Silica nano-particles produced by worms through a bio-digestion process of rice husk

It is reported the production and characterization of silica nano-particles by Californian-red worms through a bio-digestion process of rice husk; the rice husk contains, naturally, high concentrations of silica (22%). The worms were fed gradually with rice husk and water during 5 months to clean the worm’s digestive system from other types of food. The humus was collected, dried at room temperature, pH neutralized and calcined at different temperatures (500, 600 and 700 °C) to remove the organic matter. The calcined humus was digested to remove traces of inorganic compounds. The size of the silica particles was in the range from 55 to 250 nm depending on calcination temperatures. The efficiency in the production of the particles was 88%. These results were compared with those obtained using other agro-industrial wastes that contain silica: coffee (12%) and cane (8%) husk. The samples were characterized by XRD, FTIR, EDS, DLS, SEM and TEM.     

Design, synthesis and photo-cross-linking of a new photosensitive macromonomer from tetra-branched poly(ethylene oxide)s

A general procedure to increase the amount of photoreactive chromophore groups per oligoether chain is presented. In this work, a photoreactive macromonomer with four functionalities was synthesized by a four-step synthetic pathway with high yield. The photochemical behavior of this compound was studied with a view to obtaining polymeric networks. The significant advantage in this strategy is that the preparation of this material has as last operation, the obtaining and processing of polymer as thin film. In this way, the synthetic strategy based on assembling: (i) the polyether chains, (ii) a film forming backbone, and (iii) a photoactive moiety to be used for cross-linking, seems a viable solution to the problem of the continuous processing of materials.     

Löslichkeit und Adsorbierbarkeit von Benzoesäure und Salizylsäure in Gegenwart gemischter organischer Lösungsmittel

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The slagging propensity of Zn-rich scrap tyre ash in reducing environments consisting of CO and CO2 and its promotion of the slagging of Si-rich coal ash

This study includes a comprehensive investigation on the ash slagging characteristics of zinc (Zn)-rich tyre ash and its interaction with silica (Si)-rich coal ash blended at different ratios in a 5% CO in CO₂ reducing environment. Such an environment is expected to occur near the burner in a combustor, as well as serves as a fundamental study on the slagging propensity upon the effect of CO, which is a principal reducing agent in a gasifier. An approach consisting of experimental studies using modified inclined plane (M-IP) methodology, advanced analytical techniques including the scanning electron microscopy (SEM) and x-ray photoelectron (XPS) spectroscopy, and thermodynamic equilibrium calculations were used to elaborate the slagging propensities of the single and blended ashes. Furthermore, the fate of Zn within tyre ash and its potential implications on the slagging properties were evaluated. Tyre ash easily melts to liquid slag upon increasing temperature compared to the silica-rich coal ash. Zinc does not evaporate but rather remains within tyre slag mostly as a hemimorphite (Zn₄(Si₂O₇)(OH))-like coordination structure attributing to the characteristic blue colour of tyre slag. The low ionic potential value of 2.7 for Zn²⁺ is characteristic of basic ions that have a greater tendency to depolymerise the Si-rich ash slag matrix and acts as a fluxing agent in ash slag. Moreover, it was proven that Zn²⁺ plays a synergistic role with Ca²⁺ in enhancing the flowability of the Si-rich slag remarkably. Furthermore, for the pure tyre slag, Zn was found to preferentially deposit at the corundum (Al₂O₃) substrate interface and even penetrate/react with the porous corundum, causing a strong corrosion on the substrate. However, blending of tyre ash with coal ash alleviates this problem by a preferred scavenging of Zn into the entire Si matrix, which in turn protects the corundum plate.     

Structural Diversity in the Self‐Assembly of Pseudopeptidic Macrocycles

The self‐assembling abilities of several pseudopeptidic macrocycles have been thoroughly studied both in the solid (SEM, TEM, FTIR) and in solution (NMR, UV, CD, FTIR) states. Detailed microscopy revealed large differences in the morphology of the self‐assembling micro/nanostructures depending on the macrocyclic chemical structures. Self‐assembly was triggered by the presence of additional methylene groups or by changing from para to meta geometry of the aromatic phenylene backbone moiety. More interestingly, the nature of the side chain also plays a fundamental role in some of the obtained nanostructures, thus producing structures from long fibers to hollow spheres. These nanostructures were obtained in different solvents and on different surfaces, thus implying that the chemical information for the self‐assembly is contained in the molecular structure. Dilution NMR studies (chemical shift and self‐diffusion rates) suggest the formation of incipient aggregates in solution by a combination of hydrogen‐bonding and π–π interactions, thus implicating amide and aryl groups, respectively. Electronic spectroscopy further supports the π–π interactions because the compounds that lead to fibers show large hypochromic shifts in the UV spectra. Moreover, the fiber‐forming macrocycles also showed a more intense CD signature. The hydrogen‐bonding interactions within the nanostructures were also characterized by attenuated total‐reflectance FTIR spectroscopy, which allowed us to monitor the complete transition from the solution to the dried nanostructure. Overall, we concluded that the self‐assembly of this family of pseudopeptidic macrocycles is dictated by a synergic action of hydrogen‐bonding and π–π interactions. The feasibility and geometrical disposition of these interactions finally render a hierarchical organization, which has been rationalized with a proposal of a model. The understanding of the process at the molecular level has allowed us to prepare hybrid soft materials.     

SrPd4B and BaPd4B: New Type of Crystal Structure and Physical Properties

Two new intermetallic alkaline‐earth palladium borides, SrPd₄B and BaPd₄B were synthesised and their physical properties were investigated. The crystal structure of SrPd₄B was solved from powder X‐ray diffraction data: new structure type, space group Pnma, a = 6.0014(1) Å, b = 5.5041(1) Å, c = 11.8723(2) Å, R_I = 0.065, R_P = 0.093. BaPd₄B is isostructural with a = 6.0883(1) Å, b = 5.6066(1) Å, c = 12.0050(2) Å, R_I = 0.062, R_P = 0.097. The relationship of this structure type with the series of derivatives of the CaCu₅ type is discussed. Calculated electronic band structures for palladium, Pd₃B, SrPd₅, SrPd₄B and SrPd₃B are compared. The role of boron and strontium for the electronic properties is discussed in detail. SrPd₄B shows metallic behaviour with a DOS(E_F) ≈? 1.7 eV^–1 · f.u.^–1 at the Fermi level. Magnetic properties, electrical resistivity and specific heat capacity measurements reveal that the two compounds are diamagnetic metallic conductors with low electronic density of states, in agreement, with the electronic structure calculations.     

Quorum sensing regulates electric current generation of Pseudomonas aeruginosa PA14 in bioelectrochemical systems

Here, we show that quorum sensing (QS) modulates the current generation of the anode-respiring bacterium Pseudomonas aeruginosa because it controls the production of phenazines, which mediate the electron transfer to the anode. The current generation by a wildtype (WT) strain P. aeruginosa PA14 and the GacS/GacA protein-regulatory mutant retS was investigated under different environmental conditions. The retS mutant generated significantly higher current (45-fold) than the WT under anaerobic conditions. Anaerobic current generation by the WT was 28-fold higher with extraneously supplied lactones (a QS-signaling molecule). Compared to anaerobic conditions, the WT with some oxygen (microaerobic conditions) exhibited enhanced phenazine production (39-fold) and current levels (48-fold). Iron-rich medium and microaerobic conditions had a negative impact on current generation by retS. All these results were directly linked to QS activity in P. aeruginosa, thus, demonstrating the importance of this bacterial communication system for current generation in BESs. We also show that BESs represent a new tool for real-time investigation of phenazine-related QS activity.