An application of AAO template: orderly assembled organic molecules for surface-enhanced Raman scattering

High-density ordered arrays of core–shell nano-pillars of Ag–perylene were fabricated using an anodic aluminium oxide (AAO) template which was first embedded with the perylene molecules, followed by an electrochemical deposition of Ag. The surface-enhanced Raman scattering (SERS) spectrum obtained from this system showed well-resolved Raman peaks with good signal-to-noise ratios and little fluorescence background. This is in sharp contrast to the SERS of the individual Ag–perylene nanorods removed from the same AAO template, and the SERS of perylene molecules adsorbed on Ag colloidal nanoparticles. In the latter two cases, the SERS spectra consisted of broad and not-so-well-resolved Raman peaks with a strong fluorescence background. It is believed that the orderly assembly of the perylene molecules on the inner walls of the pores of the AAO template along the Ag nano-pillars led to fluorescence quenching. The high-density ordered arrays of Ag nano-pillars brought forth a surface plasmon resonance for the SERS effect. The present AAO template system offers a new substrate for studying SERS of highly fluorescing molecules.