Spectrophotometric Observations of the Adsorption of Organosulfur Compounds on Colloidal Silver Nanoparticles

A silver colloid (mean particle size 6 nm) is prepared via photochemical reduction of Ag + ions. After total silver ion reduction, the colloid exhibits an extraordinarily intense surface plasmon absorption band. The absorption band is strongly damped by small concentrations of carbon disulfide, thiophenol, and diethyl disulfide. Carbon disulfide is irreversibly adsorbed, and so is diethyl disulfide. The irreversible adsorption is attributed to the high reactivity of the nanoparticles due to their low Fermi level potential. It is proposed that this in turn leads to dissociative adsorption of the disulfides onto the silver particles. Weaker damping is observed for thiophene, thiourea, and diethyl sulfide. The damping of the plasmon absorption band is attributed to the electronic distortion of a thin layer within the particle by the adsorbate−particle interaction.