Antibonding plasmon modes in colloidal gold nanorod clusters

Area of Science:

• Nanotechnology
• Materials Science
• Physical Chemistry

Background:

• The optical properties of nanoplasmonic colloids depend on particle shape.
• Self-assembly of nanoparticles leads to new optical features like bonding/antibonding modes due to particle orientation.
• Observing these plasmon modes in liquid-phase self-assembly is challenging due to broad cluster size distributions.

Purpose of the Study:

• To demonstrate the observation of antibonding plasmon modes in low-symmetry nanoparticle clusters formed in solution.
• To investigate the mechanism of UV-light-induced self-assembly of gold nanorods (AuNRs).

Main Methods:

• Colloidal dispersions of AuNRs stabilized by poly(vinylpyrrolidone) (PVP) were irradiated with UV light.
• The morphology of the resulting AuNRs clusters was analyzed.
• Optical response of the clusters was measured to identify plasmon modes.

Main Results:

• UV-light irradiation of AuNRs in N-methyl-2-pyrrolidone (NMP) resulted in the formation of ladderlike AuNRs clusters.
• Antibonding plasmon modes were identified in these solution-phase clusters.
• A mechanism involving UV-induced radical formation and subsequent PVP cross-linking was proposed.

Conclusions:

• Low-symmetry clustering of AuNRs can reveal antibonding plasmon modes in solution.
• UV-light-induced self-assembly offers a route to control nanoparticle morphology and optical properties.
• This approach has potential applications in light-induced self-assembly for various nanomaterials.