Polyethyleneimine-stabilized palladium nanoparticles for reduction of 4-nitrophenol

Palladium nanoparticles (Pd NPs) have been drawing great interest as catalysts for water treatment. Herein, high molecular weight polyethyleneimine (PEI) (molecular weight: 70 kDa) was used as template to stabilize Pd NPs. PEI was incubated with disodium tetrachloropalladate, followed by reduction with sodium borohydride. Pd NPs had narrow size distribution with diameter from 3.64 to 6.20 nm. The PEI-stabilized palladium nanoparticles (Pd-n-PEI NPs) showed excellent long-term stability and positive zeta potential in phosphate saline buffers with different pH values. In addition, Pd-n-PEI NPs exhibited high efficiency for catalysis of 4-nitrophenol (4-NP) in aqueous solution. The catalytic reduction of 4-NP followed the pseudo-first-order behavior, which had the highest catalytic ability (k(nor) = 229). The enhanced properties can be attributed to the high stability and smaller size of Pd-n-PEI NPs in aqueous solution, resulting from the application of PEI template. This method can be used to prepare highly stable metal nanoparticles with potential applications in catalysis of polluted water in the future.