Abstract: The kinetics of silicon dioxide shell formation on metal nanoparticles by tetraethoxysilane hydrolysis in the absence of catalysts is studied. The possibility of stabilizing Au–Ag alloy nanoparticles by coating with a 5 nm thick silicon dioxide shell is shown. A model of core–shell nanoparticles consisting of a metal core and a multilayer SiO2 shell, having a phosphor based on water-soluble porphyrin encapsulated between its layers, is proposed. It is shown that encapsulation in a multilayer SiO2 shell leads to an increase in the intensity of porphyrin luminescence.