Search results for "aqueous solution"
showing 10 items of 1610 documents
Mesosynthesis of ZnO-SiO(2) porous nanocomposites with low-defect ZnO nanometric domains.
2011
Silica-based ZnO-MCM-41 mesoporous nanocomposites with high Zn content (5≤Si/Zn≤50) have been synthesized by a one-pot surfactant-assisted procedure from aqueous solution using a cationic surfactant (CTMABr = cetyltrimethylammonium bromide) as structure-directing agent, and starting from molecular atrane complexes as inorganic hydrolytic precursors. This preparative technique allows optimization of the dispersion of the ZnO nanodomains in the silica walls. The mesoporous nature of the final materials is confirmed by x-ray diffraction (XRD), transmission electron microscopy (TEM) and N(2) adsorption-desorption isotherms. The ZnO-MCM-41 materials show unimodal pore size distributions without …
Nanoparticles Built of Cross-Linked Heterotelechelic, Amphiphilic Poly(dimethylsiloxane)-b-poly(ethylene oxide) Diblock Copolymers
2000
Novel short chain α,ω-heterotelechelic amphiphilic poly(dimethylsiloxane)-b-poly(ethylene oxide) diblock copolymers (PDMS−PEO) with total molecular weights below 10 000 g/mol are synthesized, characterized, and used as basic constituent parts for functionalized nanoparticles. The self-assembly of the amphiphilic diblock copolymer in water as a solvent selective for the PEO block leads to the formation of spherical and cylindrical micellar structures with diameters between 10 and 25 nm. The core of the micelles is built of the hydrophobic PDMS chains, whereas the corona is set up by the hydrophilic PEO blocks. By using α,ω-heterotelechelic diblock copolymers, it is possible to fix the core o…
UV-tunable upper critical solution temperature behavior of azobenzene containing poly(methyl methacrylate) in aqueous ethanol
2015
A series of azobenzene containing copolymers were synthesized by post-modification of poly(methyl methacrylate-co-pentafluorophenyl methacrylate) with an amine-functionalized azobenzene. Light- and thermo-responsive behavior of these copolymers was investigated in ethanol–water solvent mixtures with various amounts of ethanol. The upper critical solution temperature (UCST) of the polymer solutions, resulting from the poly(methyl methacrylate), was found to be highly tunable by the substitution degree of the copolymers as well as the ethanol content of the solvent mixture. In addition, the copolymers are light responsive based on the cis–trans isomerization of the azobenzene group under UV i…
Rheological characterization and release properties of inulin-based hydrogels
2012
Abstract In the present study the rheological properties of hydrogels obtained through UV irradiation of an aqueous solution of methacrylated inulin (INUMA) alone or in the presence of four different crosslinkers, have been recorded as a function of irradiation time, at two different wavelengths (320 and 365 nm) and fixed frequency and amplitude by oscillatory experiments. Each hydrogel has been analyzed by measurements of the frequency-dependency of the elastic modulus, G ′, in the linear viscoelastic region. The amount of polymeric chains giving an elastic response has been correlated to the chemical nature of the crosslinker used together with INUMA. Finally the release properties of the…
Morphology, physical properties, silver release, and antimicrobial capacity of ionic silver-loaded poly(l-lactide) films of interest in food-coating …
2014
In the present study, silver ions were incorporated into a poly-(l-lactide) (PLA) matrix by a solvent casting technique using different solvents and glycerol as plasticizer. The effect of the different formulations on the morphology, thermal, mechanical and color properties were first evaluated. Additionally, a thorough study of the silver ions release to an aqueous environment was also monitored over time by anodic stripping voltammetry and correlated with the antimicrobial performance against S. enterica. The incorporation of silver contents of up to 1 wt % did not affect morphology, thermal or mechanical properties of the films. A sustainable, antibacterial effectiveness was found for th…
Effective low temperature reduction of graphene oxide with vanadium(iii)
2014
Reduction of graphene oxide (GO) with vanadium(III) trichloride under various reaction conditions has been investigated. The results show that V(III) can be used as an efficient reducing agent for GO in aqueous solutions at low concentrations and in moderate temperatures under ambient conditions. The IR spectroscopy and X-ray photoelectron spectroscopy (XPS) show that the structure of the vanadium-reduced material is similar to reduced graphene oxide prepared using TiCl3 or hydrazine as a reducing agent. The electrical conductivity of the material is also similar in all cases. However, on the basis of the XPS results, vanadium-based reduction does not leave significant reductant impurities …
Water-soluble carbon nanotubes through sugar azide functionalization
2011
In this work we report a covalent functionalization of pristine single-walled carbon nanotubes (SWCNTs) directly with three sugar azides, 2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl, 2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl or 2,3,4,6-tetra-O-acetyl-β-d-mannopyranosyl azide. Microwave-assisted functionalization was carried out for SWCNTs prepared with the HiPCO method. The as-prepared, new type of sugar-functionalized SWCNTs were analyzed by Raman and IR spectroscopy. Deacetylation of the functionalized tubes by sodium methoxide yielded nitrogen-linked, sugar-functionalized carbon nanotubes (CNTs) that formed stable dispersions in water. Reactivity of the sugar azides towards SWCNTs was es…
Ionic conduction through single-pore and multipore polymer membranes in aprotic organic electrolytes
2021
Abstract We experimentally characterize the ionic conduction of single and multipore nanoporous membranes in aprotic organic electrolytes. To this end, soft-etched (SE) membranes with pore diameters in the nanometer range and track-etched (TE) membranes with pore diameters in the tens of nanometers range are investigated. In aqueous conditions, the membrane ionic conduction rates follow the same trend of the bulk solution conductivities. However, the ionic transport through the narrow SE-nanopores dramatically decreases in aprotic electrolytes due to the formation of solvated metal cations and their adsorption on the pore surface. The current-voltage recordings of single conical nanopores i…
Water solubility in trachytic and pantelleritic melts: an experimental study
2021
International audience; Solubility experiments were performed on a trachyte and a pantellerite from Pantelleria. The trachyte has SiO 2 = 65.2 wt%, Al 2 O 3 = 15.2 wt% and a peralkaline index (P.I. = molar[(Na 2 O + K 2 O)/Al 2 O 3 ]) ∼ 1 while the pantellerite has SiO 2 = 72.2 wt%, Al 2 O 3 = 11 wt% and a P.I. = 1.3. Solubility experiments were performed in the pressure range of 50-300 MPa at T = 950°C for the trachyte and 50-200 MPa at T = 850°C for the pantellerite. The water content of experimental glasses was determined by Karl Fischer titration, elemental analyser and FT-IR spectroscopy. Water content appears similar in both compositions for analogous pressure conditions, varying from…
Atomic-force microscopy imaging of plasma membranes purified from spinach leaves
2000
Summary: Plasma membranes purified from spinach leaves by aqueous two-phase partitioning were examined by atomic-force microscopy (AFM) in phosphate buffer, and details on their structure were reported at nanometric scale. Examination of the fresh membrane preparation deposited on mica revealed a complex organization of the surface. It appeared composed of a first layer of material, about 8 nm in thickness, that practically covered all the mica surface and on which stand structures highly heterogeneous in shape and size. High-resolution imaging showed that the surface of the first layer appeared relatively smooth in some regions, whereas different characteristic features were observed in ot…