The use of nanoantennas to enhance molecular fingerprinting has an important application in the field of biomolecular reaction sensing. Nanoantennas, which are plasmonic metastructures that manipulate light to generate a localized electric field, or hotspot, can be scaled and coupled with Raman spectroscopy and surface enhancement also known as surface enhanced Raman spectroscopy (SERS) to achieve single molecule structural changes, such as signal transduction mechanisms in eukaryotic cells. In this work, we explore an optimal design of nanoantennas in the bowtie configuration using computer simulation technology (CST) microwave studio and simulate gold-contact bowtie nanoantennas with varying fabrication parameters. Simulated gold-contact bowtie nanoantennas are designed with varying tip-to-tip gap distances ranging from 20-100 nm, contact thicknesses ranging from 15-45 nm, and side lengths ranging from 20-300 nm based on the protein chain lengths involved in post translational modifications within eukaryotic cells. Based on our current Jobin Yvon BX41 Confocal Raman microscope configuration, the bowtie antennas are modeled using a one-micron diameter spot and a 532 nm light source to achieve an optimized design. The nanoantenna is fabricated using electron beam lithography (EBL), electron beam evaporation and deposition (EBED), and metal lift-off process. In comparison with other demonstrations of nanoantenna-enhanced Raman spectroscopy, our design is unique for measuring protein phosphorylated events in eukaryotic cells. Based on the optimized design, electric field intensities in the gap were estimated at 7.30 V/m.
Using surface-enhanced Raman spectroscopy (SERS), an electric field can be manipulated to map biochemical reactions in real time. The goal of this lab study will impact bio-photonics, material science, and electrical engineering fields by providing methods of Raman signal enhancement. This work involves use of nanoantennas, a nanoscale antenna like structures used for sending and transmitting electromagnetic waves. This project will present the optimization steps within the nanoantenna’s design. The team used computer simulation technology (CST) studio to perform electromagnetic simulations by modeling various bowtie nanoantenna geometries to obtain an optimized structure based on varying gap distances, side lengths, and layer thicknesses. These findings are then used to optimize bowtie nanoantenna designs. The presented CST simulations display trends producing a model of an optimized design. The design parameters that were varied are the side lengths of the nanoantennas ranging from 80-110 nanometers (nm), the gap distances between the nanoantenna pairs ranging from 20-40 nm, and the gold thickness layer ranging from 15-45 nm. We have chosen to use fixed wavelength input for our model that matches our own Raman instrument, a Jobin Yvon BX41 Confocal Raman microscope, which is equipped with a 532 nm excitation source. Results are displayed in a maximum volts/meter (V/m) calculation which is shown numerically and on a 3D phase plot. Using this data, the optimized design was found and is used to aid in biochemical reaction detection. In a brief description of our final design from CST simulation our lab found a 90nm side dimension followed by a 20nm gap distance with a 15nm gold thickness was the most optimized design.