Formation of a gold/silver-containing composite

Preparation of the Au/Ag composite in the 1 : 1 water–ethanol mixture in the presence of poly-N-vinylpyrrolidone has been optimized; the so prepared composite is applicable in the absorption spectroscopy based on the effect of plasmon resonance energy transfer. Of the studied cationic, anionic, and non-ionic polymer, only the 340 kDa poly-N-vinylpyrrolidone induced the formation of a monodisperse Au/Ag sol with the average hydrodynamic diameter of the particles of ≈73 nm. The composite structure built of the polymer core covered with the Au/Ag nanoparticles has likely formed. The prepared composite binds both anionic and cationic metal porphyrins preserving the efficient transfer of the plasmon resonance energy.