A Sensitive and Stable Surface Plasmon Resonance Sensor Based on Monolayer Protected Silver Film

Area of Science:

• Nanotechnology
• Biosensing
• Surface Chemistry

Background:

• Gold-based surface plasmon resonance (SPR) sensors are widely used but can be limited by performance and cost.
• Silver-based SPR sensors offer superior field enhancement and penetration depth compared to gold.
• Bare silver films suffer from instability in aqueous environments, hindering practical applications.

Purpose of the Study:

• To develop a stable and highly sensitive silver-based SPR sensor.
• To investigate the protective efficacy of a self-assembled monolayer (SAM) on silver films.
• To evaluate the sensor's performance in detecting biomolecules.

Main Methods:

• Fabrication of a silver-based SPR sensor.
• Protection of the silver film using a self-assembled monolayer (SAM) of 11-mercapto-1-undecanol (MUD).
• Stability testing in water and phosphate-buffered saline (PBS).
• Sensitivity and resolution measurements using NaCl solutions.
• Development of an immunosensor using a mixed SAM for rabbit immunoglobulin G (IgG) detection.

Main Results:

• The SAM-protected silver film exhibited excellent stability in water and 0.01 M PBS.
• The silver-based SPR sensor achieved a sensitivity of 127.26 deg/RIU.
• A high refractive index resolution of 2.207 × 10^-7 RIU was obtained.
• The developed immunosensor detected rabbit IgG down to 22.516 ng/mL.

Conclusions:

• Self-assembled monolayers effectively stabilize silver films for SPR sensing applications.
• Silver-based SPR sensors offer significant advantages in sensitivity and resolution over gold-based counterparts.
• The developed SAM-protected silver SPR sensor shows great potential for sensitive and stable biosensing.