Longitudinal splitting versus sequential unzipping of thick-walled carbon nanotubes: Towards controllable synthesis of high-quality graphitic nanoribbons

Despite significant efforts to develop ways to produce customized carbon-based nanostructures, facile synthesis of mass graphene/graphitic nanoribbons (GNRs) without losing the intrinsic sp(2)-structure and properties remains challenging. Here we report that bulk of multi-layered graphitic nanoribbons can be prepared by gas-phase oxidative splitting of multi-walled carbon nanotubes (MWCNTs) using HNO3 vapor. The longitudinal splitting behavior of MWCNTs is substantially dependent on three key factors: the utilization of gaseous oxidant, the use of highly-crystallined carbon nanotubes with larger diameter, and the associated high-pressure conditions. Moreover, this splitting process is evidenced to be edge selective and nonaggressive as opposed to traditional wet chemical oxidation, for which the obtained GNRs show minimized oxidation level, highly intact crystalline and robust electrical conductance. This study suggests a simple yet effective strategy for producing mass high-quality GNRs. (C) 2016 Elsevier Ltd. All rights reserved.