PolyHIPE materials are polymers, which are formed by polymerization of high internal phase emulsions. PolyHIPEs that contain glycidyl methacrylate can be functionalized due to epoxy groups it possesses. To give an example, polymer can be consequently functionalized with aldehyde groups and quaternary amine cation. Aldehyde groups can be used as reducing agent when forming nanoparticles using Tollens’ reagent and this masters’ thesis presents this procedure’s different parameters and their influence. Quaternary amine cation can be used for immobilizing silver nanoplates. This thesis presents how by addition of hydrogen peroxide the shape of silver nanoplates can be influenced. The thesis also explores the influence of silver nanoplate’s size and shape on surface plasmon resonance. Silver nanoplates were immobilized od polyHIPE samples, which were functionalized with different concentrations of quaternary amine cation and this thesis shows, how those differences influence the immobilization. The catalytic reaction in which 4-nitrophenol is reduced to 4-aminophenol was explored by using composites involving nanoparticles produced by Tollen’s reagent and nanoplates produced with hydrogen peroxide, respectively. The stability of prepared samples was also explored as it is very important in heterogeneous catalysis.