Bubble-Wrap Carbon: An Integration of Graphene and Fullerenes*

Graphene and fullerene are the two most prominent carbon allotropes. They all have unique structures and exhibit peculiar physical and chemical properties. It will be a great advantage to combine the geometry features of the two. Herein, we report a series of novel two-dimensional carbon allotropes that possess fullerene-like hollow structures (bubbles) embedded in a graphene sheet. These carbon allotropes are both thermally and dynamically stable. Calculations using hybrid functionals show that these two-dimensional carbon allotropes could be metals or semiconductors depending on the sizes and the patterns of the bubbles. The band gap can be as large as 1.66 eV. Due to the unique atomic configuration, some bubble-wrap carbons have unusual negative Poisson's ratios. The combination of graphene and fullerene provides an appealing approach to design carbon-based materials with dexterous properties. For example, the insertion of the metal atoms inside the bubbles may greatly enhance the functions of such materials in photovoltaic and catalysis.