Sample preparation for in-situ (T)EM characterisation and measurements is still difficult and often time consuming, but now there are some technological advancements which could drastically speed up this process.
In the last decade, the development of Electron Microscopy (EM) analysis tools has advanced significantly, with the addition of in-situ characterization capabilities. Especially for catalysis, material science and electronics research, this offers new insights into “black box” processes on the nanoscale. The EM analysis enables researchers to study material behaviour in real-time, under real-world conditions. Institutes all over the world are experimenting with the newest in-situ systems for Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDXS) and Electron Energy Loss Spectroscopy (EELS).
Recent publications show nanoparticles morphing during redox reactions, and studies on sintering behaviour of atom clusters give more insights for the development of new computer chips. Sample preparation is key!
This new technique is very much dependent on high-quality sample preparation. The technological advancement of in-situ EM has not changed the way we prepare samples yet, as most samples are made by hand and with little control. Many researchers agree that using crude tools and process steps in sample preparation actually limit the quality of their research. The use of MEMS (microelectromechanical system) devices from companies, like DENSSolutions, Protochip and Hummingbird Scientific, has substantially improved the efficiency of in-situ TEM research, but there is still a lot to gain.
Charlotte Vogt is a PhD candidate under supervision of prof.dr.ir. Bert Weckhuysen at the faculty of Inorganic Chemistry and Catalysis, Utrecht University.
To get a better understanding of the challenges for researchers in this field, we talked to Charlotte Vogt, researcher of the Debye Institute for Nanomaterials Science at Utrecht University, and followed her journey from the generation and deposition of nanoparticles in her lab to the analysis of the results in Oak Ridge (USA).
Charlotte performs research on catalyst materials and make use of operando spectroscopy and microscopy techniques to study how reaction conditions alter the reactivity of supported metal catalysts. Her goal is to contribute to the development of better and more efficient catalysts for a wide variety of hydrogenation reactions, including the activation of carbon dioxide.
What are the advantages of in-Situ TEM Techniques over other techniques?
Visual information has always appealed to scientists. The ability to show smaller and smaller features has revealed ever more information. With TEM we can even observe individual atoms. The high sensitivity of this technique allows us to take snapshots that can be sequenced in time and thus shown as a video. This has allowed us, for example, to see changes in nanoparticle morphology depending on different gas flows.
When EM is combined with an element specific analysis technique, such as EELS, or EDX, the presence of chemical compounds and their location can be detected. This makes this tool very useful for performing operando studies of catalysts.
What are the most common difficulties for sample preparation?
There is a lot of trial and error involved in making good catalyst materials. You are never completely certain to have a good sample until you put it under the TEM.
What results can you obtain from in-situ TEM measurements and what samples give the best results?
The visual information allows us to identify the crystal faces of nanoparticles. For most catalytic reactions, these crystal faces show a relation to catalytic activity and selectivity.
Using EELS, the concentration of molecular species and their environment can be estimated and help in making models that explain the catalytic activity of actual systems.
What advantages does the sample preparation technique from VSPARTICLE offer?
The sample preparation using the VSPARTICLE accessory is applicable for a wide range of materials as well as metal nanoparticle sizes. This ensures that valuable time on TEM machines is well used. In addition, size selection prior to deposition allows us to study the size dependency of the metal nanoparticles for a given catalytic reaction. In total, it takes less than an hour to make a sample and the same MEMS devices can be used.
Charlotte Vogt’s journey from generating and depositing nanoparticles in the VSPARTICLE lab in Delft, the Netherlands to analysing the samples in Oak Ridge, USA.
It Is Now Possible to Try the VSP-G1 Nanoparticle Generator
This section is not part of the interview. The ideas expressed belong to VSPARTICLE.
The VSP-G1 nanoparticle generator can be combined with accessories for diffusion, impaction and filtration of nanomaterials.
From a material researcher's perspective, VSPARTICLE believes this technology will become the standard in few years because every Ph.D., postdoc and research group, which is using the VSP-G1 are directly seeing the benefits in terms of time-consuming and samples accuracy.
To help lower the barrier for researchers, VSPARTICLE introduced a trial period of four months, priced just under 10K euro. Researchers can use this trial period to get acquainted with the machine and evaluate its capabilities for the intended application. After the four-month period, the researcher can decide to return the system, or buy it. When the system is bought, the trial price is fully subtracted from the purchase price.
This information has been sourced, reviewed and adapted from materials provided by VSPARTICLE B.V.
For more information on this source, please visit VSPARTICLE B.V.