Nanogold Foundry Involving High-Shear-Mediated Photocontact Electrification in Water

Area of Science:

• Nanotechnology
• Materials Science
• Physical Chemistry

Background:

• Controlling nanoparticle synthesis often requires surfactants or reducing agents.
• Existing methods for gold nanoparticle synthesis can leave residual chemicals on the surface.
• Vortex fluidic devices (VFDs) offer unique microfluidic environments for chemical reactions.

Purpose of the Study:

• To develop a novel method for synthesizing gold nanoparticles using UV irradiation and a VFD.
• To investigate the role of photo-contact electrification in nanoparticle formation.
• To explore the influence of VFD parameters on gold nanoparticle morphology and structure.

Main Methods:

• Aqueous auric acid solution was irradiated with UV light (254 nm) in a VFD.
• Contact electrification at the solid-liquid interface and photoinduced water oxidation were utilized.
• Reactive oxygen species, including superoxide radical anion, were involved in reducing Au3+ to gold.
• VFD processing parameters and auric acid concentration were varied to control morphology.

Main Results:

• Gold nanoparticles were synthesized without added reducing agents or surfactants.
• Diverse nanogold structures were formed, including 2D sheets, prisms, hierarchical structures, rosettes, and tubes.
• Processing under nitrogen yielded mainly 2D gold structures.
• The surfaces of the gold nanoparticles remained pristine.

Conclusions:

• A paradigm for VFD processing involving photo-contact electrification was established for nanoparticle synthesis.
• This method offers control over gold nanoparticle size and morphology.
• The process generates hydrogen peroxide and hydrogen gas with clean nanoparticle surfaces.