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The COVID-19 pandemic has led to the increased use of disposable face masks worldwide, resulting in a surge of potentially infectious waste. This waste must be safely managed and disposed of to prevent the spread of the virus. To address this issue, a preliminary study explored the use of hydrothermal carbonization (HTC) as a potential method for converting surgical mask waste into value-added carbonaceous materials. The HTC treatments were conducted at 220 °C for 3 h with or without the addition of acetic acid. The resulting hydrochar was characterized using several techniques, including thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and N2-physisorption analyzers. The study found that the masks formed a melt with reduced mass (−15%) and volume (up to −75%) under the applied conditions. The carbon content and higher heating value (HHV) of the produced hydrochars were higher than those of the original masks (+5%). Furthermore, when acetic acid was added during the HTC experiment, a new crystal phase, terephthalic acid, was produced. This acid is a precursor in surgical mask production. The study suggests that hydrothermal carbonization could potentially achieve sanitization and volume reduction in non-renewable and non-biodegradable surgical masks while also producing a solid fuel or a raw material for terephthalic acid production. This approach offers an innovative and sustainable solution to manage the waste generated by the increased use of disposable face masks during the pandemic.

The potential of silicon-based fluorescent platforms for the detection of trace toxic metal ions was investigated in an aqueous environment. To this aim, silicon chips were first functionalized with amino groups, and fluorescein organic dyes, used as sensing molecules, were then covalently linked to the surface via formation of thiourea groups. The obtained hybrid heterostructures exhibited high sensitivity and selectivity towards copper(II), a limit of detection compatible with the recommended upper limits for copper in drinking water, and good reversibility using a standard metal–chelating agent. The fluorophore–analyte interaction mechanism at the basis of the reported fluorescence quenching, as well as the potential of performance improvement, were also studied. The herein presented sensing architecture allows, in principle, tailoring of the selectivity towards other metal ions by proper fluorophore selection, and provides a favorable outlook for integration of fluorescent chemosensors with silicon photonics technology.

In this work, industrial waste hexafluorosilicic acid (H2SiF6 or FSA) has been proven to be a low-cost alternative to silicate esters for the synthesis of high-quality MCM-41 (high surface area, hi...

Iron oxides/oxyhydroxides, namely maghemite, iron oxide-silica composite, akaganeite, and ferrihydrite, are studied for As

Arsenic pollution in ground and drinking water is a major problem worldwide due to the natural abundance of arsenic by dissolution from ground sediment or mining activities from anthropogenic activities. To overcome this issue, iron oxides as low-cost and non-toxic materials, have been widely studied as efficient adsorbents for arsenic removal, including when dispersed within porous silica supports. In this study, two head-to-head comparisons were developed to highlight the As(V)-adsorptive ability of meso- and macrostructured silica-based adsorbents. First, the role of the textural properties of a meso-(SBA15) and macrostructured (MOSF) silica support in affecting the structural-morphological features and the adsorption capacity of the active phase (Fe2O3) have been studied. Secondly, a comparison of the arsenic removal ability of inorganic (Fe2O3) and organic (amino groups) active phases was carried out on SBA15. Finally, since silica supports are commonly proposed for both environmental and biomedical applications as active phase carriers, we have investigated secondary silicon and iron pollution. The batch tests at different pH revealed better performance from both Fe2O3-composites at pH 3. The values of qm of 7.9 mg g−1 (53 mg gact−1) and 5.5 mg g−1 (37 mg gact−1) were obtained for SBA15 and MOSF, respectively (gact stands for mass of the active phase). The results suggest that mesostructured materials are more suitable for dispersing active phases as adsorbents for water treatment, due to the obtainment of very small Fe2O3 NPs (about 5 nm). Besides studying the influence of the pore size of SBA15 and MOSF on the adsorption process, the impact of the functionalization was analyzed on SBA15 as the most promising sample for As(V)-removal. The amino-functionalized SBA15 adsorbent (3-aminopropyltriethoxysilane, APTES) exhibited a qm of 12.4 mg g−1 and faster kinetics. Furthermore, issues associated with the release of iron and silicon during the sorption process, causing secondary pollution, were evaluated and critically discussed.

Nanostructured spinel ferrites with formula M2+Fe2O4 (where M2+ ═ Fe, Co, Mn, Ni, Zn, etc.) represent a class of magnetic materials widely employed in different research fields, due to the possibility of finely tuning the magnetic properties by changing the chemical composition, size, shape, capping agents, etc. Herein, a review of the most common chemical synthesis in liquid media, distinguishing among aqueous and non-aqueous routes, is presented. The experimental procedure together with the mechanism, advantages and disadvantages, and examples are illustrated for each synthetic strategy.

A Raman study on Zinc-substituted Cobalt ferrites, with different Zn(II) contents in each sample of formula: CoFe₂O₄ (1), Zn0.30Co0.70Fe2.00O₄ (2), Zn0.46Co0.54Fe2.02O₄ (3), Zn0.53Co0.47Fe2.02O₄ (4) is reported. These samples show the same crystallite size (∼6 nm), particle size (∼7 nm) and particle size distribution (∼20%) and they have been synthesized through heating up surfactant-assisted thermal decomposition of metalorganic precursors. The effect of Zn(II) substitution in the cationic distribution is investigated by using the known metal-oxygen vibrational modes in tetrahedral and octahedral sites. The presence of Zn(II) metal ion is determined through the band at 150 cm-1 (T2g(1) phonon mode), which is not present in the pure Co-ferrite, a blue-shift of the Eg vibrational mode depending on Zn(II)/Co(II) cationic distribution and a shoulder at ∼250 cm-1, which appears when zinc enters in the structure, and a broadening and a red-shift in the A1g phonon mode is observed in Raman spectra of 2-4 samples. Interestingly the latter represents a potential key probe to monitor the Zn(II) presence in Zn-substituted Co-ferrites.

In this work, highly dispersed maghemite (λ-Fe₂O₃) in form of ultrasmall nanoparticles (about 2 nm) was embedded into a mesostructured silica MCM-41 (about 600 nm) featuring regular submicrometric hexagonal shaped particles via the two-solvent incipient wetness impregnation strategy. The obtained nanocomposite was then tested as H₂S sorbent in the mid-temperature range. When compared with a commercial sorbent (KatalkoJM 32-5), it showed superior performances after the first sulfidation which remained steady over three repeated sulfidation cycles, highlighting the regenerability properties of the composite. In order to evaluate the effect of the length of the pore channels on the accessibility of H₂S to the active phase, an analogous micrometric λ-Fe₂O₃@MCM-41, featuring micrometric channels and particles of irregular shape was used as reference.

Nanostructured spinel cobalt ferrite samples having crystallite size ranging between 5.6 and 14.1 nm were characterized by X-ray photoelectron spectroscopy and X-ray induced Auger electron spectroscopy in order to determine the chemical state of the elements, the iron/cobalt ratio and the cation distribution within tetrahedral and octahedral sites. The presence of size-dependent trends in the binding energy of the main photoelectron peaks and in the kinetic energy of the X-ray induced O KLL signal was also investigated. The results showed that iron is present as FeIII and cobalt is present as CoII. The iron/cobalt ratio determined by XPS ranges between 1.8 and 1.9 and it is in very good agreement, within experimental uncertainty, with the expected 2 : 1 ratio. The percentage of Fe in octahedral sites ranges between 62% and 64% for all samples. The kinetic energy of the O KLL signals increases with crystallite size. These results are explained in terms of changes in the ionicity of the metal–oxygen bonds. The results of this investigation highlight how the XPS technique represents a powerful tool to investigate the composition, the chemical state and inversion degree of cobalt spinel ferrites, contributing to the comprehension of their properties.

Achieving metal-organic frameworks (MOFs) in the form of nanoparticles (NanoMOFs) represents a recent challenge due to the possibility to combine the intrinsic porosity of these materials with the nanometric dimension, a fundamental requirement for strategic biomedical applications. In this outlook we envision the current/future opportunities of the NanoMOFs in the field of biomedicine, with particular emphasis on (i) biocompatible MOFs composition; (ii) MOFs miniaturization and (iii) nanoMOFs applications.

This work is a part of a research project conducted in order to characterize the volcanic ash from Mount Etna, focusing in particular on the surface reactivity of ashes and possible consequence for human health. In this framework, a sampling campaign began on 16 March 2013, taking advantage of the intense volcanic activity on Etna. The interaction between volcanic ash and human organism was simulated treating two classes of representative Etnean particles with ultrapure water (grainsize of 850 um) and Gamble's solution mimic lug fluids (grainsize38 μm) with the aim to evaluate the risk due to gastric and respiratory exposure to volcanic particles. The leachates were analysed by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Ionic Chromatography (CI) in order to highlight possible dangerous elements released in water solutions according to USGS protocol. Analyses of Gamble's solution highlighted a release of elements smaller than in watery solutions and always below the thresholds established by the Italian law. On the contrary, analyses of watery solutions evidenced, for some elements (B, Cd, Ni and As), levels higher than permitted by Italian law. Considering the effects of these elements on human health, further investigations are necessary and currently carried out in order to better constrain the release process and the specific effects on human organism.

The effect of the annealing temperature Tann on the magnetic properties of cobalt ferrite nanoparticles embedded in an amorphous silica matrix (CoFe2O4/SiO2), synthesized by a sol-gel auto-combustion method, was investigated by magnetization and AC susceptibility measurements. For samples with 15% w/w nanoparticle concentration, the particle size increases from ~2.5 to ~7 nm, increasing Tann from 700 to 900 &deg, C. The effective magnetic anisotropy constant (Keff) increases with decreasing Tann, due to the increase in the surface contribution. For a 5% w/w sample annealed at 900 &deg, C, Keff is much larger (1.7 &times, 106 J/m3) than that of the 15% w/w sample (7.5 &times, 105 J/m3) annealed at 700 &deg, C and showing comparable particle size. This indicates that the effect of the annealing temperature on the anisotropy is not only the control of the particle size but also on the core structure (i.e., cation distribution between the two spinel sublattices and degree of spin canting), strongly affecting the magnetocrystalline anisotropy. The results provide evidence that the magnetic anisotropy comes from a complex balance between core and surface contributions that can be controlled by thermal treatments.

Artificial nano-heterostructures (NHs) with controlled morphology, obtained by combining two or more components in several possible architectures, make them suitable for a wide range of applications. Here, we propose an oleate-based solvothermal approach to design silver-spinel ferrite flower-like NHs. Small oleate-coated silver nanoparticles were used as seeds for the growth of magnetic spinel ferrite (cobalt ferrite and spinel iron oxide) nanodomains on their surface. With the aim of producing homogeneous flower-like heterostructures, a careful study of the effect of the concentration of precursors, the reaction temperature, the presence of water, and the chemical nature of the spinel ferrite was carried out. The magnetic and optical properties of the NHs were also investigated. A heterogeneous growth of the spinel ferrite phase on the silver nanoparticles, through a possible defect-assisted mechanism, was suggested in the light of the high concentration of stacking faults (intrinsic and twins) in the silver seeds, revealed by Rietveld refinement of powder X-ray diffraction patterns and High-Resolution electron microscopy.

International audience; Nanosheets of two mixed linker (anilate/carboxylate)/YbIII-based two-dimensional (2D) layered coordination polymers (CPs) are herein reported. Bulky sized CPs, formulated as [Yb4(ClCNAn)5(DOBDC)1(DMSO)10]n·(DMSO)2 (1) and [Yb2(ClCNAn)2(F4BDC)(DMSO)6]n (2), are formed by two-dimensional neutral polymeric networks based on YbIII ions, heterosubstituted ClCNAn2– anilate, and dicarboxylate linkers (DOBDC2– in 1; F4BDC2– in 2): in 1, neighbor layers are eclipsed and form six-membered rings showing either hexagonal cavities, formed by ClCNAn2– and YbIII ions or rectangular cavities formed by ClCNAn2–, DOBDC2–, and YbIII while distorted square-like cavities formed by ClCNAn2–, F4BDC2–, and YbIII are obtained in 2. The 1 and 2 nanosheets, that is, 1-NS and 2-NS, are produced by exfoliation of bulk CPs by the well-known top-down approach and characterized by atomic force microscopy and high resolution transmission electron microscopy. The 1-NS and 2-NS show thickness in the range of 1–5 nm, whereas the lateral dimensions are in the micrometer scale and the presence of well-defined lattice fringes, key evidence of their robustness. Remarkably the powder X-ray diffraction (PXRD) patterns highlight that the crystallinity is retained at the nanoscale level. Nanosheets photophysics are investigated by an innovative Multiprobe Approach where lifetime, photoluminescence (PL) and integrated PL are simultaneously measured in order to study how these parameters can be affected by the presence of the different ligands. These advanced photophysical studies pave the way to challenging luminescent sensing applications and to contribute to the ongoing research on fabricating robust and crystalline hybrid (organic/inorganic) lanthanide sheetlike 2D nanomaterials.

A smart synthesis strategy exploiting the use of crystalline precursor salts, which until now has only been applied to the FePt system, was here extended to other binary alloys (CoPt, NiPt) with the aim of demonstrating the high potential of such a method and formulating a comprehensive explanation of the underlying process. Indeed, by exploiting the natural order of M(H2O)6PtCl6 (M = Fe, Co, Ni) crystalline precursor salts, consisting of M and Pt atoms on alternating planes that mimic the atomic arrangement of the L10 structure, highly ordered MPt alloy nanoparticles were obtained at lower processing temperatures and shorter reaction times than ordinary thermal processes, thus demonstrating the effectiveness and versatility of such an approach for the synthesis of L10 alloys. Comparing the results from the three different systems allowed a better comprehension of the underlying process, which involves the simultaneous occurring of the salt decomposition and the L10 ordering process. Indeed, differently to all the other existing approaches where thermal treatments are exploited to induce the disorder/order transition, the proposed strategy, which here we call Pre-ordered Precursor Reduction, is based on the opposite paradigm that is the preservation during the thermo-chemical treatment of the chemical order provided by the crystal. Thus, by properly choosing the starting salt, the proposed method can be used to synthesize a wide class of alloys, including those systems whose ordering formation is limited by kinetic and thermodynamic constraints.

In this work, the effect of the M41S support pore structure (hexagonal or cubic) and of the wall thickness of the silica mesochannels has been evaluated aimed at achieving more and more efficient and regenerable iron oxide-based sorbents for H2S removal at midtemperature. With this purpose, we set up a simple Pluronic-free synthetic strategy capable of producing silica supports with hexagonal (MCM-41) or cubic (MCM-48) pore structure with different wall thicknesses that have been used to fabricate the corresponding sorbents made up of iron oxide nanoparticles homogeneously dispersed into the mesochannels. The combined use of 57Fe-Mossbauer Spectroscopy and DC magnetometry has allowed for ascertaining the presence of maghemite in the form of ultrasmall nanoparticles in both composites and gives new insights on the influence of the different silica matrices on the active phase features. The performances of the sorbents have been evaluated at midtemperature (300 °C) through three repeated sulfidation and reg...

A green, one-pot approach based on the solvothermal amidation of carboxylic acids with amines has been developed for the synthesis of diverse aliphatic and aromatic amides. It does not require the use of catalysts or coupling reagents and it occurs in the presence of ethanol that has been proved to have a key role in the process. The proposed strategy is also extendable to biologically active amides and could represent a low-cost and waste-less alternative to the common synthetic pathways.

NiO-CeO2 mixed oxides were prepared by the soft-template method with nominal Ni/Ce molar ratios between 0.3 and 4.0. NiO and CeO2 pure oxides were also prepared through the same procedure. A second series of NiO-CeO2 mixed oxides (nominal Ni/Ce values = 0.3–1.5 mol mol−1) was synthesized by using the soft-templated ceria as the support and depositing Ni through incipient wetness impregnation. All samples were characterized by different techniques as to their chemical composition, structure, morphology, texture, and redox features. NiO nanocrystals of about 4 nm in size were obtained in the case of the soft‐templated samples, regardless of the Ni loading. Larger NiO nanocrystals (up to 20 nm in size) were formed by depositing Ni through the impregnation procedure. The catalytic performance was investigated in the CO2 methanation reaction after mild reduction pretreatment (H2 at 400 °C for 1 h). Catalytic testing was performed under atmospheric pressure, 300 °C, 72,000 cm3 h−1 gcat−1, and stoichiometric H2/CO2 molar ratio. Pure NiO as well as the two NiO-CeO2 mixed oxides series showed high CO2 conversions (up to 87 mol%) together with CH4 selectivity values close to 100 mol%. Despite the significantly different size (6–8 and 15–35 nm, respectively) of the Ni0 nanocrystals originated by NiO reduction, comparable CO2 conversion values were observed for the soft-templated and impregnated catalysts. The catalyst stability as well as the effect of reaction temperature, space velocity, and H2/CO2 molar ratio were investigated on selected samples. The catalytic results were explained by taking into account that CO2 and H2 are activated on different phases.

During the 2nd millennium BC anthropomorphic menhirs belonging to a 3rd millennium BC sanctuary were reused as building material in the Arasseda Nuraghe (Sardinia, Italy). To analyse the Arasseda menhirs and the local Monte Ironi geological samples (presenting similar visual features), chemical (pXRF, ICP-OES, ICP-MS), mineralogical-chemical (PXRD) and physical (Mohs hardness) measurements were performed. Through the experimental data, the menhirs source provenance and the technological properties (workability, durability) of the raw material chosen for sculptural purposes during Copper Age were investigated. To the authors’ knowledge this is the first archaeometric study on the Arasseda menhirs (the third on Sardinian menhirs) and one between the few recently developed on European megaliths.

Mesostructured NiO CeO2 mixed oxides, with Ni loadings in the range 5–35 wt% (gNi/gCeO2), were synthesized by the hard template procedure using SBA-15 as the template. A hard-templated CeO2 was also prepared and used as the support for depositing Ni (5–35 wt%) by impregnation. Two NiO Al2O3 catalysts were synthesized for comparison, by impregnating nickel on a commercial γ-alumina. All the samples were characterized by different techniques as to their chemical composition, structure, morphology, texture, and redox features. The catalytic performance was investigated in the CO2 methanation reaction after mild reduction pretreatment (H2 at 400 °C for 1 h). Catalytic testing was performed under atmospheric pressure, 300 °C, 72,000 cm3 h−1 gcat−1, and stoichiometric H2/CO2 molar ratio. High catalytic activity, with CH4 selectivity values ≥ 93 mol%, was obtained with the NiO CeO2 mixed oxides (CO2 conversions up to 76 mol%). When γ-Al2O3 was used as the support, catalysts with low activity (CO2 conversion ≤ 20 mol%) were obtained. On selected samples, additional catalytic runs were also performed for reaction times up to 30 h or with a higher space velocity value. The catalytic results were explained by taking into account the role of the nickel-ceria interactions both during the reduction of NiO and in the reactants activation.

An easy, low-cost, repeatable seed-mediated growth approach in solvothermal condition has been proposed to synthesize bimagnetic spinel ferrite core-shell heterostructures in the 10-20 nm particle size range. Cobalt ferrite and manganese ferrite nanoparticles (CoFe2O4 and MnFe2O4) have been coated with isostructural spinel ferrites like maghemite/magnetite, MnFe2O4, and CoFe2O4 with similar cell parameters to create different heterostructures. The conventional study of the structure, morphology, and composition has been combined with advanced techniques in order to achieve details on the interface at the nanoscale level. Clear evidence of the heterostructure formation have been obtained (i) indirectly by comparing the 57Fe Mossbauer spectra of the core-shell samples and an ad hoc mechanical mixture and (ii) directly by mapping the nanoparticles' chemical composition by electron energy loss spectroscopy (EELS) and energy-dispersive X-ray spectroscopy (EDX) in the scanning transmission electron microscopy mode (STEM). In addition, chemical-sensitive electron tomography in STEM-EDX mode has been applied in order to obtain detailed 3D images with a sub-nanometer spatial resolution.

MCM-41 is proposed to build mesostructured Fe2O3-based sorbents as an alternative to other silica or alumina supports for mid-temperature H2S removal. MCM-41 was synthesized as micrometric (MCM41_M) and nanometric (MCM41_N) particles and impregnated through an efficient two-solvent (hexane–water) procedure to obtain the corresponding γ-Fe2O3@MCM-41 composites. The active phase is homogeneously dispersed within the 2 nm channels in the form of ultrasmall maghemite nanoparticles assuring a high active phase reactivity. The final micrometric (Fe_MCM41_M) and nanometric (Fe_MCM41_N) composites were tested as sorbents for hydrogen sulphide removal at 300 °C and the results were compared with a reference sorbent (commercial unsupported ZnO) and an analogous silica-based sorbent (Fe_SBA15). MCM-41 based sorbents, having the highest surface areas, showed superior performances that were retained after the first sulphidation cycle. Specifically, the micrometric sorbent (Fe_MCM41_M) showed a higher SRC value than the nanometric one (Fe_MCM41_N), due to the low stability of the nanosized particles over time caused by their high reactivity. Furthermore, the low regeneration temperature (300–350 °C), besides the high removal capacity, renders MCM41-based systems an alternative class of regenerable sorbents for thermally efficient cleaning up processes in Integrated Gasification Combined Cycles (IGCC) systems.