Silver nanoparticles decorated polyhedral oligomeric silsesquioxane nanocages as an effective nanoadditive for improved structural and biological properties of poly(vinylidene fluoride-co-hexafluoropropylene) nanofiltration membrane

Incorporation of a well-defined functionalized polyhedral oligomeric silsesquioxane (POSS) into a polymer matrix represents a new chemical advancement for applied membrane technology. Herein, POSS nanocages densely decorated with silver (Ag) nanoparticles (NPs) were used as effective hydrophilic and antibacterial additive. In this work, first, a facile and simple chemical reduction strategy is employed to prepare the organic–inorganic hybrid nanocages of Ag@POSS by in situ reduction of the Ag NPs with octa-ammonium molecules of POSS. These Ag@POSS nanocages were added as nanofiller for the fabrication of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanohybrid membrane. Ag@POSS nanocages added PVDF-HFP membrane exhibited formation of homogeneous and stable films compared to the unmodified polymeric membranes due to van der Waals and hydrogen bonding interactions of Ag@POSS with –CH2 groups and F atoms of polymer matrix. Pure water flux measurement of nanohybrid membrane showed that Ag@POSS PVDF membrane displays dramatic increase in the permeability (1,554.6 L/m2/h) and hydrophilicity (67°) properties. Furthermore, antibacterial activity and protein adsorption capacity of Ag@POSS PVDF membrane were evaluated by quantitative analysis of living bacterial cells and protein mass adsorption using Escherichia coli and bovine serum albumin (BSA) protein, respectively. The E. coli colonies (108 CFU/mL) on the Ag@POSS PVDF membrane samples tended to decline with 0.5 × 106 CFU/mL compared to neat PVDF-HFP membrane sample (1.3 × 108 CFU/mL). The improvement in biological properties of Ag@POSS PVDF membrane is due to the formation of Ag-octamine on the surface of POSS which lead to the formation of a boundary protection film. The surface–modified POSS with Ag NPs can be used as a nanofiller in polymeric membrane for developing high-performance permeable nanofiltration and antibacterial/antifouling polymeric membranes