Plasma-induced nanogap narrowing and morphological transformation in gold nanoparticle assemblies

Area of Science:

• Nanotechnology
• Materials Science
• Surface Chemistry

Background:

• Plasmonic properties of gold nanoparticle (AuNP) assemblies are highly sensitive to interparticle nanogaps.
• Controlling nanogap size is crucial for tuning optical and electromagnetic responses.

Purpose of the Study:

• To investigate the effect of plasma treatment on gold nanoparticle assemblies.
• To understand the mechanism of nanogap narrowing and nanoparticle fusion induced by plasma.
• To explore the fabrication of novel nanoparticle morphologies using plasma treatment.

Main Methods:

• Plasma treatment of self-assembled gold nanoparticle layers.
• UV-vis spectroscopy to monitor plasmon coupling peak shifts.
• Surface-enhanced Raman spectroscopy (SERS) to assess molecular changes.
• Transmission electron microscopy (TEM) to visualize nanoparticle morphology and nanogaps.

Main Results:

• Plasma treatment effectively narrows nanogaps and induces nanoparticle fusion.
• Observed sequential changes in UV-vis spectra: redshift, weakening, broadening, and blueshift.
• SERS indicated linker molecule removal and subsequent intensity changes.
• TEM revealed significant nanoparticle deformation and the formation of new shapes like nano-snowmen.

Conclusions:

• Oxidative desorption of thiol linkers by plasma causes self-assembled monolayer collapse, leading to nanogap narrowing and particle fusion.
• Plasma treatment offers a versatile method for controlling nanogap distances in nanoparticle assemblies.
• This technique facilitates the fabrication of exotic nanoparticle shapes and structures.