A method for the coating of a polymer inclusion membrane with a monolayer of silver nanoparticles

The preparation of silver nanoparticles (AgNPs) is described using a polymer inclusion membrane (PIM) consisting of 45% (m/m) di-(2-ethylhexyl)phosphoric acid (D2EHPA) and 55% (m/m) poly(vinyl chloride) (PVC) as a template. The Ag(I) ion was firstly extracted into the membrane via cation-exchange and then subsequently reduced with NaBH4, trisodium citrate, citric acid, or l-ascorbic acid to form AgNPs. The most effective reducing agent was found to be l-ascorbic acid which at pH 2.0 formed a uniform monolayer of AgNPs of an average size of 360 nm on the surface of the PIM. Citric acid also produced AgNPs but these were embedded in the bulk of the membrane and did not provide a good surface coverage. NaBH4 and trisodium citrate, on the other hand, gave rise to the formation of black silver oxide on the membrane surface. Factors such as the membrane loading with Ag(I), PIM composition, reduction time, temperature and shaking time were found to have a significant influence on the surface coverage and size of the AgNPs.