Improved Biosensing Capability with Novel Suspended Nanodisks

In this work, we provide a theoretical and experimental study of the adverse effects that inherently arise when plasmonic nanoparticles are attached to a solid support. Using the example of short-ordered arrays of gold nanodisks, we show that the right choice for the thin metal adhesion layer that is used to ensure stable binding of the nanodisks to the substrate is extremely important to achieve competitive limits of detection. Furthermore, we show that the presence of the high refractive index support undisputedly results in lower bulk and surface sensing sensitivities. To minimize this effect, we propose an isotropic chemical etch of the supporting substrate, resulting in dielectric nanopillars which distance the nanodisks from this high refractive index material. We demonstrate that this novel method not only preserves the mechanical stability but also strongly increases the sensing performance of these suspended nanodisk arrays. This is demonstrated via the label-free detection of DNA hybridization, reflecting the robustness and the surface-regenerative capabilities of these pillar-supported nanodisk arrays. Furthermore, through the successful implementation of this sensitivity enhancing method to more complex nanostructures, such as arrays of closely distanced nanodisk dimers, this method profiles itself as a simple strategy to improve the limits of detection of a wide variety of nanoplasmonic sensors.