Solvent-free mechanochemical synthesis of bio-derived nitrogen-doped graphene nanoplatelets, combining high electrical conductivity with improved dispersibility for sustainable advanced materials. Credit: Image adapted from Madhusha et al., ACS Sustainable Chemistry & Engineering (2025).

Graphene is often described as a wonder material. It is strong, electrically conductive, thermally efficient, and remarkably versatile. Yet despite more than a decade of excitement, many graphene-based technologies still struggle to move beyond the laboratory.

One of the key challenges is that graphene does not readily dissolve in common solvents, forcing researchers to rely on harsh, multi-step functionalization/modification processes to make it usable.

As a researcher working at the intersection of green chemistry and nanomaterials, I have often found myself asking a simple question: Can we design advanced materials without relying on environmentally costly processes?

In our recent study published in ACS Sustainable Chemistry & Engineering, my colleagues and I explore how nitrogen-doped graphene nanoplatelets can be produced using a solvent-free, bio-derived mechanochemical approach, offering a more sustainable pathway for functionalized graphene materials.

Why functionalizing graphene is a problem

Pristine graphene already has impressive properties, but many advanced applications such as smart coatings, self-healing polymers, and conductive composites require graphene to be chemically modified in order to get better dispersibility. One popular strategy is nitrogen doping, which alters graphene’s electronic structure and improves its interaction with solvents/polymer matrices.

However, conventional nitrogen-doping methods often come with serious drawbacks. They may rely on:

• Toxic nitrogen precursors
• Harsh purification steps involving acid washing
• High-temperature post-annealing steps (often above 600 °C)
• Multi-step processes that generate significant chemical waste

While these approaches can produce high-quality materials, their environmental footprint is difficult to justify, especially when sustainability is increasingly a priority for materials manufacturing.

A solvent-free alternative: Mechanochemistry

In our work, we turned to mechanochemistry, a technique that uses mechanical forces (shear, impact, friction) to drive chemical reactions. Mechanochemistry has gained attention in green chemistry because it can eliminate solvents, reduce energy demand, and simplify processing and scaling up.

Using a ball-milling process, we directly functionalized graphite with a bio-derived nitrogen source (amino acids) under ambient conditions. Instead of heating materials in furnaces or refluxing them in solvents, we allowed mechanical forces to break and reform bonds directly in the solid state.

The result was nitrogen-doped graphene nanoplatelets (N-GNPs) produced without solvents/toxic reagents and controlled atmospheres. Importantly, the resulting N-GNPs combined high electrical conductivity with good dispersibility, addressing two key challenges in graphene processing at the same time.

Measuring sustainability, not just performance

To evaluate how green the process truly was, we examined not only what the material could do, but how it was made. This involved both qualitative considerations, including green chemistry principles, and quantitative metrics, including waste generation (E-factor) and overall energy demand.

The process achieved a high material yield (around 80%), which is notable for a solid-state synthesis route. More importantly, the method showed a significantly lower E-factor, which is a standard green chemistry metric that measures how much waste is generated per unit of product compared with many commonly reported graphene functionalization strategies.

By removing solvents and post-annealing steps, the overall energy consumption was also reduced. These factors collectively demonstrate how process design choices can strongly influence the sustainability of advanced materials, even when the final product appears similar.

What makes nitrogen-doped graphene special?

Nitrogen atoms can integrate into the graphene lattice in several configurations, subtly changing how electrons move through the material. This can enhance electrical conductivity, improve chemical reactivity, and strengthen interactions with surrounding polymers.

In our study, the N-GNPs retained high structural quality while gaining functional benefits from nitrogen incorporation. When used as nanofillers, they showed strong potential to improve electrical, thermal, and mechanical properties in composite systems.

This balance of maintaining performance while improving sustainability is crucial. Green chemistry should not mean compromising material functionality; rather, it should encourage smarter design from the outset.

Enabling smarter, self-healing materials

One particularly exciting outcome of this work is the compatibility of N-GNPs with vitrimers; a class of polymers that combine the mechanical strength of thermosets with the reprocessability of thermoplastics.

When incorporated into vitrimer matrices, nitrogen-doped graphene nanoplatelets can act as multifunctional fillers. They enable electrically triggered self-healing, enhance mechanical strength, and improve electrical/thermal conductivity; all while preserving the material’s inherent network stability.

From a materials engineering perspective, this opens the door to repairable coatings, recyclable composites, and longer-lasting structural materials and applications where both performance and sustainability matter.

Why this matters beyond graphene

Although our research focuses on graphene, the broader message is about rethinking how advanced materials are made. Many high-performance materials rely on processes developed decades ago, when environmental impact was not a primary concern.

Mechanochemical, solvent-free strategies show that it is possible to rethink these pathways. By integrating green chemistry principles early in materials design, researchers can reduce waste, lower energy use, and create processes that are more compatible with large-scale manufacturing.

For industries exploring electronics, aerospace, energy storage, or smart coatings, these considerations are becoming increasingly important not only for environmental reasons but also for cost, safety, and regulatory compliance.

Looking ahead

Our work represents one step toward aligning nanomaterials innovation with sustainability goals. Future research will explore how this green synthesis approach can be adapted to other dopants, composite systems, and scalable manufacturing routes.

Ultimately, the goal is not just to create better materials, but to create better ways of making materials. As the demand for advanced functional materials continues to grow, sustainable synthesis strategies will play a key role in shaping the technologies of tomorrow.

This story is part of Science X Dialog, where researchers can report findings from their published research articles. Visit this page for information about Science X Dialog and how to participate.

More information: Chamalki Madhusha et al, Green Mechanochemical Production of Amino-Acid-Derived N-Doped Graphene for Functional Vitrimer Composites, ACS Sustainable Chemistry & Engineering (2025). DOI: 10.1021/acssuschemeng.5c09378

Chamalki Madhusha is a Ph.D. researcher at Monash University working at the interface of green chemistry, nanomaterials, and advanced composites. Her research focuses on developing sustainable, solvent-free routes to functional graphene materials and translating them into high-performance advanced polymer composite systems. Her research, published in leading Q1 journals and recognized through several awards, spans sustainability-driven materials design and advanced engineering applications. Her publications can be found on Google Scholar.

Citation: How sustainability is driving innovation in functionalized graphene materials (2025, December 25) retrieved 25 December 2025 from https://phys.org/news/2025-12-sustainability-functionalized-graphene-materials.html

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