Extended characterization methods for covalent functionalization of graphene on copper

TL;DR

This paper develops and compares covalent functionalization methods for graphene on copper, demonstrating successful grafting, characterization, and transfer, with potential for contamination-free processing.

Contribution

It introduces protocols for covalent graphene modification directly on copper, with comprehensive characterization and transfer capabilities, advancing functionalization techniques.

Findings

Successful covalent functionalization confirmed by spectroscopy and microscopy.

Copper substrate enhances Raman signals via plasmonic effects.

Functionalized graphene can be transferred post-grafting without contamination.

Abstract

Graphene is a material of great potential in a broad range of applications, for each of which specific tuning of the materials properties is required. This can be achieved, for example, by covalent functionalization. We have exploited two protocols for surface grafting, either by diazonium salts or by nucleophilic exchange, to perform graphene covalent modification directly on a copper substrate, which is routinely used for the synthesis of the material, and investigated the difference in reactivity compared with other substrates. The successful functionalization was confirmed by Raman and surface-enhanced Raman spectroscopy, mass spectrometry, X-ray photoelectron spectroscopy and scanning electron microscopy with energy-dispersive X-ray spectroscopy. In addition, we have found that the copper substrate can serve as a plasmonic surface enhancing the Raman spectra. Furthermore, the covalent grafting was shown to tolerate the transfer process, thus allowing ex post transfer from copper to other substrates. This protocol avoids wet processing and enables an all-gas-phase transformation of functionalized graphene, which eliminates the main sources of contamination.