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The preparation of monodisperse and biocompatible water-soluble superparamagnetic iron oxide nanoparticles (SPIONs) with high sensitivity in Magnetic Resonance Imaging (MRI) represents a challenge for the development of contrast agents. Here we report the synthesis of highly monodisperse citric acid (CA) coated SPIONs with an average diameter of 9 nm and spherical shape, prepared through a suitably optimized coprecipitation method. CA-SPIONs show a high solubility and stability in aqueous medium. Imaging of CA-SPIONs aqueous suspensions was performed in a clinical 1.5-T MRI scanner and different clinical acquisition sequences were exploited. Results show that image contrast can be effectively improved when concentrations of SPIONs lower than 1 ppm are present, and that the echo time is the main parameter influencing the image contrast of SPION-loaded solutions. Moreover, we found that CA-SPIONs show a high value of transverse relaxivity of 128 L mmol-1 s-1 (higher than the commercial contrast agents). Our results are encouraging for the further development of clinical application of SPIONs in MRI, and can represent a starting point for the optimization of clinical imaging exploiting the contrast enhancement of such agents. Namely, it seems possible to achieve an optimal image contrast with low concentration of SPIONs; this could lead to a lower probability of side effects. [ABSTRACT FROM AUTHOR]

The properties of BEA, MFI and Silicalite-1 zeolites in the ammonium and protonic forms are studied in the etherification of HMF (5-hydroxymethylfurfural) in anhydrous ethanol and compared with FTIR data on ammonium ion siting and displacement by competitive adsorption, as well as data on ammonium ion dissolution in aqueous solution. For the first time it is demonstrated that ammonium-exchanged zeolites are active and show better performances (particularly for the BEA structure) in the acid-catalyzed etherification reaction. This behavior is associated to a reversible dissociation of NH4+ ions, which is favored by the BEA zeolite structure. A critical condition for enhanced catalytic performances is that dissociated ammonia remains in the zeolite cages, and may be reversibly re-adsorbed. It is thus likely that the dissociated ammonia participates in the reaction or induces a confinement effect. [ABSTRACT FROM AUTHOR]

The use of biomass, bio-waste and CO2 derived raw materials, the latter synthesized using H2 produced using renewable energy sources, opens new scenarios to develop a sustainable and low carbon chemical production, particularly in regions such as Europe lacking in other resources. This tutorial review discusses first this new scenario with the aim to point out, between the different possible options, those more relevant to enable this new future scenario for the chemical production, commenting in particular the different drivers (economic, technological and strategic, environmental and sustainability and socio-political) which guide the selection. The case of the use of non-fossil fuel based raw materials for the sustainable production of light olefins is discussed in more detail, but the production of other olefins and polyolefins, of drop-in intermediates and other platform molecules are also analysed. The final part discusses the role of catalysis in establishing this new scenario, summarizing the development of catalysts with respect to industrial targets, for (i) the production of light olefins by catalytic dehydration of ethanol and by CO2 conversion via FTO process, (ii) the catalytic synthesis of butadiene from ethanol, butanol and butanediols, and (iii) the catalytic synthesis of HMF and its conversion to 2,5-FDCA, adipic acid, caprolactam and 1,6-hexanediol. [ABSTRACT FROM AUTHOR]

Molecular mechanisms for N2 fixation (solar NH3) and CO2 conversion to C2+ products in enzymatic conversion (nitrogenase), electrocatalysis, metal complexes and plasma catalysis are analyzed and compared. It is evidenced that differently from what is present in thermal and plasma catalysis, the electrocatalytic path requires not only the direct coordination and hydrogenation of undissociated N2 molecules, but it is necessary to realize features present in the nitrogenase mechanism. There is the need for (i) a multi-electron and -proton simultaneous transfer, not as sequential steps, (ii) forming bridging metal hydride species, (iii) generating intermediates stabilized by bridging multiple metal atoms and (iv) the capability of the same sites to be effective both in N2 fixation and in COx reduction to C2+ products. Only iron oxide/hydroxide stabilized at defective sites of nanocarbons was found to have these features. This comparison of the molecular mechanisms in solar NH3 production and CO2 reduction is proposed to be a source of inspiration to develop the next generation electrocatalysts to address the challenging transition to future sustainable energy and chemistry beyond fossil fuels. [ABSTRACT FROM AUTHOR]

The electrocatalytic reduction of CO2 (CO2RR) in high value products represents a high potential strategy in addressing global climate change. Vulcan XC-72 carbon black is considered to be a promising catalyst support for metals nanoparticles in the CO2RR due to its good electrical properties, high mesoporous distribution and low cost. In this work we reported how the surface chemical modification of Vulcan XC-72 carbon leads to the introduction of oxygenated functionalities with a significant increase of the activity in the electrocatalytic reduction of CO2 to formic acid. The presence of oxygen-containing species results advantageous for the dispersion and anchoring of Sn nanoparticles onto carbon surface increasing the Faradaic selectivity to formic acid up to 80%. [ABSTRACT FROM AUTHOR]

The chelating and sequestering ability of a glyphosate metabolite, the aminomethylphosphonic acid (AMPA) towards bi- and trivalent metal cations, such as Ca 2+ , Mg 2+ , Zn 2+ , Cu 2+ and Al 3+ , were investigated in aqueous solutions of NaCl, in an ionic strength range of 0.1 ≤ I/mol dm -3  ≤ 1.0 and at constant temperature of T = 298.15 ± 0.15 K. The investigations on the acid-base properties and complexing ability were performed, by means of potentiometry, in conditions of different c M :c AMPA molar ratios and pH values. The formation of insoluble species was experimentally observed in the M n+ /AMPA 2- systems, and the solid phases were characterized by means of X-Ray Diffractometry (XRD), Scanning Electron Microscopy (SEM) and InfraRed Attenuated Total Reflection spectroscopy (IR-ATR). The dependence on ionic strength of the stability constants of the M n+ /AMPA 2- complexes species, determined at different ionic strengths, was modelled by the Debye-Hückel type equation. The sequestering ability of AMPA toward the investigated metal cations was evaluated by pL 0.5 parameter., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

We report on the facile synthesis of SiO 2 @nitrized-TiO 2 nanocomposite (NST) by calcination of TiO 2 xerogel with OctaAmmonium POSS® (N-POSS; POSS=polyhedral oligomeric silsesquioxanes). The as-obtained nanoporous mixed oxide is constituted by uniformly distributed SiO 2 and nitrized-TiO 2 , where the silica component is present in an amorphous state and TiO 2 in an anatase/rutile mixed phase (92.1 % vs. 7.9 %, respectively) with very small anatase crystallites (3.7 nm). The TiO 2 lattice is nitrized both at interstitial and substitutional positions. NST features a negatively charged surface with a remarkable surface area (406 m 2  g -1 ), endowed with special adsorption capabilities towards cationic dyes. Its photocatalytic behavior was tested by following the degradation of standard aqueous methylene blue and methyl orange solutions under UV and visible light irradiation, according to ISO 10678:2010. For comparison, analogous investigations were carried out on a silica-free N-TiO 2 , obtained by using NH 4 Cl as nitrogen source., (© 2021 The Authors. Published by Wiley-VCH GmbH.)

Molecular mechanisms for N 2 fixation (solar NH 3 ) and CO 2 conversion to C2+ products in enzymatic conversion ( nitrogenase ), electrocatalysis, metal complexes and plasma catalysis are analyzed and compared. It is evidenced that differently from what is present in thermal and plasma catalysis, the electrocatalytic path requires not only the direct coordination and hydrogenation of undissociated N 2 molecules, but it is necessary to realize features present in the nitrogenase mechanism. There is the need for (i) a multi-electron and -proton simultaneous transfer, not as sequential steps, (ii) forming bridging metal hydride species, (iii) generating intermediates stabilized by bridging multiple metal atoms and (iv) the capability of the same sites to be effective both in N 2 fixation and in CO x reduction to C2+ products. Only iron oxide/hydroxide stabilized at defective sites of nanocarbons was found to have these features. This comparison of the molecular mechanisms in solar NH 3 production and CO 2 reduction is proposed to be a source of inspiration to develop the next generation electrocatalysts to address the challenging transition to future sustainable energy and chemistry beyond fossil fuels.