutants, were studied together with their stability in water. After 24 h of contact, the silica monoliths were able to adsorb up to the 70% of 1.5 × 10-2 mM Rhodamine B in water solution.

Bifunctional Europium(III) and Niobium(V)-Containing Saponite Clays for the Simultaneous Optical Detection and Catalytic Oxidative Abatement of Blister Chemical Warfare Agents.

For the first time, the co-presence in the saponite structure of luminescent EuIII and catalytic NbV metal sites was exploited for the simultaneous detection and catalytic abatement of sulfur-containing blister chemical warfare agents. Metal centers were introduced in structural positions of the saponite (in the interlayer space or inside the inorganic framework) following two different synthetic methodologies. The functionalized saponites were able to reveal the presence of a sulfur mustard simulant (2-chloroethyl)ethyl sulfide (CEES) after few seconds of contact time and more than 80 % of the substrate was catalytically decomposed after 24 h in the presence of aqueous hydrogen peroxide.

More Efficient Prussian Blue Nanoparticles for an Improved Caesium Decontamination from Aqueous Solutions and Biological Fluids.

Any release of radioactive cesium-137, due to unintentional accidents in nuclear plants, represents a dangerous threat for human health and the environment. Prussian blue has been widely studied and used as an antidote for humans exposed to acute internal contamination by Cs-137, due to its ability to act as a selective adsorption agent and to its negligible toxicity. In the present work, the synthesis protocol has been revisited avoiding the use of organic solvents to obtain Prussian blue nanoparticles with morphological and textural properties, which positively influence its Cs+ binding capacity compared to a commercially available Prussian blue sample. The reduction of the particle size and the increase in the specific surface area and pore volume values compared to the commercial Prussian blue reference led to a more rapid uptake of caesium in simulated enteric fluid solution (+35% after 1 h of contact). Then, after 24 h of contact, both solids were able to remove >98% of the initial Cs+ content. The Prussian blue nanoparticles showed a weak inhibition of the bacterial luminescence in the aqueous phase and no chronic detrimental toxic effects.

Toluene Adsorption by Mesoporous Silicas with Different Textural Properties: A Model Study for VOCs Retention and Water Remediation.

In this work, different mesoporous silicas were studied as potential sorbents for toluene, selected as a model molecule of aromatic organic fuel-based pollutants. Three siliceous materials with different textural and surface properties (i.e., fumed silica and mesoporous Santa Barbara Amorphous (SBA)-15 and Mobil Composition of matter (MCM)-41 materials) were considered and the effect of their physico-chemical properties on the toluene adsorption process was studied. In particular, FT-IR spectroscopy was used to qualitatively study the interactions between the toluene molecule and the surface of silicas, while volumetric adsorption analysis allowed the quantitative determination of the toluene adsorption capacity. The combined use of these techniques revealed that textural properties of the sorbents, primarily porosity, are the driving forces that control the adsorption process. Considering that, under real conditions of usage, the sorbents are soaked in water, their hydrothermal stability was also investigated and toluene adsorption by both the gas and aqueous phase on hydrothermally pre-treated samples was studied. The presence of ordered porosity, together with the different pore size distribution and the amount of silanol groups, strongly affected the adsorption process. In toluene adsorption from water, SBA-15 performed better than MCM-41.

Combination of solid-state NMR and 1H NMR relaxometry for the study of intercalated saponite clays with the macrocyclic derivatives of Gd(iii) and Y(iii).

Positively charged Gd(iii) and Y(iii) complexes were intercalated in the gallery of a synthetic saponite. A combination of solid-state NMR and 1H NMR relaxometric investigations has been employed to characterize these hybrid systems. This enabled us to gain atomic level insights into the local environment of the chelates and to evaluate the interactions of the metal species with the co-intercalated water molecules.

Novel light-emitting clays with structural Tb3+ and Eu3+ for chromate anion detection.

Tb3+ 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.

Non-Porous versus Mesoporous Siliceous Materials for CO2 Capture.

In this study, the adsorption properties of a Stöber silica-based material towards CO2 were evaluated for the first time. The use of Stöber silica as support is interesting for real technological applications mainly due to economic factors. Furthermore, a direct comparison between the non porous Stöber sample with an ordered porous material (based on MCM-41 silica) allowed to evaluate the effect of the porosity on the CO2 adsorption properties. In order to make silica materials reactive towards CO2, they were functionalized by introducing amino groups via grafting of 3-[2-(2-aminoethyl)aminoethyl]aminopropyltrimethoxysilane. After a qualitative study of the CO2 adsorption, the quantitative determination of CO2 adsorption capacity at 35 °C revealed that the mesoporous material is more efficient compared to the Stöber-based one (adsorption capacity values of 0.49 and 0.58 mol/kg for Stöber-based and mesoporous samples). However, since the difference in the adsorption capacity is only about 15 % and the Stöber-based sample is considerably cheaper, the non-porous sample should be considered as a favourable adsorbent material for CO2 capture applications.

On the adsorption of toluene on amorphous mesoporous silicas with tunable sorption characteristics.

The development of novel adsorbents for the purification of natural gas from aromatic hydrocarbons and the optimization of adsorption processes represent some of the most crucial environmental challenges. In this work, two amorphous mesoporous silica (AMS) samples with different sorption characteristics were prepared by modifying the synthesis method of amorphous mesoporous silica-aluminas, and tested as adsorbents of aromatic molecules for the purification of natural gas. The physico-chemical properties of the obtained materials were finely characterized by means of different experimental techniques (including FTIR and solid-state NMR) with the aim of determining their sorption and surface features. The adsorption capacity of the produced solids towards toluene, chosen as the reference of aromatic molecules, was determined by using FTIR, solid-state NMR spectroscopy and microgravimetric analysis. Finally, in view of applications under more realistic conditions, the adsorption properties of the AMS materials were also investigated after prolonged treatments in water.

Combined solid-state NMR, FT-IR and computational studies on layered and porous materials.

Understanding the structure-property relationship of solids is of utmost relevance for efficient chemical processes and technological applications in industries. This contribution reviews the concept of coupling three well-known characterization techniques (solid-state NMR, FT-IR and computational methods) for the study of solid state materials which possess 2D and 3D architectures and discusses the way it will benefit the scientific communities. It highlights the most fundamental and applied aspects of the proactive combined approach strategies to gather information at a molecular level. The integrated approach involving multiple spectroscopic and computational methods allows achieving an in-depth understanding of the surface, interfacial and confined space processes that are beneficial for the establishment of structure-property relationships. The role of ssNMR/FT-IR spectroscopic properties of probe molecules in monitoring the strength and distribution of catalytic active sites and their accessibility at the porous/layered surface is discussed. Both experimental and theoretical aspects will be considered by reporting relevant examples. This review also identifies and discusses the progress, challenges and future prospects in the field of synthesis and applications of layered and porous solids.

Novel paramagnetic clays obtained through intercalation of Gd3+-complexes.

Novel paramagnetic lanthanide-exchanged saponite clays, bearing in the interlamellar region positively charged Gd3+-complexes, were synthesized using a hydrothermal approach followed by a classical ion exchange reaction. A detailed characterization was performed to assess the physico-chemical properties of the samples, which showed a hydrodynamic diameter between 50 and 90 nm and good thermal stability. 1H-NMR relaxometric studies in aqueous solution as a function of magnetic field and temperature were carried out to evaluate the local chemical environment of the intercalated paramagnetic centres and their interaction with water molecules. The data indicate a strong interaction of the confined complexes with the lamellae, resulting in a restriction of the local rotational dynamics and of the exchange process of water molecules between the inner coordination sphere of Gd3+ and the bulk. The stability over time in aqueous solutions of varying complexity was also studied by relaxometric techniques.

Experimental Determination of the Molar Absorption Coefficient of n-Hexane Adsorbed on High-Silica Zeolites.

Determination of the molar absorption coefficients of the CH3 bending mode at ν˜ =1380 cm-1 (ϵ1380 ) of n-hexane adsorbed from the gas phase on two different dealuminated zeolites is derived by a combination of IR spectroscopy and microgravimetric analysis. High-silica zeolite Y (HSZ-Y) and zeolite ZSM-5 (with SiO2 /Al2 O3 ratios of 200 and 280, respectively) with different textural and surface features are selected to evaluate the effect of the pore structure and architecture on the value of ϵ1380 of the adsorbed n-hexane. Experimental data indicate that the molecule experiences a different adsorption environment inside zeolites; thus resulting in a significant change of the dipole moment and very different ϵ1380 values: (0.278±0.018) cm µmol-1 for HSZ-Y and (0.491±0.032) cm µmol-1 for ZSM-5. Experimental data are also supported by computational modeling, which confirms the effect of different matrices on the IR absorption intensity. This study reveals that the use of probe molecules for quantitative measurements of surface sites has to be judiciously adopted, especially if adsorption occurs in the restricted spaces of microporous materials.