DirectionalPlasmonicNanoSensors_Report

Abstract

For the last decade plasmonic nanoparticles has been considered as promising candidates for future sensing applications. Due to their incredible ability to detect minute changes in their local dielectric environment, plasmonic nanoparticles exhibit numerous properties suitable for material and biomedical industries. General methods, which utilizes localized surface plasmon resonances (LSPR) for sensing, are based on detecting extinction resonance peak shift in order to observe changes in refractive index of the local environment. In this study we instead focus on a selfreferenced label-free sensing scheme based on directional scattering from samples consisting of asymmetric monometallic Au dimers. LSPR peak shift measurements moreover often relies on complicated and expensive measuring devices such as microscopes and spectrometers. In order to further suppress economic cost and simultaneously increase simplicity a microscope-free optical setup was designed and manufactured to perform single-wavelength experimental sensing measurements. All samples were manufactured using the hole-mask colloidal lithography method. We also present theoretical models illustrating how supreme sensitivity can be achieved, using a sensing scheme which measures ratio of intensities scattered in opposite directions from asymmetric nanostructures. Moreover experimental bulk- and local refractometric measurements are conducted to support the ability of performing biosensing.