Switchable Polyacrylic Acid Polyelectrolyte Brushes for Surface Plasmon Resonance Applications.

Area of Science:

• Nanotechnology and Materials Science
• Surface Chemistry and Polymer Science
• Optical Sensing and Microscopy

Background:

• Surface Plasmon Resonance (SPR) microscopy is a powerful label-free technique for detecting nano-objects.
• Enhancing the sensitivity and spatial resolution of SPR sensors is crucial for advanced nano-detection applications.
• Polyelectrolyte brushes offer tunable surface properties responsive to environmental stimuli like pH.

Purpose of the Study:

• To design and investigate polyacrylic acid polyelectrolyte brushes (PAA PEBs) for enhanced SPR microscopy.
• To explore the pH-dependent switching behavior of PAA PEBs and its impact on sensor performance.
• To evaluate the improvement in sensitivity and spatial resolution of SPR sensors coated with PAA PEBs.

Main Methods:

• Fabrication of SPR sensors utilizing gold (Au) layers coated with PAA PEBs.
• Characterization of PAA PEBs' chemical, morphological, optical, and electrical properties across a pH range (1-9).
• Experimental measurements and theoretical analysis of SPR sensor performance, including signal-to-noise ratio and image linewidth.

Main Results:

• PAA PEBs exhibit significant pH-responsive swelling, transitioning from a collapsed state (pH ~1) to an extended state (pH 9) due to COOH/COO- group dissociation.
• Coating Au layers with PAA PEBs increased the signal-to-noise ratio from 6 to 18, demonstrating enhanced detection sensitivity.
• The linewidth of recorded SPR images decreased from 6 to 5 pixels, indicating improved spatial resolution.

Conclusions:

• PAA PEBs effectively enhance the sensitivity of SPR microscopy sensors for nano-object detection.
• The pH-triggered conformational changes of PAA PEBs are key to modulating SPR sensor performance.
• PAA PEB-coated SPR sensors offer a promising platform for high-resolution, sensitive nano-imaging.