Synthesis of uniformly distributed single- and double-sided zinc oxide (ZnO) nanocombs

• Uniformly distributed single and double-sided zinc oxide (ZnO) nanocomb structures.
• Single-sided comb structures were obtained in the higher carrier-gas flow rate.
• Single-sided comb structures have nanonail-shaped teeth.
• Lower gas flow rate was favorable for production of double-sided comb structures.
• Double-sided structures was attributed to the formation of a bicrystal comb ribbon.

Uniformly distributed single- and double-sided zinc oxide (ZnO) nanocomb structures have been prepared by a vapor–liquid–solid technique from a mixture of ZnO nanoparticles and graphene nanoplatelets. The ZnO seed nanoparticles were synthesized via a simple precipitation method. The structure of the ZnO nanocombs could easily be controlled by tuning the carrier-gas flow rate during growth. Higher flow rate resulted in the formation of uniformly-distributed single-sided comb structures with nanonail-shaped teeth, as a result of the self-catalysis effect of the catalytically active Zn-terminated polar (0001) surface. Lower gas flow rate was favorable for production of double-sided comb structures with the two sets of teeth at an angle of ~110° to each other along the comb ribbon, which was attributed to the formation of a bicrystal nanocomb ribbon. The formation of such a double-sided structure with nanonail-shaped teeth has not previously been reported.