Optical Properties of Anisotropic Gold Nanoframes

In recent years, a lot of effort has been made to design and create anisotropic plasmonic nanostructures including metallic bowtie and anisotropic ring or frame nanostructures to achieve plasmonic hotspots in particular for enhanced-spectroscopies and sensing applications. Among all, triangular gold nanoframes (TGNFs) are of high interest due to their optical anisotropy, tunable dimensions, and also their strong, high coverage plasmonic fields resulting from the coupling between the external and internal plasmon modes. Here we show that using TGNFs has four-fold advantage in comparison to triangular silver nanoprism (TSNP): 1) A nanoframe has 70% less material than nanoprism but generates up to seven-fold increase in the total electric field enhancement. 2) TGNFs are much more stable than TSNP due to chemical inertness of gold. 3) TGNFs have no surfactant/organic molecule which allows for an increased reactivity and LSPR intensity. 4) TGNFs are more sensitive both for LSPR sensing and Surface-Enhanced Raman Scattering (SERS) applications. The results from TGNFs will guide us to design other frame-based structures with various shape and compositions to generate high electric field enhancement.