Search results for "surface"
showing 10 items of 9345 documents
Synthesis of gold nanotubes with variable wall thicknesses
2013
We report the synthesis of gold nanotubes with variable wall thicknesses that is accomplished by the deposition of sacrificial hydrophobic polymer cores followed by gold shells within an anodic aluminum oxide template. We demonstrate that by varying polymer core hydrophobicity, the resulting gold shell thickness can be varied. There are two requirements for gold shell formation: (1) the polymer core must be able to be electrodeposited into a tubular (as opposed to wire-like) structure, and (2) the polymer must be hydrophobic, such that it collapses upon exposure to an aqueous solution. An array of gold nanotubes has variable plasmonic properties and can function as a surface enhanced Raman …
Water-compatible molecularly imprinted polymers obtained via high-throughput synthesis and experimental design.
2003
A technique allowing high-throughput synthesis and evaluation of molecularly imprinted polymer sorbents at a reduced scale (mini-MIPs) was developed and used for the optimization of MIPs for use in pure aqueous environments. The technique incorporated a 4-port liquid-handling robot for the rapid dispensing of monomers, templates, solvents and initiator into the reaction vessels of a 96-well plate. A library of 80 polymers, each ca. 50 mg, could thus be prepared in 24 h. The MIP rebinding capacity and selectivity could be rapidly assessed in the batch mode by quantifying nonbound fractions in parallel using a UV monochromator plate reader. This allowed a complete evaluation of the binding ch…
Improvement of solubility and biocompatibility of MnO based nanoparticles in aqueous solutions
2011
ABSTRACTMnO nanoparticles were surface modified using two different multifunctional polymers. By introducing a PEG group, the long term stability, MRI applicability and sterile filtration could be greatly improved. Furthermore, PEGylated MnO NPs were less toxic compared to non-PEGylated NPs. The results suggest that these nanoparticles are suitable for in vivo applications.
Metachromatic behavior of methylorange in the presence of ionenes
1994
The addition of different ionenes, polycations with defined structure and charge distances, to methylorange1 in very dilute solutions of water resulted in an observable shift of the absorption maxima from 464 nm to shorter wavelengths. The extent of this so-called metachromasy effect was found to be dependent on the nature of the hydrophobic unit of the polymer backbone. The comparison of UV/VIS spectra's of these solutions with the absorption of a film of a model substance — a dication with methylorange as counteranion — lead to the conclusion that ionenes undergo an exchange of the counteranions when added to a dilute solution of methylorange. Precipitation is slowed down, but the absorpt…
The Swelling Behavior of Polyelectrolyte Multilayers in Air of Different Relative Humidity and in Water
2002
The swelling properties of physisorbed polyelectrolyte multilayer self-assemblies with alternating polyion charge in humid air and in aqueous environment were investigated via X-ray and neutron reflectometry as well as optically, using surface plasmon spectroscopy. The sorption behavior was similar to that found for neutral polymers and was related to an internal screening of the charges of the adjacent layers owing to the high entanglement of the polyelectrolyte chains and the resulting low mobility of the polymer segments. The screening was found to be incomplete only in the top layer, resulting in a net charged surface.
A simple method to prepare solid nanoparticles of water-soluble salts using water-in-oil microemulsions
2000
A new and simple method to prepare solid nanoparticles of water-soluble salts using water-in-oil microemulsions is described. In particular, starting from water/sodium bis(2-ethylhexyl)sulfosuccinate/n-heptane microemulsions carrying inside the aqueous core of the reversed micelles some water-soluble salts [CaCl2, Na2HPO4, Cu(NO3)2], after evaporation of the volatile components (water and apolar organic solvent), the resulting inorganic salt/surfactant composites were found to be totally dispersible in pure n-heptane. The presence of nanoparticles in these resuspended composites was ascertained by transmission electron microscopy observation of samples obtained by gentle evaporation of the …
A Simple and Versatile Route to Stable Quantum Dot−Dye Hybrids in Nonaqueous and Aqueous Solutions
2008
Hybrid systems consisting of core/shell semiconductor quantum dots (QDs) and organic rylene dyes have been prepared and characterized. Complex formation is mediated by bidentate carboxylate moieties covalently linked to the dye molecules. The complexes were very stable with respect to time (at least months), dilution (sub nM), and precipitation. After preparation in organic solvent, complexes could be easily transferred into water. The strong quenching of QD emission by the dye molecules (transfer efficiencies up to 95%) was satisfactorily modeled by an FRET process. Single complexes immobilized in thin polymer films were imaged by confocal fluorescence microscopy.
Polymer−Surfactant Interactions. A Quantitative Approach to the Enthalpy of Transfer of Poly(Ethylene Glycol)s from Water to the Aqueous Sodium Perfl…
2000
The enthalpy of transfer (ΔHt) of nonionic polymers at a fixed concentration from water to aqueous substrate solutions as a function of the substrate concentration (fSmS) was determined. The substrates studied are sodium perfluorobutanoate to sodium perfluorooctanoate, and the polymers are poly(ethyleneglycol)s with molecular weights of 400 and 35 000. For the PEG 400-sodium perfluoroheptanoate−water systems, measurements were also performed at some polymer compositions. As a general feature, the enthalpy of transfer steeply changes with fSmS, reaching a maximum beyond which it decreases, tending to level off. A qualitative analysis of the enthalpy data assigned the steep increase of ΔHt to…
Joint Aqueous Solutions of Dextran and Bovine Serum Albumin: Coexistence of Three Liquid Phases
2014
The phase diagram of the system water/dextran (DEX)/BSA was measured as well as modeled. On the experimental side, cloud points were determined and the coexisting phases were analyzed. The theoretical calculations use an approach capable of describing solutions of chain polymers and of globular proteins with the same formalism. The required thermodynamic input comes from experiments concerning the binary subsystems, except for the polymer blend for which one interaction parameter had to be adjusted. Both sources of information yield the same essential features: the existence of a large composition area of immiscibility, starting from the subsystem DEX/BSA and extending well into the region …
On the origin of functionalization in one-pot radiation synthesis of nanogels from aqueous polymer solutions
2016
Radiation-engineered poly(N-vinyl pyrrolidone) nanogels are very interesting biocompatible nanocarriers for i.v. administration of therapeutics and contrast agents for bioimaging. The manufacturing process is fast and effective, it grants excellent control of particle size and simultaneous sterilization of the formed nanogels. Interestingly, primary amino groups and carboxyl groups, useful for (bio)conjugation, are also formed in a dose-dependent fashion. In this paper, by means of both numerical simulations and experiments, the origin of nanogel size control and functionalization is investigated. This understanding offers a new dimension for the design and production of radiation-sculpture…