Size-Controlled Synthesis of Magnetite Nanoparticles in the Presence of Polyelectrolytes

Abstract

Magnetite nanoparticles of nearly uniform size have been prepared by precipitating ferrous ions in the presence of two different polyelectrolytes, viz., poly(acrylic acid) and the sodium salt of carboxymethyl cellulose at high pH (∼13). The size of the magnetite nanoparticles can be controlled easily by varying the concentration of the polyelectrolyte in the medium. Transmission electron microscopy study indicates that the average particle size varies from 5 to 15 nm, depending on the concentration and the nature of the polyelectrolyte. X-ray diffraction study shows the presence of only magnetite phase. FTIR spectroscopy and thermogravimetric analysis confirmed the presence of polyelectrolyte on the magnetite surface. The magnetization and Mössbauer studies were performed on two samples with mean diameters 7.0 and 14.7 nm. Magnetization measurements suggest that both of these particles are of single magnetic domain. The measurements also estimate the superparamagnetic blocking temperature, T B = 145 K for smaller particles, while T B > 300 K for the larger particles. Mössbauer spectra at 300 K show only a quadrupole doublet for the smaller particles and mostly a magnetically separated sextet for the larger ones, indicating also the marked size dependence of moment dynamics.

In Situ Synthesis of Magnetite Nanoparticles in Carrageenan Gels

“…As a first approximation, the nanoparticles magnetic moment µ can be estimated by using the Langevin law 36 to model the M(H) curve (in this approximation we consider negligible the µ distribution, dipolar interactions, and anisotropy): µ ≈ 8000µ B . Assuming that the sample is mainly composed of spherical magnetite particles, the saturation magnetization of bulk magnetite at room temperature is ∼82 emu/g Fe 3 O 4 , and the density of magnetite is ∼5 g/cm 3 , the nanoparticles radius can be estimated as 10 nm. This value agrees with that found on the basis of susceptibility measurements ( Figure S1 in Supporting Information) and is on the order of that found by XRD.…”

Interparticle interaction and size effect in polymer coated magnetite nanoparticles

“…Single phase of the magnetite nanoparticle was characterized by X-ray powder diffraction and electron diffraction using Transmission Electron Microscope (TEM) described in our earlier report [18]. The characteristic features of the magnetite nanoparticles taken for the present study are given in respectively.…”

“…The characteristic features of the magnetite nanoparticles taken for the present study are given in respectively. The attachment of the polymer on the particle surface was confirmed by FTIR spectroscopy [18]. The amount of the polymer content (given in Table 1) was estimated by thermogravimetric analysis using a Mettler Toledo Star System TGA/SDTA851e in presence of N 2 gas.…”

XAFS study of starch-stabilized magnetite nanoparticles and surface speciation of arsenate

“…Starch-stabilized magnetite nanoparticles were synthesized by modifying the methods of Si et al (Si et al, 2004) and He et al (He and Zhao, 2005). In brief, a solution of FeCl 3 (0.50 mol/L, 100 ml) and FeCl 2 (0.25 mol/L, 100 ml) were added dropwise to a series of starch solutions under continuous shaking and N 2 purging.…”