N-Heterocyclic Carbenes Excel at Functionalizing Diverse Carbon Surfaces with Robust Organic Monolayers

The controlled deposition of organic monolayers on carbon substrates is a well-known challenge, with existing methods yielding partial coverages or non-uniform, uncontrollable multilayers. N-heterocyclic carbenes (NHCs) have recently been shown to form stable self-assembled monolayers (SAMs) on a range of metals. Here, we demonstrate that NHCs with diverse alkylated backbones and a variety of terminal groups can also be reliably deposited as uniform layers at up to monolayer coverages on a wide range of carbon surfaces, including planar carbons and highly surface-defective carbon powders. Tunable surface coverages, strong support for NHC chemisorption, and excellent electrochemical and thermal stability of these monolayers is observed, comparable to NHC or alkylthiol SAMs on metals. We showcase one application of NHCs on carbon, demonstrating an impedimetric sensor for bacterial biomarker detection, achieving performances associated with metal-supported SAMs. This work positions NHCs as transformative tools for carbon surface modification, enabling applications previously restricted only to metal-supported SAMs.