A few-layer covalent network of fullerenes

Area of Science:

• Materials Science
• Solid-State Physics
• Nanotechnology

Background:

• Carbon exists in natural allotropes like diamond (sp3) and graphite (sp2).
• Synthetic carbon allotropes offer diverse properties by combining hybridizations and geometries.
• Bridging molecular and extended carbon materials remains a key challenge.

Purpose of the Study:

• To introduce graphullerene, a novel 2D crystalline polymer of C60.
• To synthesize macroscopic, charge-neutral, purely carbon-based crystals of graphullerene.
• To investigate the properties and potential applications of this new carbon material.

Main Methods:

• Synthesis of single crystals of layered polymeric (Mg4C60)∞ via chemical vapor transport.
• Removal of magnesium using dilute acid to yield graphullerene.
• Mechanical exfoliation to produce molecularly thin flakes.
• Characterization using transmission electron microscopy and nano-photoluminescence spectroscopy.

Main Results:

• Macroscopic, charge-neutral, purely carbon-based graphullerene crystals were synthesized.
• Graphullerene can be mechanically exfoliated into thin flakes with clean interfaces.
• The material exhibits significantly higher thermal conductivity than molecular C60 due to in-plane covalent bonding.
• Moiré-like superlattices were observed in few-layer graphullerene flakes.

Conclusions:

• Graphullerene represents a new class of 2D carbon materials, bridging molecular and extended forms.
• Its properties make it suitable for creating heterostructures and optoelectronic devices.
• The synthesis method provides a pathway for designing novel 2D carbon materials with tunable properties.