Application of monosaccharides derivatives in colloidal processing of aluminum oxide

Obtaining highly loaded, time-stable and relatively low viscosity suspensions approaches colloidal processing to be very convenient and effective route of shaping of nanopowders. In order to obtain well dispersed, homogenous ceramic slurries, certain additives are given. Saccharides, particularly monosaccharides, as well as their derivatives, were found to be a group of effectively working processing agents in case of alumina, which has been used as a solid phase of highly loaded nanosuspensions. This class of chemical compounds can be described by a series of advantages – they are non-toxic, water-soluble, inexpensive, etc. In this paper suspensions of nano- and submicro-alumina powders with addition of d-fructose, 1-O-methyl-d-fructose, d-glucose and 3-O-acrylic-d-glucose have been studied in terms of their rheological properties, moreover the properties of as-received green bodies have been presented.     

Influence of core-shell structure on the cure depth in photopolymerizable alumina dispersion

The heterogeneous nucleation-and-growth processing was used to obtain core-shell particles based on alpha alumina core with silica layer. Presence of silica shell was confirmed by transmission electron microscopy (TEM) and zeta potential measurement. The coverage of aluminum oxide surface by SiO₂ improved a cure of the depth of photopolymerizable ceramic dispersion around 20%. The proposed surface modification enables the production of thicker cured layer which is favorable for additive manufacturing methods such as stereolithography. Thus, the number of layers that have to be printed to form the 3D object might significantly decrease, thereby reducing time and costs of fabrication.     

Surface properties of nanozirconia and their effect on its rheological behaviour and sinterability

Water leaching procedure was successfully applied for modification of surface properties and improvement of sinterability of commercial nano-ZrO₂. It has been shown that the process effectively removes some ionic impurities thus influencing the compositional, electrokinetic and acidic/basic properties of nanozirconia surface. The process purifies the surface and improves the deflocculation susceptibility of nano-ZrO₂ if d-fructose is used as a dispersant. The studies revealed that by using a purified powder, it is feasible to obtain green and sintered samples of satisfactory densification and microstructural features. SEM micrographs of polished sintered bodies have provided some evidences that homogeneous and fully densified microstructure of the samples can be obtained by using water-leached nanozirconia powders.     

Multimodal Spectroscopic Imaging of Pea Root Nodules to Assess the Nitrogen Fixation in the Presence of Biofertilizer Based on Nod-Factors

Multimodal spectroscopic imaging methods such as Matrix Assisted Laser Desorption/Ionization Mass Spectrometry Imaging (MALDI MSI), Fourier Transform Infrared spectroscopy (FT-IR) and Raman spectroscopy were used to monitor the changes in distribution and to determine semi quantitatively selected metabolites involved in nitrogen fixation in pea root nodules. These approaches were used to evaluate the effectiveness of nitrogen fixation by pea plants treated with biofertilizer preparations containing Nod factors. To assess the effectiveness of biofertilizer, the fresh and dry masses of plants were determined. The biofertilizer was shown to be effective in enhancing the growth of the pea plants. In case of metabolic changes, the biofertilizer caused a change in the apparent distribution of the leghaemoglobin from the edges of the nodule to its centre (the active zone of nodule). Moreover, the enhanced nitrogen fixation and presumably the accelerated maturation form of the nodules were observed with the use of a biofertilizer.     

When an Encapsulating Oxide Layer Promotes Reaction on Noble Metals: Dewetting and In situ Formation of an “Inverted” FeO x /Pt Catalyst

An ultra-thin FeO(111) film grown on Pt(111) is found to exhibit a much higher rate of CO oxidation at stoichiometric CO:O₂ ratios than the clean Pt(111) surface. This unexpected result is rationalized on the basis of reaction induced dewetting of the oxide film, ultimately resulting in highly dispersed FeO _x nanoparticles on Pt(111). The effect may have a strong impact on the catalytic properties of the noble metal particles encapsulated by the reducible oxide support as a result of strong metal-support interaction.     

Effect of change in angle between microelectrode surface and jet direction in flow system on current response in solutions of different ionic strength

The influence of stream orientation versus surface of microelectrode detector was examined in the range between vertical and parallel flow for various jet velocities and various levels of supporting electrolyte. The flow cell was equipped with a conical body Pt microdisk electrode, and the measurements involved voltammetry and chronoamperometry. Ferrocene, two its charged derivatives (sodium ferrocenylo sulfate and ferrocenylomethyltrimethylamino hexafluorophosphate) and sodium iodide were employed as the substrates in the experiments. The strongest convectional transport and the highest signal of the analytes was obtained for alpha = 60 degrees (alpha is the angle between the electrode surface and the stream direction). The measured current increased by up to 1.85 times versus the traditional setup, and therefore, this new geometry of the detector is analytically advantageous. The value of alpha corresponding to the highest signal tended to decrease to approximately 45 degrees in the absence of supporting electrolyte provided that either flow rate or analyte concentration was above a certain threshold value. The experiments indicated that the interplay of the convectional and migrational components in the analyte transport is different for the charge increase and the charge cancellation processes. These experimental facts were confirmed by digital simulation results.     

Gelcasting of alumina suspensions containing nanoparticles with glycerol monoacrylate

An acrylic monomer of low toxicity containing two hydroxyl groups has been synthesized and used for gelcasting in water. The results have been compared to those achieved with the use of a commercially available monomer (2-hydroxyethyl acrylate). Due to the chemical structure of the synthesized monomer, no addition of the crosslinking agent was necessary for gelation and similar results in terms of rheology of suspensions, density and microstructure of the bodies were obtained with respect to those obtained with the commercial monomer. However, higher time for gelation was observed.Two alumina powders with very different particle sizes were used in this study: a commercial submicron-sized powder (d₅₀ = 0.35 μm) and a nanometer-sized alumina obtained by freeze-drying from aluminum sulphate solutions. The rheological behavior of concentrated suspensions was studied in order to establish their stability and to analyse the effect of the different monomers used in the process. Once the suspensions were optimized, the influence of the size of the powder on the gelation process was studied. The sintered density of submicrometer-sized alumina was higher (99%) than that measured when the bimodal suspension was used due to the difficulty to obtain highly concentrated suspensions from nanometric powder.     

Three-phase electrochemistry with a hanging drop of water-insoluble liquid: Precipitation of decamethylferrocenium species as a marker of ion transfer route

A recently developed new experimental setup for the three-phase voltammetry was used to detect the follow-up reaction products. Decamethylferrocene was dissolved in a nitrobenzene drop while inorganic salts with various anions were present in the aqueous phase. The third phase was represented by a Pt microcylindrical electrode. The drop was punctured by this electrode to various depths. The reported experiments show how the contribution of migration to the anion transport in the organic phase increases while the puncture depth grows. The use of the new three-phase electrode allowed easy removal of the microcylinder from the cell and optical inspection of its surface. It appeared that the oxidation of decamethylferrocene may be followed by the precipitation of its salts with the corresponding anions. The precipitate was identified by voltammetry and Raman spectroscopy. The length of the wire covered by the precipitate is relatively big in the case of perchlorate and very small (practically the deposit is located at the three-phase boundary) for the nitrate anion, which confirms that ClO₄⁻ easily enters nitrobenzene while NO₃⁻ does not. In the presence of chloride the situation was entirely different: the precipitation appeared on the part of microelectrode present in the aqueous phase. This proves that the electrooxidation of decamethylferrocene in the nitrobenzene drop leads rather to the transfer of the decamethylferrocenium cation to the aqueous phase and not to penetration of nitrobenzene by the chloride anion.     

Indoleamine 2,3 Dioxygenase 1—The Potential Link between the Innate Immunity and the Ischemia-Reperfusion-Induced Acute Kidney Injury?

Ischemia-reperfusion injury (IRI) is of the most common causes of acute kidney injury (AKI); nevertheless, the mechanisms responsible for both early kidney injury and the reparative phase are not fully recognised. The inflammatory response following ischemia is characterised by the crosstalk between cells belonging to the innate immune system—dendritic cells (DCs), macrophages, neutrophils, natural killer (NK) cells, and renal tubular epithelial cells (RTECs). A tough inflammatory response can damage the renal tissue; it may also have a protective effect leading to the repair after IRI. Indoleamine 2,3 dioxygenase 1 (IDO1), the principal enzyme of the kynurenine pathway (KP), has a broad spectrum of immunological activity from stimulation to immunosuppressive activity in inflamed areas. IDO1 expression occurs in cells of the innate immunity and RTECs during IRI, resulting in local tryptophan (TRP) depletion and generation of kynurenines, and both of these mechanisms contribute to the immunosuppressive effect. Nonetheless, it is unknown if the above mechanism can play a harmful or preventive role in IRI-induced AKI. Despite the scarcity of literature in this field, the current review attempts to present a possible role of IDO1 activation in the regulation of the innate immune system in IRI-induced AKI.