The preparation of palladium nanoparticles on the surface of a polymer inclusion membrane (PIM) consisting of 30 wt% di-(2-ethylhexyl)phosphoric add and 70 wt%, poly(vinyl chloride) is described. The Pd(II) ion was firstly extracted into the membrane via cation-exchange and then subsequently reduced to form clusters of palladium nanoparticles on the membrane surface. The reducing agents investigated were NaBH4, trisodium citrate, sodium formate, and L-ascorbic acid. Best results were obtained with L-ascorbic acid which at pH 2.0 formed a uniform layer of palladium nanoparticle clusters on the surface of the PIM with an average nanoparticle size of 38 nm. Factors such as pH, temperature and intensity of mixing of the L-ascorbic acid solution, reduction time and Pd(II) loading of the PIM were found to have a significant influence on the surface coverage and size of the palladium nanoparticles. (C) 2015 Elsevier B.V. All rights reserved.