Dynamic molecular ordering in multiphasic nanoconfined ionogels detected with time-resolved diffusion NMR

Molecular motion in nanosized channels can be highly complicated. For example, water molecules in hydrophobic nanopores move rapidly and coherently in a chain, following the so-called single file motion. Surprisingly, fast molecular motion is also observed in viscous charged fluids, such as room temperature ionic liquids (RTILs) confined in a nanoporous carbon or silica matrix. The microscopic mechanism of this intriguing effect is still unclear. Here, by combining NMR diffusion experiments in different relaxation windows with ab-initio molecular dynamics simulations, we show that the imidazolium-based RTIL [BMIM]+[TCM]-, entrapped in the MCM-41 silica nanopores, exhibits a complex dynamic molecular ordering (DMO); adsorbed RTIL molecules near the pore walls orient almost vertically to the walls, while at the center of the pores anion-cation pairs diffuse collectively in a single file (SFD). Enlightening this extraordinary effect is of primary importance in designing RTIL-based composite materials with tuned electrochemical properties.

Atomic Absorption Spectrometry as an Alternative to Determine the Presence of Gold Nanoparticles on or in Silica Matrix

Two different gold-silica-based nanomaterials were prepared: (i) silica-supported gold nanoparticles (AuNP/SiO2); and (ii) gold-silica core-shell nanoparticles (AuNP@SiO2). Three strategies for sample treatment (S), consisting in acid treatments, were employed: (S1) HNO3; (S2) HNO3 + HCl; and (S3) HF + HNO3 + HCl, applying microwave oven digestion for S2 and S3. From three calibration curves, slope, intercept, and linear correlation coefficient were obtained. The accuracy of the methods was evaluated by comparing the gold contents in a sample determined by flame atomic absorption spectrometry (FAAS) and by inductively coupled plasma atomic emission spectrometry (ICP-OES). Finally, the amount of gold for all samples was determined by FAAS. UV-Vis spectroscopy and transmission electron microscopy (TEM) were used to compare the material before and after sample treatment. By comparison, the application of S2 and S3 allowed the presence of gold on or in the silica matrix to be determined and the amount quantified.

Silica-supported Fe/Fe–O nanoparticles for the catalytic hydrogenation of nitriles to amines in the presence of aluminium additives

The hydrogenation of nitriles to amines represents an important and frequently used industrial process due to the broad applicability of the resulting products in chemistry and life sciences. Despite the existing portfolio of catalysts reported for the hydrogenation of nitriles, the development of iron-based heterogeneous catalysts for this process is still a challenge. Here, we show that the impregnation and pyrolysis of iron(II) acetate on commercial silica produces a reusable Fe/Fe–O@SiO2 catalyst with a well-defined structure comprising the fayalite phase at the Si–Fe interface and α-Fe nanoparticles, covered by an ultrathin amorphous iron(III) oxide layer, growing from the silica matrix. These Fe/Fe–O core–shell nanoparticles, in the presence of catalytic amounts of aluminium additives, promote the hydrogenation of all kinds of nitriles, including structurally challenging and functionally diverse aromatic, heterocyclic, aliphatic and fatty nitriles, to produce primary amines under scalable and industrially viable conditions.

Impact of Magneto-optical Properties Depending on the Orientation in the Plane of Cobalt Ferrite Locked in a Silica Matrix

In this work, we discuss the magneto-optical properties according to the orientation of 15nm-sized cobalt ferrite blocked in a silica matrix in comparison to the study done on 20nm-sized cobalt ferrite. This measurement shows that it is possible to increase the remanence of the Faraday effect by creating a magnetic orientation in the solid matrix, which is interesting for the production of self-polarized components. In addition, this remanence is greater for 15 nm than for 20 nm.A gelation field applied perpendicular to the plane of the layer therefore produces a preferential orientation of the magnetic moments in the direction of the field applied during the measurement.

TEOS-PDMS-Calcium Oxalate Hydrophobic Nanocomposite for Protection and Stone Consolidation

A treatment for both protection and consolidation, was synthesized in a simplified procedure through the sol gel process. Synthesized nano-calcium oxalate (CaOx) was incorporated into tetraethoxysilane (TEOS) and polydimethylsiloxane (PDMS), providing a hybrid hydrophobic consolidant nanocomposite. Oxalic acid was selected due to its ability to catalyse the hydrolysis of TEOS, as a drying control agent, but also because of its contribution at the formation of the calcium oxalate in reaction with calcium hydroxide. CaOx, incorporated into the silica matrix of the final copolymer, exhibits interfacial compatibility with the stone substrate and simultaneously strengthens the treated surface, since CaOx appears to be more stable than calcium carbonate. The hydrolysis of TEOS, as well as the formation of CaOx was evaluated through thermogravimetric analysis (TG/DTA). The nanocomposite consists of particles with approximately 7–700 nm in size range, as shown in TEM images. The consolidation, in combination with the hydrophobicity of surface resulted in an increase of the resistance to decay. Mechanical properties were enhanced as evaluated by ultrasonic pulse velocity on treated and untreated surfaces. Furthermore, water contact angle, as well as water absorption by capillarity test, showed improved water repellency of treated stones. Finally, this treatment doesn’t alter the aesthetic surface parameters, a fact that is essential in cultural heritage conservation, while the consolidant remains intact under UV and moisture exposure.

Exploiting the Potential of Supported Magnetic Nanomaterials as Fenton-like Catalysts for Environmental Applications

In recent years, the application of magnetic nanoparticles as alternative catalysts to conventional Fenton processes has been investigated for the removal of emerging pollutants in wastewater. While this type of catalyst reduces the release of iron hydroxides with the treated effluent, it also presents certain disadvantages, such as slower reaction kinetics associated with the availability of iron and mass transfer limitations. To overcome these drawbacks, the functionalization of the nanocatalyst surface through the addition of coatings such as polyacrylic acid (PAA) and their immobilization on a mesoporous silica matrix (SBA15) can be factors that improve the dispersion and stability of the nanoparticles. Under these premises, the performance of the nanoparticle coating and nanoparticle-mesoporous matrix binomials in the degradation of dyes as examples of recalcitrant compounds were evaluated. Based on the outcomes of dye degradation by the different functionalized nanocatalysts and nanocomposites, the nanoparticles embedded in a mesoporous matrix were applied for the removal of estrogens (E1, E2, EE2), accomplishing high removal percentages (above 90%) after the optimization of the operational variables. With the feasibility of their recovery in mind, the nanostructured materials represented a significant advantage as their magnetic character allows their separation for reuse in different successive sequential batch cycles.