Surface-enhanced Raman scattering and catalytic activity studies over nanostructured Au-Pd alloy films prepared by DC magnetron sputtering

Nanostructured Au33Pd67 alloy films were fabricated on glass using one-step air plasma DC magnetron sputtering. The films exhibited highly sensitive detection of dye molecules (RhB and CV) by the surface-enhanced Raman scattering (SERS). The synthesized films also showed good catalytic properties for the reduction in 4-nitrophenol at pH approximate to 9.8. Such unique characteristic of the films was linked to the evolution of nanostructure, which can be controlled simply by the sputtering time. At the shorter sputtering time (10 and 20 s), the film was composed of isolated particles. By increasing the sputtering time (30 and 40 s), agglomeration of such nanoparticles resulted in the formation of the partially connected island nanostructures (about 38 nm) which can be confirmed by TEM and electrical resistivity measurement. The detection limit of 1 x 10(-12) M RhB and 1 x 10(-8) M CV with an enhancement factor of 7 x 10(7) and 3.3 x 10(4), respectively, was achieved over the film synthesized at the sputtering time of 30 s. The high sensitivity of this film can be ascribed to the strong electromagnetic field at the junction spots formed between the two adjacent islands. Moreover, this film has a slightly lower SERS, and better catalytic properties, in contrast to Au (30 s) film. Finally, the film providing efficient SERS enhancement is not the most active catalyst. Unlike the SERS, the catalytic activity depends highly on the amount of AuPd deposited.