PRECIPITATION OF HYBRID HYDROXYAPATITE / AUTOFIBRIN NANOCOMPOSITES

Синтезированы гибридные нанокомпозиты на основе гидроксиапатита и аутофибрина в форме фибринового сгустка либо цитратной плазмы путем осаждения при pH 9. «Мягкие» условия осаждения и быстрое выделение нанокомпозитов способствовали сохранению биополимерной матрицы аутофибрина. Дестабилизация дополнительной фазы аморфного фосфата кальция с образованием стехиометрического гидроксиапатита обусловлена влиянием макромолекул фибрина. Формирование кальцийдефицитного гидроксиапатита с x« 0,1 и Ca / P 1,65 происходило в среде цитратной плазмы, который после 800 °С превращался в смесь гидроксиапатит / 3 -трикальцийфосфат. Синтез композитов на основе биомиметического апатита осуществляли при добавлении 30 об.% модельного раствора Simulated Body Fluid (SBF). Влияние ионов Mg, CO~, входящих в состав SBF, способствовало стабилизации аморфного фосфата кальция и образованию карбонатзамещенного гидроксиапатита, устойчивого к термическим превращениям до 800°С. Совокупное влияние аутофибрина и ионов введенного SBF позволило управлять составом минеральной составляющей гибридных нанокомпозитов без разрушения биополимерной матрицы. Hybrid composites based on hydroxyapatite and autofibrin were synthesized by precipitation in a medium with pH = 9. Soft precipitation conditions and rapid isolation of the composite precipitates favored preservation of a biopolymer matrix of autofibrin. An effect of fibrin macromolecules contributed to destabilization of the amorphous calcium phosphate phase and formation of stoichiometric hydroxyapatite. The medium of the citrated plasma stimulated precipitation of calcium-deficient hydroxyapatite with x « 0,1 and the Ca / P ration of 1,65 which transformed into the mixture of hydroxyapatite / 3 -tricalcium phosphate at 800 °С. Biomimetic apatite composites were synthesized with an addition of 30 vol. % of a Simulated Body Fluid (SBF) model solution. The effect of Mg, CO~ ions of SBF promoted the stabilization of amorphous calcium phosphate and formation of carbonated hydroxyapatite that exhibited thermal stability up to 800 °С. The cummulative effect of autofibrin and ions of induced SBF provided controlling composition of the mineral part of hybrid nanocomposites without disruption of an autofibrin matrix.

On the Electrochemical Insertion of Mg2+in Na7V4(P2O7)4(PO4) and Na3V2(PO4)3 Host Materials

Next generation energy storage technologies need to be more sustainable and cheaper. Among Post-Li chemistries, Mg batteries are emerging as a possible alternative with desirable features like abundance of Mg on the Earth`s crust and a doubled volumetric capacity with respect to the current Li metal. However, research and development of Mg-batteries is still in its infancy stage and still many hurdles are to be understood and solved. For instance, cathode materials showing high capacities, operating at high potentials and with sufficient fast kinetics need to be designed and developed. Polyanionic materials are a class of sustainable and environmentally friendly materials that emerged as possible Mg2+ hosts. In this work the insertion of Mg cations inside the NASICON Na3V2(PO4)3 and, for the first time, in the mixed phosphate phase Na7V4(P2O7)4(PO4), is reported, structurally and electrochemically characterized.

Vibrational Study on Structure and Bioactivity of Protein Fibers Grafted with Phosphorylated Methacrylates

In the last decades, silk fibroin and wool keratin have been considered functional materials for biomedical applications. In this study, fabrics containing silk fibers from Bombyx mori and Tussah silk fibers from Antheraea pernyi, as well as wool keratin fabrics, were grafted with phosmer CL and phosmer M (commercial names, i.e., methacrylate monomers containing phosphate groups in the molecular side chain) with different weight gains. Both phosmers were recently proposed as flame retarding agents, and their chemical composition suggested a possible application in bone tissue engineering. IR and Raman spectroscopy were used to disclose the possible structural changes induced by grafting and identify the most reactive amino acids towards the phosmers. The same techniques were used to investigate the nucleation of a calcium phosphate phase on the surface of the samples (i.e., bioactivity) after ageing in simulated body fluid (SBF). The phosmers were found to polymerize onto the biopolymers efficiently, and tyrosine and serine underwent phosphorylation (monitored through the strengthening of the Raman band at 1600 cm−1 and the weakening of the Raman band at 1400 cm−1, respectively). In grafted wool keratin, cysteic acid and other oxidation products of disulphide bridges were detected together with sulphated residues. Only slight conformational changes were observed upon grafting, generally towards an enrichment in ordered domains, suggesting that the amorphous regions were more prone to react (and, sometimes, degrade). All samples were shown to be bioactive, with a weight gain of up to 8%. The most bioactive samples contained the highest phosmers amounts, i.e., the highest amounts of phosphate nucleating sites. The sulphate/sulphonate groups present in grafted wool samples appeared to increase bioactivity, as shown by the five-fold increase of the IR phosphate band at 1040 cm−1.

Synthesis of Phosphate Phases on Polysaccharide Template

New method of synthesis of biocompatible, biodegradable and nontoxic composite materials based on polysaccharide chitosan and inorganic phosphate component will be presented in this work. Materials structure was changed by in situ transformation of phosphate phases. Transformation of initial precursors to hydroxyapatite as one of the most stable phosphate phase occurred as a result of thermal and alkaline treatment. XRD and SEM methods were applied to investigate structure and morphology of obtained samples.

The obtaining of the anhydride products by oxidation of n-pentane on the VPO catalysts

It was investigated VPMeO catalysts (Me=Fe, Mo, Te, W, Ni, Ti, La, Bi, Zr і Ag) in oxidation of n-pentane. On these catalytic samples the main products of reaction are maleic (MA), phthalic (PhA), citraconic (CA) anhydrides, carbon oxides and in-significant quantity of acetic and of acrylic acids. It was established that a change of physical-chemical properties of the VPMeO catalysts affects a course of reaction of n-pentane oxidation. It was determined that the introduction of additives into the basic VPO composition and its content influences a phase composition, a morphol-ogy, acidic properties of catalyst surface, a crystallization temperature of active component and a oxidation degree of vanadium in it. It was established that addi-tives in the VPO sample may be distributed in two ways: a) evenly, high disperse (Fe, Te, Ni, Ag ions), b) with formation of X-ray amorphous additive phosphate phase (Ti, Bi, La, W, Zr ions). Additives that decrease temperature of the active phase formation of a catalyst and increase temperature of its oxidation (Fe, Ti, Bi, Zr ions) positively influence the life of exploitation of catalytic pattern without losing its se-lectivity in the n-pentane oxidation. Additives that reduce the O 1s-electrons energy and increase an oxygen content (O/(V+P+Me)) on the VPO composition surface en-hance the specific rate of the hydrocarbon oxidation. A growth of phosphorous con-tent on the surface of synthesized compositions also contributes to the increase of the time of their stable work. The influence of ratio of Bronsted and Lewis acid cen-ters on surface of the VPМеO pattern on a selectivity of anhydrides production was established. The growth of acidic centers content on the surface of patterns increas-es the CA selectivity. The rise of quantity of Lewis centers favors the PhA formation while the MA selectivity reduces in the reaction products. According to experimental data the modification of the VPO catalyst is affect its physical-chemical and cata-lytic properties. The change of defined physical-chemical properties allows to regu-late a process of the n-pentane oxidation in the direction of formation of one of the anhydrides.

Struvite Crystallisation and the Effect of Co2+ Ions

The controlled crystallisation of struvite (MgNH4PO4∙6H2O) is a viable means for the recovery and recycling of phosphorus (P) from municipal and industrial wastewaters. However, an efficient implementation of this recovery method in water treatment systems requires a fundamental understanding of struvite crystallisation mechanisms, including the behavior and effect of metal contaminants during struvite precipitation. Here, we studied the crystallisation pathways of struvite from aqueous solutions using a combination of ex situ and in situ time-resolved synthesis and characterization techniques, including synchrotron-based small- and wide-angle X-ray scattering (SAXS/WAXS) and cryogenic transmission electron microscopy (cryo-TEM). Struvite syntheses were performed both in the pure Mg-NH4-PO4 system as well as in the presence of cobalt (Co), which, among other metals, is typically present in waste streams targeted for P-recovery. Our results show that in the pure system and at Co concentrations < 0.5 mM, struvite crystals nucleate and grow directly from solution, much in accordance with the classical notion of crystal formation. In contrast, at Co concentrations ≥ 1 mM, crystallisation was preceded by the transient formation of an amorphous nanoparticulate phosphate phase. Depending on the aqueous Co/P ratio, this amorphous precursor was found to transform into either (i) Co-bearing struvite (at Co/P < 0.3) or (ii) cobalt phosphate octahydrate (at Co/P > 0.3). These amorphous-to-crystalline transformations were accompanied by a marked colour change from blue to pink, indicating a change in Co2+ coordination in the formed solid from tetrahedral to octahedral. Our findings have implications for the recovery of nutrients and metals during struvite crystallisation and contribute to the ongoing general discussion about the mechanisms of crystal formation.