Clay-graphene nanoplatelets functional conducting composites

An approach to functionalize graphene-based materials has been developed by assembling graphene nanoplatelets (GNP) with clay minerals. Under convenient sonomechanical treatment, clay–GNP mixtures may produce very stable water dispersions in particular using sepiolite fibrous clay. While in the absence of clay a rapid decantation of GNP in water is observed, in the presence of sepiolite the resulting dispersions remain stable during months without syneresis effects. Rigid but flexible self-supported films are easily obtained by filtering of these dispersions. As the electrical percolation threshold corresponds to sepiolite/GNP composites of 0.5:1 in weight, doping these systems with multiwalled carbon nanotubes (MWCNTs) significantly enhances their electrical conductivity. The particular microporosity of the sepiolite component allows interactions with molecules, such as organic dyes, as well as polymers, such as biopolymers, opening the way to functional materials for advanced applications due to their inherent conductivity afforded by the GNP and MWCNTs carbonaceous components. In fact, using very small amount of MWCNT together with GNP can obtain composites with significant electrical conductivity, maintaining the enhanced mechanical properties, at a lower cost.This work was partially supported by the MINECO, Spain (Project MAT2012‐31759 and MAT2015‐71117‐R) and FCT/MEC, Portugal (CICECO‐Aveiro Institute of Materials – POCI‐01‐0145‐FEDER‐007679, FCT UID/CTM/50011/2013), through national funds and where applicable co‐financed by the FEDER, within the PT2020 Partnership Agreement. EU COST Action MP1202 is also acknowledged. C. Nunes and P. Ferreira thank FCT for their grants SFRH/BPD/100627/2014 and IF/00327/2013, respectively