Understanding and optimising the packing density of perylene bisimide layers on CVD-grown graphene

TL;DR

This study investigates how the packing density of perylene bisimide monolayers on CVD-grown graphene affects surface chemistry, revealing insights into non-covalent functionalisation and its potential for scalable, ambient-condition applications.

Contribution

It provides direct STM observations of packing densities and adsorption orientations of perylene bisimide layers on large-scale CVD graphene, linking surface contamination to monolayer packing.

Findings

Densely packed perylene layers adsorb with the conjugated {c0}-system perpendicular to graphene.

STM imaging confirms the formation of self-assembled monolayers on transferred CVD graphene.

Surface contamination influences the packing density of the functional layers.

Abstract

The non-covalent functionalisation of graphene is an attractive strategy to alter the surface chemistry of graphene without damaging its superior electrical and mechanical properties. Using the facile method of aqueous-phase functionalisation on large-scale CVD-grown graphene, we investigated the formation of different packing densities in self-assembled monolayers (SAMs) of perylene bisimide derivatives and related this to the amount of substrate contamination. We were able to directly observe wet-chemically deposited SAMs in scanning tunnelling microscopy (STM) on transferred CVD graphene and revealed that the densely packed perylene ad-layers adsorb with the conjugated {\pi}-system of the core perpendicular to the graphene substrate. This elucidation of the non-covalent functionalisation of graphene has major implications on controlling its surface chemistry and opens new pathways for adaptable functionalisation in ambient conditions and on the large scale.