Nanoparticles superficial density of charge in electric double-layered magnetic fluid: A conductimetric and potentiometric approach

Abstract

We analyze potentiometric and conductimetric measurements simultaneously performed on Electric Double-Layer Magnetic Fluid based on cobalt ferrite nanoparticles, in order to obtain the pHdependence of the particle surface charge density. We propose a mechanism for the charging of the particle surface. This model considers the ferrofluid solution as a mixture of strong and weak diprotic acids. We show how an exact analytical treatment involving proton transfer between the particle surface and the bulk solution allows the construction of a speciation diagram of the charged superficial sites. The saturation value of the superficial density of charge is found to be equal to 0.326 ± 0.065 C m −2 .

Controlling protein–particle adsorption by surface tailoring colloidal alumina particles with sulfonate groups

“…The particles were then back titrated with 0.1 M KOH in a nitrogen-flushed vessel to determine the total amount of protons in the sample. The amount of hydroxyl groups on alumina was determined by the difference from a reference sample without particles, as described by Campos et al [37]. The amount of SO 3 H groups was calculated from the difference between functionalized and unfunctionalized particles.…”

Gravitational and magnetic separation in self-assembled clay-ferrofluid nanocomposites

“…This global scattering function describes both regimes at low and high values of the scattering vector q. In general, the value of the exponent n is between 3 to 4 in the case of fractal surfaces, smaller than 3 for fractal masses and larger than 4 for diffuse interfaces [17,[24][25][26]. These models have been successfully used to characterize a disordered cluster structure [28], a fractal mass of particles [29] as well as to distinguish between individual polydisperse particles and aggregates [30].…”

“…clay and ferrofluid, have their own phase behavior as a function of several parameters and are in the present case strongly dependent on the electrostatic interactions [4]. The chemical synthesis [16] and the colloidal stability [17] of magnetic nanoparticles in aqueous media are relatively well known, and their phase behavior as a function of ionic strength and temperature has been studied using small angle neutron scattering.…”

Surface Charge Density Determination in Water Based Magnetic Colloids: a Comparative Study

“…In another strategy, PCM 10,16 , the titrations of the magnetic colloid samples start from acidic (pH ≤ 3) or alkaline (pH ≥ 11) medium, when simultaneous potentiometric and conductometric readings are carried out. The single potentiometric curve does not allow the evaluation of the equivalence points since it does not present sharp breaks.…”