pH-Sensitive Optical Nanocomposites Using Polymer-Coated Gold Nanorods

Area of Science:

• Materials Science
• Nanotechnology
• Polymer Chemistry

Background:

• Gold nanorods exhibit unique optical properties governed by their surface plasmon resonance (SPR).
• Polymer coatings can modify the properties of nanomaterials, enabling new functionalities.
• pH-responsive polymers offer tunable characteristics based on environmental acidity.

Purpose of the Study:

• To synthesize and characterize pH-responsive, reversible nanocomposites using polymer-coated gold nanorods.
• To investigate the influence of pH on the optical properties, specifically the SPR peaks, of these nanocomposites.
• To explore the potential applications of these tunable nanocomposites in optical molecular imaging and pH sensing.

Main Methods:

• Synthesis of gold nanorods coated with polystyrene sulfonate (PSS) and poly(allylamine hydrochloride) (PAH).
• Fabrication of nanocomposites by assembling PSS- and PAH-coated gold nanorods.
• Characterization of nanocomposite swelling/shrinking behavior across a pH range (approx. 5.4 to 7.2).
• Measurement of surface plasmon resonance (SPR) peak shifts in response to pH changes.

Main Results:

• Demonstrated pH-dependent swelling and shrinking of the polymer-coated gold nanorod nanocomposites.
• Observed a significant red-shift (approximately 60 nm) in SPR peaks as pH increased from 5.4 to 7.2.
• Attributed the SPR shift to increased side-by-side interactions between adjacent gold nanorods at higher pH.
• Confirmed the reversibility of the pH-induced changes in nanocomposite structure and optical properties.

Conclusions:

• Successfully synthesized pH-responsive, reversible nanocomposites of polymer-coated gold nanorods.
• The tunable SPR peaks of these nanocomposites are sensitive to environmental pH changes.
• These materials show promise as advanced optical materials for pH sensing and as contrast agents in optical molecular imaging.