Zbigniew Rozynek

Electrorheological properties of organically modified nanolayered laponite: influence of intercalation, adsorption and wettability

Cetyltrimethylammonium bromide (CTAB) modified synthetic laponite is synthesized by an ion exchange method and characterized by simultaneous small-angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive spectrometry (EDS), atomic force microscopy (AFM), thermal analysis and rheometry. Through the formation of the organoclay, the properties of clay change from hydrophilic to hydrophobic. Morphology results show that the hydrophilic particles are aggregating easily, whereas the suitable CTAB modified laponite can get near monodispersed nanoparticles due to its hydrophobic properties. It is proposed that CTAB is intercalated and adsorbed onto the laponite partially depending on the substituted concentration of the surfactant cation exchange capacity (CEC) (0.5CEC to 6CEC). The electrorheological (ER) effect is investigated for suspensions of CTAB modified laponite dispersed in silicone oil. The two-dimensional SAXS images from ER bundles of CTAB modified laponite exhibit markedly anisotropic SAXS patterns, giving a measure for laponite particle alignment within the ER structure. An optimum electrorheological effect can be attained at a particular CEC substituted concentration. On the basis of the structure analysis and dielectric measurements, we attribute the enhancement of ER activity to the improvement in the dielectric properties that showed an increase in the dielectric constant and the dielectric loss at low frequency and their regular optimum change with CTAB modification.

Minute synthesis of extremely stable gold nanoparticles

We describe a rapid environmentally friendly wet-chemical approach to synthesize extremely stable non-toxic, biocompatible, water-soluble monodispersed gold nanoparticles (AuNPs) in one step at room temperature. The particles have been successfully achieved in just a few minutes by merely adding sodium hydroxide (NaOH) acting as an initiator for the reduction of HAuCl(4) in aqueous solution in the presence of polyvinylpyrrolidone (PVP) without the use of any reducing agent. It is also proved to be highly efficient for the preparation of AuNPs with controllable sizes. The AuNPs show remarkable stability in water media with high concentrations of salt, various buffer solutions and physiological conditions in biotechnology and biomedicine. Moreover, the AuNPs are also non-toxic at high concentration (100 microM). Therefore, it provides great opportunities to use these AuNPs for biotechnology and biomedicine. This new approach also involved several green chemistry concepts, such as the selection of environmentally benign reagents and solvents, without energy consumption, and less reaction time.

Active structuring of colloidal armour on liquid drops

Adsorption and assembly of colloidal particles at the surface of liquid droplets are at the base of particle-stabilized emulsions and templating. Here we report that electrohydrodynamic and electro-rheological effects in leaky-dielectric liquid drops can be used to structure and dynamically control colloidal particle assemblies at drop surfaces, including electric-field-assisted convective assembly of jammed colloidal ‘ribbons’, electro-rheological colloidal chains confined to a two-dimensional surface and spinning colloidal domains on that surface. In addition, we demonstrate the size control of ‘pupil’-like openings in colloidal shells. We anticipate that electric field manipulation of colloids in leaky dielectrics can lead to new routes of colloidosome assembly and design for ‘smart armoured’ droplets.

Electroformation of Janus and patchy capsules

Janus and patchy particles have designed heterogeneous surfaces that consist of two or several patches with different materials properties. These particles are emerging as building blocks for a new class of soft matter and functional materials. Here we introduce a route for forming heterogeneous capsules by producing highly ordered jammed colloidal shells of various shapes with domains of controlled size and composition. These structures combine the functionalities offered by Janus or patchy particles, and those given by permeable shells such as colloidosomes. The simple assembly route involves the synergetic action of electro-hydrodynamic flow and electro-coalescence. We demonstrate that the method is robust and straightforwardly extendable to production of multi-patchy capsules. This forms a starting point for producing patchy colloidosomes with domains of anisotropic chemical surface properties, permeability or mixed liquid–solid phase domains, which could be exploited to produce functional emulsions, light and hollow supra-colloidosome structures, or scaffolds.

Structuring from nanoparticles in oil-based ferrofluids

Abstract.The effect of magnetic field on the structure formation in an oil-based magnetic fluid with various concentrations of magnetite particles was studied. The evaluation of the experimental data obtained from small-angle X-ray scattering and ultrasonic attenuation indicates the formation of chain-like aggregates composed of magnetite particles. The experimental data obtained from ultrasonic spectroscopy fit well with the recent theoretical model by Shliomis, Mond and Morozov but only for a diluted magnetic fluid. In this model it is assumed that a dimer is the main building block of a B -field-induced chain-like structure, thus the estimation of the nematic order parameter does not depend on the actual length of the structure. The scattering method used reveals information about the aggregated structure size and relative changes in the degree of anisotropy in qualitative terms. The coupling constant

Guided self-assembly of nanostructured titanium oxide

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Dipolar structuring of organically modified fluorohectorite clay particles

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Oxygen-Controlled Phase Segregation in Poly(N‑isopropylacrylamide)/Laponite Nanocomposite Hydrogels

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Assembly and Rearrangement of Particles Confined at a Surface of a Droplet, and Intruder Motion in Electro-Shaken Particle Films

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Dynamic column formation in Na-FLHC clay particles: Wide angle X-ray scattering and rheological studies

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