A two-step immobilisation of silver nanoparticles on solid substrates using polyethylenimine as an adhesive and a reduction linker, where the primary coating of solid substrates by polyethylenimine occurs followed by production of silver nanoparticles covalently anchored on the polymer surface due to a reduction effect of the polyethylenimine functional groups and therefore, no nanoparticles are released to environment. The method permits working under aqueous conditions, does not use any reducing agents, stabilisers or toxic solvents and can universally be applied for anti-microbial treatments of all types of solid substrates.