en Research Paper Research Paper Modification of MnFe₂O₄@SiO₂core-shell nanoparticles with (3-aminopropyl) triethoxysilane (APTES) was investigated. The magnetite MnFe₂O₄ nanoparticles with an average size of ~33 nm were synthesized through a simple co-precipitation method followed by coating with silica shell using tetraethoxysilane (TEOS); that has resulted in a high density of hydroxyl groups loaded on nanoparticles. The prepared MnFe₂O₄@SiO₂nanoparticles were further functionalized with APTES <em>via</em> silanization reaction. For having suitable surface coverage of APTES, controlled hydrodynamic size of nanoparticles with a high density of amine groups on the outer surface, the APTES silanization reaction was investigated under different reaction temperatures and reaction times. Based on dynamic light scattering (DLS) and zeta potential results, the best conditions for the formation of APTES-functionalized MnFe₂O₄@SiO₂nanoparticles were defined at a reaction temperature of 70 &deg;C and the reaction time of 90 min. The effectiveness of our surface modification was established by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Fourier transforms infrared spectroscopy (FTIR), and vibrating sample magnetometer&nbsp;(VSM). The prepared magnetite nanostructure can be utilized as precursors for synthesizing multilayered core-shell nanocomposite particles for numerous applications such as medical diagnostics, drug, and enzyme immobilization, as well as molecular and cell separation. Magnetite nanostructure,APTES,Magnetite nanostructure,MnFe2O4 core-shell nanoparticles,Silanization,Silica shell 77 86 http://ijmse.iust.ac.ir/browse.php?a_code=A-10-2590-2&slc_lang=en&sid=1 N. Akhlaghi nedaakhlaghi4@gmail.com 1800319475328460011420 1800319475328460011420 No Faculty of Chemical EngineeringBabol Noshirvani University of TechnologyBabol, Iran Post Code 47148-71167 G. Najafpour najafpour8@gmail.com 1800319475328460011421 1800319475328460011421 Yes Distinguished ProfessorFaculty of Chemical EngineeringBabol Noshirvani University of TechnologyBabol, Iran Post Code 47148-71167 M. Mohammadi m.mohammadi@nit.ac.ir 1800319475328460011422 1800319475328460011422 No Faculty of Chemical EngineeringBabol Noshirvani University of TechnologyBabol, Iran Post Code 47148-71167