Cascaded plasmon resonant field enhancement in protein-conjugated gold nanoparticles: Role of protein shell

We study the cascaded plasmon resonant field enhancement in core–shell nanoparticles using the coupled dipole method. It is found that internal field inside protein-conjugated gold nanoparticles remains constant for large wavelengths of light but is significantly enhanced at 5944 nm due to the screening from the protein shell. The maximum ratio of the internal field to the incident field can reach up to 12. Effects from surrounding nanoparticles on the peak position in the internal field spectra are relatively weak. These findings pave a pathway for designing the state-of-the-art biosensing based on plasmonic-nanoantenna in infrared regime.