Nanocomposites In Water Research Articles

Nanocomposite gold/poly(ethylene oxide)-like plasma polymers prepared by plasma-assisted vacuum evaporation and magnetron sputtering

A new method of deposition of nanocomposite gold/poly(ethylene oxide)-like thin films was investigated where gold was sputtered from an r. f. magnetron and poly(ethylene oxide)-like plasma polymer was simultaneously deposited via vacuum evaporation of conventional poly(ethylene oxide). Such method allows formation of the plasma polymer matrix with composition very close to that of precursor, a feature difficult to obtain in plasma polymerization processes. The films with different content of gold were prepared by varying the evaporation rate of poly(ethylene oxide) at constant power of the magnetron discharge. Chemical composition and cross-linking density of polymeric phase as well as the size distribution of gold nanoparticles were shown to be strongly dependent on the discharge power conditions. Stability of resultant nanocomposites in water was also studied. Such films are perspective for use in biomedical applications.

Preparation of Ag/PVP Nanocomposites as a Solid Precursor for Silver Nanocolloids Solution

A polyvinylpyrrolidone (PVP)/Ag nanocomposites was prepared by the simultaneous thermal reduction and radical polymerization route. The in situ synthesis of the Ag/PVP nanocomposites is based on the finding that the silver n-propylcarbamate (Ag-PCB) complex can be directly dissolved in the NVP monomer, and decomposed by only heat treatment in the range of 110 to to form silver metal. Silver nanoparticles with a narrow size distribution (5 - 40 nm) were obtained, which were well dispersed in the PVP matrix. A successful synthesis of Ag/PVP nanocomposites then proceeded upon heat treatment as low as . Moreover, important advantages of the in situ synthesis of Ag/PVP composites include that no additives (e.g. solvent, surface-active agent, or reductant of metallic ions) are used, and that the stable silver nanocolloid solution can be directly prepared in high concentration simply by dissolving the Ag/PVP nanocomposites in water or organic solvent.

Structure-Defined C60/Polymer Colloids Supramolecular Nanocomposites in Water

We report a new supramolecular method for the synthesis of well-defined pristine C 60/polymer colloid nanocomposites in water. The colloids include polymer micelles and emulsion particles. To a polymer colloid solution in water or alcohol, we introduced C 60 solution in a solvent that is miscible with water or alcohol. After the two solutions mixed, polymer colloids and C 60 spontaneously assembled into stable colloidal nanocomposites. After a dialysis process, a nanocomposite dispersion in pure water was obtained. As characterized by DLS and (Cryo-)TEM, the nanocomposites have a core-shell structure with C 60 aggregated on the surface of emulsion particles or micellar cores. The resulting nanocomposites have many potential applications such as biomedicals and photovoltaics.

Preparation of nano-and submicrosized aluminum oxide fibers by the dehydration of a hybrid gel

The spontaneous growth of hybrid (organoinorganic) microfibers on the surface of a gel prepared by dispersing an organoinorganic nanocomposite in water and subjected to dehydration in air, has been investigated. Aluminum oxide nano-and submicrofibers have been prepared by the thermal treatment of the microfibers.

Sliding wear performance of polyamide 6–clay nanocomposites in water

Polyamide 6 (PA6) clay nanocomposites, a new class of specialty polymer, shows improved tribological properties under dry sliding conditions. In food and chemical industry, the polymeric materials are widely used in the machine elements due its excellent chemical inertness. Water, being a widely used solvent, tends to have contact with the machine elements and can either act as a lubricant or as a contaminant. Many factors such as the interaction of polymer with water, surface wettability, etc., play a major role on the friction and wear of polymers in aqueous conditions. This work reports the sliding wear performance of PA6 clay nanocomposites in water. Addition of clay affects the crystallinity of the nanocomposites, which in turn affects the plasticization. Plasticization of the surface by water causes increase in wear and decreases the coefficient of friction.

Silver Ion Release from Polymethyl Methacrylate Silver Nanocomposites

Polymethyl methacrylate (PMMA) silver nanocomposites were prepared by the thermal reduction of silver(I) trifluoroacetate. Transmission electron microscopic investigations reveal that the silver nanoparticles were spherical and their particle sizes were between 5 nm and 50 nm. The particles were distributed randomly in the PMMA matrix. Immersion of the nanocomposites in water led to a release of silver ions. The silver ion release from the PMMA silver nanocomposites was measured by anodic stripping voltammetry. When a nanocomposite sample having a surface area of 36.8 cm2 and a silver content of 0.12 wt% was immersed in water, the silver ion concentration in the surrounding water was about 0.05 mg/l after two days. This is sufficient to kill bacteria. Using conventional silver powder as a filler, a silver content 30 times higher is necessary to achieve the same silver ion concentration in the surrounding water under the same conditions. The silver ion concentration in the water increased with increasing nanosilver content of the composites. The composites incorporating conventional silver powder are not transparent. In contrast, PMMA silver nanocomposites containing less than 0.25 wt% silver show a translucency sufficient for use in packaging materials.

Preparation and characterization of polypyrrole–silica colloidal nanocomposites in water–methanol mixtures

The effect of methanol cosolvent on the synthesis of polypyrrole–silica colloidal nanocomposites using ultrafine silica sols in combination with both FeCl 3 and APS oxidants has been investigated. Two protocols were evaluated: the addition of methanol to an aqueous silica sol and the addition of water to a methanolic silica sol. The latter protocol proved to be more robust, since it allowed colloidally stable dispersions to be prepared at higher methanol content (up to 50 vol% using the APS oxidant). This allowed greater control over the particle size of the nanocomposite particles. In general, the spectroscopic data, the particle size range, silica contents and electrical conductivities of these nanocomposites were similar to those reported earlier for purely aqueous formulations. Polypyrrole contents ranged from 49 to 71% by mass and particle diameters varied from around 160 to 360 nm. In terms of colloid stability, the APS oxidant was preferred for nanocomposite syntheses in the presence of methanol. However, the FeCl 3 oxidant generally gave higher conductivities and narrower size distributions under comparable conditions. HF etching experiments combined with transmission electron microscopy studies indicated that, to a first approximation, these nanocomposite particles had core–shell morphologies, with a hydrophobic polypyrrole core and a hydrophilic silica shell that compose approximately one monolayer of silica sol particles. Finally, aqueous electrophoresis measurements suggested that the polypyrrole–silica nanocomposites were silica-rich and that the methanolic silica sol was more hydrophobic (lower surface charge density) than the aqueous silica sol.