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pH-programmable self-assembly of plasmonic nanoparticles: hydrophobic interaction versus electrostatic repulsion
Weikun Li1, Istvan Kanyo, Chung-Hao Kuo
1Department of Chemistry, University of Connecticut, Storrs, CT 06269, USA. jie.he@uconn.edu.
Nanoscale
|December 3, 2014
Summary
Researchers developed pH-programmable self-assembly for gold nanoparticles (AuNPs) using charged polymers. This method allows precise control over nanoparticle arrangement, creating specific nanostructures for applications in plasmon coupling.
Area of Science:
- Materials Science
- Nanotechnology
- Polymer Chemistry
Background:
- Controlling the self-assembly of plasmonic nanoparticles is crucial for advanced optical applications.
- Existing methods often lack precise control over nanoparticle arrangement and structure formation.
- pH-responsive polymers offer a tunable platform for dynamic control over nanoparticle interactions.
Purpose of the Study:
- To present a general strategy for pH-programmable self-assembly of plasmonic gold nanoparticles (AuNPs).
- To demonstrate the use of random copolymers of poly(styrene-co-acrylic acid) (P(St-co-AA)) for controlled nanoparticle assembly.
- To engineer specific nanostructures of AuNPs by manipulating pH-induced changes in polymer charge and interactions.
Main Methods:
- Synthesized AuNPs tethered with P(St-co-AA) copolymers.
- Utilized pH as an external stimulus to alter the ionization degree of acrylic acid moieties in the polymer tethers.
- Investigated the effect of pH on interparticle attractive (hydrophobic) and repulsive (electrostatic) forces to control assembly.
Main Results:
- Achieved pH-dependent control over AuNP assembly, forming anisotropic 1-D chains at high pH (electrostatic repulsion dominant).
- Observed formation of side-to-side aggregates (clusters, multi-line chains) at low pH (reduced electrostatic repulsion).
- Demonstrated sequential, two-step pH-programmable assembly to create sophisticated 'multi-block' chains using different sized AuNPs.
Conclusions:
- The developed strategy provides a general and effective method for programming the self-assembly of plasmonic nanoparticles.
- The pH-responsive polymer tethers enable stepwise control over nanostructure formation.
- This approach offers potential for precise engineering of nanoparticle assemblies for tailored plasmon coupling applications.
