Periodic Reporting for period 1 - HYPERGRAPH (High-Quality Graphene Supports for Microspectroscopic Techniques.)
Reporting period: 2023-08-01 to 2025-01-31
Transmission electron microscopy (TEM) is an indispensable characterisation tool for many applications in materials and life science. Over the last decades, the field has significantly evolved, with most developments focusing on hardware optimisation resulting e.g. in drastically improved spatial resolution. Because of these advances, the outcome of a TEM experiment is nowadays ultimately determined by the quality of the sample as well as the sample support. It is therefore surprising that the importance of thin and ultraclean TEM sample supports has been majorly overlooked so far.
On the other hand, graphene, a monolayer of tightly bound carbon atoms arranged with a six-fold symmetry, shows unparalleled properties in terms of structure, conductivity and thickness, resulting in the ideal sample support for TEM. Over the last 5 years, the potential of graphene as a support has been recognised by the TEM community, but commercially available “graphene grids” unfortunately show a very poor coverage and are dominated by unwanted contaminants. Therefore, to fully exploit the many benefits of graphene, the aim of this PoC was to produce high-quality graphene supports and deliver these to the TEM community through the following objectives:
• Benchmarking of the HYPERGRAPH grids against the current technologies and definition of quality specifications based on a market survey to define customer needs.
• Further product development to improve reproducibility, throughput, cost-efficiency and shelf-life.
• Development of the business strategy.
On the other hand, graphene, a monolayer of tightly bound carbon atoms arranged with a six-fold symmetry, shows unparalleled properties in terms of structure, conductivity and thickness, resulting in the ideal sample support for TEM. Over the last 5 years, the potential of graphene as a support has been recognised by the TEM community, but commercially available “graphene grids” unfortunately show a very poor coverage and are dominated by unwanted contaminants. Therefore, to fully exploit the many benefits of graphene, the aim of this PoC was to produce high-quality graphene supports and deliver these to the TEM community through the following objectives:
• Benchmarking of the HYPERGRAPH grids against the current technologies and definition of quality specifications based on a market survey to define customer needs.
• Further product development to improve reproducibility, throughput, cost-efficiency and shelf-life.
• Development of the business strategy.
To benchmark our technology a market survey was conducted in work package 1, confirming that for the materials science market indeed coverage and cleanliness of the graphene are the most important quality specifications. Many respondents commented negatively about the current quality of the commercially available graphene TEM grids. Our grids, on the other hand, were well received by beta testers. It was shown that graphene grids can be used to improve the signal-to-noise ratio, to mitigate electrostatic charging of vitrified samples during TEM analysis and to reduce electron beam damage in specific samples.
In the second work package, the reproducibility of the transfer and cleaning process was improved through the implementation of a spin coater and the careful optimization of the grain size of activated carbon used during the cleaning process. Upscaling of the process to 25 times larger batches was successful and resulted in an improved cost-efficiency. It was found that to improve shelf-life of the grids, storing them under vacuum conditions is required.
In the final work package a business plan was drafted based on a survey of the graphene ecosystem and a freedom to operate analysis. Other markets were explored and the application of our technology was proven successful for MEMS devices for in-situ TEM end the production of graphene liquid cells to study materials in a liquid environment in the TEM.
In the second work package, the reproducibility of the transfer and cleaning process was improved through the implementation of a spin coater and the careful optimization of the grain size of activated carbon used during the cleaning process. Upscaling of the process to 25 times larger batches was successful and resulted in an improved cost-efficiency. It was found that to improve shelf-life of the grids, storing them under vacuum conditions is required.
In the final work package a business plan was drafted based on a survey of the graphene ecosystem and a freedom to operate analysis. Other markets were explored and the application of our technology was proven successful for MEMS devices for in-situ TEM end the production of graphene liquid cells to study materials in a liquid environment in the TEM.
Our optimised protocol resulted in high-quality graphene TEM grids with unparallelled cleanliness and coverage. Because of their high cleanliness, these grids enable to see low contrast materials with a minimal support background. E.g. during the project, our grids were crucial in enabling off-axis electron holography of unstained bacteriophages (Karim et al., 2025, doi: 10.1016/j.jsb.2025.108169). The high degree of coverage in turn increases the chance of finding the sample of interest on the graphene support and therefore optimises the expensive microscopy time and potential sample throughput of the experiment.
In addition, different procedures and protocols were developed to encapsulate samples in a liquid environment in between two graphene layers. It was shown that in high-quality graphene liquid cells the structure of the ligand shell around gold nanoparticles and the ligand-gold interface could be observed in a liquid environment. In this way the anisotropy, composition and dynamics of the ligand distribution on gold nanorod surfaces could be investigated (Pedrazo-Tardajos, Claes, Wang et al., 2024, doi: 10.1039/s41557-024-01574-1).
In addition, different procedures and protocols were developed to encapsulate samples in a liquid environment in between two graphene layers. It was shown that in high-quality graphene liquid cells the structure of the ligand shell around gold nanoparticles and the ligand-gold interface could be observed in a liquid environment. In this way the anisotropy, composition and dynamics of the ligand distribution on gold nanorod surfaces could be investigated (Pedrazo-Tardajos, Claes, Wang et al., 2024, doi: 10.1039/s41557-024-01574-1).