Disclosed is a multifunctional colloidal nanocomposite derived from nucleophilic substitution-induced layer-by-layer assembly in organic media. The multifunctional colloidal nanocomposite includes: silica colloids coated with aminopropyltrimethoxysilane; and a plurality of nanoparticle layers highly densely adsorbed onto the coated silica colloids. The multifunctional colloidal nanocomposite has a highly dense multilayer structure in which 2-bromo-2-methylpropionic acid (BMPA)-stabilized quantum dot nanoparticles and an amine-functionalized polymer are adsorbed onto silica colloids using a nucleophilic substitution reaction-based layer-by-layer assembly method. Due to this structure, the multifunctional colloidal nanocomposite can be dispersed in various organic solvents, including polar and nonpolar organic solvents. In addition, the multifunctional colloidal nanocomposite can be utilized in various applications, such as nonvolatile memory devices, magnetic cards, and optical display films due to its strong magnetic and photoluminescent properties, high crystallinity and functional stability, and good superhydrophobicity. Further disclosed a method for preparing the multifunctional colloidal nanocomposite.