One-step synthesis and applications of highly concentrated silver nanoparticles with an ultra-thin silica shell

A one-step method for synthesizing high concentrations of 40–400 nm silver nanoparticles coated with an ultra-thin silica shell is described. The shell thickness can be further increased via post-synthetic precipitation of sodium silicate. The nanoparticles exhibit remarkable stability and can be concentrated to as much as 50% by weight in water and some organic solvents. It was also demonstrated that silica species catalyze the seeding and growth of silver nanoparticles. The herein described particles were used to develop simple surface-enhanced Raman spectroscopy substrates and chemiresistors.