Cellulose diacetate semipermeable membrane embodying noble metal nanoparticles (Au and Pt) was prepared. AuCl4- or ptCl(6)(2-) immobilized in the semipermeable membrane during the transition process of sol to gel was reduced to nanoparticles by the penetration of NaBH4. Semipermeable membrane was essential to protect nanoparticles from aggregation as well as remove byproducts from the membrane. Electrochemical studies demonstrated the electrochemical properties of Au nanoparticles and the electrocatalytic behavior of Pt nanoparticles embedded in the membrane. The embedded nanoparticles could be further leached out from the semipermeable membrane by Iodine treatment. This system could be found applications in fields such as electrochemistry, biosensors, catalysis, bioseparation, etc. (c) 2005 Elsevier B.V. All rights reserved.