How to avoid a negative shift in reflection-type surface plasmon resonance biosensors with metallic nanostructures

Area of Science:

• Plasmonics
• Nanotechnology
• Biosensing

Background:

• Surface Plasmon Resonance (SPR) is a label-free optical technique used for detecting biomolecular interactions.
• Metallic nanostructures on metal films can exhibit unpredictable negative SPR shifts upon analyte adsorption.
• Anomalous dispersion and destructive interactions between plasmon modes can cause these shifts.

Purpose of the Study:

• To demonstrate a method for preventing negative SPR shifts using a dielectric film.
• To enhance the sensitivity and reliability of SPR-based biosensing systems.
• To explore the applicability of this SPR system for biomolecular reactions.

Main Methods:

• Experimental demonstration of a reflection-type SPR system.
• Coating metallic nanostructures with a low refractive index dielectric film (MgF2).
• Utilizing gold nanorods for plasmonic properties.

Main Results:

• The dielectric film successfully prevented negative SPR shifts.
• The SPR system showed an enhanced sensitivity of over 6 times.
• A reliable positive SPR shift was observed, indicating improved performance.

Conclusions:

• Dielectric film integration compensates for anomalous dispersion and prevents destructive plasmon interactions.
• The proposed SPR system offers enhanced sensitivity and reliable detection for biomolecular binding events.
• This approach broadens the applicability of SPR technology in diverse biosensing applications.