Synthesis of homogeneous silver nanosheet assemblies for surface enhanced Raman scattering applications

Conducting polymers have been proved to be effective reducing agents in the synthesis of noble metal nanoparticles. We demonstrate here the fabrication of homogeneous Ag nanosheet assemblies on conducting polymer membranes with 5 wt% polyaniline (PANI) substituted by conductive additives like graphite (G) or multi-walled carbon nanotubes (CNTs). The inclusion of conductive additives that act as electrical connectors for the PANI particles changes the surface property and creates a homogeneous nucleation environment, leading to the membrane surface completely covered by the Ag nanosheet structures. The pack density of the nanosheets can be simply tuned by modulating the concentration of AgNO(3) aqueous solution. The as-prepared Ag nanosheet assemblies with abundant interstitial sites show strong SERS responses toward the mercaptobenzoic acid (MBA) molecules, with a detection sensitivity down to 5 ppm. A proper acid etching of these Ag nanosheet structures in 0.1 M HNO(3) aqueous solution makes the nanoparticles that form the nanosheets much more exposed to the analyte molecules, and an even stronger Raman enhancement can be obtained. We believe the homogeneous Ag nanosheet assemblies supported on conducting polymer membranes can be sensitive and cost-effective SERS substrates in molecule detection.