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Twelve samples of waste cooking oil (WCO) were prepared by four different deep-frying procedures. The edible and the waste oil samples were characterised by Raman spectroscopy, revealing few and almost negligible differences between them. Therefore, the possibility of classifying the different groups of samples by extracting valuable data from the Raman spectra through statistical multivariate analysis was explored. Even if the number of samples was not enough to draw definitive conclusions, unsupervised principal component analysis (PCA) and supervised partial least square discriminant analysis (PLS-DA) conducted on the raw Raman signals, allowed to distinguish within edible and waste vegetable oil, and to select the most relevant combination of variables associated with each family. Using sparse partial least square discriminant analysis (S-PLS-DA), we determined a chemical fingerprint characteristic of each sample by creating a Variable In Projection (VIP) plot. The methodology herein presented could find relevant application in the detection of waste adulteration in vegetable oils sold for industrial purposes other than food.

Despite the wide application of graphene-based materials, the information of the toxicity associated to some specific derivatives such as aminated graphene oxide is scarce. Likewise, most of these studies analyse the pristine materials, while the available data regarding the harmful effects of degraded forms is very limited. In this work, the toxicity of graphene oxide (GO), aminated graphene oxide (GO-NH 2 ), and their respective degraded forms (dGO and dGO-NH 2 ) obtained after being submitted to high-intensity sonication was evaluated applying in vitro assays in different models of human exposure. Viability and ROS assays were performed on A549 and HT29 cells, while their skin irritation potential was tested on a reconstructed human epidermis model. The obtained results showed that GO-NH 2 and dGO-NH 2 substantially decrease cell viability in the lung and gastrointestinal models, being this reduction slightly higher in the cells exposed to the degraded forms. In contrast, this parameter was not affected by GO and dGO which, conversely, showed the ability to induce higher levels of ROS than the pristine and degraded aminated forms. Furthermore, none of the materials is skin irritant. Altogether, these results provide new insights about the potential harmful effects of the selected graphene-based nanomaterials in comparison with their degraded counterparts., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

The reactive spark plasma sintering (R-SPS) method was compared in this work with the two-step SHS-SPS route, based on the combination of the self-propagating high-temperature synthesis (SHS) with the SPS process, for the fabrication of dense (Hf 0.2 Mo 0.2 Ti 0.2 Ta 0.2 Nb 0.2 )B 2 -SiC and (Hf 0.2 Mo 0.2 Ti 0.2 Ta 0.2 Zr 0.2 )B 2 -SiC ceramics. A multiphase and inhomogeneous product, containing various borides, was obtained at 2000 °C/20 min by R-SPS from transition metals, B 4 C, and Si. In contrast, if the same precursors were first reacted by SHS and then processed by SPS under the optimized condition of 1800 °C/20 min, the desired ceramics were successfully attained. The resulting sintered samples possessed relative densities above 97% and displayed uniform microstructures with residual oxide content <2.4 wt.%. The presence of SiC made the sintering temperature milder, i.e., 150 °C below that needed by the corresponding additive-free system. The fracture toughness was also markedly improved, particularly when considering the Nb-containing system processed at 1800 °C/20 min, whereas the fracture toughness progressively decreased (from 7.35 to 5.36 MPa m 1/2 ) as the SPS conditions became more severe. SiC addition was found to inhibit the volatilization of metal oxides like MoO 3 formed during oxidation experiments, thus avoiding mass loss in the ceramics. The benefits above also likely took advantage of the fact that the two composite constituents were synthesized in parallel, according to the SHS-SPS approach, rather than being produced separately and combined subsequently, so that strong interfaces between them were formed.

The development of novel advanced nanomaterials (NMs) with outstanding characteristics for their use in distinct applications needs to be accompanied by the generation of knowledge on their potential toxicological impact, in particular, that derived from different occupational risk exposure routes, such as inhalation, ingestion, and skin contact. The harmful effects of novel graphene-metal oxide composites on human health are not well understood, many toxicological properties have not been investigated yet. The present study has evaluated several toxicological effects associated with graphene decorated with manganese oxide nanoparticles (GNA15), in a comparative assessment with those induced by simple graphene (G2), on human models representing inhalation (A549 cell line), ingestion (HT29 cell line) and dermal routes (3D reconstructed skin). Pristine and degraded forms of these NMs were included in the study, showing to have different physicochemical and toxicological properties. The degraded version of GNA15 (GNA15d) and G2 (G2d) exhibited clear structural differences with their pristine counterparts, as well as a higher release of metal ions. The viability of respiratory and gastrointestinal models was reduced in a dose-dependent manner in the presence of both GNA15 and G2 pristine and degraded forms. Besides this, all NMs induced the production of reactive oxygen species (ROS) in both models. However, the degraded forms showed to induce a higher cytotoxicity effect. In addition, we found that none of the materials produced irritant effects on 3D reconstructed skin when present in aqueous suspensions. These results provide novel insights into the potentially harmful effects of novel multicomponent NMs in a comprehensive manner. Furthermore, the integrity of the NMs can play a role in their toxicity, which can vary depending on their composition and the exposure route., (© 2023. The Author(s).)

In this work, we highlight and measure the intensity of mechanochemical effects at work in the hydrogenation of carbon monoxide by comparing the activity of a supported Co-Fe catalyst subjected, respectively, to ball milling and simple powder agitation. Paying due regard to the discontinuous nature of ball milling, we show that mechanochemical hydrogenation proceeds at significantly higher rate and disclose its connection with individual impacts. Experimental evidence suggests that the enhanced catalytic activity we observe can be ascribed to local processes affecting the amount of powder that gets involved in individual impacts., (© 2023. The Author(s).)

Lead-free (Ba 0.92 Ca 0.08 ) (Ti 0.95 Zr 0.05 ) O 3 (BCZT) ceramics were prepared by a solid-state route (SSR) using ultra-low synthesis (700 °C/30 min and 700 °C/2 h) and sintering temperatures (from 1150 °C to 1280 °C), due to prior activation and homogenization by attrition milling of the starting high purity raw materials for 6 h before the synthesis and of the calcined powders for 3 h before the sintering. The comparison of the thermal analysis of the mixture of the starting raw materials and the same mixture after 6 h attrition milling allowed to evidence the mechanisms of activation, resulting in a significant decrease of the perovskite formation temperature (from 854 °C down to 582 °C). The secondary phases that limit the functional properties of the ceramic and their evolution with the sintering conditions were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), which allowed the design of a two-step sintering method to eliminate them. A pure tetragonal BCZT perovskite phase (P4mm, c/a = 1.004) and homogeneous ceramic microstructure was obtained for synthesis at 700 °C for 2 h and sintering with the use of a two-step sintering treatment (900 °C for 3 h and 1280 °C for 6 h). The best electromechanical properties achieved were d 33 = 455 pC/N, k p = 35%, Q m = 155.

The origin of fluorescence in carbon dots (C-dots) is still a puzzling phenomenon. The emission is, in most of the cases, due to molecular fluorophores formed in situ during the synthesis. The carbonization during C-dots processing does not allow, however, a fine control of the properties and makes finding the source of the fluorescence a challenging task. In this work, we present a strategy to embed a pre-formed fluorescent molecule, safranin O dye, into an amorphous carbonaceous dot obtained by citric acid carbonization. The dye is introduced in the melted solution of citric acid and after pyrolysis remains incorporated in a carbonaceous matrix to form red-emitting C-dots that are strongly resistant to photobleaching. Embedding dyes in amorphous C-dots represents an alternative method to optimize the emission in the whole visible spectrum.

Starting from 1970s, the use of mechanical forces to induce chemical transformations has radically changed vast areas of metallurgy and materials science. More recently, mechanochemistry has expanded to core sectors of chemistry, showing the promise to deeply innovate chemical industry while enhancing its sustainability and competitiveness. We are still far, however, from unveiling the full potential of mechanical activation. This study marks a step forward in this direction focusing on the chemical effects induced on the surrounding gaseous phase by the mechanical processing of granite. We show that fracturing granite blocks in oxygen can result in the generation of ozone. The refinement of coarse granite particles and the friction between fine ones are also effective in this regard. Combining experimental evidence related to the crushing of large granite samples by uniaxial compression and the ball milling of coarse and fine granite powders, we develop a model that relates mechanochemical ozone generation to the surface area effectively affected by fracture and frictional events taking place during individual impacts. We also extend the investigation to gaseous phases involving methane, oxygen, benzene and water, revealing that chemical transformations occur as well., (© 2022. The Author(s).)

Heterostructures formed by anatase nanotitania and bidimensional semiconducting materials are expected to become the next-generation photocatalytic materials with an extended operating range and higher performances. The capability of fabricating optically transparent photocatalytic thin films is also a highly demanded technological issue, and increasing the performances of such devices would significantly impact several applications, from self-cleaning surfaces to photovoltaic systems. To improve the performances of such devices, WS 2 /TiO 2 heterostructures obtained by incorporating two-dimensional transition metal dichalcogenides layers into titania mesoporous ordered thin films have been fabricated. The self-assembly process has been carefully controlled to avoid disruption of the order during film fabrication. WS 2 nanosheets of different sizes have been exfoliated by sonication and incorporated in the mesoporous films via one-pot processing. The WS 2 nanosheets result as well-dispersed within the titania anatase mesoporous film that retains a mesoporous ordered structure. An enhanced photocatalytic response due to an interparticle electron transfer effect has been observed. The structural characterization of the heterostructure has revealed a tight interplay between the matrix and nanosheets rather than a simple additive co-catalyst effect.

Graphene-enhanced Raman scattering (GERS) produces enhancement of the Raman signal, which is based on chemical rather than electromagnetic mechanism such as in the surface-enhanced Raman scattering. Graphene oxide, amino- and guanidine-functionalized graphene oxide, exfoliated graphene, and commercial graphene nanoplatelets have been used to investigate the GERS response with the change of graphene properties. Different graphene nanostructures have been embedded into organic-inorganic microporous films to build a platform for the fast and sensitive detection of pesticides in water. The graphene nanostructures vary in the number of layers, lateral size, degree of oxidation, and surface functionalization. The GERS performances of the graphene nanostructures cast on silicon substrates and embedded in the nanocomposite films have been comparatively evaluated. After casting a few droplets of the pesticide aqueous solution on the graphene nanostructures, the Raman band enhancements of the analytes have been measured. In the nanocomposite films, the characteristic Raman bands originating from pesticides such as paraoxon, parathion, and glyphosate could be traced at concentrations below 10 -7 , 10 -5 , and 10 -4 M, respectively. The results show that the surface functionalization reduces the GERS effect because it increases the ratio between the sp 3 carbon and sp 2 carbon. On the other hand, the comparison among different types of graphenes shows that the monolayers are more efficient than the few-layer nanostructures in enhancing the Raman signal., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

The transformation of olivine during the conversion of CO 2 to light hydrocarbons activated by mechanochemical treatments at different impact frequencies was studied by a combination of several complementary characterization methods including X-ray diffraction, Raman and 57 Fe Mössbauer spectroscopy. Several olivine samples were studied as a function of the milling time, indicating the gradual transformation of Fe II -containing olivine into new Fe III -containing weathering products including iron oxides, magnesium iron carbonates and silicates. The results presented here complement those of a previous study on the weathering process of olivine promoted by mechanochemical activation, by demonstrating the role of the redox activity of the iron species during the activation process. These additional spectroscopic results allow us to thoroughly understand the complex weathering mechanism and to correlate it with the efficiency of the CO 2 conversion and storage properties of mechanochemically activated olivine., Supplementary Information: The online version contains supplementary material available at 10.1007/s10853-022-06962-x., Competing Interests: Conflict of interestThe authors declare that they have no conflict of interest., (© The Author(s) 2022.)

Due to the ever-increasing limitations of the use of lead-based materials, the manufacturing of lead-free piezoceramics with competitive piezoelectric properties and established nontoxicity is considered a priority for the scientific and industrial community. In this work, a lead-free system based on sodium potassium niobate (KNN), opportunely modified with MgNb 2 O 6 (MN), was prepared through a combination of a mechanochemical activation method and air sintering, and its toxicity was evaluated. The effect of the mechanical processing on the microstructure refinement of the processed powders was established by X-ray diffraction and the average crystallite size content of the Nb 2 O 5 species was evaluated. The experimental evidence was rationalized using a phenomenological model which permitted us to obtain the amount of powder processed at each collision and to optimize the activation step of the pre-calcined reagents. This influenced the final density and piezoresponse of the as-sintered pellets, which showed optimal properties compared with other KNN systems. Their toxicological potential was evaluated through exposure experiments to the pulverized KNN-based pellets, employing two widely used human and environmental cellular models. The in vitro assays proved, under the selected conditions, the absence of cytotoxicity of KNN-bases systems here studied.

In this work, piezoceramics of the lead-free composition K 0.5 Na 0.5 NbO 3 with an increasing amount of MgNb 2 O 6 (0, 0.5, 1, 2 wt.%) were prepared through conventional solid-state synthesis and sintered in air atmosphere at 1100 °C. The effect of magnesium niobate addition on structure, microstructure and piezoelectric properties was evaluated. The ceramics maintain the orthorhombic Amm2 phase for all compositions, while an orthorhombic Pbcm secondary phase was found for increasing the concentration of MgNb 2 O 6 . Our results show that densification of these ceramics can be significantly improved up to 94.9 % of theoretical density by adding a small amount of magnesium-based oxide (1 wt.%). Scanning electron microscopy morphology of the 1 wt.% system reveals a well-packed structure with homogeneous grain size of ∼2.72 μm. Dielectric and piezoelectric properties become optimal for 0.5-1.0 wt.% of MgNb 2 O 6 that shows, with respect to the unmodified composition, either higher piezoelectric coefficients, lower anisotropy and relatively low piezoelectric losses (d 33 =97 pC N -1 ; d 31 =-36.99 pC N -1 and g 31 =-14.04×10 -3  mV N -1 ; Q p (d 31 )=76 and Q p (g 31 )=69) or enhanced electromechanical coupling factors (k p =29.06 % and k 31 =17.25 %)., (© 2021 The Authors. Published by Wiley-VCH GmbH.)

The fabrication of optically active heterostructures in the shape of mesostructured thin films is a highly challenging task. It requires an integrated process to allow in one-step incorporating the two-dimensional materials within the mesoporous ordered host without disrupting the pore organization. Hexagonal boron nitride (BN) nanosheets have been successfully introduced into titania mesoporous films using a template-assisted sol-gel synthesis and evaporation-induced self-assembly. Two types of BN sheets have been used, with and without defects, to investigate the role of defects in heterostructure properties. It has been found that the defects increase the ultraviolet radiation A (UVA) absorbance and enhance the photocatalytic response of the film. The BN sheets are optically transparent and do not exhibit any photocatalytic property but contribute to anatase crystallization via heterogeneous nucleation.

In this work, we propose the synthesis of ZnO nanostructures through the thermal oxidation of ball-milled powders with the introduction of Mg and Sn doping species at the preliminary step of milling. We investigate the advantages and challenges of this two steps process for the production and fabrication of highly crystalline ZnO nanowires. This simple method allows us to fabricate ZnO nanowires with a higher quality core crystal at a much lower temperature and for a shorter processing time than the state-of-the-art, and decorated with by ZnO 2 nanoparticles as determined via TEM analysis. The main findings will show that the crystalline core of the nanowires is of hexagonal ZnO while the nanoparticles on the surface are ZnO 2 cubic type. Generally, the method proves to be suitable for applications that require a high surface-to-volume ratio, for example, catalysis phenomena, in which the presence of zinc oxides species can play an important role.

Due to the considerable interest in vanadium niobium oxides as a lithium storage material, the kinetics and transformation processes of the V2O5-5Nb2O5 system have been investigated by in situ synchrotron powder X-ray diffraction. The diffraction data after the thermal treatments selected with a view on the most significant features were supplemented with specific ex situ experiments conducted using a laboratory rotating anode X-ray diffractometer. The morphological changes of the mixed powders assuming an amorphous and nanocrystalline solid solution structure as a function of the temperature were inspected by scanning electron microscopy observations. The structural solution of the powder diffraction pattern of the phase recorded in situ at a temperature of about 700 °C was compatible with an orthorhombic crystal structure with the space group Amm2. The obtained lattice parameters for this structure were a = 3.965 Å; b = 17.395 Å, c = 17.742 Å, and the cell composition was V4Nb20O60, Pearson symbol oA84, and density = 4.10 g cm-3. In this structure, while the niobium atoms may be four-, five-, and six-fold coordinated by oxygen atoms, the vanadium atoms were six-fold or seven-fold coordinated. At the temperature of 800 °C and just above, the selected 1 : 2 and 1 : 3 V2O5-Nb2O5 compositions, respectively, returned mostly a tetragonal VNb9O25 phase, in line with earlier observations conducted for determination of the stability phase diagram of such quasi-binary systems.

The effects of ball milling treatment on both the structure and properties of guar gum (GG), tara gum (TG), and methylcellulose (MC) were analyzed prior to assessing their potential interactions with starch components when they are used alone or in blends in a corn starch-rice flour system. X-ray diffraction profiles showed that the ball milling caused a reduction in the crystallin domain and, in turn, a diminished viscosity of the GG aqueous solutions. Despite an increase in its viscosity properties, effects on TG were minimal, while the milled MC exhibited reduced crystallinity, but similar viscosity. When both milled and un-milled hydrocolloids were individually added to the starch-flour system, the pasting properties of the resulting mixtures seemed to be affected by the type of hydrocolloid added rather than the structural changes induced by the treatment. All hydrocolloids increased the peak viscosity of the binary blends (especially pure GG), but only milled and un-milled MC showed values of setback and final viscosity similar to those of the individual starch. Ball milling seemed to be more effective when two combined hydrocolloids (milled GG and MC) were simultaneously used. No significant differences were observed in the viscoelastic properties of the blends, except for un-milled GG/starch, milled TG/starch, and milled MC/milled TG/starch gels.

Highly fluorescent blue and green-emitting carbon dots have been designed to be integrated into sol-gel processing of hybrid organic-inorganic materials through surface modification with an organosilane, 3-(aminopropyl)triethoxysilane (APTES). The carbon dots have been synthesised using citric acid and urea as precursors; the intense fluorescence exhibited by the nanoparticles, among the highest reported in the scientific literature, has been stabilised against quenching by APTES. When the modification is carried out in an aqueous solution, it leads to the formation of silica around the C-dots and an increase of luminescence, but also to the formation of large clusters which do not allow the deposition of optically transparent films. On the contrary, when the C-dots are modified in ethanol, the APTES improves the stability in the precursor sol even if any passivating thin silica shell does not form. Hybrid films containing APTES-functionalized C-dots are transparent with no traces of C-dots aggregation and show an intense luminescence in the blue and green range.

In this work, the possibility of creating a polymer-based adaptive scaffold for improving the hydrogen storage properties of the system 2LiH+MgB 2 +7.5(3TiCl 3 ·AlCl 3 ) was studied. Because of its chemical stability toward the hydrogen storage material, poly(4-methyl-1-pentene) or in-short TPX TM was chosen as the candidate for the scaffolding structure. The composite system was obtained after ball milling of 2LiH+MgB 2 +7.5(3TiCl 3 ·AlCl 3 ) and a solution of TPX TM in cyclohexane. The investigations carried out over the span of ten hydrogenation/de-hydrogenation cycles indicate that the material containing TPX TM possesses a higher degree of hydrogen storage stability.

Thermal decomposition of citric acid is one of the most common synthesis methods for fluorescent carbon dots; the reaction pathway is, however, quite complex and the details are still far from being understood. For instance, several intermediates form during the process and they also give rise to fluorescent species. In the present work, the formation of fluorescent C-dots from citric acid has been studied as a function of reaction time by coupling infrared analysis, X-ray photoelectron spectroscopy, liquid chromatography/mass spectroscopy (LC/MS) with the change of the optical properties, absorption and emission. The reaction intermediates, which have been identified at different stages, produce two main emissive species, in the green and blue, as also indicated by the decay time analysis. C-dots formed from the intermediates have also been synthesised by thermal decomposition, which gave an emission maximum around 450 nm. The citric acid C-dots in water show short temporal stability, but their functionalisation with 3-aminopropyltriethoxysilane reduces the quenching. The understanding of the citric acid thermal decomposition reaction is expected to improve the control and reproducibility of C-dots synthesis., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A new and solvent-free synthesis route has been adopted and optimized to prepare crystalline VNbO 5 from the mechanochemical reaction between Nb 2 O 5 and V 2 O 5 as starting reagents. The substantially amorphous mixture of equimolar pentoxide V and Nb metals observed after extended mechanical treatment transforms into a crystalline powder following calcination under mild conditions at 710 K. The structure solution of the X-ray diffraction pattern using a global optimization approach, combined with Rietveld refinement, points to a space group P2 1 2 1 2 1 (no. 19) different from Pnma (no. 62) previously proposed in the literature assuming it to be isostructural to VTaO 5 . The new space group helps to describe weak peaks that remained previously unaccounted for and allows more reliable determination of atomic fractional coordinates and interatomic distance distribution. The as-prepared VNbO 5 has been tested as a dopant (5 wt%) for the purpose of solid state hydrogen storage, decreasing significantly the release of hydrogen of MgH 2 /Mg (620 K) and further enhancing the hydrogen sorption kinetic properties.

The properties and structure of relevant interfaces involving molten alkali carbonates are studied using molecular dynamics simulation. Lithium carbonate and the Li/Na/K carbonate eutectic mixture are considered. Gas phases composed of pure CO 2 or a model flue gas mixture are analyzed. Similarly, the adsorption of these gas phases on graphene are studied, showing competitive CO 2 and N 2 adsorption that develops liquid-like layers and damped oscillation behavior for density. The interaction of the studied carbonates with graphene is also characterized by development of adsorption layers through strong graphene-carbonate interactions and the development of hexagonal lattice arrangements, especially for lithium carbonate. The development of molten salts-vacuum interfaces is also considered, analyzing the ionic rearrangement in the interfacial region. The behavior of the selected gas phases on top of molten alkyl carbonate is also studied, showing the preferential adsorption of CO 2 molecules when flue gases are considered.

Polymeric electrospun fibers are becoming popular in microbial biotechnology because of their exceptional physicochemical characteristics, biodegradability, surface-to-volume ratio, and compatibility with biological systems, which give them a great potential as microbial supports to be used in production processes or environmental applications. In this work, we analyzed and compared the ability of Escherichia coli, Pseudomonas putida, Brevundimonas diminuta, and Sphingobium fuliginis to develop biofilms on different types of polycaprolactone (PCL) microfibers. These bacterial species are relevant in the production of biobased chemicals, enzymes, and proteins for therapeutic use and bioremediation. The obtained results demonstrated that all selected species were able to attach efficiently to the PCL microfibers. Also, the ability of pure cultures of S. fuliginis (former Flavobacterium sp. ATCC 27551, a very relevant strain in the bioremediation of organophosphorus compounds) to form dense biofilms was observed for the first time, opening the possibility of new applications for this microorganism. This material showed to have a high microbial loading capacity, regardless of the mesh density and fiber diameter. A comparative analysis between PCL and polylactic acid (PLA) electrospun microfibers indicated that both surfaces have a similar bacterial loading capacity, but the former material showed higher resistance to microbial degradation than PLA.

The modification of carbon nanomaterials with biological molecules paves the way toward their use in biomedical and biotechnological applications, such as next-generation biocatalytic processes, development of biosensors, implantable electronic devices, or drug delivery. In this study, different commercial graphene derivatives, namely, monolayer graphene oxide (GO), graphene oxide nanocolloids (GOCs), and polycarboxylate-functionalized graphene nanoplatelets (GNs), were compared as biomolecule carrier matrices. Detailed spectroscopic analyses showed that GO and GOC were similar in composition and functional group content and very different from GN, whereas divergent morphological characteristics were observed for each nanomaterial through microscopy analyses. The commercial α-l-rhamnosidase RhaB1 from the probiotic bacterium Lactobacillus plantarum, selected as a model biomolecule for its relevant role in the pharma and food industries, was directly immobilized on the different materials. The binding efficiency and biochemical properties of RhaB1-GO, RhaB1-GOC, and RhaB1-GN composites were analyzed. RhaB1-GO and RhaB1-GOC showed high binding efficiency, whereas the enzyme loading on GN, not tested in previous enzyme immobilization studies, was low. The enzyme showed contrasting changes when immobilized on the different material supports. The effect of pH on the activity of the three RhaB1-immobilized versions was similar to that observed for the free enzyme, whereas the activity-temperature profiles and the response to the presence of inhibitors varied significantly between the RhaB1 versions. In addition, the apparent K m for the immobilized and soluble enzymes did not change. Finally, the free RhaB1 and the immobilized enzyme in GOC showed the best storage and reutilization stability, keeping most of their initial activity after 8 weeks of storage at 4 °C and 10 reutilization cycles, respectively. This study shows, for the first time, that distinct commercial graphene derivatives can influence differently the catalytic properties of an enzyme during its immobilization.

The crystal structure of a mixed amide-imide phase, RbMgND 2 ND, has been solved in the orthorhombic space group Pnma ( a = 9.55256(31), b = 3.70772(11) and c = 10.08308(32) Å). A new metal amide-hydride solid solution, Rb(NH 2 ) x H (1- x) , has been isolated and characterized in the entire compositional range. The profound analogies, as well as the subtle differences, with the crystal chemistry of KMgND 2 ND and K(NH 2 ) x H 1- x are thoroughly discussed. This approach suggests that the comparable performances obtained using K- and Rb-based additives for the Mg(NH 2 ) 2 - 2LiH and 2LiN H 2 -MgH 2 hydrogen storage systems are likely to depend on the structural similarities of possible reaction products and intermediates.

The present work concerns the catalytic effect of VNbO 5 , a ternary oxide prepared via a solid-state route, on the sorption performance of MgH 2 . Three doped systems, namely 5, 10 and 15 wt% VNbO 5 -MgH 2 have been prepared by ball milling and thoroughly characterized. Hydrogen sorption, evaluated by temperature programmed desorption experiments, revealed a significant reduction of the desorption temperature from 330 °C for the un-doped sample (prepared and tested for comparison) to 235 °C for the VNbO 5 -doped sample. Furthermore, more than 5 wt% of hydrogen can be absorbed in 5 minutes at 160 °C under 20 bar of hydrogen, which is remarkable compared to the 0.7 wt% achieved for the un-doped system. The sample doped with 15 wt% of additive, showed good reversibility: over 5 wt% of hydrogen with negligible degradation even after 70 consecutive cycles at 275 °C and 50 cycles at 300 °C. The kinetics analysis carried out by Kissinger's method exhibited a considerable reduction of the activation energy for the desorption process. Finally, pressure-composition-isotherm experiments conducted at three different temperatures allowed estimating the thermodynamic stability of the system and shed light on the additive role of VNbO 5 .

The hydrogen desorption pathways and storage properties of 2 Mg(NH 2 ) 2 -3 LiH-xLiBH 4 samples (x=0, 1, 2, and 4) were investigated systematically by a combination of pressure composition isotherm (PCI), differential scanning calorimetric (DSC), and volumetric release methods. Experimental results showed that the desorption peak temperatures of 2 Mg(NH 2 ) 2 -3 LiH-xLiBH 4 samples were approximately 10-15 °C lower than that of 2 Mg(NH 2 ) 2 -3 LiH. The 2 Mg(NH 2 ) 2 -3 LiH-4 LiBH 4 composite in particular began to release hydrogen at 90 °C, thereby exhibiting superior dehydrogenation performance. All of the LiBH 4 -doped samples could be fully dehydrogenated and re-hydrogenated at a temperature of 143 °C. The high hydrogen pressure region (above 50 bar) of PCI curves for the LiBH 4 -doped samples rose as the amount of LiBH 4 increased. LiBH 4 changed the desorption pathway of the 2 Mg(NH 2 ) 2 -3 LiH sample under a hydrogen pressure of 50 bar, thereby resulting in the formation of MgNH and molten [LiNH 2 -2 LiBH 4 ]. That is different from the dehydrogenation pathway of 2 Mg(NH 2 ) 2 -3 LiH sample without LiBH 4 , which formed Li 2 Mg 2 N 3 H 3 and LiNH 2 , as reported previously. In addition, the results of DSC analyses showed that the doped samples exhibited two independent endothermic events, which might be related to two different desorption pathways., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The doping effect of Sr(OH) 2 on the Mg(NH 2 ) 2 -2LiH system is investigated considering different amounts of added Sr(OH) 2 in the range of 0.05 to 0.2 mol. Experimental results show that both the thermodynamic and the kinetic properties of Mg(NH 2 ) 2 -2LiH are influenced by the presence of Sr(OH) 2 . The addition of 0.1 mol Sr(OH) 2 leads to a decrease in both the dehydrogenation onset and peak temperatures of ca. 70 and 13 °C, respectively, and an acceleration in the de/re-hydrogenation rates of one time at 150 °C compared to Mg(NH 2 ) 2 -2LiH alone. Based on differential scanning calorimetry (DSC) analysis, the overall reaction enthalpy of the 0.1 Sr(OH) 2 -doped sample is calculated to be 44 kJ per mol-H 2 and there are two absorption events occurring in the doped sample instead of one in the pristine sample. For the applied experimental conditions, according to the in situ synchrotron radiation powder X-ray diffraction (SR-PXD) and Fourier Transform Infrared spectroscopy (FT-IR) analysis, the reaction mechanism has been finally defined: Sr(OH) 2 , Mg(NH 2 ) 2 and LiH react with each other to form SrO, MgO and LiNH 2 during ball milling. After heating, SrO interacts with Mg(NH 2 ) 2 producing MgO and Sr(NH 2 ) 2 . Then Mg(NH 2 ) 2 , LiNH 2 and Sr(NH 2 ) 2 react with LiH to produce Li 2 NH, SrNH, Li 2 Mg(NH) 2 and Li 2 Mg 2 (NH) 3 in traces. After re-hydrogenation, LiSrH 3 , LiH and LiNH 2 are formed along with amorphous Mg(NH 2 ) 2 . The reasons for the improved kinetics are: (a) during dehydrogenation, the in situ formation of SrNH appears to increase the interfacial contacts between Mg(NH 2 ) 2 and LiH and also weakens the N-H bond of Mg(NH 2 ) 2 ; (b) during absorption, the formation of LiSrH 3 at around 150 °C could be the key factor for improving the hydrogenation properties.

Usually, mechanochemical reactions between solid phases are either gradual (by deformation-induced mixing), or self-propagating (by exothermic chemical reaction). Here, by means of a systematic kinetic analysis of the Bi-Te system reacting to Bi 2 Te 3 , we establish a third possibility: if one or more of the powder reactants has a low melting point and low thermal effusivity, it is possible that local melting can occur from deformation-induced heating. The presence of hot liquid then triggers chemical mixing locally. The molten events are constrained to individual particles, making them distinct from self-propagating reactions, and occur much faster than conventional gradual reactions. We show that the mechanism is applicable to a broad variety of materials systems, many of which have important functional properties. This mechanistic picture offers a new perspective as compared to conventional, gradual mechanochemical synthesis, where thermal effects are generally ignored.

We report for the first time the formation of a metal amide-hydride solid solution. The dissolution of KH into KNH 2 leads to an anionic substitution, which decreases the interaction among NH 2 - ions. The rotational properties of the high temperature polymorphs of KNH 2 are thereby retained down to room temperature.

New amide-chloride phases were successfully synthesized by mechanical milling of the LiNH2-AlCl3 mixture at a molar ratio of 1 : 0.11 and further heating at 150 °C under argon (0.1 MPa) or under hydrogen pressure (0.7 MPa). Powder X-ray diffraction measurements as a function of milling time increase revealed that the milling of the LiNH2-0.11AlCl3 mixture results in the formation of a FCC solid solution with an excess of LiNH2. Subsequent heating of the LiNH2-0.11AlCl3 sample ball milled for 5 hours at 150 °C under argon or under hydrogen induces the appearance of an amide-chloride phase isostructural with cubic Li4(NH2)3Cl. This Li-Al-N-H-Cl phase transforms progressively into the trigonal phase after prolonged heating at 300 °C under hydrogen pressure. The thermal behaviour of the amide-chloride without and with LiH addition displays dissimilar decomposition pathways. The decomposition of amide-chloride alone involves the formation of ammonia and hydrogen from 120 to 300 °C. Conversely, the amide-chloride material in the presence of LiH only releases hydrogen avoiding the emission of ammonia. The resultant material is able to be rehydrogenated under moderate conditions (300 °C, 0.7 MPa H2), providing a new reversible hydrogen storage system.

New insights into the reaction pathways of different potassium/magnesium amide-hydride based systems are discussed. In situ SR-PXD experiments were for the first time performed in order to reveal the evolution of the phases connected with the hydrogen releasing processes. Evidence of a new K-N-H intermediate is shown and discussed with particular focus on structural modification. Based on these results, a new reaction mechanism of amide-hydride anionic exchange is proposed.

We evaluate the influence of the use of different titania precursors, calcination rate, and ligand addition on the morphology, texture and phase content of synthesized mesoporous titania samples, parameters which, in turn, can play a key role in titania photocatalytic performances. The powders, obtained through the evaporation-induced self-assembly method, are characterized by means of ex situ X-Ray Powder Diffraction (XRPD) measurements, N₂ physisorption isotherms and transmission electron microscopy. The precursors are selected basing on two different approaches: the acid-base pair, using TiCl₄ and Ti(OBu)₄, and a more classic route with Ti(O i Pr)₄ and HCl. For both precursors, different specimens were prepared by resorting to different calcination rates and with and without the addition of acetylacetone, that creates coordinated species with lower hydrolysis rates, and with different calcination rates. Each sample was employed as photoanode and tested in the water splitting reaction by recording I-V curves and comparing the results with commercial P25 powders. The complex data framework suggests that a narrow pore size distribution, due to the use of acetylacetone, plays a major role in the photoactivity, leading to a current density value higher than that of P25.

The hydrolysis of borohydride salts represents one of the most promising processes for the generation of high purity molecular hydrogen under mild conditions. In this work we show that the sodium borohydride hydrolysis exhibits a fingerprinting periodic oscillatory transient in the hydrogen flow over a wide range of experimental conditions. We disproved the possibility that flow oscillations are driven by supersaturation phenomena of gaseous bubbles in the reactive mixture or by a nonlinear thermal feedback according to a thermokinetic model. Our experimental results indicate that the NaBH4 hydrolysis is a spontaneous inorganic oscillator, in which the hydrogen flow oscillations are coupled to an "oscillophor" in the reactive solution. The discovery of this original oscillator paves the way for a new class of chemical oscillators, with fundamental implications not only for testing the general theory on oscillations, but also with a view to chemical control of borohydride systems used as a source of hydrogen based green fuel.

We synthesized Na(2)[B(12)H(12)] by a solid state procedure and thermal decomposition of Na[B(3)H(8)], and calculated from a first-principles approach the thermodynamic and structural properties. In particular, the calculated enthalpy of formation of the monoclinic structure, at T = 0 K, of -1086.196 kJ mol(-1) showed that it is a very stable compound. Therefore, in case it were formed during the thermal decomposition of NaBH(4), it would be rather considered a product, which, in addition, prevents the subsequent re-hydrogenation process because of its low reactivity to hydrogen. We reported the isotherms of absorption of H(2), O(2), and H(2)O, calculated both theoretically and experimentally.