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

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

Characteristics of 2.45 GHz Surface-Wave-Sustained Argon Discharge for Bio-Medical Applications

Cold atmospheric plasma (CAP) applications in various fields, such as biology, medicine and agriculture, have significantly grown during recent years. Many new types of plasma sources operating at atmospheric pressure in open air were developed. In order to use such plasmas for the treatment of biological systems, plasma properties should fulfil strong requirements. One of the most important is the prevention from heating damage. That is why in many cases, the post-discharge region is used for treatment, but the short living particles in the active discharge zone and reactions with them are missed in that case. We use the active region of surface-wave-sustained argon plasma for biological systems treatment. The previous investigations showed good bactericidal, virucidal, seeds germination and decontamination effects at a short treatment time, but the discharge conditions for bio-medical applications need specific adjustment. A detailed theoretical and experimental investigation of the plasma characteristics and their possible optimization in order to meet the requirements for bio-medical applications are presented in this paper. The length of the plasma torch, the temperature at the treatment sample position and the microwave radiation there are estimated and optimized by the appropriate choice of discharge tube size, argon flow rate and microwave power

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

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

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

Effect of Nanodiamond Particles Incorporation in Hydroxyapatite Coatings

Nanodiamond particles (ND, 4-6 nm in size) were added to a simulated body fluid (SBF) and electrodeposition (ED) at biological conditions (370C, pH 7.4) was performed on Ti surfaces. The novelty in this work was the addition of the ND particles to the SBF solution used as the electrolyte for the ED of biomimetic HA. The results from Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), coupled with energy dispersive X-ray (EDX) spectroscopy revealed that the Ti surface was covered by white, dense and homogeneous HA layer. X-ray photoelectron spectra (XPS) confirmed the formation of calcium phosphate, calcium carbonate, calcium oxide and hydrated surface layer. The ND particles incorporation yielded increased Vickers hardness of the HA. No cracks were observed in the SEM images of the HA-ND layer, which testifies for its ductility and good residual stress