Nanomaterials that simultaneously exhibit stable dispersibility and high electrical and thermal properties are central to the development of next-generation multifunctional composite systems. In this work, we demonstrate a sustainable mechanochemical strategy for producing nitrogen-doped graphene nanoplatelets (N-GNPs) using a solvent-free ball-milling process. Graphite is milled with the amino acid glycine, a bio-based nitrogen precursor that functions both as a nitrogen source and an exfoliation facilitator, while potassium hydroxide promotes nucleophilic activation. This single-step approach enables concurrent graphite exfoliation and nitrogen incorporation under ambient conditions.
Chemical characterization confirms the formation of pyridinic, pyrrolic, and graphitic nitrogen functionalities within the graphene lattice. The resulting N-GNPs exhibit an uncommon combination of long-term colloidal stability in a range of solvents (up to one month) and high electrical conductivity, reaching approximately 30% of that of pristine graphite powder. The process achieves a high material yield of approximately 80% and requires substantially lower energy input than conventional hydrothermal or high-temperature annealing methods.
From a sustainability perspective, the synthesis has an intrinsically low environmental impact, eliminating volatile organic solvents and toxic nitrogen dopants while utilizing a renewable feedstock. Evaluation using green chemistry metrics, including E-factor and carbon footprint, indicates improvements in waste reduction and environmental impact, aligning the process with multiple principles of green chemistry.
When incorporated into epoxy-based vitrimer matrices, the N-GNPs act as multifunctional nanofillers, enabling electrically triggered self-healing, enhanced mechanical performance, and improved electrical and thermal conductivity. Notably, the dynamic behaviour of the vitrimer network is accelerated, with faster stress relaxation observed without altering the topology-freezing temperature. These results underscore the potential of green mechanochemical graphene production to enable advanced, multifunctional composites through environmentally responsible design.