An absorption-based surface plasmon resonance sensor applied to sodium ion sensing based on an ion-selective optode...

Area of Science:

• Analytical Chemistry
• Materials Science
• Sensor Technology

Background:

• Surface plasmon resonance (SPR) is a powerful optical sensing technique.
• Developing selective and sensitive ion sensors remains a key challenge in analytical chemistry.
• Previous work established an absorption-based SPR principle for sensor development.

Purpose of the Study:

• To experimentally and theoretically describe an SPR sodium ion sensor.
• To validate the absorption-based SPR principle for ion sensing applications.
• To determine sodium ion concentrations using an ion optode membrane film.

Main Methods:

• Utilized an ion optode membrane film composed of plasticized poly(vinyl chloride), a sodium ionophore, a pH-sensitive cationic dye, and an anionic additive.
• Employed surface plasmon resonance (SPR) based on an absorption principle.
• Experimentally measured and theoretically simulated SPR curves using a three-layer Fresnel equation.

Main Results:

• Successfully determined sodium ion concentrations ranging from 10(-6) to 10(-1) M.
• Demonstrated that SPR curve behavior depends on excitation frequency relative to the film's absorption maximum and gold film thickness.
• Confirmed that the SPR sensor physically measures the complex refractive index influenced by optical absorption in the ion optode film.

Conclusions:

• The absorption-based SPR principle was experimentally validated for sodium ion sensing.
• The developed SPR sensor allows for flexible and accurate ion detection.
• This approach overcomes limitations of traditional SPR sensors for complex ion sensing scenarios.