Grant number: 15/20555-2 Support type: Scholarships in Brazil - Doctorate Effective date (Start): September 01, 2016 Effective date (End): July 31, 2019 Field of knowledge: Physical Sciences and Mathematics - Physics Principal Investigator: Antonio Martins Figueiredo Neto Grantee: Eduardo Sell Gonçalves Home Institution: Instituto de Física (IF). Universidade de São Paulo (USP). São Paulo , SP, Brazil Associated research grant: 11/13616-4 - Optical and structural properties of elastomers and complex fluids of biological interest, AP.TEM Abstract When electric fields as such as those derived from electromagnetic radiations interact with materials, its atoms and molecules can be polarized. Usually, this polarization is proportional to electric field's modulus. However, in the case of very intense fields, on the order of interatomic interactions, nonlinear optical effects can be found. Among the various phenomena of scientific and technological interest, great attention is focused on the effects of second harmonic generation (SHG) in which the nonlinear material irradiated by a beam of wavelength $\lambda$ emits photons with twice the energy. Although this effect does not occur in materials with inversion symmetry, it's possible to verify SHG in colloidal dispersions macroscopically non-symmetric, even if the nanoparticles themselves are centrosymmetric. Therefore, ferrofluids are very important materials in the study of SHG phenomena since the formation and the dimensions of non isotropic internal structures can be controlled according to the intensity of uniform magnetic fields. However, despite this controllability, little attention has been directed to the study of nonlinear optical phenomena in magnetic nanoparticles, both from the fundamental and applied point of view. Therefore, it's sought the construction of an experimental arrangement which enables the detection of the second harmonic generation on the laboratories of Grupo de Fluidos Complexos, IF-USP. Colloidal dispersions of magnetic nanoparticles based on ferrites, sintetized at \emph{Universidade de Brasília}, are going to be studied in order to determine the relationship between the second order susceptibility tensor $\chi^{(2)}$ and the applied magnetic field, aiming to describe the SHG controllability. Likewise, it's seek to identify quantum confinement phenomena due to the nano-particles diameter studing solutions formed by particles of different sizes and their relationship with the second order electric susceptibility.