Stable silver colloidal dispersions using short chain polyethylene glycol

Herein we report a ‘one pot’ facile method for environmentally benign production of stable Ag colloids, using short chain polyethylene glycol as solvent, reducing agent and stabilizer. Stable spherical metal particles 15–30 nm in diameter with a well-crystallized structure were obtained at 30 °C. Heating to 60 °C resulted in increased spherical sizes, and heating over 90 °C led to a mixture of shapes: smaller spherical crystallites and bigger triangular and pentagonal nano-sized prisms. The stability of the Ag colloids submitted to normal chemical laboratory light over a 6-month period was monitored by UV–vis and electron microscopy. The colloids prepared at 30 and 60 °C were stable, while in the colloids obtained at 120 °C we observed significant particle growth and aggregation of nanoparticle assemblies sized up to several micrometers.