Fabrication of surface enhanced raman scattering (SERS)-active substrates by using dip-pen nanolithography

In this study, we propose an effective strategy to prepare a stable surface enhanced Raman scattering (SERS)-active substrate by using dip-pen nanolithography (DPN) with top-down wet chemical etching. This method was made by DPN to pattern arrays, 16- mercaplohexadecaoic acid (MHA) on Au/Cr/Si substrates and then ferri/ferrocyanide etching was adopted to remove the exposed gold. It is found that a nanostructure with φ 300 nm gold dots and the distance between dot and dot is 400 nm can be obtained on the surface of substrates after etching. These nanostructure gold dots can enhance local electromagnetic fields, inducing enhancement of analytes' Raman signal. This process supplies the effective and stable SERS-active substrate which can be used as biomedical applications, such as protein chip, and microorganisms' discrimination chip.