One-Step Synthesis of Tunable-Size Gold Nanoplates on Graphene Multilayers.

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• Conventional synthesis of gold nanoplates (quasi-two-dimensional single crystals) typically requires multiple steps and seed crystals.
• Existing methods often involve complex mixtures of gold precursors.
• There is a need for simplified and controllable synthesis routes for anisotropic nanomaterials.

Purpose of the Study:

• To report a novel synthesis of micrometer-scale gold nanoplates using a single precursor, potassium tetrabromoaurate (KAuBr4), on graphene multilayers.
• To investigate the controllable variation of nanoplate size and thickness.
• To elucidate the kinetic mechanisms governing nanoplate formation.

Main Methods:

• Synthesis of gold nanoplates using potassium tetrabromoaurate (KAuBr4) as the sole gold precursor on graphene multilayers.
• Controlled variation of nanoplate size by introducing chloroauric acid (HAuCl4) to KAuBr4.
• Tuning nanoplate thickness by adjusting synthesis time and precursor composition (mixtures of HAuCl4, KAuBr4, KBr, or [Bmim]Br).

Main Results:

• Successfully synthesized truncated-hexagonal {111}-oriented gold nanoplates ranging from tens of nanometers to micrometers in size.
• Demonstrated controllable variation of nanoplate thickness from approximately 13 nm to 46 nm.
• Identified optimal precursor concentrations and synthesis times for achieving desired nanoplate dimensions.

Conclusions:

• Gold nanoplates can be synthesized on graphitic layers using a single precursor (KAuBr4), with graphene acting as a reducing agent.
• Nanoplate formation is kinetically limited, with preferential growth of {111} facets facilitated by bromide ions.
• Chloride ions enhance gold deposition rate, and the ratio of chloride to bromide ions influences shape anisotropy, suggesting potential for synthesizing other metal nanoplates on van der Waals layers.