In situ static and dynamic light scattering and scanning electron microscopy study on the crystallization of the dense zinc imidazolate framework ZIF-zni

The kinetics and mechanism of crystallization of the dense zinc imidazolate framework with zni topology, from comparatively dilute methanol solutions containing Zn(NO3)·6H2O and imidazole with variation of the zinc-to-imidazole ratio, were followed in situ by time-resolved static and dynamic light scattering. The light scattering data revealed that metastable primary particles of about 100 nm in diameter form rapidly upon mixing the component solutions. After a lag time that is dependent on the imidazole concentration, the primary particles aggregate into secondary particles by a monomer addition mechanism with the primary particles as the monomers. Complementary scanning electron microscopy revealed that further evolution of the secondary particles is a complex process involving polycrystalline intermediates, the non-spherical morphologies of which depend on the initial zinc-to-imidazole ratio. Time and location of the first appearance of crystalline order could so far not be established. The pure-phase ZIF-zni crystals obtained after 240 min are twins. The aspect ratio of the tetragonal crystals can be controlled via the zinc-to-imidazole ratio. © 2011 The Owner Societies

The Advantages of Polymer Composites with Detonation Nanodiamond Particles for Medical Applications

ISBN 978-953-307-271-

On the Magnetic Excitation Spectra of High Tc Cu Oxides up to the Energies far above the Resonance Energy

Magnetic excitation spectra c"(q,w) of YBa2Cu3Oy and La214 systems have been studied. For La1.88Sr0.12CuO4, c"(q,w) have been measured up to ~30 meV and existing data have been analyzed up to the energy w~150 meV by using the phenomenological expression of the generalized magnetic susceptibility c(q,w)=c0(q,w)/{1+J(q)c0(q,w)}, where c0(q,w) is the susceptibility of the electrons without the exchange coupling J(q) among them. In the relatively low energy region up to slightly above the resonance energy Er, it has been reported by the authors' group that the expression can explain characteristics of the q- and w-dependence of the spectra of YBa2Cu3Oy (YBCO or YBCOy). Here, it is also pointed out that the expression can reproduce the rotation of four incommensurate peaks of c"(q,w) within the a*-b* plane about (p/a, p/a) {or so-called (p, p)} point by 45 degree, which occurs as w goes to the energy region far above Er from E below Er. For La2-xSrxCuO4 and La2-xBaxCuO4, agreements between the observed results and the calculations are less satisfactory than for YBCO, indicating that we have to take account of the existence of the "stripes" to consistently explain the observed c"(q,w) of La214 system especially near x=1/8.Comment: 14 pages, 5 figure

Photo-assisted preparation of nanocomposites

In dieser Doktorarbeit wird ein nichtwässriger, organometallischer Weg zu den Nanokompositen $\underline {Cu@TiO2}$ und $\underline {Cu@ZnO}$ vorgestellt. Die photoassistierten Ablagerungen von Cu auf mit Ölsäure stabilisierten TiO$_{2}$ Nanostäbchen, und auf monodispersen ZnO Nanopartikeln ($\varnothing$ = 3,5 nm), bedeckt mit HDA, wurden mithilfe von [Cu(OCH(CH$_{3}$)CH$_{2}$N(CH$_{3}$)$_{2}$)$_{2}$] durchgeführt. Der Kupfer Precursor durchdringt die organische Schale und wird direkt auf der Halbleiteroberfläche zu Cu$^{0}$ reduziert. Die Nanokomposite zeigten keine morphologischen Änderungen des Trägers und waren weiterhin in unpolaren, organischen Lösungsmitteln dispergierbar. Die Kolloide wurden mit UV-VIS, XRD, DLS, AAS, Fluoreszenzspektroskopie, EDX und HRTEM charakterisiert. FTIR Gas Adsorptionsuntersuchungen bewiesen das Vorhandensein von Cu$^{0}$, das auf der Oxidoberfläche verankert ist. Zudem wird die Konvertierung von CO$_{2}$-Molekülen auf der ZnO Oberfläche zu einer Karbonatspezies präsentiert.A non-aqueous, organometallic route to nanocomposite Cu@TiO2 and $\underline {Cu@ZnO}$ materials is presented. TiO$_{2}$ nanorods, stabilized with oleic acid and HDA capped, monodispersed, ZnO nanoparticles with a diameter of 3,5 nm were used as support for the photo-assisted deposition of Cu using [Cu(OCH(CH$_{3}$)CH$_{2}$N(CH$_{3}$)$_{2}$)$_{2}$]. The copper precursor penetrates through the organic shell at the nanoparticulate oxide surface and is photo reduced to deposit Cu$^{0}$ directly onto the semiconductor surface. The obtained Cu decorated nanocomposites were still soluble in nonpolar organic solvents without change of the morphology of carrier. The colloids were characterized by means of UV-VIS, XRD, DLS, AAS, Fluorescence spectroscopy, EDX and HRTEM. FTIR gas adsorption studies provided evidence for Cu$^{0}$ anchored at the titania surface. The facile penetration of CO$_{2}$ molecules through the organic shell of ZnO nanoparticles and their subsequent conversion to a CO$_{3}$$^{2-}$ species at the oxide surface is also presented

Protein adsorption on detonation nanodiamond/polymer composite layers

Composite layers of the detonation nanodiamond/polymer type possess a spatial organization of components with new structural features and physical properties, as well as complex functions due to the strong synergistic effects between the nanoparticles and polymer [1]. Composite layers were deposited by a plasma polymerization (PP) process of the detonation nanodiamond (DND) particles added to a hexamethyl disiloxan (HMDS) monomer [1]. The incorporation of silver ions in the polymer leads to the production of materials that are highly efficient against bacterial colonization and allows better cell adhesion and spreading. [2] For cell culture processes, fibronectin (FN) treatment is one of the commonly used approaches to enhance the cell adhesion on a surface [3]. As an integrated part of our search for improved materials for life science applications such as biomaterials and biosensors, the objective of the present study is to investigate the interaction of Ag-based composite surfaces with FN protein. Two types of composite layers, Ag-ND/PPHMDS and Ag-nano/PPHMDS were obtained by plasma polymerization of HMDS and nanoparticles of Ag and Ag-DND. The composite layers are representative of the different incorporation of the Ag in the polymer net. The structures studied, consisting of composite layers with adsorbed FN were optically characterized with Ellipsometry, Fourier Transform Infrared (FTIR) and Ultra Violet (UV) Spectroscopy as well as by stylus profiling (Talysurf). The kinetic study of the FN adsorption indicates that the process depends on the FN concentration and the exposure time as well as on the surface chemistry of the composites. Compared to the reference sample, all composite layers exhibit an indication of a stronger ability to initiate the intrinsic pathway of coagulation. © 2012 Materials Research Society

Petrografske, mineraloške i kemijske karakteristike boksita iz ležišta u Posušju, Bosna i Hercegovina – AGEMERA projekt istraživanja

The exploitation of bauxite in the wider area of Posušje in Bosnia and Herzegovina has been known since the first half of the 20th century, and to date more than 1100 deposits or occurrences of various sizes and structures have been discovered. Bauxite deposits of Posušje represent typical karst bauxites, formed during the emersion phase between Upper Cretaceous rudist limestones in the footwall and various carbonate and clastic rocks of Paleocene/ Eocene and Oligocene ages in the hanging wall. The most intensive mineralogical and geochemical bauxite research in these areas was carried out during the 70s and 80s. Afterwards, despite numerous newly discovered deposits, no petrographic, mineralogical and geochemical analysis on the bauxites has been published. The present study is focused on recently discovered bauxite deposits in Posušje and their petrographic and mineralogical description. The bauxites show ooidic to pelitomorphic, but in places also clastic textures. Micro-ooids and spheroids are mostly smaller than 0.1 mm, and in places fragments of the former ooid can be found. In some bauxites, pebbles of resedimented bauxite prevail, mostly larger than 2 mm but sometimes larger than 1 cm, which define their conglomerate texture. Gibbsite and boehmite are the main Al-bearing minerals of the bauxites, and diaspore has not been observed. The ratio of gibbsite to boehmite varies between deposits, and in some deposits boehmite is the only aluminium phase present. Where present, the gibbsite is developed into relatively large hypidiomorphic crystals larger than 0.25 mm, with clearly defined polysynthetic lamellae. Hematite is the dominant Fe-phase in all deposits. Although rarely, goethite-rich bauxites can be found in the form of isolated layers, with just traces or no hematite. Zircon, apatite and calcite are minor and accessory minerals, and X-ray analysis indicated significant amounts of anatase and rutile. Kaolinite was detected in only one sample. Chemical analyses indicate a negative correlation of Al and Fe content. The Al2O3 content ranges from 53.4 to 63.9 wt.%, and Fe2O3 from 22.5 to 35.2 wt.%. The SiO2 and TiO2 content varies from 1.6 to 5.6 wt.% and 3.5 to 4.6 wt.%, respectively. The chemical composition of the analysed samples defines them as ferrous bauxites. A change in the chemical composition was observed in relation to the footwall distance. The relatively high content of Zn (up to 627 ppm) gradually decreases towards host carbonates of the footwall, and a similar trend is observed in the Fe, Cr and Zr content, while Al, P, Ca and Ti, on the other hand, increase closer to the footwall. Mineralogical, petrological and chemical studies of the recently opened bauxite mines in Posušje revels heterogenic properties and indicate a complex genesis of the deposits, with possibly diverse source material

Selective photo deposition of Cu onto the surface of monodisperse oleic acid capped TiO2 nanorods probed by FT IR CO adsorption studies

A novel, non aqueous, organometallic route to nanocomposite Cu TiO2 materials is presented. TiO2 nanorods stabilized with oleic acid OLA were used as support for the photo assisted deposition of Cu using the organometallic Cu II precursor [Cu OCH CH3 CH2N CH3 2 2] 1 . The copper precursor 1 penetrates through the shell of OLA and is photo reduced to deposit Cu0 directly at the surface of the TiO2 rods. The obtained Cu decorated nanorods were still soluble in nonpolar organic solvents without change of the morphology of nanorods. The Cu TiO2 colloid was characterized by means of UV VIS, XRD, AAS, and HRTEM. CO adsorption FTIR studies give evidence for Cu0 anchored at the titania surface by a characteristic absorption at 2080 cm 1. Comparative studies of Cu deposition were done using a CuCl2 as simple Cu source which proved, that the concept of organometallic disguise of the metal centre results in a higher reaction rate and the circumvention of non selective reduction, parasitic side reactions and undesired agglomeration of the OLA stabilized titania nanorod

Petrografske, mineraloške i kemijske karakteristike boksita iz ležišta u Posušju, Bosna i Hercegovina – AGEMERA projekt istraživanja

The exploitation of bauxite in the wider area of Posušje in Bosnia and Herzegovina has been known since the first half of the 20th century, and to date more than 1100 deposits or occurrences of various sizes and structures have been discovered. Bauxite deposits of Posušje represent typical karst bauxites, formed during the emersion phase between Upper Cretaceous rudist limestones in the footwall and various carbonate and clastic rocks of Paleocene/ Eocene and Oligocene ages in the hanging wall. The most intensive mineralogical and geochemical bauxite research in these areas was carried out during the 70s and 80s. Afterwards, despite numerous newly discovered deposits, no petrographic, mineralogical and geochemical analysis on the bauxites has been published. The present study is focused on recently discovered bauxite deposits in Posušje and their petrographic and mineralogical description. The bauxites show ooidic to pelitomorphic, but in places also clastic textures. Micro-ooids and spheroids are mostly smaller than 0.1 mm, and in places fragments of the former ooid can be found. In some bauxites, pebbles of resedimented bauxite prevail, mostly larger than 2 mm but sometimes larger than 1 cm, which define their conglomerate texture. Gibbsite and boehmite are the main Al-bearing minerals of the bauxites, and diaspore has not been observed. The ratio of gibbsite to boehmite varies between deposits, and in some deposits boehmite is the only aluminium phase present. Where present, the gibbsite is developed into relatively large hypidiomorphic crystals larger than 0.25 mm, with clearly defined polysynthetic lamellae. Hematite is the dominant Fe-phase in all deposits. Although rarely, goethite-rich bauxites can be found in the form of isolated layers, with just traces or no hematite. Zircon, apatite and calcite are minor and accessory minerals, and X-ray analysis indicated significant amounts of anatase and rutile. Kaolinite was detected in only one sample. Chemical analyses indicate a negative correlation of Al and Fe content. The Al2O3 content ranges from 53.4 to 63.9 wt.%, and Fe2O3 from 22.5 to 35.2 wt.%. The SiO2 and TiO2 content varies from 1.6 to 5.6 wt.% and 3.5 to 4.6 wt.%, respectively. The chemical composition of the analysed samples defines them as ferrous bauxites. A change in the chemical composition was observed in relation to the footwall distance. The relatively high content of Zn (up to 627 ppm) gradually decreases towards host carbonates of the footwall, and a similar trend is observed in the Fe, Cr and Zr content, while Al, P, Ca and Ti, on the other hand, increase closer to the footwall. Mineralogical, petrological and chemical studies of the recently opened bauxite mines in Posušje revels heterogenic properties and indicate a complex genesis of the deposits, with possibly diverse source material

Zeolitic imidazolate framework-71 nanocrystals and a novel SOD-type polymorph: solution mediated phase transformations, phase selection via coordination modulation and a density functional theory derived energy landscape

We report a rapid additive-free synthesis of nanocrystals (NCs) of RHO-type ZIF-71 (1) of composition [Zn(dcim)₂] (dcim = 4,5-dichloroimidazolate) in 1-propanol as solvent at room temperature. NC-1 has a size of 30–60 nm and exhibits permanent microporosity with a surface area (SBET = 970 m² g−¹) comparable to that of microcrystalline material. When kept under the mother solution NC-1 undergoes transformation into a novel SOD-type polymorph (2), which in turn converts into known ZIF-72 (3) with lcs topology. It is shown that microcrystals (MCs) of 2 can be favourably synthesised using 1-methylimidazole as a coordination modulator. NC-2 with size <200 nm was prepared using NC-ZIF-8 as a template with SOD topology in a solvent assisted ligand exchange-related process. DFT-assisted Rietveld analysis of powder XRD data revealed that novel polymorph 2 possesses an unusual SOD framework conformation. 2 was further characterised with regard to microporosity (SBET = 597 m² g−¹) and thermal as well as chemical stability. DFT calculations were performed to search for further potentially existing but not-yet synthesised polymorphs in the [Zn(dcim)₂] system