pH-Modulated Nanogaps in Self-Assembling Gold Nanoparticle Metasurface.

Area of Science:

• Materials Science
• Nanotechnology
• Polymer Science

Background:

• Achieving real-time modulation of optical properties in tunable metamaterials is challenging.
• Stimuli-responsive polymers offer potential for optical modulation and sensing applications due to their rapid response.
• Nanoparticle (NP) self-assembly at liquid-liquid interfaces presents a novel platform for creating functional optical materials.

Purpose of the Study:

• To develop a novel approach for controlling interparticle spacing and enabling pH sensing.
• To construct a plasmonic metasurface using nanoparticle self-assembly for optical modulation.
• To investigate the pH-responsive behavior of polymer-modified gold nanoparticles (AuNPs).

Main Methods:

• Fabrication of a plasmonic metasurface via self-assembly of gold nanoparticles (AuNPs) modified with poly(4-vinylpyridine) (P4VP) at a liquid-liquid interface.
• Analysis of surface plasmon resonance (SPR) peak position and reflectance to determine interparticle spacing.
• Utilizing surface-enhanced Raman scattering (SERS) to detect pH-induced changes in nanoparticle interactions.

Main Results:

• Demonstrated tunable interparticle distances ranging from 14 to 2.2 nm through pH-induced coupling and decoupling of plasmonic modes.
• Achieved linear pH sensing over a broad range (pH 3 to 11) by monitoring changes in SERS spectra.
• Validated the pH-responsive behavior of P4VP-modified AuNPs, showing reversible optical property modulation.

Conclusions:

• The proposed self-assembly method effectively controls interparticle spacing for tunable optical properties.
• The P4VP-modified AuNP metasurface serves as a sensitive and reversible platform for real-time pH sensing.
• This approach holds promise for advanced optical modulation and sensing applications.