Agradecimentos: This is a contribution of INCTAA (CNPq 465768/2014-8 and FAPESP 2014/50951-4) and INOMAT - National Institute of Science and Technology in Complex Functional Materials (CNPq 465452/2014-0 and FAPESP 2014/50906-9). FAPESP (grants 2013/22127-2, 2014/50906-9) and CNPq (grant 407591/2016-8) are also acknowledged for the financial support. EAN (grant 141438/2016-9), IMRJ (grant 308424/2019-0) and IOM (grant 310131/2020-0) are thankful to CNPq for the fellowships. RDLG thanks FAPESP for the postdoctoral fellowship (grant 2018/20997-3) Ver menos

Abstract: The synthesis and characterization of Fe3O4 magnetic nanoparticles (MNPs) obtained by the solvothermal method in ethyleneglycol with the addition of polyethyleneglycol (PEG) with molar mass of 4000, 8000 and 20000 g mol-1 are described, aimed at evaluating its effect on the size, morphology and stability of the nanoparticle. The syntheses were carried out by solubilizing the precursors at 85 and 140 °C, providing smaller nanoparticles as well as smaller crystallites at higher temperatures, while the effect of PEG was less evident. Measurements of nanoparticle surface areas synthesized with PEG 4000 and 20000 g mol-1 at 140 °C provided values of 76 and 14 m2 g-1, respectively, indicating that PEG 4000 surrounds the crystallites, while PEG 20000 preferably surrounds the whole MNP. As a consequence, MNP with very dissimilar porosities were obtained. Electron energy loss spectroscopy (EELS) indicated that MNP synthesized with PEG 20000 possesses higher electronic density than those obtained with PEG 4000, in agreement with the surface area results. Infrared spectroscopy and thermogravimetric analysis demonstrated the presence of PEG in the particles, whose amount increased as the particle size decreased. Dynamic Light Scattering (DLS) measurements showed that MNP hydrodynamic radius increases with the PEG size and stability in solution increases from pH 5.0 to 9.0 for smaller NP, while polymer presents slight effect on stability for the larger particles. The results obtained in this work show that properties of MNP can be tuned by the dissolution temperature of the chemical precursors and the PEG molar mass, changing their porosity and stability in solution, that are important variables in processes of adsorption, drug delivery and sensor developing Ver menos