One-dimensional carbon nanostructures: sustainable processing in water via cellulose nanocrystals

Carbon nanostructures have attracted much attention in recent decades due to their extraordinary electrical and mechanical properties. These properties arise from the sp(2) hybridisation of carbon, subsequently forming a wide range of materials. In particular, unidimensional carbon nanostructures may be mainly classified into carbon nanofibers, single-walled and multi-walled carbon nanotubes. In order to exploit their properties, well defined processing strategies are needed for these nanostructures, preferably in water, which presents a great challenge as they are hydrophobic. Traditionally, non-volatile organic solvents have been used for such purpose, but the use of water as a solvent offers a less toxic and a more sustainable option. However, in order to comply with a full aqueous processing, carbon nanostructures require the use of surfactants, the majority of which are toxic and difficult to remove or their functionalization, thus altering their intrinsic electronic properties. For these reasons, novel and environmentally friendly altematives are emerging, in particular through the use of natural or biologically-derived dispersants. Following this trend, we highlight the strategy developed in recent years by the G-CNN group involving cellulose nanocrystals, with a special focus on their applications in biomedicine and conductive inks.