Gilat Nizri - Academia.edu (original) (raw)

Papers by Gilat Nizri

Research paper thumbnail of Crystallization of Polyelectrolyte-Surfactant Complexes at the Air-Water Interface

Research paper thumbnail of Induced Nucleation of Polyelectrolyte-Surfactant Complexes at the air-Water Interface

Research paper thumbnail of Induced Crystallization of Polyelectrolyte-Surfactant Complexes at the Gas-Water Interface

Physical Review Letters, 2004

Synchrotron x-ray and surface-tension studies of a strong polyelectrolyte (PE) in the semidilute ... more Synchrotron x-ray and surface-tension studies of a strong polyelectrolyte (PE) in the semidilute regime (0:1M monomer charges) with varying surfactant concentrations show that minute surfactant concentrations induce the formation of a PE-surfactant complex at the gas-solution interface. X-ray reflectivity and grazing angle x-ray diffraction show the complex PE-surfactant resides at the interface and the alkyl chains of the surfactant form a two-dimensional liquidlike monolayer. With the addition of salt (NaCl), columnar crystals with distorted-hexagonal symmetry are formed.

Research paper thumbnail of Dispersion of magnetic nanoparticles in suspension

Micro & Nano Letters, 2006

Pure magnetite nanoparticles (Fe 3 O 4) have been synthesised in water by coprecipitation using t... more Pure magnetite nanoparticles (Fe 3 O 4) have been synthesised in water by coprecipitation using two different approaches (from ferrous sulphate and a mixture of ferrous and ferric chlorides). All materials aggregated in aqueous suspension, but their subsequent dispersion on treatment with a variety of agents was observed to be different. Magnetite produced using ferrous sulphate could not be disaggregated, whereas magnetite produced from a mixture of ferrous and ferric chlorides could be disaggregated to a quasi-monodispersed form. The dispersing agents were tetramethyl ammonium hydroxide, Disperbyk 190 and polyacrylic acid. The finding has potentially important implications for the surface activation of superparamagnetic magnetite nanoparticles and their ability to be used in bio/life science applications.

Research paper thumbnail of Nanostructures Formed by Self-Assembly of Negatively Charged Polymer and Cationic Surfactants

Langmuir, 2009

The formation of nanoparticles by interaction of an anionic polyelectrolyte, sodium polyacrylate ... more The formation of nanoparticles by interaction of an anionic polyelectrolyte, sodium polyacrylate (NaPA), was studied with a series of oppositely charged surfactants with different chain lengths, alkyltrimethylammonium bromide (C n TAB). The binding and formation of nanoparticles was characterized by dynamic light scattering,-potential, and self-diffusion NMR. The inner nanostructure of the particles was observed by direct-imaging cryogenic-temperature transmission electron microscopy (cryo-TEM), indicating aggregates of hexagonal liquid crystal with nanometric size.

Research paper thumbnail of Microstructural Characterization of Micro- and Nanoparticles Formed by Polymer−Surfactant Interactions

Langmuir, 2004

We have studied the nano-and microparticles formed by complexation of PDAC [poly(diallyldimethyla... more We have studied the nano-and microparticles formed by complexation of PDAC [poly(diallyldimethylammoniumchloride)] and SDS (sodium dodecyl sulfate). The complexation phenomenon was characterized by light scattering and-potential measurements. The nature of the complexes was revealed by directimaging cryogenic temperature transmission electron microscopy (cryo-TEM), showing nanometric details of the complexes formed around the point of neutralization. The images also reveal how those aggregates are solubilized by excess surfactant, first into faceted particles with threadlike micelles attached to their surfaces, prior to complete solubilization, then into lacelike aggregates, and finally into spheroidal micelles. The nanostructure of the complexes strongly suggests they are made of a hexagonal liquid crystalline phase. This was further supported by small-angle X-ray scattering (SAXS).

Research paper thumbnail of Solubilization of hydrophobic molecules in nanoparticles formed by polymer–surfactant interactions

Journal of Colloid and Interface Science, 2005

The interaction between the anionic surfactant, sodium dodecyl sulfate, and the polyelectrolyte, ... more The interaction between the anionic surfactant, sodium dodecyl sulfate, and the polyelectrolyte, poly(diallyldimethylammonium chloride), may lead to formation of nanoparticles dispersed in water. The morphology of the resulting nanoparticles and their ability to solubilize hydrophobic molecules were evaluated. As shown by SEM and AFM imaging, the particles are spherical, having a diameter of about 20 nm. The solubilization within the nanoparticles was tested with pyrene, a fluorescence probe, and Nile Red, a solvatochromic probe. It was found that for Nile Red the solubilization within the nanoparticles is at lower polarity than for SDS micelles, and from pyrene solubilization it appears that the hydrophobicity of the nanoparticles depends on the ratio between the SDS molecules and the charge unit of the polymer.

Research paper thumbnail of Polymer–surfactant interactions: Binding mechanism of sodium dodecyl sulfate to poly(diallyldimethylammonium chloride)

Journal of Colloid and Interface Science, 2008

The binding mechanism of poly(diallyldimethylammonium chloride), PDAC, and sodium dodecyl sulfate... more The binding mechanism of poly(diallyldimethylammonium chloride), PDAC, and sodium dodecyl sulfate, SDS, has been comprehensively studied by combining binding isotherms data with microcalorimetry, zeta potential, and conductivity measurements, as well as ab initio quantum mechanical calculations. The obtained results demonstrate that surfactant-polymer interaction is governed by both electrostatic and hydrophobic interactions, and is cooperative in the presence of salt. This binding results in the formation of nanoparticles, which are positively or negatively charged depending on the molar ratio of surfactant to PDAC monomeric units. From microcalorimetry data it was concluded that the exothermic character of the interaction diminishes with the increase in the surfactant/polymer ratio as well as with an increase in electrolyte concentration.

Research paper thumbnail of Crystallization of Polyelectrolyte-Surfactant Complexes at the Air-Water Interface

Research paper thumbnail of Induced Nucleation of Polyelectrolyte-Surfactant Complexes at the air-Water Interface

Research paper thumbnail of Induced Crystallization of Polyelectrolyte-Surfactant Complexes at the Gas-Water Interface

Physical Review Letters, 2004

Synchrotron x-ray and surface-tension studies of a strong polyelectrolyte (PE) in the semidilute ... more Synchrotron x-ray and surface-tension studies of a strong polyelectrolyte (PE) in the semidilute regime (0:1M monomer charges) with varying surfactant concentrations show that minute surfactant concentrations induce the formation of a PE-surfactant complex at the gas-solution interface. X-ray reflectivity and grazing angle x-ray diffraction show the complex PE-surfactant resides at the interface and the alkyl chains of the surfactant form a two-dimensional liquidlike monolayer. With the addition of salt (NaCl), columnar crystals with distorted-hexagonal symmetry are formed.

Research paper thumbnail of Dispersion of magnetic nanoparticles in suspension

Micro & Nano Letters, 2006

Pure magnetite nanoparticles (Fe 3 O 4) have been synthesised in water by coprecipitation using t... more Pure magnetite nanoparticles (Fe 3 O 4) have been synthesised in water by coprecipitation using two different approaches (from ferrous sulphate and a mixture of ferrous and ferric chlorides). All materials aggregated in aqueous suspension, but their subsequent dispersion on treatment with a variety of agents was observed to be different. Magnetite produced using ferrous sulphate could not be disaggregated, whereas magnetite produced from a mixture of ferrous and ferric chlorides could be disaggregated to a quasi-monodispersed form. The dispersing agents were tetramethyl ammonium hydroxide, Disperbyk 190 and polyacrylic acid. The finding has potentially important implications for the surface activation of superparamagnetic magnetite nanoparticles and their ability to be used in bio/life science applications.

Research paper thumbnail of Nanostructures Formed by Self-Assembly of Negatively Charged Polymer and Cationic Surfactants

Langmuir, 2009

The formation of nanoparticles by interaction of an anionic polyelectrolyte, sodium polyacrylate ... more The formation of nanoparticles by interaction of an anionic polyelectrolyte, sodium polyacrylate (NaPA), was studied with a series of oppositely charged surfactants with different chain lengths, alkyltrimethylammonium bromide (C n TAB). The binding and formation of nanoparticles was characterized by dynamic light scattering,-potential, and self-diffusion NMR. The inner nanostructure of the particles was observed by direct-imaging cryogenic-temperature transmission electron microscopy (cryo-TEM), indicating aggregates of hexagonal liquid crystal with nanometric size.

Research paper thumbnail of Microstructural Characterization of Micro- and Nanoparticles Formed by Polymer−Surfactant Interactions

Langmuir, 2004

We have studied the nano-and microparticles formed by complexation of PDAC [poly(diallyldimethyla... more We have studied the nano-and microparticles formed by complexation of PDAC [poly(diallyldimethylammoniumchloride)] and SDS (sodium dodecyl sulfate). The complexation phenomenon was characterized by light scattering and-potential measurements. The nature of the complexes was revealed by directimaging cryogenic temperature transmission electron microscopy (cryo-TEM), showing nanometric details of the complexes formed around the point of neutralization. The images also reveal how those aggregates are solubilized by excess surfactant, first into faceted particles with threadlike micelles attached to their surfaces, prior to complete solubilization, then into lacelike aggregates, and finally into spheroidal micelles. The nanostructure of the complexes strongly suggests they are made of a hexagonal liquid crystalline phase. This was further supported by small-angle X-ray scattering (SAXS).

Research paper thumbnail of Solubilization of hydrophobic molecules in nanoparticles formed by polymer–surfactant interactions

Journal of Colloid and Interface Science, 2005

The interaction between the anionic surfactant, sodium dodecyl sulfate, and the polyelectrolyte, ... more The interaction between the anionic surfactant, sodium dodecyl sulfate, and the polyelectrolyte, poly(diallyldimethylammonium chloride), may lead to formation of nanoparticles dispersed in water. The morphology of the resulting nanoparticles and their ability to solubilize hydrophobic molecules were evaluated. As shown by SEM and AFM imaging, the particles are spherical, having a diameter of about 20 nm. The solubilization within the nanoparticles was tested with pyrene, a fluorescence probe, and Nile Red, a solvatochromic probe. It was found that for Nile Red the solubilization within the nanoparticles is at lower polarity than for SDS micelles, and from pyrene solubilization it appears that the hydrophobicity of the nanoparticles depends on the ratio between the SDS molecules and the charge unit of the polymer.

Research paper thumbnail of Polymer–surfactant interactions: Binding mechanism of sodium dodecyl sulfate to poly(diallyldimethylammonium chloride)

Journal of Colloid and Interface Science, 2008

The binding mechanism of poly(diallyldimethylammonium chloride), PDAC, and sodium dodecyl sulfate... more The binding mechanism of poly(diallyldimethylammonium chloride), PDAC, and sodium dodecyl sulfate, SDS, has been comprehensively studied by combining binding isotherms data with microcalorimetry, zeta potential, and conductivity measurements, as well as ab initio quantum mechanical calculations. The obtained results demonstrate that surfactant-polymer interaction is governed by both electrostatic and hydrophobic interactions, and is cooperative in the presence of salt. This binding results in the formation of nanoparticles, which are positively or negatively charged depending on the molar ratio of surfactant to PDAC monomeric units. From microcalorimetry data it was concluded that the exothermic character of the interaction diminishes with the increase in the surfactant/polymer ratio as well as with an increase in electrolyte concentration.