Edge-Grafted Molecular Junctions between Graphene Nanoplatelets: Applied Chemistry to Enhance Heat Transfer in Nanomaterials

TL;DR

This study demonstrates that edge functionalization of graphene nanoplatelets via diazonium chemistry significantly improves heat transfer properties in nanostructured materials, with covalent bonds providing the greatest enhancement.

Contribution

It introduces a novel chemical functionalization approach to enhance thermal conductivity and heat exchange efficiency in graphene-based nanomaterials.

Findings

Covalent molecular junctions increase thermal conductance by a factor of 6.

Functionalization leads to a 20% increase in in-plane thermal conductivity.

Cross-plane thermal conductivity is boosted by 150% with covalent junctions.

Abstract

The edge-functionalization of graphene nanoplatelets (GnP) was carried out exploiting diazonium chemistry, aiming at the synthesis of edge decorated nanoparticles to be used as building blocks in the preparation of engineered nanostructured materials for enhanced heat transfer. Indeed, both phenol functionalized and dianiline-bridged GnP (GnP-OH and E-GnP, respectively) were assembled in nanopapers exploiting the formation of non-covalent and covalent molecular junctions, respectively. Molecular dynamics allowed to estimate the thermal conductance for the two different types of molecular junction, suggesting a factor 6 between conductance of covalent vs. non-covalent junctions. Furthermore, the chemical functionalization was observed to drive the self-organization of the nanoflakes into the nanopapers, leading to a 20% enhancement of the thermal conductivity for GnP-OH and E-GnP while the cross plane thermal conductivity was boosted by 150% in the case of E-GnP. The application of chemical functionalization to the engineering of contact resistance in nanoparticles network was therefore validated as a fascinating route for the enhancement of heat exchange efficiency on nanoparticle networks, with great potential impact in low-temperature heat exchange and recovery applications