Plasmonic and metamaterial nanoparticles for nano-light sources and next generation biomedical sensors

Nanogap-based structures have emerged as a powerful platform for enhancing light-matter interaction on the nanoscale due to their ability to confine electromagnetic fields into subwavelength volumes. This results in a high local density of optical states (LDOS), enhanced quantum yield, and efficient emission coupling, making them promising for applications such as ultrafast light sources, and biosensing. This thesis investigates and compares various nanogap configurations including all-metal, all-dielectric, hybrid dielectric/metal, and metaparticle -based nanogaps, to identify designs that maximize emission efficiency for ultrafast light sources and achieve high refractive index sensitivity for biological sensing applications.Two primary hybrid configurations were examined: silicon nanorods (SiNRs) on gold film and gold nanorods (AuNRs) on silicon substrate. Their performance was compared to their all-metal (AuNRs-Au) and all-dielectric (SiNRs-silicon) counterparts.Nanogaps were formed using polyelectrolyte multilayers (thickness ~ 14 nm), along with a monolayer of CdTe quantum dots, enabling the evaluation of emission rate and photoluminescence intensity.Experimental results showed up to 51-fold and 15-fold enhancements in the emission rate of AuNR-Si nanogaps and SiNR-Au nanogaps respectively. Compared to all-metal and all-dielectric nanogaps, the hybrid structures exhibited substantially higher emission rates, indicating stronger light-matter coupling and improved radiative efficiency. These findings are consistent with FDTD simulations.Additionally, metaparticles-based nanogap structures (MetaP1 and MetaP2) fabricating via wet-chemistry on gold film with 10 nm spacer to tune the optical response of CdTe QD monolayer. These structures showed experimental emission rate enhancements up to 30-fold, compared to 43-fold predicted by Lumerical FDTDsimulations.For biomedical sensing, plasmonic nanogap structures were developed and tested for the detection of DNA hybridization and Hepatitis B surface antigen (HBsAg). Theoretical calculations revealed outstanding performance with a bulk sensitivity of 2088.5 ± 11.5 nm/RIU and a surface sensitivity of 953.7 + 11.9 nm/RIU, exceeding many reported values.These results demonstrate the versatility and high performance of the proposed nanogap structures across emission control and biosensing applications.