Optical and electrical properties of three-dimensional interlinked gold nanoparticle assemblies

Area of Science:

• Nanotechnology
• Materials Science
• Physical Chemistry

Background:

• Gold nanoparticles (Au-NPs) are crucial for plasmonics and electronics.
• Organic linkers modulate nanoparticle properties and film conductivity.
• Understanding structure-property relationships is key for designing advanced nanomaterials.

Purpose of the Study:

• To investigate how linker molecule structure affects optical and electrical properties of Au-NP films.
• To compare the influence of benzene vs. cyclohexane cores and thiol vs. dithiocarbamate substituents.
• To elucidate charge transport mechanisms and plasmon resonance behavior.

Main Methods:

• Fabrication of thin films (11-20 nm) with ~4 nm Au-NPs linked by organic dithiol/bis-dithiocarbamate derivatives.
• Characterization of optical properties via plasmon absorption spectroscopy (554-626 nm).
• Electrical conductivity measurements and activation energy determination for charge transport.

Main Results:

• Thiol-linked films showed thermally activated transport (59-71 meV) with plasmon bands at 554-589 nm.
• Dithiocarbamate-linked films exhibited red-shifted plasmon bands (~626 nm) and lower activation energy (14 meV).
• Cyclohexane cores reduced conductivity by an order of magnitude compared to benzene cores.

Conclusions:

• Molecular structure, particularly the linker's core and substituents, dictates film conductivity and optical properties.
• Charge transport is governed by nonresonant tunneling through nonconjugated molecular segments.
• The findings enable rational design of nanoparticle-based electronic devices.