Study of single nanoparticle spectroscopy and Exciton-plasmon coupling

Abstract

Plasmonic nanostructures give major insights into the interaction between light and matter at nanoscale. Also, they have potential practical applications in various elds such as in biosensing(sensing of di erent types of molecules, proteins), plasmonic circuits, as metama- terials. The realization of their practical application is possible only when one understands their properties entirely. Therefore, in this thesis, we study the technique to understand localized surface plasmon resonance(LSPR) properties. Also, we have made an attempt to probe the plasmon-exciton coupling. Therefore this thesis is divided into two parts. In the rst part, we have studied a technique which can collect single particle spectra called dark eld spectroscopy. The setup is based on Total Internal Re ection of light. The study is majorly focused on scattering due to sub-wavelength structures. Gold nanos- tars prepared by us was probed by dark eld scattering technique. We have discussed the information that we can extract from the spectra obtained. The next part is focused on coupling of plasmonic nanostructure with two-dimensional material Molybdenum disul de MoS2 which is an excitonic material. 2-D material MoS2 has tremendous applications in the eld of optoelectronics because of their direct bandgap nature because of which it shows Photoluminescence. Our system comprises of silver nanowires on few layers of MoS2. In our experiments, we have compared the Photoluminescence emission from MoS2 and that from wire on MoS2, both its magnitude and directionality. Our results show that silver nanowire on MoS2 shows nanoantenna e ect. Taking this study forward can give major insights about coupling of excitons and plasmons, also the results themselves have implications in nanophotonic circuits.