The synthesis of silver nanoprisms in aqueous solution using poly(N-vinyl-2-pyrrolidone) (PVP) with different molecular weights (29, 55 and 1300 kg mol⁻¹) as a stabilizing agent is described. Low molecular weight PVP (55 kg mol⁻¹) is indicated for the preparation of a stable blue solution containing Ag nanoprisms via extended irradiation of a yellow colloidal solution of nanospheres with polychromatic visible light. The fluorescence properties of some cationic dyes (acridine, 9-aminoacridine, Nile Blue and auramine), free and bound to poly(methacrylic acid), have been studied in the presence of different shaped Ag colloidal particles in solution. Only auramine displays an amplification of the fluorescence signal with increasing colloid concentration, while the fluorescence of the other dyes is quenched by interaction with the polymer-stabilized metal nanoparticles.