Redox equilibria of iron oxides in aqueous-based magnetite dispersions: Effect of pH and redox potential

Pang, Suh Cem; Chin, Suk Fun; Anderson, Marc A.

doi:10.1016/j.jcis.2007.02.058

Cited by 84 publications

(69 citation statements)

References 40 publications

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“…Besides their environmental relevance, these are important from biomedical application point of view. Although magnetite nanoparticles can be easily prepared by coprecipitation of Fe(II) and Fe(III) salts in an alkaline solution, different coating layers on the surface of particles have to be developed to prevent particle aggregation and to improve their colloidal and chemical stability [10]. Surfactants are often used to disperse nanoparticles entirely in an appropriate medium.…”

Section: Introductionmentioning

confidence: 99%

Adsorption of organic acids on magnetite nanoparticles, pH-dependent colloidal stability and salt tolerance

Tombácz

Tóth

Nesztor

et al. 2013

Colloids and Surfaces A: Physicochemical and Engineering Aspect

111

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Graphical abstractH-type isotherms HA, PAM, GA, and CA Highlights  Organic acids either stabilize or destabilize oxide nanoparticles in natural waters.  The stabilizing/destabilizing effect depends on pH, salinity and organic concentration.  Specific configuration of carboxylic groups is necessary to surface complexation.  Surface complexation leads to high affinity adsorption isotherms.  Higher molecular weight organic acids provide better stability than smaller ones. AbstractThe adsorption of different organic acids and their influence on the pH-dependent charging, salt tolerance and so the colloidal stability of magnetite nanoparticles are compared. Adsorption isotherms of citric acid -CA, gallic acid -GA, poly(acrylic acid) -PAA, poly(acrylic-co-maleic acid) -PAM and humic acid -HA were measured. The pH-dependent charge state of MNPs was characterized by electrophoretic mobility and their aggregation by dynamic light scattering. The salt tolerance was tested in coagulation kinetic experiments. Although the adsorption capacities, the type of bonding (either H-bonds or metal ioncarboxylate complexes) and so the bond strengths are significantly different, the following general trends have been found. Small amount of organic acids at pH < ~8 (the pH of PZC of magnetite) -relevant condition in natural waters -only neutralizes the positive charges, and so promotes the aggregation and sedimentation of nanoparticles. Greater amounts of organic acid, above the charge neutralization, cause the sign reversal of particle charge, and at high

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Section: Introductionmentioning

confidence: 99%

Adsorption of organic acids on magnetite nanoparticles, pH-dependent colloidal stability and salt tolerance

Tombácz

Tóth

Nesztor

et al. 2013

Colloids and Surfaces A: Physicochemical and Engineering Aspect

111

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“…Besides our several years experience with humic acids, their interaction with magnetite (Fe 3 O 4 , magnetic iron oxide) has been also studied [4,5]. Although magnetite nanoparticles can be easily prepared by co-precipitation of Fe(II) and Fe(III) salts in an alkaline solution, different coatings on the surface of particles have to be developed to prevent particle aggregation and to improve their colloidal and chemical stability [6]. Surfactants are often used to disperse nanoparticles entirely in an appropriate medium.…”

Section: Introductionmentioning

confidence: 99%

Surface charging, polyanionic coating and colloid stability of magnetite nanoparticles

Hajdú

Illés

Tombácz

et al. 2009

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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a b s t r a c tThe formation of small and large molecular polyanionic coating on the surface of magnetite (Fe 3 O 4 ) nanoparticles and their role in the stability enhancement of aqueous magnetic fluids are compared. Magnetite was synthesized and stabilized with citric (CA) and humic (HA) acids. The macromolecular HA, a notable fraction of the natural organic matter (NOM), contains mainly carboxylic groups similarly to the CA, and both acids are able to form surface complexes on the ≡Fe-OH sites of iron oxides. The pHdependent charge state of particles and their aggregation were quantified, and the enhanced salt tolerance of stabilized systems was studied. The dynamic light scattering (DLS) method was used to characterize colloidal stability under different conditions. The average particle size and electrophoretic mobility were measured, and the electrolyte tolerance was tested in coagulation kinetic measurements. The colloidal stability of magnetite dispersions depends sensitively on the pH and the concentration of organic acids present. The trace amount of HA neutralizes the positive charges on magnetite surface under acidic condition only in part, and so it promotes the aggregation between the particles having both positive sites and negative humate patches on the surface. Above the adsorption saturation, the surface becomes completely covered causing the reversal of charge sign and overcharging of nanoparticles. The magnetite nanoparticles become stabilized in a way of combined steric and electrostatic effects. The thicker layer of macromolecular HA provides better electrosteric stability than that of CA coating. However, in the presence of either CA or HA, the dissolution of magnetite is enhanced due to the complexation of iron ions in the aqueous medium.

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“…the mean diameter of Fe 3 O 4 nanoparticles in hydrochloric acid solution (pH 1.7-4.5) was 82 nm, while that in tetramethylammonium hydroxide (pH 9.4-12.1) solution was 58 nm. The most stable dispersions were formed in the ranges 2-4 and 10-12 [70].…”

Section: Structure and Synthesis Of Magnetic Nanoparticlesmentioning

confidence: 99%

Magnetic Nanoparticles and Intracellular Delivery of Biopolymers

Kornev

Dubina

2015

Neurosci Behav Physi

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We review here the main methods for intracellular delivery of biopolymers. The structure and synthesis of magnetic nanoparticles are described, along with methods for stabilizing them with surfactant substances; examples of the interaction of nanoparticles with biopolymers, i.e., nucleic acids and proteins, are presented. The fi nal part of the review addresses the questions of how physiological and biocompatible magnetic nanoparticles are.

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Redox equilibria of iron oxides in aqueous-based magnetite dispersions: Effect of pH and redox potential

Cited by 84 publications

References 40 publications

Adsorption of organic acids on magnetite nanoparticles, pH-dependent colloidal stability and salt tolerance

Adsorption of organic acids on magnetite nanoparticles, pH-dependent colloidal stability and salt tolerance

Surface charging, polyanionic coating and colloid stability of magnetite nanoparticles

Magnetic Nanoparticles and Intracellular Delivery of Biopolymers

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