Influence of Stabilizing Ion Content on the Structure, Photoluminescence and Biological Properties of Zr1–xEuxO2–0.5x Nanoparticles

Quasi-spherical nanoparticles of ZrO2 containing EuO1.5 from 2 to 15 mol.% were synthesized from the chlorides of the corresponding metals under hydrothermal conditions. The structural changes of Zr1–xEuxO2–0.5x (x = 0.02 ÷ 0.15) nanoparticles depending on the content of europium (III) ions were studied using the complementary methods (X-ray diffraction, electron microdiffraction, Raman and photoluminescence spectroscopy). It was shown that increasing the Eu3+ concentration in the Zr1–xEuxO2–0.5x nanoparticles leads to a transition from the equilibrium monoclinic zirconia phase to metastable tetragonal and cubic polymorphic modifications. In this case, the size of the nanoparticles decreases from 11.5 nm to 9 nm; the specific surface area grows from 80.2 to 111.3 m2/g, and the electrokinetic potential increases monotonously from −8.7 to 16.3 mV. The evolution of the phase composition of Zr1–xEuxO2-0.5x nanoparticles from monoclinic to tetragonal/cubic allomorphs with an increase in the molar fraction of stabilizer ions was correlated with changes in the sublevel structure of 5D0 → 7F2 and 5D0 → 7F4 optical transitions for Eu3+ in the luminescence spectra. Besides, for the nanoparticles obtained by hydrothermal synthesis from chlorides, the quantum efficiency does not exceed 3%. According to the M.T.T. assay, as a result of three-day human fibroblast cultivation in the aqueous dispersion of Zr1–xEuxO2–0.5x (x = 0.02 ÷ 0.15) nanoparticles, the proliferation activity of the cells is maintained, indicating that they do not have cytotoxic properties. Such nanoparticles can be used in organic–inorganic composites for medical applications in order to strengthen the polymer scaffolds and visualize changes in their structure within time

Magnetization of Ultraviolet-Reduced Graphene Oxide Flakes in Composites Based on Polystyrene

This work presents our study results of the magnetization of multilayer UV-reduced graphene oxide (UV-rGO), polymer matrix (polystyrene), and a conjugated composite based on them. The mesoscopic structure of the composites synthesized in this work was studied by such methods as X-ray diffraction, SEM, as well as NMR-, IR- and Raman spectroscopy. The magnetization of the composites under investigation and their components was measured using a vibrating-sample magnetometer. It has been shown that the UV-reduction process leads to the formation of many submicron holes distributed inside rGO flakes, which can create edge defects, causing possibly magnetic order in the graphite samples under investigation on the mesoscopic level. This article provides an alternative explanation for the ferromagnetic hysteresis loop in UV-rGO on the base of superconductivity type-II

Effect of Domain Structure of Segmented Poly(urethane-imide) Membranes with Polycaprolactone Soft Blocks on Dehydration of <i>n</i>-Propanol via Pervaporation

Segmented poly(urethane-imide)s (PUIs) were synthesized by polyaddition reaction and applied for preparation of membranes. Tolylene-2,4-diisocyanate, pyromellitic dianhydride, and m-phenylenediamine for chain extension were used to form hard aromatic blocks. Polycaprolactone diols with molecular weights equal to 530 and 2000 g mol&#8722;1 were chosen as soft segments. The effect of the length of soft segments on the structure, morphology, and transport properties of segmented poly(urethane-imide) membranes were studied using atomic force microscopy, small-angle and wide-angle X-ray scattering, and pervaporation experiments. It was found that a copolymer with a shorter soft segment (530 g mol&#8722;1) consists of soft domains in a hard matrix, while the introduction of polycaprolactone blocks with higher molecular weight (2000 g mol&#8722;1) leads to the formation of hard domains in a soft matrix. Additionally, the introduction of hard segments prevents crystallization of polycaprolactone. Transport properties of membranes based on segmented PUIs containing soft segments of different length were tested for pervaporation of a model mixture of propanol/water with 20 wt % H2O content. It was found that a membrane based on segmented PUIs containing longer soft segments demonstrates higher flux (8.8 kg &#956;m m&#8722;2 h&#8722;1) and selectivity (179) toward water in comparison with results for pure polycaprolactone reported in literature. The membrane based on segmented PUIs with 530 g mol&#8722;1 soft segment has a lower flux (5.1 kg &#956;m m&#8722;2 h&#8722;1) and higher selectivity (437)

Structure and Transport Properties of Mixed-Matrix Membranes Based on Polyimides with ZrO2 Nanostars

Mixed-matrix membranes based on amorphous and semi-crystalline polyimides with zirconium dioxide (ZrO2) nanostars were synthesized. Amorphous poly(4,4′-oxydiphenylenepyromellitimide) and semi-crystalline polyimide prepared from 1,4-bis(4-aminophenoxy)benzene and 4,4’-oxydiphthalic anhydride were used. The effect of ZrO2 nanostars on the structure and morphology of nanocomposite membranes was studied by wide-angle X-ray scattering, scanning electron microscopy, atomic force microscopy, and contact angle measurements. Thermal properties and stability were investigated by thermogravimetric analysis and differential scanning calorimetry. Transport properties of hybrid membranes containing 5 wt % ZrO2 were tested for pervaporation of a mixture of butanol–water with 10 wt % H2O content. It was found that a significant amount of the ZrO2 added to the semi-crystalline polyimide is encapsulated inside spherulites. Therefore, the beneficial influence of inorganic filler on the selectivity of mixed-matrix membrane with respect to water was hampered. Mixed-matrix membranes based on amorphous polymer demonstrated the best performance, because water molecules had higher access to inorganic particles

Luminescence of Eu 3+ ions in hybrid polymer-inorganic composites based on poly(methyl methacrylate) and zirconia nanoparticles

Spherical nanoparticles of ZrO2 with 2 and 10 mol% EuO1.5 up to 20 nm size were prepared by the method of hydrothermal synthesis for luminescent functionalization of the polymer–inorganic nanocomposites based on poly(methyl methacrylate). Surface modification of oxide nanoparticles was carried out by 3‐(trimethoxysilyl)propyl methacrylate, dimethoxymethylvinyl silane and 2‐hydroxyethyl methacrylate to provide uniform distribution and to prevent agglomeration of nanosized filler in the polymer matrix. Polymer–inorganic composites were synthesized by in situ free radical polymerization in bulk. Structuring of ZrO2‐EuO1.5 nanoparticles in the poly(methyl methacrylate) was studied by very‐small‐angle neutron scattering. According to the results, the dependence of photoluminescent properties of ZrO2‐EuO1.5 nanoparticles on the content of lanthanide, the symmetry of the crystal field, surface treatment and the polymer matrix were established. A correlation was shown between Stark splitting in luminescence spectra of ZrO2‐EuO1.5 nanoparticles and their phase composition. Using MMT‐assay it was shown that composites based on poly(methyl methacrylate) and ZrO2‐EuO1.5 nanoparticles do not have cytotoxic properties, which makes it possible to use them as prosthesis materials with contrasted and luminescent imaging properties

Domain Structure, Thermal and Mechanical Properties of Polycaprolactone-Based Multiblock Polyurethane-Ureas under Control of Hard and Soft Segment Lengths

A series of multiblock polyurethane-ureas (PUU) based on polycaprolactone diol (PCL) with a molecular mass of 530 or 2000 g/mol, as well as hard segments of different lengths and structures, were synthesized by the step-growth polymerization method. The chemical structure of the synthesized multiblock copolymers was confirmed by IR- and NMR-spectroscopy. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were used to determine the relaxation and phase transition temperatures for the entire series of the obtained PUU. The X-ray diffraction (XRD) method made it possible to identify PUU compositions in which the crystallizability of soft segments (SS) is manifested due to their sufficient length for self-organization and structuring. Visualization of the crystal structure and disordering of the stacking of SS with an increase in their molecular mobility during heating are shown using optical microscopy. The change in the size of the hard phase domains and the value of the interdomain distance depending on the PCL molecular mass, as well as the length and structure of the hard block in the synthesized PUU, were analyzed using small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS). The evolution of the domain structure upon passing through the melting and crystallization temperatures of PUU soft blocks was studied using SANS. The studies carried out made it possible to reveal the main correlations between the chemical structure of the synthesized PUU and their supramolecular organization as well as thermal and mechanical properties