Towards controlling the morphology of cobalt loaded nanocomposites in polyol process with polyethylene glycol

The polyol process is one of the simple, efficient and productive methods for the synthesis of metal loaded polymer composites. Functional properties of metal-polymer nanocomposites are determined by chemical composition, size and morphology of their particles. Finding effective ways to control the nanoparticle's properties during the polyol process is a crucial task. The effect of molar ratio Mn+/OHPEG on the formation of cobalt loaded metal-polymer nanocomposites during a one-pot two-component polyol process by polyethylene glycol with Mr = 4000 g·mol–1 (PEG) was studied. The PEG-based polyol process and the formation of cobalt nanophase were studied at molar ratios νCo2+/νOH(PEG) = 1:1, 1:10, 1:100 and 1:500 using UV-Vis, diffuse reflectance IR and ATR FT-IR spectroscopy, nanoparticle tracking analysis (NTA), dynamic light scattering (DLS). It was found that PEG can act as a reducing agent and stabilizing matrix for the cobalt nanophase at a ratio higher than Mn+/OHPEG= 1:10. The composition and morphology of Co/PEG nanocomposites were determined by XRD and TEM methods. Two types of spheroid particles with average diameters of 88±55 nm / 8±4 nm and 12±3 nm / 3±1 nm, respectively, represent Co/PEG nanocomposites 1:500 and 1:100. Scaly structures with a diameter of 15±5 nm are formed at a molar ratio of νCo2+/νOH(PEG) = 1:10. An increase in the Co2+ content in the PEG-based polyol process leads to the immobilized cobalt nanophase Co3O4 (1:500), Co0/CoO (1:100), CoO (1:10) in PEG. Co/PEG nanocomposites are hemocompatible. The HC50value depends on the composition and morphology of the nanoparticles

TESTING DIFFERENT METHODS OF ARTIFICIAL VESICLES INDUCTION FROM T CELLS

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Direct Growth of the Oriented Nanocrystals of Gamma-Iron on Graphene Oxide Substrate. The Detailed Analysis of the Factors Affecting Unexpected Formation of the Gamma-Iron Phase

In bulk, face-centered gamma-iron exists only at temperatures above 917 ?C, returning back to body-centered alpha-iron upon cooling below this temperature. In this work, we report formation of the gamma-iron phase at temperatures significantly lower than the 917 ?C threshold in the form of nanoparticles. Moreover, the as-grown nanoparticles have specific orientation along the (002) plane as the result of the templating effect of the graphene oxide substrate. Also, we provide a complete account of the factors responsible for the formation of the gamma-phase. Namely, we demonstrate the role of the type of carbon substrate, and the effect of the temperature and time of annealing and the graphene oxide/iron ion ratio. We demonstrate that the gamma-phase is not formed when using three-dimensional forms of carbon, elucidating the "magic" role of graphene oxide in this process.12923-1293

Catechol-Containing Schiff Bases on Thiacalixarene: Synthesis, Copper (II) Recognition, and Formation of Organic-Inorganic Copper-Based Materials

For the first time, a series of catechol-containing Schiff bases, tetrasubstituted at the lower rim thiacalix[4]arene derivatives in three stereoisomeric forms, cone, partial cone, and 1,3-alternate, were synthesized. The structure of the obtained compounds was proved by modern physical methods, such as NMR, IR spectroscopy, and HRMS. Selective recognition (Kb difference by three orders of magnitude) of copper (II) cation in the series of d-metal cations (Cu2+, Ni2+, Co2+, Zn2+) was shown by UV-vis spectroscopy. Copper (II) ions are coordinated at the nitrogen atom of the imine group and the nearest oxygen atom of the catechol fragment in the thiacalixarene derivatives. High thermal stable organic-inorganic copper-based materials were obtained on the base of 1,3-alternate + Cu (II) complexes

Gamma-Iron Phase Stabilized at Room Temperature by Thermally Processed Graphene Oxide

Stabilizing nanoparticles on surfaces, such as graphene, is a growing field of research. Thereby, iron particle stabilization on carbon materials is attractive and finds applications in charge-storage devices, catalysis, and others. In this work, we describe the discovery of iron nano-particles with the face-centered cubic structure that was postulated not to exist at ambient conditions. In bulk, the y-iron phase is formed only above 917 ?C, and transforms back to the thermodynamically favored a-phase upon cooling. Here, with X-ray diffraction and Mossbauer spectroscopy we unambiguously demonstrate the unexpected RT stability of the y-phase of iron in the form of the nanoparticles with low carbon content from 0.60% through 0.93%. The nanoparticles have controllable diameter range from 30 nm through 200 nm. They are stabilized by a layer of Fe/C solid solution on the surface, serving as the buffer controlling carbon content in the core, and by layer graphene as an outermost shell

Effect of the Synthetic Approach on the Formation and Magnetic Properties of Iron-Based Nanophase in Branched Polyester Polyol Matrix

This article shows the success of using the chemical reduction method, the polyol thermolytic process, the sonochemistry method, and the hybrid sonochemistry/polyol process method to design iron-based magnetically active composite nanomaterials in a hyperbranched polyester polyol matrix. Four samples were obtained and characterized by transmission and scanning electron microscopy, infrared spectroscopy and thermogravimetry. In all cases, the hyperbranched polymer is an excellent stabilizer of the iron and iron oxides nanophase. In addition, during the thermolytic process and hybrid method, the branched polyol exhibits the properties of a good reducing agent. The use of various approaches to the synthesis of iron nanoparticles in a branched polyester polyol matrix makes it possible to control the composition, geometry, dispersity, and size of the iron-based nanophase and to create new promising materials with colloidal stability, low hemolytic activity, and good magnetic properties. The NMR relaxation method proved the possibility of using the obtained composites as tomographic probes

Growth of invar nanoparticles on a grapheme oxide support

Binary nanoparticles, composed of two different metals, attract significant attention because they possess properties not typical for their respective single-component nanoparticles. In the bulk form, iron and nickel form an alloy called invar in which the two metals are mixed in a ratio of Fe : Ni = 2 : 1. In this work, we demonstrate the formation of alloyed nanoparticles of invar, as opposed to the theoretically possible formation of particles from the two individual metals. The formation of the alloyed nanoparticles is conducted in a two-step process: liquid phase impregnation of graphene oxide with the salts of the metals, and subsequent annealing of the as-formed dry composite. Unlike the solution phase reaction conditions, in this approach, the binary nanoparticles are assembled under conditions where the metal atoms are immobilized on the surface of the decomposing graphene oxide, and at temperatures significantly lower than the melting points of the two metals. The structure of the as-grown nanocrystals is investigated by Mössbauer spectroscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The majority of the Fe/Ni nanoparticles are in a magnetically ordered state, and the composite is a soft magnet.4092-409

Revisiting the Mechanism of Oxidative Unzipping of Multiwall Carbon Nanotubes to Graphene Nanoribbons

Unzipping multiwall carbon nanotubes (MWCNTs) attracted great interest as a method for producing graphene nanoribbons (GNRs). However, depending on the production method, the GNRs have been proposed to form by different mechanisms. Here, we demonstrate that the oxidative unzipping of MWCNTs is intercalation-driven, not oxidative chemical-bond cleavage as was formerly proposed. The unzipping mechanism involves three consecutive steps: intercalation-unzipping, oxidation, and exfoliation. The reaction can be terminated at any of these three steps. We demonstrate that even in highly oxidative media one can obtain nonoxidized GNR products. The understanding of the actual unzipping mechanism lets us produce GNRs with hybrid properties varying from nonoxidized through heavily oxidized materials. We answer several questions such as the reason for the innermost walls of the nanotubes remaining zipped. The intercalation-driven reaction mechanism provides a rationale for the difficulty in unzipping single-wall and few-wall CNTs and aids in a reevaluation of the data from the oxidative unzipping process

Hybrid Nanostructures of Hyperbranched Polyester Loaded with Gd(III) and Dy(III) Ions

Hyperbranched polymers are successful nanoscale functional platforms for loading metal ions and creating promising nanomaterials for medicine. This work presents the synthesis of metal–polymer nanostructures based on a second generation hyperbranched polyester with eight terminal benzoylthiocarbamate (BTC) groups loaded with Gd(III) or Dy(III) ions. Their structure (Fourier transform infrared spectroscopy) and morphology (transmission electron microscopy), photophysical (ultraviolet–visible and luminescence spectroscopy), thermophysical, magnetic activity, relaxivity, and aggregation properties (nanoparticle tracking analysis) were studied. The formation of the metal–polymer complex is carried out by chelation of lanthanide ions −CO and −CS groups of the BTC fragment of polyester. Coordination units with composition Ln(III)-3BTC (Ln = Dy, Gd) were localized on the branched polymer platform. The load is three lanthanide ions per branched polyester polybenzoylthiocarbamate macromolecule. Logarithms of stability constants of complexes and composition of coordination polyhedron have been determined. The dysprosium complex is in a paramagnetic state with antiferromagnetic correlations, and the gadolinium complex is in a paramagnetic state. The relaxivity of the Dy(III) and Gd(III) complexes increased by 2.5 and 3 times, respectively, compared to their nitrates. An important achievement is the identification of rare-earth metal (REM)-controlled morphology and self-organization for Dy(III) and Gd(III) complexes with branched polyester polybenzoylthiocarbamate in solution and on the surface. Spherical nanostructures for the dysprosium complex and nanorods for the gadolinium complex were observed. Synthesized REM-loaded nanostructures with polyester polybenzoylthiocarbamates have low hemotoxicity and can be applied in biomedicine