Strong Spatial and Spectral Localization of Surface Plasmons in Individual Randomly Disordered Gold Nanosponges

Area of Science:

• Nanotechnology
• Plasmonics
• Spectroscopy

Background:

• Porous nanosponges with 10 nm ligaments show potential for plasmon-enhanced spectroscopy and catalysis.
• Surface plasmon localization in hot spots is theorized to cause their unique optical properties.
• The existence of these hot spots has not been experimentally confirmed.

Purpose of the Study:

• To experimentally prove the existence of hot spots in gold nanosponges.
• To characterize the spatial and spectral confinement of these hot spots.
• To demonstrate the potential of nanosponges for advanced optical applications.

Main Methods:

• Scattering-type scanning near-field nanospectroscopy (s-SNOM) was employed.
• Local near-field scattering spectra were recorded on individual gold nanosponges.
• The nanoscale optical properties were investigated at the 10 nm scale.

Main Results:

• Spatially and spectrally confined modes were observed at the 10 nm scale.
• Individual hot spots exhibited high quality factors exceeding 40.
• Predicted Purcell factors reached up to 10^6, indicating significant field enhancement.

Conclusions:

• The experimental evidence confirms the existence of nanoscale hot spots in gold nanosponges.
• These hot spots enable strong light localization and enhancement.
• Gold nanosponges are a promising platform for nonlinear optics and strong-coupling physics.