The effect of silver nanoparticle size on performance and antibacteriality of polysulfone ultrafiltration membrane

Antibacterial polysulfone ultrafiltration membranes were fabricated using different silver nanoparticles in the casting solution. X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle and dead end filtration experiment were carried out to characterize the morphology and performance of the prepared membranes while inhibition zone and filtration of bacterial suspension were used to investigate the antibacterial behavior of the membranes. Sliver release was measured in order to investigate the kinetic of silver leaching from the membranes. Less crystalline structure was obtained for membrane with smaller silver nanoparticles as confirmed by the XRD patterns. In addition, SEM studies also showed that surface pores size was reduced by adding silver nanoparticle in the casting solution. Cross section of membranes were totally affected by the addition of silver nanoparticles so that tighter finger-like structure appeared by adding 70 nm silver nanoparticles. As shown in SEM images, a dense cross section was formed by addition of 2 wt.% silver nanoparticles with size of 30 nm in the casting solution. Surface roughness parameters obtained from AFM images showed that the silver nanoparticles with size of 70 nm caused rougher surface for membrane. However, the silver nanoparticles with the size of 30 nm resulted in formation of membranes with smoother surfaces. Contact angle measurement also proved more hydrophilic surface for silver modified membranes. Inhibition zone and bacterial filtration showed higher antibacteriality for membranes with smaller silver nanoparticles. (C) 2012 Elsevier B.V. All rights reserved.