Femtomolar molecular detection with CNT based SERS substrate

Abstract

We report a highly sensitive substrate for surface enhanced Raman spectroscopy (SERS) enabled by arrays of metal (gold and silver) nanowires on the template of vertically aligned (VA-) carbon nanotubes (CNTs) coated with a high-k dielectric hafnia (HfO2) layer as a potential barrier. Femtomolar detection of 1,2 bis-(4-pyridyl)-ethylene (BPE) is demonstrated with this non-resonant substrate. Comparison of SERS performance with and without the hafnia potential barrier establishes the critical contribution of this dielectric nano spacer to the large sensitivity. This behavior is attributed to the relief of electric charge leakage from metal to the CNT template in the presence of the virtual energy potential barrier. The VA-CNT substrate, when covered by dielectric barriers, can be a great template for a practical and reproducible SERS substrate.