The influence of 1,2-alkanediol on the crystallinity of magnetite nanoparticles

• Crystallinity of nanoparticles investigated from an atomic view via magnetic hyperfine field.
• 1,2‐alkanediol has a great influence on the shape and size of particles.
• Formula able to calculate the fraction of sample with crystalline structure is proposed.

Magnetic nanoparticles of magnetite have been synthesized by thermal decomposition and investigated by measuring the magnetic hyperfine field. Preformed Fe3O4 nanoparticles were used as seeds to produce a series of magnetic nanoparticles, with different sizes and shapes. Samples were characterized by X-ray diffraction, transmission electron microscopy, and magnetization measurements. The perturbed angular correlation (PAC) technique was used to study the influence of 1,2-octanediol on the seeding growth of the Fe3O4 by measuring hyperfine interactions. The nuclear probes 111In →→111Cd were introduced into the samples through the synthesis of first core of Fe3O4, remained in the samples after the consecutive growth. The PAC results show the presence of two probe site fractions, one characterized by a well-defined magnetic dipole frequency with population fI and another characterized with a broad distributed electric quadrupole frequency with population fO, which were, respectively, assigned to probes at substitutional Fe sites in crystalline Fe3O4 formed at inner region of the nanoparticles and probes at non-crystalline iron oxide in the outer region of nanoparticles. A mathematical model was proposed to fit the behavior of fO with the particle size.