Crystal structure and oxygen nonstoichiometry of the Ho xSr 1-xCoO 3-δ

Samples with overall composition Ho xSr 1-xCoO 3-δ within the range 0.05 ≤ x ≤ 0.9 were prepared by a solid-state technique at 1100 °C in air. Single-phase Ho xSr 1-xCoO 3-δ oxides were obtained within the range 0.05 ≤ x ≤ 0.30. Solid solutions of Ho0.05Sr0.95CoO3-δ and Ho 0.1Sr 0.9CoO 3-δ were indexed in the cubic structure (Pm3m sp. gr.) with the unit cell parameters a = 3.846 Å and a = 3.842 Å, respectively. Further introduction of holmium leads to a change of crystal structure from cubic to a tetragonal 2a p × 2a p × 4a p superstructure. All samples with x > 0.3 were multiphase, containing a saturated solid solution with approximate composition Ho 0.3Sr 0.7CoO 3-δ with Ho 2O 3 and CoO. The change of oxygen nonstoichiometry was measured by thermogravimetric analysis within the temperature range 25 ≤ T (°C) ≤ 1100. The absolute value of oxygen nonstoichiometry was calculated from the results of chromatometric titration. Thermal expansion coefficients of Ho 1-xSr xCoO 3-δ were measured by dilatometry within the temperature range 25 ≤ T (°C) ≤ 1100 in air. © 2012 Materials Research Society

Synthesis, structure and properties of LnBa(Co,Me)2O 5+δ (Ln = Nd, Sm, Ho and Y; Me = Fe, Ni, Cu) as potential cathodes for SOFCs

Layered LnBa(Co,Me)2O5+δ (Ln = Nd, Sm, Ho and Y; Me = Fe, Ni, Cu) with double perovskite structure were synthesized by the solid-state reaction and glycerin-nitrate technique and characterized by X-ray diffraction, thermogravimetric analysis, iodometric titration and dilatometry. Homogeneity ranges for the solid solutions were determined. The oxygen content in LnBa(Co,Me)2O5+δ decreases with decreasing rare-earth cation size. Partial substitution of cobalt by iron increases oxygen content while introduction of copper decrease it. The average thermal expansion coefficients were calculated. Chemical compatibility of studied perovskites with Ce0.8Sm0.2O2 and Zr0.85Y 0.15O2 solid electrolytes has been studied. © 2012 Materials Research Society

Effect of Chitosan and Amphiphilic Polymers on the Photosensitizing and Spectral Properties of Rose Bengal

The influence of chitosan (CS) and amphiphilic polymers (AP: pluronic F108 and polyvinylpyrrolidone (PVP)) on the photocatalytic activity of rose bengal (RB) in a model reaction of tryptophan photo-oxidation in phosphate-buffered saline (PBS) was studied. It was shown that in the presence of CS, the effective rate constant keff of tryptophan photo-oxidation catalyzed by RB in PBS solution decreases by a factor of two. This is due to the ionic interaction of the RB with the chitosan. Rose bengal in a slightly acidic environment (pH 4.5) passes into a neutral lactone form, which sharply reduces the photosensitizing properties of the dye. It was demonstrated that the introduction of AP into a solution containing RB and CS prevents direct interaction between RB and CS. This is evidenced by the presence of photocatalytic activity of the dye in the RB-AP-CS systems, as well as bathochromic shifts of the main absorption bands of the dye, and an increase in the optical density and luminescence intensity of the RB when AP is introduced into a buffer solution containing RB and chitosan. The presence of RB-CS and RB-AP interaction in aqueous and PBS media is confirmed by the increase in the degree of fluorescence anisotropy (r) of these binary systems. In an aqueous solution, the value of r for the RB-F108-CS system decreases by a factor of 3.5 (compared to the value of r for the RB-CS system), which is associated with the localization of the dye in pluronic micelles. In PBS, the fluorescence anisotropy is practically the same for all systems, which is related to the stability of the dye structure in this medium. The presence of interaction between RB and AP in aqueous solutions was confirmed by the proton NMR method. In addition, the formation of RB-F108 macromolecular complexes, which form associates during solution concentration (in particular, during evaporation), was shown by AFM. Such RB-AP-CS systems may be promising for practical application in the treatment of local foci of infections by aPDT

Specific features of early stage of the wound healing process occurring against the background of photodynamic therapy using fotoditazin photosensitizer-amphiphilic polymer complexes

There is a growing demand on the studies of the wound healing potentials of photodynamic therapy. Here we analyze the effects of Fotoditazin, an e6 chlorine derivative, and its complexes with amphiphilic polymers, on the early stage of wound healing in a rat model. A skin excision wound model with prevented contraction was developed in male albino rats divided into eight groups according to the treatment mode. All animals received injections of one of the studied compositions into their wound beds and underwent low-intensity laser irradiation or stayed un-irradiated. The clinical monitoring and histological examination of the wounds were performed. It has been found that all the Fotoditazin formulations have significant effects on the early stage of wound healing. The superposition of the inflammation and regeneration was the main difference between groups. The aqueous solution of Fotoditazin alone induced a significant capillary hemorrhage, while its combinations with amphiphilic polymers did not. The best clinical and morphological results were obtained for the Fotoditazin-Pluronic F127 composition. Compositions of Fotoditazin and amphiphilic polymers, especially Pluronic F127, probably, have a great potential for therapy of wounds. Their effects can be attributed to the increased regeneration and suppressed reactions changes at the early stages of repair.10 page(s

Photocurable Methacrylate Derivatives of Polylactide: A Two-Stage Synthesis in Supercritical Carbon Dioxide and 3D Laser Structuring

A two-stage polylactide modification was performed in the supercritical carbon dioxide medium using the urethane formation reaction. The modification resulted in the synthesis of polymerizable methacrylate derivatives of polylactide for application in the spatial 3D structuring by laser stereolithography. The use of the supercritical carbon dioxide medium allowed us to obtain for the first time polymerizable oligomer-polymer systems in the form of dry powders convenient for further application in the preparation of polymer compositions for photocuring. The photocuring of the modified polymers was performed by laser stereolithography and two-photon crosslinking. Using nanoindentation, we found that Young’s modulus of the cured compositions corresponded to the standard characteristics of implants applied in regenerative medicine. As shown by thermogravimetric analysis, the degree of crosslinking and, hence, the local stiffness of scaffolds were determined by the amount of the crosslinking agent and the photocuring regime. No cytotoxicity was observed for the structures