Reliable Physical-Chemical Characterization of Graphene-Related 2D Materials: Current Activities in Standardisation and Regulation

Reliable physical-chemical characterization of Graphene-Related 2D Materials: Current activities in standardisation and regulation

Graphene-related 2D materials (GR2M) can be found in more and more products with an increasing participation of end-user industries [1]. After the hype at the begin and the typical disillusionment the phase of sustained marked growth begins with settling graphene in various application fields, e.g. batteries, composites, (flexible) electronics, paintings, and coatings [2]. In this phase, suppliers begin to develop products together with potential customers and the community begins to build trust through standardization and regulation activities within ECHA-REACH and OECD. For this purpose, reliable physical-chemical characterization protocols are essentials.

Critical parameters for the characterisation are still under discussion, but great efforts were done in the last years like the Graphene Classification Framework [3] or an ISO standard under development ISO/CD TS 9651 [4]. Despite this ongoing discussion about the necessary parameter for characterizing graphene it is broadly accepted that properties like particle size, particle shape, chemical composition, impurities are crucial for the physical-chemical characterization of graphene in particle form. We will present the latest state in the development of reference methods for measuring the morphology like size and shape as well as the elemental composition of graphene in particle form. The key for establishing such reliable protocols is the validation with interlaboratory comparisons (ILCs). For performing such ILCs, the Versailles Project on Advanced Materials and Standards (VAMAS) was established 1982. Under this umbrella, ILCs are being performed in the field of GR2M. The results reveal that the same sample preparation and the same approach for measuring the particle size are essential for the comparability of the results. The next steps in the way of standardized protocols like establishing “simple” methods for quality control or characterizing more realistic (or complex) samples with graphene nanoplatelets in a matrix will be discussed.

These projects have received funding from the Horizon Europe Research and Innovation Programmes under the Grants Agreement No. 101092796 (ACCORDs: Green deal inspired correlative imaging-based characterization for safety profiling of 2D materials) and 101119461 (Graphene EU CSA).

1. [1] Barkan, T., Ratwani, C.R., Johnson, D., Thodkar, K., and Hill, C. Nat. Rev. Phys. 6, 646 (2024) https://doi.org/10.1038/s42254-024-00754-9
2. [2] Chemello et al 2023 Adv. Mater. Interfaces 10 230000116 DOI 10.1002/admi.202300116
3. [3] The Graphene Council: https://www.thegraphenecouncil.org/page/GCF
4. [4] International Standardisation Organisation: ISO/CD TS 9651 https://www.iso.org/standard/84232.html?browse=tc

Physical-chemical Characterization of Graphene-Related 2D Materials: Development of Approaches for Reliable Quantification

An accurate characterisation of the morphological, structural, and chemical properties of nano and advanced materials is key for the understanding of the material functionality and constitutes the basis for future optimisation or even prediction of the product performance. Further, the correlation of the physical-chemical properties with results from biological testing leads to an understanding of the potential toxicological effects so that a minimisation of the materials risks becomes possible.

The presentation will highlight with examples the importance of the selection of the relevant parameters/descriptors and particularly their measurement for the reliable characterisation of the morphology, structure, and chemistry of graphene-related 2D-materials (GR2M’s) [1-3]. One crucial aspect is also one of most challenging ones in the characterisation chain: the proper sample preparation, which shall be tailored to the accurate measurement of the defined analytical parameter. Practical examples of measurement of morphological descriptors of GR2M’s, such as equivalent circular diameter (ECD), minimum and maximum Feret, and aspect ratio with electron microscopy, or of the thickness with atomic force microscopy (AFM) will be showed, together with quantitative chemical characterisation with X-ray photoelectron spectroscopy (XPS) and, newly, with energy-dispersive X-ray spectroscopy with a scanning electron microscope (SEM/EDX) [4] by evaluating accurately the elemental content as the ratio of O/C and the composition of impurities.

Another relevant, but challenging part of the characterisation of GR2M’s, particularly as the final products containing mostly low amounts of GR2M’s, is the analysis of homogeneity of the chemical composition by sensitive imaging methods. Examples of successful analysis with secondary ion mass spectrometry (SIMS), even if not quantitative, will be showed.

This project has partly received funding from the Horizon Europe Research and Innovation Programmes under the Grant Agreement No. 101092796 (ACCORDs: Green deal inspired correlative imaging-based characterization for safety profiling of 2D materials).

1. [1] ISO /DTS 23359 Nanotechnologies — Chemical characterization of graphene-related two-dimensional materials from powders and liquid dispersions, under development at ISO/TC 229, Geneva.
2. [2] Chemello et al 2023 Adv. Mater. Interfaces 10 230000116 DOI 10.1002/admi.202300116
3. [3] Chemello et al 2025 Nano Express (accepted manuscript) DOI 10.1088/2632-959X/adae28
4. [4] ISO 22309:2011 Microbeam analysis — Quantitative analysis using energy-dispersive spectrometry (EDS) for elements with an atomic number of 11 (Na) or above, 2011, Geneva.

Speakers:

Dr. Vasile-Dan Hodoroaba is head of the Division Surface and Thin Film Analysis at BAM and a representative of the Competence Center nano@BAM (www.bam.de/Navigation/EN/Topics/Materials/Nano/safe-nanomaterials.html). His current research activities focus on correlative approaches for accurate physico-chemical characterization of nano and advanced materials, mainly by means of electron and X-ray spectroscopies/microscopies with increased consideration of graphene-related 2D materials. Dan is author of 150 WoS articles, editor of the book Characterization of Nanoparticles, and has leading roles in European research projects on characterisation of nanomaterials as well as in national and international (pre-)standardisation bodies.