Surface enhanced Raman scattering from transition metal nano-wire array and the theoretical consideration

Abstract

Co, Ni, Pt and Pd nano-wire arrays with diameter of about 50 nm were fabricated by means of template synthesis. By alternating current (AC) electrodeposition these metals were filled into channels of anodic aluminum oxide (AAO) film respectively. Nano-electrode arrays having good electric contact with the substrate was also fabricated by employing combined electroless deposition and the AC electrodeposition. Strong surface enhanced Raman scattering (SERS) was observed from both metal nano-wire arrays and nano-electrode arrays after partial removal of the AAO film. The SERS intensity of probe molecules adsorbed at the arrays depends critically on the length of the nano-wire explored at the surface. The experimental results agree well with the corresponding theoretic calculations based on electromagnetic enhancement. The lightning rod effect may play an important role for the enhancement of the Ni nano-rod under the favorable length. It has been shown that metal nano-wire arrays can be developed to a new generation of substrate exhibiting very high SERS activity, especially for transition metals. These well-ordered surface nano-structures can also be served as a proper model for the SERS mechanism study.