This paper is dedicated to the further development of the Intermatrix synthesis (IMS) technique, which permits to produce a wide variety of polymer-metal nanocomposites (PMNCs) containing monometallic or bimetallic catalytically active polymer-stabilized nanoparticles (PSNPs) with the most favourable distribution of nanocatalysts inside the polymer, which is achieved by the purposeful application of the Donnan exclusion effect in the course of IMS. PMNCs containing low cost Cu-PSNPs can be used as an active element in construction of amperometric sensors for H2O2 detection. But, due to the high trend of copper nanoparticles (Cu-NPs) for oxidation under measurement conditions (in buffer solution) the sensors rapidly loose their sensitivity. The coating of Cu-NPs with platinum group metal-shell (PGM-shell) of the minimal thickness results in the protection of Cu core against oxidation while maintaining the sensitivity of core-shell NP-modified sensors at sufficiently high level. The sensitivity of the sensors in the last case enhances when applying the step-wise formation of PGM-shell of higher purity by excluding the shell contamination with core-metal. (C) 2011 Elsevier Ltd. All rights reserved.