Preparation and characterization of polyoxometalate–Ag nanoparticles composite multilayer films

The multifunctional thin films (BW12/Ag NPs)n (BW12 = BW12O40, NPs = nanoparticles) were prepared by layer-by-layer self-assembly method. The (BW12/PEI–Ag+)n (PEI = polyethylenimine) composite films were achieved through alternately depositing anionic BW12 and cationic PEI–Ag+ complex. The deposition process of (BW12/PEI–Ag+)10 multilayer is linear layer-by-layer self-assembly. Under UV irradiation, Ag ions in (BW12/PEI–Ag+)n multilayer films were reduced photochemically into Ag NPs and (BW12/Ag NPs)10 films were obtained. Through UV–vis measurements, the presence of surface plasma absorption peak at 445 nm demonstrated the formation of silver NPs. The electrochemical and antibacterial activities of (BW12/Ag NPs)n films were investigated. The electrochemical results indicate that the glassy carbon electrode modified with (BW12/Ag NP)n film exhibits the electroreduction toward O2. Moreover, the (BW12/Ag NP)10 multilayer films exhibit long-lasting antibacterial properties toward Escherichia coli (E. coli).