Nanoparticles-nanostructure Cavities as Plasmonic Substrates for Sensing Applications

Y. Sharma, A. Dhawan
Indian Institute of Technology, Delhi, IN

Keywords: surface enhanced Raman scattering, plasmonics, sub-5 nm, large area fabrication, biosensing

Summary:

We present ‘nanoparticle-nanostructure’ plasmonic substrates which allow easily achievable sub-5 nm gaps and a possibility of large area fabrication. These substrates — based on plasmonic nanocavities formed by arrays of plasmonic nanoparticles lying inside periodic metallic nanostructures — can be used as tunable surface-enhanced Raman scattering (SERS) substrates and localized surface plasmon resonance (LSPR) sensors due to the tunability of cavity modes in the gap regions. Theoretical studies were conducted, using Finite Difference Time Domain (FDTD) modeling, to understand the plasmon resonance tunability as a function of gaps in these hybrid plasmonic substrates. Our analysis revealed that these gaps — between the nanostructures and nanoparticles as well as between two neighbouring nanoparticles — play a combined role in tuning the resonance wavelength and the magnitude of electromagnetic field enhancement. Replacing the spherical nanoparticle arrays inside the nanostructures with nanorod arrays revealed the possibility of tuning the plasmon resonance to the near-infrared regime.Thus, these gap-controlled novel plasmonic substrates can provide strong and tunable field enhancements, and will be employed for chemical and biological sensing applications.