Scattering vs Interference in Interferometric Scattering Spectroscopy of Plasmonic Nanoparticles

Area of Science:

• Nanotechnology
• Plasmonics
• Surface Science

Background:

• Interferometric scattering (iSCAT) is vital for studying single plasmonic nanoparticles (NPs), especially when they are too small for conventional scattering detection.
• The iSCAT signal combines NP scattering with reflected light interference, making it sensitive to substrate and environmental factors.
• This sensitivity can lead to discrepancies between iSCAT and dark-field scattering spectra, even for larger NPs.

Purpose of the Study:

• To investigate how environmental factors influence iSCAT spectra of gold NPs.
• To understand and control the interplay between scattering and interference regimes in iSCAT.
• To demonstrate a method for accurate kinetic analysis of NP morphological changes using iSCAT.

Main Methods:

• Tuning iSCAT contrast by altering the refractive index of the embedding medium, substrate reflectivity, and NP size.
• Comparing iSCAT spectra with dark-field scattering spectra.
• Utilizing a dipole oscillator model to interpret spectral lineshapes.
• Performing multi-wavelength iSCAT measurements during electrodissolution experiments.

Main Results:

• iSCAT contrast spectra of gold NPs can be shifted between scattering- and interference-dominated regimes.
• Interference effects in iSCAT can displace spectral features from the intrinsic plasmon resonance.
• A dipole oscillator model successfully explains the observed iSCAT spectral characteristics.
• Multi-wavelength iSCAT is necessary for accurate kinetic parameter extraction during NP morphological changes.

Conclusions:

• The iSCAT technique's sensitivity to environmental conditions must be carefully managed for reliable NP analysis.
• Understanding and controlling the interference contribution is crucial for interpreting iSCAT data.
• Multi-wavelength iSCAT measurements are essential for quantitative studies of dynamic NP processes like electrodissolution.