Bispyrene Functionalization Drives Self-Assembly of Graphite Nanoplates into Highly Efficient Heat Spreader Foils.

Giuseppe Ferraro,Fabrizio Giorgis,Silvia Ronchetti,Fabio Carniato,Alberto Fina,Mauro Tortello,M Mar Bernal,Chiara Novara

doi:10.1021/acsami.1c00319

Abstract

Thermally conductive nanopapers fabricated from graphene and related materials are currently showing great potential in thermal management applications. However, thermal contacts between conductive plates represent the bottleneck for thermal conductivity of nanopapers prepared in the absence of a high temperature step for graphitization. In this work, the problem of ineffective thermal contacts is addressed by the use of bifunctional polyaromatic molecules designed to drive self-assembly of graphite nanoplates (GnP) and establish thermal bridges between them. To preserve the high conductivity associated to a defect-free sp2 structure, non-covalent functionalization with bispyrene compounds, synthesized on purpose with variable tethering chain length, was exploited. Pyrene terminal groups granted for a strong π–π interaction with graphene surface, as demonstrated by UV–Vis, fluorescence, and Raman spectroscopies. Bispyrene molecular junctions between GnP were found to control GnP organization and orientation within the nanopaper, delivering significant enhancement in both in-plane and cross-plane thermal diffusivities. Finally, nanopapers were validated as heat spreader devices for electronic components, evidencing comparable or better thermal dissipation performance than conventional Cu foil, while delivering over 90% weight reduction.

Highlights

Thermal management in modern electronic devices requires the development of new generation of materials to guarantee for both flexibility and heat dissipation, in particular for applications in flexible electronics[1] as well as in wearable and implantable devices.[2,3] Graphene was demonstrated as a good candidate for heat management, based on its outstanding thermal conductivity[4−6] and mechanical properties.[7]
Single layer graphene currently remains of limited availability for applications in bulk materials, a wide family of graphene related materials (GRM) has become largely available, including reduced graphene oxide (RGO), multilayer graphene (MLG), and graphite nanoplates (GnP).[8]
Aiming at the non-covalent cross-linking of GnP, bifunctional molecules able to provide a sufficiently strong surface interaction with graphene layers were designed and synthesized

Summary

Introduction

Thermal management in modern electronic devices requires the development of new generation of materials to guarantee for both flexibility and heat dissipation, in particular for applications in flexible electronics[1] as well as in wearable and implantable devices.[2,3] Graphene was demonstrated as a good candidate for heat management, based on its outstanding thermal conductivity[4−6] and mechanical properties.[7]. Being a facile and scalable process, this approach was largely explored with GO suspended in water.[17−19] owing to the extensive disruption of sp[2] carbon lattice upon graphene oxidation,[20] GO membranes exhibit low thermal conductivity values and require proper reduction and thermal annealing to recover sufficient thermal conductivity. Preparation of conductive nanopapers from low-oxidized GRM was explored and proven effective for thermal conductivity.[22−27] This latter route allows avoiding the harsh chemical processes for GO production and subsequent reduction of the film, but may Received: January 6, 2021 Accepted: March 17, 2021 Published: March 25, 2021

Methods

Results

Conclusion