Surface Characterization of Passivated Ag Nanoparticles

Abstract

Nanoparticles, typically formed from a metal passivated with an organic monolayer, have interesting electronic and optical properties due to their nanometer size. We seek to chemically alter the surface of Ag nanoparticles so hydrophobic ligands are positioned on one hemisphere of the nanoparticle and hydrophilic ligands are situated on the opposite side. A Langmuir-Blodgett trough was used to characterize films of the nanoparticles arranged at the air-water interface. Passivated Ag nanoparticles were synthesized and diluted in chloroform or toluene and spread at the air-water interface. A section of the film was transferred onto the surface of mica by the Langmuir-Schaefer technique and the contact angle was measured using a home-built goniometer. The average contact angle that we obtained for water with the nanoparticle film was 20? ? 2?. Infrared (IR) spectroscopy was used to characterize solid silver nanoparticles within a potassium bromide pellet. Although IR spectroscopy could not distinguish the position or arrangement of the ligands, it was capable of revealing the components that were associated with the surface of the silver nanoparticle.