Enhancing Surface Plasmon Resonance Detection Using Nanostructured Au Chips

Area of Science:

• Nanotechnology
• Optical Sensors
• Surface Science

Background:

• Surface Plasmon Resonance (SPR) refractometers are crucial for sensing applications.
• Enhancing SPR sensor sensitivity is key for detecting subtle changes in refractive index.
• Current SPR sensors have limitations in sensitivity and dynamic range.

Purpose of the Study:

• To investigate methods for increasing the sensitivity of SPR refractometers.
• To explore the effect of nanostructured surfaces on SPR sensor performance.
• To optimize SPR sensor design for specific environmental conditions.

Main Methods:

• Fabrication of gold (Au) coated chips with sub-micron periodic relief gratings using interference lithography and chalcogenide photoresists.
• Systematic variation of grating depth and spatial frequency.
• Experimental testing of nanostructured chips with glycerol-water solutions to measure SPR response.
• Analysis of sensitivity enhancement and refractive index variation intervals (Δn).

Main Results:

• Increasing grating depth from 13.5±2 nm to 21.0±2 nm reduced Δn from 0.009 to 0.0031.
• SPR sensor sensitivity increased from 110 deg./RIU for standard chips to 264 and 484 deg./RIU for nanostructured chips.
• Grating spatial frequency adjustment allowed tuning the sensor's working range to the environment's refractive index.

Conclusions:

• Nanostructuring the Au surface with periodic gratings significantly enhances SPR refractometer sensitivity.
• Grating depth is a critical parameter controlling the trade-off between sensitivity enhancement and the range of refractive index variation.
• The working range of SPR sensors can be precisely adjusted through surface modification and grating design.