Potential of graphene for shape-directing agent free growth of highly oriented silver particles and their application in surface enhanced Raman scattering

Controlling the shape of metal nanoparticles is generally accomplished using shape-directing agents. Particle synthesis without shape-directing agents and shape control have attracted strong interest given the side effects of the shape-directing agents. Here, the potential of graphene in the deposition of metallic nanoparticles with different morphologies without using shape-directing agents was investigated. Doping graphene with nitrogen via plasma treatment enhanced the metal reduction. The nitrogen content was varied by changing the plasma treatment time. Nitrogen doping mainly occurred at boundary-like defects and involved pyrrolic nitrogen as the major chemical configuration. Graphene grown on copper substrate grown via chemical vapor deposition was used to deposit spherical silver nanoparticles throughout the graphene along with microparticles that were randomly distributed on the surface. Transition of microparticles of silver from dendrites to well-defined platelets morphologies was observed with nitrogen-doped graphene after 10 min of nitrogen plasma exposure. The number density of silver particles was controlled by varying the plasma treatment time. Surface-enhanced Raman scattering activity of these silver particles grown on graphene using copper substrates was assessed using a Rhodamine 6G Raman probe in the concentration range of 10 nM to 1 mM.