Chain formation and aging process in biocompatible polydisperse ferrofluids: Experimental investigation and Monte Carlo simulations

Effect of magnetic dipolar interactions on nanoparticle heating efficiency: Implications for cancer hyperthermia

“…It is well established with a variety of methods that in magnetic colloids mean chain length increases with increasing particle concentration1314153738. Among the methods used to characterize chain formation, electron magnetic resonance (EMR) has been used to correlate SLP data more directly with chain length14.…”

“…Among the methods used to characterize chain formation, electron magnetic resonance (EMR) has been used to correlate SLP data more directly with chain length14. This technique enables study of averaged properties of samples containing large particle concentrations and with rapid data acquisition, thus providing distinct advantages over other methods such as magneto-optical153738 and cryogenic-TEM39.…”

“…For symmetrical coherent reversal, the magnetic moments of neighbor nanoparticles are assumed to be at the same angle with respect to the chain anisotropy axis41. Considering that the center to center distance between nanoparticles is r = D p + d s – s , where D p is the mean diameter and d s – s the surface-to-surface mean distance between nanoparticles forming the chain, we obtain the following free energy (in CGS units) for a nanoparticle in a coherent-like chain configuration14 where Q is the chain length (see the supplementary material for SI units). The first term corresponds to the dipole-dipole interaction term of a chain formed of Q particles, the second term is demagnetization contribution, the third the effective magnetic anisotropy (assumed uniaxial), while the last represents the Zeemann interaction.…”

“…This means that the chain value extracted from EMR should be regarded as approximate. Further, according to the literature1438 the dependence of mean chain size on the volume fraction is given by, with φ the particle volume fraction and E a dimensionless energy parameter between particles in the chain. The solid line in Fig.…”

“…This however, is typically not observed experimentally in either free suspension4131415, gel phantoms12, and in biological systems1617. In free suspension, interparticle interactions can produce clustering and formation of structures in absence of magnetic fields4131415. Such clustering has been shown to affect amplitude-dependent heating behavior that may lead to observed differences among particle formulations718.…”