Functional bioglass/carbon nanocomposite scaffolds from vat photopolymerization of a novel preceramic polymer-based nanoemulsion

Silicone polymers are already known as feedstock for a variety of silicate bioceramics, in the form of scaffolds with complex shapes, obtained by Vat Photopolymerization. Printing is enabled by using silicone blended with photocurable acrylates. The development of a particular silicate composition that functions as a glass or glass-ceramic precursor is possible by the addition of suitable oxide fillers (especially carbonate powders), suspended in the polymer blend. Oxides, from the fillers, easily react with silica left by the thermal transformation of the silicone. The fillers, however, also determine complications in Vat Photopolymerization, due to light scattering; in addition, local oxide concentrations generally impede the obtainment of glassy products. The present paper illustrates a simple solution to these issues, based on the inclusion of a Ca salt in nano-emulsion within a silicone-containing blend. Homogeneous printed samples are later converted into crack-free, fully amorphous ceramic composites, by firing at only 700 °C. The glass matrix, resembling 70S30C (70 % SiO2 and 30 % CaO) bioglass, is achieved according to the quasi-molecular CaO distribution. The secondary phase, promoted by treatment in N2 atmosphere and consisting of pyrolytic carbon, provides a marked photothermal effect

Novel correlations between spectroscopic and morphological properties of activated carbons from waste coffee grounds

Massive quantities of spent coffee grounds (SCGs) are generated by users around the world. Different processes have been proposed for SCG valorization, including pyrolytic processes to achieve carbonaceous materials. Here, we report the preparation of activated carbons through pyrolytic processes carried out under different experimental conditions and in the presence of various porosity activators. Textural and chemical characterization of the obtained carbons have been achieved through Brunauer–Emmett–Teller (BET), ESEM,13C solid state NMR, XPS, XRD, thermogravimetric and spectroscopic determinations. The aim of the paper is to relate these data to the preparation method, evaluating the correlation between the spectroscopic data and the physical and textural properties, also in comparison with the corresponding data obtained for three commercial activated carbons used in industrial adsorption processes. Some correlations have been observed between the Raman and XPS data

Synthesis and characterization of bulk nanostructured thermoelectric Ca3Co4O9

Nanostructuring has been proposed as an effective strategy for the reduction of the phonon contribution to the thermal conductivity, resulting in an increase in the figure of merit of thermoelectric materials. However, obtaining bulk samples presenting high relative density and nanometric grain size can be quite challenging, particularly in the case of ceramic phases. Only few examples have been reported and none in the case of Ca3Co4O9. In this work, we used a sol–gel synthesis coupled with ball milling to prepare powders of Ca3Co4O9 presenting a grain size as small as 4 nm. These nanopowders were then sintered at different temperature and pressures using the High-Pressure Field-Assisted Sintering Technique (HP-FAST). Relative densities up to 95 vol% where obtained while maintaining a nanometric grain size. The microstructural and electrical properties of the sintered samples have been characterized. The results show that in this oxide a reduction to the nanometric grain size produces a drastic reduction in the electrical conductivity, which cannot be compensated by the reduction in the thermal conductivity. The Seebeck effect, on the other hand, appears to be affected only marginally by the grain size and porosity

Nanostructured calcium cobalt oxide Ca3Co4O9 as thermoelectric material. Effect of nanostructure on local coordination, Co charge state and thermoelectric properties

The preparation of pure Ca3Co4O9 materials in the form of dense bodies made of nano-sized grains was investigated by combining a sol-gel route, different thermal cycles, a ball-milling post-treatment and final densification with HP-FAST (High Pressure-Field Assisted Sintering). We found that an effective way for obtaining nano-sized compact bodies with only a marginal increase of the particle sizes of the original powder was the operation of HP-FAST at extremely high pressures (up to 430 MPa) and comparatively low temperatures. A ball-milling treatment before HP-FAST compaction was then required to hinder the large plastic deformation occurring when using these pressures. In contrast, un-milled powders could be densified by HP-FAST only at lower pressure and therefore required higher temperatures, thus losing their nanostructure. For all powders, X-ray absorption spectroscopy assessed a mean Co oxidation state slightly higher than III, coupled to absence of localized Co(II) and presence of localized Co(IV). Ball milling induced a decrease of the mean oxidation state of Co coupled to an increased disorder. The latter effect was confirmed by X-ray Absorption Fine Structure. Nanostructure had a complex effect on the different properties of compact bodies. According to the different conditions of HP-FAST, densities of 75–98% were achieved; the decrease in thermal conductivity was of a factor 2–3, while the electronic transport properties – in particular electrical conductivity – of nano-sized compact bodies were reduced to a larger extent with respect to their micro-sized counterparts. This demonstrates that, for bulk Ca3Co4O9 materials, nanostructure was not an effective approach toward a performing thermoelectric material

Molecular, Electronic, and Crystal Structures of Self-Assembled Hydrothermally Synthesized Zn(II) 12Mercaptonicotinate: A Combined Spectroscopic and Theoretical Approach

A Zn(II) 2-mercaptonicotinate coordination polymer (Zn1), with Zn(II) ions chelated by both sulfur and oxygen in a distorted square pyramidal environment, and a molecular Zn(II) 2-hydroxynicotinate complex (Zn2) were synthesized by the reaction of zinc acetylacetonate with 2-mercaptonicotinic (Zn1) and 2-hydroxynicotinc (Zn2) acid, respectively, under hydrothermal conditions. The crystal structures of Zn1 and Zn2 were determined by single crystal X-ray diffraction measurements. Dispersion-corrected density functional theory (DFT) calculations reproduce very well the experimental structures and show that Zn1 is stable against hydration, whereas Zn2 is stable against dehydration over wide ranges of temperature and pressure, in agreement with thermogravimetric analysis results. The electronic structure of the two compounds is computed with the DFT+U method. The theoretical valence band agrees well with the X-ray photoelectron spectroscopy experiments. Furthermore, the band gap of Zn1 is found to be narrower than that of Zn1 and is characterized by the presence of sulfur lone pairs at the edge of the valence band

Plasma-activated water triggers rapid and sustained cytosolic Ca2+ elevations in Arabidopsis thaliana

Increasing evidence indicates that water activated by plasma discharge, termed as plasma-activated water (PAW), can promote plant growth and enhance plant defence responses. Nevertheless, the signalling pathways activated in plants in response to PAW are still largely unknown. In this work, we analysed the potential involvement of calcium as an intracellular messenger in the transduction of PAW by plants. To this aim, Arabidopsis thaliana (Arabidopsis) seedlings stably expressing the bioluminescent Ca2+ reporter aequorin in the cytosol were challenged with PAW generated by a plasma torch. Ca2+ measurement assays demonstrated the induction by PAW of rapid and sustained cytosolic Ca2+ elevations in Arabidopsis seedlings. The dynamics of the recorded Ca2+ signals were found to depend upon different parameters, such as the operational conditions of the torch, PAW storage, and dilution. The separate administration of nitrate, nitrite, and hydrogen peroxide at the same doses as those measured in the PAW did not trigger any detectable Ca2+ changes, suggesting that the unique mixture of different reactive chemical species contained in the PAW is responsible for the specific Ca2+ signatures. Unveiling the signalling mechanisms underlying plant perception of PAW may allow to finely tune its generation for applications in agriculture, with potential advantages in the perspective of a more sustainable agriculture

Structural texture induced in SnSe thermoelectric compound via open die pressing

Outstanding ZT values registered on single crystals recently renewed the interest of thermoelectric community for SeSn compound. Owing to the strong anisotropy of the phenomenon, so far only single crystals proved to be the suitable for its application. Here we present the production and the characterization of bulk polycrystalline materials processed by open die pressing, aimed at reducing the gap with single crystal materials by taking advantage from the highly texture degree derived by the processing and by the improved phonon scattering promoted by grain boundaries. The resulting bulks display good compaction, improved mechanical properties and strong texture of the phase. Structural and morphological analyses confirmed the successful orientation according to the (400) cleavage plane. The structural transition responsible for the ultra-low thermal conductivity has been investigated and possible irreversible effects on the starting phase due to thermal cycling have been evaluated. Preliminary measurements of thermal conductivity are reported

LGCA dell'et\ue0\ua0 pediatrica: studio immunoistochimico dell'espressione di ALK-1 e di molecole citotossiche

Rivista Italiana di Pediatri

Facile and reproducible synthesis of nanostructured colloidal ZnO nanoparticles from zinc acetylacetonate: effect of experimental parameters and mechanistic investigations

A facile and reproducible route to nanostructured colloidal ZnO nanoparticles was developed by controlled hydrolysis and condensation of zinc acetylacetonate in alkaline conditions. By reaction of an ethanolic solution of Zn(acac)2 with NaOH in a 1:2 molar ratio, after reflux, ZnO spherical nanoparticles were obtained that displayed a homogeneous size distribution; particle diameters ranged from 6 to 10 nm, as evidenced by transmission electron microscopy (TEM) analysis. The same reaction was carried out also in water, glycerol and 1,2-propanediol, to investigate the effect of the solvent viscosity and dielectric constant on the final features of the obtained material. Irrespective of the nature of the solvent, X-ray diffraction (XRD) analysis shows the formation ofhexagonal ZnO, whereas the presence of residual unreacted Zn(acac)2 could be ruled out. Indeed, different particle sizes and very different morphologies were obtained. Also the reflux step was shown to be a key factor in avoiding the fast precipitation of a floc and achieving a pure compound, which was isolated and thoroughly characterised. The composition of the obtained ZnO was determined by elemental analysis, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA), showing the formation of pure ZnO. IR spectroscopy evidenced the presence of adsorbed organic ligands on the colloid surfaces. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) revealed the presence of medium- to high-strength acidic sites on the ZnO surface. To gain a deeper insight into the formation mechanisms of these nanostructures, time-resolved UV/Vis and XAS studies were performed on the ethanol solution used for the synthesis of the oxide and also on the solid specimen, obtained after the refluxing step. No remarkable changes could be evidenced in the solution after the addition of an understoichiometric amount of NaOH, but the growth of the ZnO nanoparticles could be followed by UV/Vis spectra. (\ua9 Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009