Solution conductivity as a key factor for thin silica coating on colloidal silver

In order to utilize silver nanoparticles for various applications such as photocatalysts while maintaining their chemical stability, enhanced electric fields on the nanoparticle surfaces induced by localized surface plasmon excitation must be used effectively. For satisfying these requirements, an ultrathin silica coating with a thickness of only a few nm was formed around silver nanoparticles by a chemical reaction in a solution, while parameters such as the amount of sodium silicate and the number of dialysis procedures performed were changed. As a result, it was found that a key factor for obtaining stable thin-silica-coated silver nanoparticles is the conductivity of the solution. Using a solution with an appropriate conductivity above 2.7 mS/m, silica films can be coated on silver nanoparticles without causing deterioration of the plasmonic activity resulting from the aggregation of silver.