Capping effect of CTAB on positively charged Ag nanoparticles

A facial synthesis process of silver nanoparticles (NPs) capped by cetyltrimethylammonium bromide (CTAB) is reported with exploration for the capping effect of CTAB on particles’ stability and surface properties in aqueous medium. Multidisciplinary approaches including electrophoresis, UV-visible absorption spectroscopy, Fourier-transformed infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), thermal gravimetric analysis (TGA) and small angle X-ray scattering (SAXS) are conducted to systematically investigate surface charge and the adsorbed CTAB layer structure on Ag clusters. Obtained results indicate that CTAB molecules bind strongly to silver surface via their headgroups and form a bilayer shell. Detailed analysis of SAXS and NMR data and discussion on the interaction between CTAB molecules and NPs’ surface, provide a clearer model of capped molecules on Ag clusters.