Search results for "emulsion"
showing 10 items of 344 documents
Silanization as a versatile functionalization method for the synthesis of polymer/magnetite hybrid nanoparticles with controlled structure
2016
We compare the use of different trimethoxysilane compounds for the surface functionalization of magnetite nanoparticles and their subsequent incorporation in hybrid particles formed by in situ polymerization. For the encapsulation of inorganic nanoparticles via miniemulsion polymerization, surface functionalization of the inorganic material is necessary to hydrophobize the otherwise hydrophilic inorganic material and to compatibilize it with the polymer. Hydrophobic magnetite nanoparticles are usually prepared by surface functionalization with oleic acid, which leads to effective hydrophobization, but offers only limited control over the structure of the hybrid particles. As an alternative,…
Spin Crossover Phenomenon in Nanocrystals and Nanoparticles of [Fe(3-Fpy)2M(CN)4] (MII = Ni, Pd, Pt) Two-Dimensional Coordination Polymers
2010
The two-dimensional spin crossover (SCO) polymers [Fe(3-Fpy)2M(CN)4] (MII = Ni(1), Pd(2), Pt(3)) were nanostructured in the form of nanocrystals and nanoparticles, and their chemical, structural, and physical characterization was carried out using different experimental methods (powder X-ray diffraction, magnetic susceptibility measurements, Mossbauer and infrared spectroscopy, transmission and scanning electronic microscopy, etc.). Surfactant-free nanocrystals of average dimensions 400 × 400 × 30 nm (1a, 1a*, 2a, 3a) were synthesized from water in oil microemulsions (w/o) while nanoparticles of average size 200 × 100, 100 × 60, and 70 × 30 nm were obtained in poly(vinylpyrrolidone) (PVP) c…
Optical and morphological properties of infrared emitting functionalized silica nanoparticles
2013
Abstract The loading process of functionalized silica nanoparticles was investigated in order to obtain nanoparticles having functional groups on their surface and Near-Infrared (NIR) emission properties. The NIR emission induced by O 2 loading was studied in silica nanoparticles, produced by pyrogenic and microemulsion methods, with size ranging from 20 to 120 nm. Loading was carried out by thermal treatments in O 2 atmosphere up to 400 °C and 90 bar. The effects of the thermal treatments on the NIR emission and on the structural properties were studied by luminescence and Raman techniques, whereas the morphological features were investigated by Transmission Electron Microscopy and Atomic …
Detaching Microparticles from a Liquid Surface.
2018
The work required to detach microparticles from fluid interfaces depends on the shape of the liquid meniscus. However, measuring the capillary force on a single microparticle and simultaneously imaging the shape of the liquid meniscus has not yet been accomplished. To correlate force and shape, we combined a laser scanning confocal microscope with a colloidal probe setup. While moving a hydrophobic microsphere (radius 5-10 μm) in and out of a 2-5 μm thick glycerol film, we simultaneously measured the force and imaged the shape of the liquid meniscus. In this way we verified the fundamental equations [D. F. James, J. Fluid Mech. 63, 657 (1974)JFLSA70022-112010.1017/S0022112074002126; A. D.…
Physico-chemical characterization of Pd nanoparticles synthesized in w/o microemulsions
1998
Abstract The long time stability of surfactant-coated Pd nanoparticles in w/o microemulsions has been investigated. It has been proven that in suitable conditions, the use of the functionalized surfactant Pd(AOT)2 allows to obtain very stable nanosized Pd particles and to finely control their average size.
A new approach for crystallization of copper(II) oxide hollow nanostructures with superior catalytic and magnetic response.
2015
We report the synthesis of copper(II) oxide hollow nanostructures at ambient pressure and close to room temperature by applying the soft templating effect provided by the confinement of droplets in miniemulsion systems. Particle growth can be explained by considering a mechanism that involves both diffusion and reaction control. The catalytic reduction of p-nitrophenol in aqueous media is used as a model reaction to prove the catalytic activity of the materials: the synthesized hollow structures show nearly 100 times higher rate constants than solid CuO microspheres. The kinetic behavior and the order of the reduction reaction change due to the increase of the surface area of the hollow str…
ZnO-latex hybrids obtained by polymer-controlled crystallization: a spectroscopic investigation.
2007
Micro- and submicrosized ZnO-polymer hybrid materials were synthesized by precipitating zinc oxide from an aqueous medium in the presence of poly(styrene-acrylic acid) latex nanoparticles, prepared by miniemulsion polymerization. Up to 10 wt % of the latex becomes incorporated into the crystals. Although the long-range order of the inorganic material is essentially not altered by the polymer, studies by photoluminescence (PL) spectroscopy and electron paramagnetic resonance (EPR) show that the latex particles influence the optical and paramagnetic properties of the hybrids, which can be correlated with changes in the defect structure. Typical PL emission spectra showed a narrow UV peak and …
Pickering Emulsions of Fluorinated TiO2: A New Route for Intensification of Photocatalytic Degradation of Nitrobenzene
2020
International audience; Fluorination of the TiO2 surface has been often reported as a tool to increase the photocatalytic efficiency due to the beneficial effects in terms of production of oxidizing radicals. Moreover, it is shown that the unique amphiphilic properties of the fluorinated TiO2 (TiO2-F) surface allow one to use this material as a stabilizer for the formulation of Pickering emulsions of poorly soluble pollutants such as nitrobenzene (NB) in water. The emulsions have been characterized in terms of size of the droplets, type of emulsion, possibility of phase inversion, contact angle measurements, and optical microscopy. The emulsified system presents micrometer-sized droplets of…
E-beam irradiation and UV photocrosslinking of microemulsion-laden poly(N-vinyl-2-pyrrolidone) hydrogels for ‘‘in situ’’ encapsulation of volatile hy…
2011
Gelled microemulsions are the subject of considerable scientific and commercial interest. Many efforts are currently devoted to improving their toxicological profile and functioning as biocompatible diffusion barrier for the controlled delivery of hydrophobic compounds. In the present investigation, a non-ionic polymeric surfactant was chosen to generate an oil-in-water microemulsion of a model fragrance in the presence of poly(N-vinyl-2-pyrrolidone) (PVP). The microemulsion was then subjected to either electron-beam or UV-irradiation to induce free-radical crosslinking of PVP at low temperature and in the absence of crosslinking agents, catalysts and initiators. Irradiation conditions with…
Surfactant-Free Emulsion Polymerization of Various Methacrylates: Towards Monodisperse Colloids for Polymer Opals
2004
A systematic investigation of the surfactant-free emulsion polymerization (SFEP) on three different methacrylates (MMA, tert-butyl methacrylate and 2,2,2-trifluoro ethyl methacrylate) is described to obtain monodisperse colloids for the preparation of artificial polymer opals. The experimental results are in agreement with a model, in which seed particles are formed very early during the polymerization process. The particles are formed very early during the polymerization process. The particles grow afterwards into the colloids until all monomer is consumed. This gives rise to a linear relationship between the volume of the colloids and the ratio of monomer to water in the reaction batch. T…