Self-Assembled SERS Substrates with Tunable Surface Plasmon Resonances

The fabrication of surface-enhanced Raman spectroscopy (SERS) substrates that are optimized for use with specific laser wavelength-analyte combinations is addressed. In order to achieve large signal enhancement, temporal stability, and reproducibility over large substrate areas at low cost, only self-assembly and templating processes are employed. The resulting substrates consist of arrays of gold nanospheres with controlled diameter and spacing, properties that dictate the optical response of the structure. Tunability of the extended surface plasmon resonance is observed in the range of 520-1000 nm. It is demonstrated that the enhancement factor is maximized when the surface plasmon resonance is red-shifted with respect to the SERS instrument laser line. Despite relying on self-organization, site-to-site enhancement factor variations smaller than 10% are obtained.