Nanoheterogeneous Structure Research Articles

Nanoheterogeneity in Protic and Aprotic Alkylimidazolium Bistriflimide Ionic Liquids

Many ionic liquids, including alkylimidazolium salts, form a nanoheterogeneous structure with polar and apolar domains in their liquid phase. Using molecular dynamics simulations, the influence of the structure of the cations of a series of aprotic ([CnC1Im][TFSI], [CnCnIm][TFSI]) and protic ([HCnIm][TFSI]) alkylimidazolium bistrilimides on the domain structure of their liquid phase was studied. The characteristic sizes of domains and the extent of domain segregation in different liquids have been compared. It has been shown that the latter, but not the former, is a key factor determining the magnitude of the Gibbs free energy of cavity formation in nanostructured ionic liquids, which in turn governs their solvation properties.

Thermodynamic regulation over nano-heterogeneous structure of electrolyte solution to improve stability of flow batteries

The microstructure of the electrolyte solution determines the performance and stability of a flow battery. Herein, the effect of the concentration and redox state of a bipyridinium derivative (12+) on the microstructure is investigated. First, molecular dynamics simulation reveals that the 12+ stays discrete, and the singly-reduced monoradical (1•+) tends to aggregate and yields a nano-heterogeneous structure (NHS). Second, the introduction of tetrabutylammonium chloride (TBAC) can regulate the NHS by generating cage-like nanoreactors in solution, which can spatially confine the 1•+ against its aggregation and the consequent side reaction. As a result, the battery cyclability shows that the capacity decay rate of 0.50 M electrolyte is 0.080% per cycle and drops to 0.016% per cycle upon adding 1.0 M TBAC. This work provides a thermodynamic strategy to regulate the microstructure of the electrolyte solution and improve the stability of a flow battery from an engineering point of view.

Ecotoxicity Study of New Composite Materials Based on Epoxy Matrix DER-331 Filled with Biocides Used for Industrial Applications.

The impact of fillers in the epoxy oligomer on the test culture of the marine ecosystem was investigated. The content of additive—biocides—was selected based on the complex research using STAT-GRAPHICS® Centurion XVI. The ecotoxicity of composite surfaces was determined in model systems using methods which are standard in eco-microbiology. The microorganism was identified by studying morphological, cultural, biochemical, and antigenic properties. Studies of the structure and the microrelief of the surfaces of composite materials were conducted using scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy. Based on comprehensive research, it was established that the composition of oxytetracycline with content of q = 1.5 wt% and nanosilver with a content of q = 0.075 wt% per 100 wt% of the DER-331 oligomer and 10 parts by the mass of the TETA hardener ensures the formation of a porous nano-heterogeneous structure of the coating, which leads to the acceleration of the release of silver ions from the surface of the polymer. The rational content of the complex additives of biocides ensures adhesion to the cell wall of bacteria with subsequent penetration into it and subsequent change to the cell membrane, its death, and, therefore, the suppression of the fouling process of metal structures.

The coloration of smalt produced at Ust-Ruditsa glass factory from 1753 to 1768

The Ust-Ruditsa glass factory, founded in 1753 by the Russian scientist Mikhail Lomonosov has produced a variety of smalt glasses for mosaics and bijouterie. Lomonosov, which was the glass-technologist of the factory, by using a limited number of glass colorants elaborated the glass receipts with the aim to obtain colored glasses. At that site several hundred colored glasses were prepared, investigated and employed. We report and discuss here the use of copper as colorant in the preparation of glasses having the same composition of selected Ust-Ruditsa glasses. A series of K2O-PbO-SiO2 glasses (KPS) doped with copper 9.5K2O·xPbO·(90-x)SiO2·0.5CuO (x = 10.1, 19.0, 27.0, 38.0, 47.3, 52.1, 56.8, 61.4 % in mass) has been prepared by melt-quenching technique. The Brillouin and Rayleigh scattering was measured with a 532 nm laser by using the calculated glasses refraction indexes. We found that the color changes due to the bathochromic shift of charge transfer band with increasing lead concentration. The copper center coordination environment is always a distorted octahedron. Upon reduction of copper by carbon the melt glass changes to an opaque orange smalt coloration due to the presence of Cu2O dendrimers. The calculation of Landau-Placzek ratio shows a non-monotonic change with increasing lead concentration. The nano-heterogeneous structure of glasses, characterized by an elevated Landau-Placzek ratio, is confirmed by TEM.

Novel nano heterogeneous structure hydrogels with mechanically robust, extensive stretching and highly swelling

Stimuli-responsive hydrogels that can change their properties as a result of external stimuli have shown great promise in various applications, but it is still a great challenge to simultaneously provide hydrogels with excellent mechanical properties and significant response. Herein, we propose a facile synthesis of smart PAAm based hydrogels with highly elastic and swellable by introducing the activated nanoparticles into the hydrogel networks. Due to the heterogeneous microporous structure of the hydrogels, this material demonstrates the highly elastic property to withstand slicing and high level of compression and deformations, as well as significant swelling ratio (~5500%). Moreover, photonic hydrogel elastomers are fabricated by incorporating monodispersed SiO2@PS microspheres within this hydrogel elastomer matrix. The as formed materials possess structural color and the highly elasticity enables their good mechanochromic capability. Our strategy is a straightforward way to design smart hydrogels whose response and mechanical properties can be tuned through the judicious choice of the polymerization time and content of activated nanogel, extending the potential application of hydrogels.

Thermal activation of Pd/CeO2-SnO2 catalysts for low-temperature CO oxidation

In this work, the counter precipitation method was used to synthesise Pd/CeO2-SnO2 catalysts, which possess excellent low-temperature activity and high thermal stability. It was revealed that calcination of Pd/CeO2-SnO2 catalysts at 800−1000 °C induces significant growth of catalytic activity in CO oxidation at T<150 °C. This effect of thermal activation for Pd/CeO2-SnO2 catalysts was enhanced when water was admitted to the reaction mixture. In the presence of water the T50 value for the Pd/CeO2-SnO2 catalyst calcined at 900 °C becomes 45 °C lower than for the Pd/CeO2 catalyst. It was found that calcination of the catalysts at T<600 °C leads to the formation of solid solutions based on the fluorite and rutile structures. As the calcination temperature is raised above 600 °C, the solid solutions decompose with formation of catalytically active PdxCe1-xO2-δdispersed phase on the surface of SnO2 nanoparticles. The formed nanoheterogeneous structure provides both high thermal stability and high water resistance of Pd/CeO2-SnO2 catalysts.

Structure of glasses and composites in As&lt;sub&gt;2&lt;/sub&gt;S&lt;sub&gt;3&lt;/sub&gt;–Sb&lt;sub&gt;2&lt;/sub&gt;S&lt;sub&gt;3&lt;/sub&gt;–SbI&lt;sub&gt;3&lt;/sub&gt; system

Purpose. Composites on the basis x (As 2 S 3 ) y (Sb 2 S 3 ) z (SbI 3 ) glasses are suitable for creation of ferroelectric glassceramics, nonlinear dielectrics, memory media, elements for infrared and nonlinear optics, various sensors. This paper presents the results of thermal, X-ray diffraction and Raman studies of the conditions of formation and nature of crystalline inclusions in the glass matrix of the As 2 S 3 -Sb 2 S 3 -SbI 3 system during their thermal treatment. Methods. Differential thermal analysis (DTA), Raman and X-Ray diffraction spectroscopy. DTA curves were carried out in the temperature interval of 293–700 K. Heating rate was equal 3 K/min. Results. Danoheterogenous structure of glasses in As 2 S 3 -Sb 2 S 3 -SbI 3 system established on the basis of Raman spectra investigations. Their structural network is formed by only binary structural groups with heteropolar bonds (AsS 3/2 , SbS 3/2 , SbI 3 , AsI 3 ) and contains a certain amount molecular fragments with homopolar As-As and S-S bonds (As 4 S 4 , S 8 ). It has been established that the crystallization of glasses takes place in several stages. DTA curves of glasses recorded at 3 K/min revealed three exothermic effects. For example, for 40(As 2 S 3 )30(Sb 2 S 3 )30(SbI 3 ) glass temperatures maxima of these effects are equal 341, 398 and 530 K. The first and second effects are less pronounced due to nucleus formation and the formation of nanocrystals in glass matrix. The structure of the phase that arises in the glass matrix at annealing (348 and 398 K) corresponds to the structure of the crystalline SbSI. The formation of triple units SbS 2/2 I occurs as a result of the glass structural relaxation during its softening, which is accompanied by breaking and switching of homopolar and heteropolar chemical bonds in the binary groups that form the structural network of glasses. This process is accompanied by the diffusion of atoms in a distances of interatomic order. The sizes of antimony sulfoiodsde crystalline inclusions increase with annealing temperature and annealing time. The matrixes of the annealed As 2 S 3 -Sb 2 S 3 -SbI 3 system glasses, in which crystalline SbSI inclusions of different dimensions are formed, are determined mainly by As 4 S 4 structural groups linked together by fragments of chains or rings of sulfur atoms. Conclusions. DTA curves, X–ray powder diffraction patterns and Raman spectra of glasses in As 2 S 3 -Sb 2 S 3 -SbI 3 were investigated. The nanoheterogeneous structure of glasses was established. The crystallization of glasses takes place in several stages. The structure of the phase that arises in the glass matrix at annealing corresponds to the structure of crystalline antimony sulfoiodide. The sizes of SbSI crystalline inclusions are dependent on the heat treatment regimes.

Dynamic and static properties of mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate and alcohols with various alkyl chain lengths

The dynamic and static properties of mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) and alcohols with various alkyl chain lengths were investigated. For alcohol concentrations of 20 mol% or less, where the alcohol/ionic liquid system maintains a nano-heterogeneous structure, the self-diffusion coefficient and the chemical shift of anions and cations in the alcohol/[BMIM][BF4] system were not dependent on the alkyl chain length of the alcohol, but were almost coincident with each other when comparing the same solvent concentration. This indicates that the solution structure of pure [BMIM][BF4] was almost maintained in the alcohol/ionic liquid system. Moreover, alcohol having short alkyl chain length and water moved clearly faster than the IL, but the movement of alcohol having long alkyl chain length moved close to that of the IL suggesting that the alcohols may not be able to move significantly in the IL.

The effect of alkyl ammonium ionic liquids on thermal denaturation aggregation of β-lactoglobulin

Differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), small-angle neutron scattering (SANS) measurements, and scanning and transmission electron microscope (SEM and TEM) of β-lactoglobulin (β-LG) are performed in alkyl (methyl, ethyl, and propyl) ammonium nitrate ionic liquids (RAN-ILs) – water mixtures at 25–100 °C. The addition of these RANs decreased the thermal denaturation temperature of β-LG, and the effect is larger with an increase of the hydrophobic part of the cation of the ILs. In ethyl ammonium nitrate (EAN) and propyl ammonium nitrate (PAN) mixtures, the fractal aggregate structure of β-LG was found after the thermal denaturation occurred. On the other hand, in methyl ammonium nitrate (MAN) mixture, an amorphous aggregate was formed as well as in NaCl and NaNO3 solutions. The difference of the effect between MAN and EAN (and PAN) could arise from the balance of hydrophobic/hydrophilic parts of the cation of RAN. These results are similar to those of alcohol-water mixtures. The nanoheterogeneous structure of the RAN-water mixture which consists of the hydrophobic and hydrophilic parts might affect the aggregation structure of β-LG.

Mechanical heterogeneity in ionic liquids.

Molecular dynamics (MD) simulations of five ionic liquids based on 1-alkyl-3-methylimidazolium cations, [C n C1im]+, have been performed in order to calculate high-frequency elastic moduli and to evaluate heterogeneity of local elastic moduli. The MD simulations of [C n C1im][NO3], n = 2, 4, 6, and 8, assessed the effect of domain segregation when the alkyl chain length increases, and [C8C1im][PF6] assessed the effect of strength of anion-cation interaction. Dispersion curves of excitation energies of longitudinal and transverse acoustic, LA and TA, modes were obtained from time correlation functions of mass currents at different wavevectors. High-frequency sound velocity of LA modes depends on the alkyl chain length, but sound velocity for TA modes does not. High-frequency bulk and shear moduli, K ∞ and G ∞ , depend on the alkyl chain length because of a density effect. Both K ∞ and G ∞ are strongly dependent on the anion. The calculation of local bulk and shear moduli was accomplished by performing bulk and shear deformations of the systems cooled to 0 K. The simulations showed a clear connection between structural and elastic modulus heterogeneities. The development of nano-heterogeneous structure with increasing length of the alkyl chain in [C n C1im][NO3] implies lower values for local bulk and shear moduli in the non-polar domains. The mean value and the standard deviations of distributions of local elastic moduli decrease when [NO3]- is replaced by the less coordinating [PF6]- anion.

Impact of Interfacial Interactions on the Formation of Nanoheterogeneous Structure in Polymer–Polymer Blends

Impact of Interfacial Interactions on the Formation of Nanoheterogeneous Structure in Polymer–Polymer Blends

High Ionic Liquid Concentration-Induced Structural Change of Protein in Aqueous Solution: A Case Study of Lysozyme

The structural change of chicken egg white lysozyme in aqueous 1-butyl-3-methylimidazolium nitrate ([bmim][NO(3)]) solutions (0-24 M) has been investigated by optical spectroscopy and small-angle X-ray scattering (SAXS) methods. Fourier-transform infrared (FTIR) and circular dichroism (CD) spectra and SAXS profiles indicated that the addition of up to 6 M of [bmim][NO(3)] induces unfolding of lysozyme resulting from disruption of the α-helix by the NO(3)(-) ion. On the other hand, even with the addition of more than 10 M of [bmim][NO(3)], lysozyme aggregation is inhibited and the protein adopts a partially globular state (the secondary structure is partially refolded while the tertiary structure is disrupted). Observation of the structural features of the aqueous [bmim][NO(3)] solution by Raman OD stretching spectra indicated that bulk-like water still remains at concentrations above 10 M and form an "aggregated water" (water pool) in the nanoheterogeneous structure consisting of a polar domain (the high charge-density region) and nonpolar areas (the alkyl-chain region) in the IL. At these concentrations (above 10 M), lysozyme is not sufficiently hydrated because of the reduced number of water molecules. Consequently lysozyme above 10 M assumes the partially globular state. We propose that the changes of the unique IL solution structure (nanoheterogeneous) between the lower and higher [bmim][NO(3)] concentrations strongly correlated to the differences in the protein stability of the present results.

Nano-heterogeneous structure of (1-x)KNbO 3–xSiO 2 glasses in the low glass-forming oxide content range 0.05 ≤ x ≤ 0.3

Glasses with a high content of niobium oxide are of significant interest for electro-optics and nonlinear optics. In the present paper we report the results of the investigation of the submicroscopic structure and nonlinear optical properties of (1- x)KNbO 3– xSiO 2 (KNS) glasses (x = 0.05–0.30) by XRD, SANS, electron microscopy and second harmonic generation (SHG) technique. Vitreous samples were fabricated by rapid melt cooling, via pressing the melt by steel plates, quenching between rotating metal rolls or splat cooling in air or nitrogen flow. Glasses with x < 0.15 are shown to possess a micro-inhomogeneous structure with regions enriched by SiO 2. On the contrary, as-quenched glasses with x > 0.15 are found by SANS to be homogeneous, but form nanostructures enriched by SiO 2 after heat-treatment. At temperatures below ~( T g + 50 °C), SiO 2-enriched regions grow slightly, whereas their chemical composition shifts considerably closer to SiO 2. The data on the nano-inhomogeneous structure enables clarifying the complicated T g ( x) dependence of KNS glasses. SHG-active KNbO 3 phase precipitates at later stages of crystallization when the glass starts to lose its transparency, and crystallization of perovskite-like KNbO 3 is accompanied by the enhancement of SHG efficiency by several orders of magnitude.

Formation and structure of crystalline inclusions in As 2S 3–SbSI and As 2Se 3–SbSI systems glass matrices

The main aim of the study presented in this paper is the investigation of the structure of (As 2S 3) 100−x(SbSI) x and (As 2Se 3) 100−x(SbSI) x (0 ≤ × ≤ 40) glasses by Raman spectroscopy and X-ray methods, also the nature of the crystalline inclusions which arise up in their matrix at heat treatment. We have found that in conditions of continuous heating in the interval “glassforming temperature–crystallization temperature” a crystallization with predominant mechanism of stable phase SbSI separation is taking place. The formation mechanism of crystalline inclusions of antimony sulphoiodide in glass matrix is discussed in the light of our results. It was established that all investigated glasses have a nano-heterogeneous structure.

The nanoheterogeneous structure of aqueous solutions of n-propanol

The results of positron spectroscopy and molecular light scattering studies, the data on radiationchemical yields and optical absorption spectra of solvated electrons formed under the action of ionizing radiation, and the data on the concentration dependences of viscosity, adiabatic compressibility, the velocity of sound, and partial molar volume were used to determine the structure of water-n-propanol mixtures. The conclusion was drawn that the insertion of alcohol molecules into water network voids over the range of alcohol mole fractions 0 x2 > 0.9), its molecules combined into nanodrops.

A new Experimental Way to Obtain Information about Glass Nano-Heterogeneous Structure

The heterogeneous character of the glass structure is, from long-time, in the attention of researchers. Some calculation methods for obtaining information concerning the nature and distribution of nano aggregates in glass were published in the middle of the 20th century. The experimental methods borrowed from other fields of chemistry are hardly useful the results are mostly qualitative and their use to select the calculation method giving closer to reality data is practically impossible. For these reasons, a new combined experimental and calculation method was imagined, allowing the obtainment of quantitative data about the concentration and distribution of nano-aggregates in glasses. By means of the method for experimental determination of the basicity of glass, with Cu2+ as probe ion, relationships were deduced allowing obtaining the composition and the amount of each nano-aggregate in glass from the recorded maximum of the charge transfer transition absorption. The results obtained for some silicate glasses, compared with the theoretical calculated data, seem to validate this approaching way. By means of the new experimental method, the direct following of the technological parameters influence on glass structure and properties become possible.

Heterogeneity of glass transition dynamics in polyurethane‐poly(2‐hydroxyethyl methacrylate) semi‐interpenetrating polymer networks

AbstractThe peculiarities of segmental dynamics over the temperature range of −140 to 180 °C were studied in polyurethane‐poly(2‐hydroxyethyl methacrylate) semi‐interpenetrating polymer networks (PU‐PHEMA semi‐IPNs) with two‐phase, nanoheterogeneous structure. The networks were synthesized by the sequential method when the PU network was obtained from poly(oxypropylene glycol) (PPG) and adduct of trimethylolpropane (TMP) and toluylene diisocyanate (TDI), and then swollen with 2‐hydroxyethyl methacrylate monomer with its subsequent photopolymerization. PHEMA content in the semi‐IPNs varied from 10 to 57 wt %. Laser‐interferometric creep rate spectroscopy (CRS), supplemented with differential scanning calorimetry (DSC), was used for discrete dynamic analysis of these IPNs. The effects of anomalous, large broadening of the PHEMA glass transition to higher temperatures in comparison with that of neat PHEMA, despite much lower Tg of the PU constituent, and the pronounced heterogeneity of glass transition dynamics were found in these networks. Up to 3 or 4 overlapping creep rate peaks, characterizing different segmental dynamics modes, have been registered within both PU and PHEMA glass transitions in these semi‐IPNs. On the whole, the united semi‐IPN glass transition ranged virtually from −60 to 160 °C. As proved by IR spectra, some hybridization of the semi‐IPN constituents took place, and therefore the effects observed could be properly interpreted in the framework of the notion of “constrained dynamics.” The peculiar segmental dynamics in the semi‐IPNs studied may help in developing advanced biomedical, damping, and membrane materials based thereon. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 963–975, 2007

A new class of systems exhibiting microphase separation: polymer blends with a nonlocal entropy of mixing

The stability of a binary polymer blend with respect to macro- and microphase separation is considered. It is shown that the loss of stability of the spatially homogeneous state of the blend via microphase separation resulting in formation of an equilibrium microdomain nanoheterogeneous structure is possible. The conditions for this effect are (i) a significant negative entropic contribution to the Flory-Huggins χ parameter, i,e,, an entropic contribution to miscibility, and (ii) the nonlocal character of this contribution with a high value of the nonlocality radius. Both these conditions can be met for miscible polymer blends somewhat above their glass transition temperature. It is argued that the nanoheterogeneity recently observed in polystyrene/poly(vinyl methyl ether) blends can be explained by this effect

Characterization and Processing of CVD Powders for Fabrication of Composite and Compound Ceramics

ABSTRACTTwo-component oxide powders were prepared in the systems Al2O3-ZrO2. Al2O3-TiO2. and Al2O3-SiO2 by a CVD (chemical vapor deposition) technique using a combustion flame for the purpose of fabricating respective composite or compound ceramics. The CVD powders were spherical and ultrafine (av. 30–70 nm) with log-normal size distribution, and exhibited either very homogeneous or nanoheterogeneous structure and crystallographic metastability in phases and solid solutions. By starting from these CVD powders, not only uniform and excellent microstructure was achieved in the sintered products, but also better sinterability and novel microstructure became possible owing to the metastability which reflected the formation mechanism of two-component powders at high temperatures. CVD powders, which were previously considered difficult to sinter, proved to be excellent starting materials for fabrication of composite and compound ceramics when improved processing techniques were applied.