Nanospheres of silver nanoparticles: agglomeration, surface morphology control and application as SERS substrates.

This paper reports a high-yield synthesis of Ag nanospheres made up of primary nanoparticles. The size of the silver nanospheres can be controlled by changing the concentration of poly(vinylpyrrolidone) (PVP) which acts as a stabilizer. In addition, the surface morphology of the nanospheres can be well controlled through controlling the shape of primary Ag nanoparticles by introducing a small quantity of ionic capping agents in the solution. Different surface morphologies of Ag nanospheres lead to different surface plasmon resonance (SPR) and surface-enhanced Raman scattering (SERS) properties. The SERS property of the nanospheres used as substrates is very sensitive to the nanoscale characteristics of the surfaces, and the nanospheres with sharp tips on their surface exhibit much better Raman scattering enhancement than non-agglomerated spherical Ag nanoparticles.