Localized surface plasmon resonance based bowtie nanoantenna for optical biodetection

Abstract

Local Surface Plasmon Resonance is now considered one of the most promising topics due to its various applications in optics, photo catalysis, medicine and photovoltaics. Among these, Plasmonic nanoantennas have attracted considerable attention primarily due to the capability of such structures to confine and significantly enhance the incident electromagnetic field in nanometer-sized region. These metallic materials patterned at the nanoscale, exhibit interesting optical properties due to the large enhancement and localization of the electromagnetic fields. For our paper, we investigate the dependency of this energy of plasmons on the size, geometry and composition of the nanostructures as well as on the dielectric environment that surrounds them. Subsequently many such structures have been engineered to provide diverse functions including, as we report here, for biosensing. We report the behavior of two nanoparticles when they are close enough, based on their wavelength shift properties. When strong coupling takes place between them, electromagnetic fields of several times that of the incident light arise in their gap. Our paper includes, refractive index variations in the gap resulting in significantly greater displacements of resonance peaks compared to non-coupled metal nanostructures. Moreover, we report the SPR shift differences when various analytes of different refractive index is tested for biomolecular surface sensing.