Sensitivity and optimization of localized surface plasmon resonance transducers

Area of Science:

• Nanotechnology
• Materials Science
• Optical Physics

Background:

• Gold nanoisland films exhibit localized surface plasmon resonance (LSPR), making them promising for optical sensing.
• Understanding the relationship between film morphology and sensing performance is critical for developing effective biosensors.

Purpose of the Study:

• To investigate the surface plasmon distance sensitivity and refractive index sensitivity (RIS) of gold nanoisland films with varying thicknesses and morphologies.
• To evaluate the relative sensitivity to adsorption on and between gold islands.
• To resolve discrepancies in RIS measurements and establish correlations with film properties.

Main Methods:

• Fabrication of gold nanoisland films on glass via evaporation and annealing.
• Utilizing layer-by-layer polyelectrolyte multilayer assembly to probe sensitivity.
• Independent determination of RIS using various solvents.
• Analysis of optical response changes (wavelength shift and intensity change).

Main Results:

• A direct correlation was observed between surface plasmon decay length and RIS; both increase with average island size.
• An apparent discrepancy in RIS behavior for wavelength shift versus intensity change was resolved by normalizing intensity change RIS to island surface density.
• Optimal sensing performance requires balancing RIS and decay length with analyte-receptor system dimensions.

Conclusions:

• Larger gold islands generally provide better sensitivity for thicker adlayers.
• Smaller gold islands yield a larger response for thinner adlayers, despite lower RIS.
• Transducer design for LSPR sensing must consider the interplay between island size, RIS, and decay length for specific applications.