Plasmonics and SERS activity: beyond gold and silver

Abstract

The search for new plasmonic nanostructures has received significant attention recently, owing to applications in diverse fields of nanoscience and nanotechnology, and being of interest for the life sciences. Metallic nanoparticles (NP) can strongly absorb and scatter light due to their ability to support localized surface plasmon resonances (LSPR) and, therefore, play an important role in plasmonic-based techniques such as surface enhanced Raman scattering (SERS) and metal-enhanced fluorescence (MEF). Interestingly, most research in the field is still confined to Ag, Au, and less intensively Cu nanostructures, and there is an open field for the investigation of other elements such as the poor metals. In this work, we investigate plasmonic properties of different metal nanoparticles, including the post-transition metals Bi, In, Pb, and Sn; the metalloid Sb; the transition metals Ni and Co; and the metal alloy Terfenol-D. All these nanoparticles were experimentally tested for LSPR and SERS, and our results indicate SERS responses and enhancement factors comparable to the ones obtained with gold NP. The nanoparticles used in this study were produced via laser ablation synthesis in solution (LASiS) and characterized by UV-Vis optical absorption, dynamic light scattering (DLS), transmission electron microscopy (TEM), atomic force microscopy (AFM) and surface area electron diffraction (SAED). These laser-synthesized NP present increased LSPR in the near UV spectral region, yet also reveal multi-peak LSPR extending towards the visible, an interesting feature to be considered in the development of plasmonic sensors. For the Raman experiments, several organic and biological molecules were tested, and SERS activity was demonstrated for diverse combinations of NP and test-analytes at varying concentrations, down to single molecule detection.