Reverse hydrotropy by complex formation

Alkylated azacrown ethers lower significantly interfacial tension and are capable of solubilising water-soluble dyes, despite not being able to aggregate in non-polar solvents.</p

Identifying the location of Cu ions in nanostructured SAPO 5 molecular sieves and its impact on the redox properties

Combining X ray Absorption Fine Spectroscopy XAFS with Anomalous Small Angle X ray Scattering ASAXS determines the location of Cu2 ions in silicoaluminophosphate SAPO 5 frameworks prepared by hydrothermal crystallization or impregnation. As expected, for the hydrothermally prepared sample, incorporation in the SAPO 5 framework was observed. For the first time preferential location of Cu2 ions at the inner and outer surfaces of the framework is determined. Temperature Programmed Reduction TPR and X ray Photoelectron Spectroscopy XPS investigations demonstrated that such Cu2 is stable in an argon Ar atmosphere up to 550 C and can only be reduced under a hydrogen atmosphere. In contrast, Cu2 deposited by impregnation on the pure SAPO 5 framework can be easily reduced to Cu in an Ar atmosphere. At lower Cu amounts, mononuclear tetrahedrally coordinated Cu species were formed which are relatively stable in the monovalent form. In contrast, at higher Cu amounts, CuO particles were found which change easily between the mono and bivalent specie

Crystallization of BaF2 from droplets of phase separated glass evidence of a core shell structure by ASAXS

Crystallization of BaF2 from droplets of phase separated glass evidence of a core shell structure by ASAXS Armin Hoell, Vikram Singh Raghuwanshi, Christian Bocker, Andreas Herrmann, Christian Rüssel and Thomas Höche Glasses with the mol compositions 1.88 Na2O 15.04 K2O 7.52 Al2O3 69.56 SiO2 6.00 BaF2 and 1.88 Na2O 15.03 K2O 7.52 Al2O3 69.52 SiO2 6.00 BaF2 0.05 SmF3 were studied using X ray diffraction, transmission electron microscopy, and anomalous small angle X ray scattering ASAXS . While the glass doped with samarium showed liquid liquid phase separation of droplets with sizes of around 100 nm, the glass without samarium did not. The samples were annealed at 580 C or at 600 C which led to the crystallization of cubic BaF2. The X ray diffraction patterns showed strongly broadened lines. Hence, the BaF2 crystals possess sizes in the nm range. ASAXS gave evidence of a core shell structure. In agreement with earlier studies, it is assumed that the shell acts as a diffusion barrier that hinders crystal growth. Surprisingly, the cores and shells from the crystallization of the homogeneous glass and from the second glass, which is Sm doped and shows liquid liquid phase separation, both possess similar dimensions, even though the origin of the barrier is very different. The doped samples show long luminescence lifetimes of nearly 5 ms at a wavelength of 600 nm, which is nearly as long as those in fluoride phosphate glasse

Structural analysis of Fe Mn O nanoparticles in glass ceramics by small angle scattering

Magnetic nanocrystals containing Fe and Mn were obtained by annealing of silicate glasses with the composition 13.6Na2O 62.9SiO2 8.5MnO 15.0Fe2O3 x mol at 580 C for different periods of time. Here, we present Small Angle Neutron Scattering using Polarized neutrons SANSPOL and Anomalous Small Angle X ray Scattering ASAXS investigation on these glass ceramic samples. Analysis of scattering data from both methods reveals the formation of spherical core shell type of nanoparticles with mean sizes between 10nm and 100 nm. ASAXS investigation shows the particles have higher concentration of iron atoms and the shell like region surrounding the particles is enriched in SiO2. SANSPOL investigation shows the particles are found to be magnetic and are surrounded by a nonmagnetic shell like region

Crystallization of ZrTiO4 Nanocrystals in Lithium Alumino Silicate Glass Ceramics Anomalous Small Angle X amp; 8209;ray Scattering Investigation

We report on anomalous small angle X ray scattering ASAXS investigations of the formation and structure of nanosized ZrTiO4 crystals in lithium aluminosilicate LAS glass during heat treatment at 750 C for different periods of time. For a sample annealed for 30 min, ASAXS measurements near the X ray absorption edge of Ti and Zr reveal the formation of particles ZrTiO4 surrounded by a shell like region. The sample annealed for 240 min shows the formation of two different types of particles spherical core amp; 8722;shell ZrTiO4 and large spherical particles LiAlSi2O6 . Additionally, ASAXS results allow quantitative determination of the average composition and volume fraction of the nanocrystals, the surrounding region shell , and the remaining glass matrix. Data analysis reveals the formation of an alumina enriched region around ZrTiO4. This alumina enriched layer makes the glass network rigid and hinders further growth of ZrTiO4 nanoparticles. For a prolonged annealing time 240 min , a new phase LiAlSi2O6 is formed additionally, and the Al Si ratio in the shell surrounding the ZrTiO4 crystals decreases. Moreover, the unannealed sample also shows the formation of a Ti enriched phase during cooling of the samples. The obtained quantitative information helps to understand the crystallization and growth mechanisms of ZrTiO4 nanocrystals in LAS glass ceramic

Experimental evidence of a diffusion barrier around BaF2 nanocrystals in a silicate glass system by ASAXS

Nanocrystals of BaF2 precipitate during controlled annealing of silicate glasses composed of SiO2, Al2O3, K2O, Na2O, BaF2 and BaO. Structural characteristics such as size, shape, volume fraction and size distribution of nanoparticles in the glass matrix were studied by anomalous small angle x ray scattering ASAXS . Fitted ASAXS curves near the Ba absorption edge reveal the formation of a core shell structure. Furthermore, ASAXS results allowed to determine quantitatively the composition of the nanocrystals, the surrounding region shell and the matrix. The evaluated composition gives evidence for an enrichment of Si atoms in a shell, that surrounds the particles and acts as a diffusion barrier. Resonant curve analysis reveals the quantitative information of the Ba atoms used in the formation of BaF2 nanoparticle

Self assembly of gold nanoparticles on deep eutectic solvent DES surfaces

Self assembly of gold nanoparticles was obtained by sputter deposition on DES. SAXS and TEM investigations reveal the formation of spherical nanoparticles with a mean diameter of 5 0.5 nm. For extended sputtering times, the number density of AuNPs increases linearly and a very pronounced 1st and 2nd shell ordering is observe

Deep Eutectic Solvents for the Self Assembly of Gold Nanoparticles A SAXS, UV Vis, and TEM Investigation

In this work, we report the formation and growth mechanisms of gold nanoparticles AuNPs in eco friendly deep eutectic solvents DES; choline chloride and urea . AuNPs are synthesized on the DES surface via a low energy sputter deposition method. Detailed small angle X ray scattering SAXS , UV amp; 8722;Vis, and cryogenic transmission electron microscopy cryo TEM investigations show the formation of AuNPs of 5 nm diameter. Data analysis reveals that for a prolonged gold sputtering time there is no change in the size of the particles. Only the concentration of AuNPs increases linearly in time. More surprisingly, the self assembly of AuNPs into a first and second shell ordered system is observed directly by in situ SAXS for prolonged gold sputtering times. The self assembly mechanism is explained by the templating nature of DES combined with the equilibrium between specific physical interaction forces between the AuNPs. A disulfide based stabilizer, bis 2 mercaptoethyl trimethylammonium disulfide dichloride, was applied to suppress the self assembly. Moreover, the stabilizer even reverses the self assembled or agglomerated AuNPs back to stable 5 nm individual particles as directly evidenced by UV amp; 8722;Vis. The template behavior of DES is compared to that of nontemplating solvent castor oil. Our results will also pave the way to understand and control the selfassembly of metallic and bimetallic nanoparticle