Henrique Vilhena

PhD Student
Project title: Development of meta-material based photonic sensors for environmental monitoring

Surface-enhanced Raman spectroscopy (SERS) has been used in the development of sensing devices that can challenge other chemical analysis techniques. SERS sensors show promise in the detection of environmentally relevant compounds such as pharmaceutical residues by being highly sensitive, compact and requiring no sample preparation. Arrays of periodic nanostructures such as pairs of gold dipoles over silica can be tuned to the Raman excitation laser wavelength. This will result in the formation of areas of highly intensive electric field named “hot spots” which can greatly enhance the Raman scattering of molecules in their vicinity. When compared to their non-periodical counterparts, these structures show great controllability but suffer from low enhanced Raman intensity. In this project we aim to increase the sensitivity and effectiveness of these structures by optimizing the nanoparticle density per area. This process needs to be carefully monitored as it can result in increasing local heating as well as shifts in the resonant wavelength. Through simulations, nanofabrication and characterization we have designed and fabricated arrays of these dipolar structures and their optimized optical and Raman responses were measured. We believe that our results will pave the way for the development of more reliable and sensitive environmental monitoring devices.