Surfactant mediated silver synthesis: Influence of surfactant molecular structure on the size and shape of silver particles

Abstract

The current work employs non-ionic surfactants polyethylene glycol tert-octylphenyl ether (Triton X-114) and polyoxyethylene (20) sorbitan monolaurate (Tween 20) as capping agents for synthesizing silver particles. Formation of icosahedrons and Wulff polyhedrons are thermodynamically preferable for FCC silver, and anisotropic morphologies such as triangular/hexagonal platelets are less likely. Yet, with the use of Triton X-114, appreciable quantity of platelets is obtained. Beyond the molar ratio of 2.5 (Triton X-114: AgNO3), only anisotropic particles are identified. It is believed that preferential adsorption of the surfactant inhibits crystal growth along 〈111〉 direction. Instead, the particles grow along the edges of the hexagonal/triangular plates. In contrast, the use of Tween 20 yielded silver (nano)particles with spherical shape. The presence of multiple polymeric chains in the Tween 20 molecule exhibits strong interaction with the silver particles by restricting growth along multiple facets. These observations indicate the significant role of the molecular structure of capping agents in determining particle size and morphology.