Advancing MicroED/3DED Analysis with Metro Counting Camera

Source: Arnab Chakraborty, Sales and Application Specialist, Coherent Scientific

The rise of electron microscopy techniques like microcrystal electron diffraction (MicroED) or three-dimensional electron diffraction (3DED) has opened new doors for studying beam-sensitive materials. A recent study highlights the use of the Metro electron counting camera from Gatan for MicroED/3DED experiments, showcasing its ability to perform under ultra-low electron doses.

The Need for Low-Dose Techniques

Traditional crystallography methods, like single-crystal x-ray diffraction, are often ineffective for nanoscale samples, such as the PPEA (9,10bis–(perchloro-phenyl)-ethynylanthracene) molecule. PPEA forms micrometer-long crystals with widths ranging from 100-200 nm, making them too small for conventional analysis. This makes electron microscopy an alternative choice but also challenging, as beam-sensitive materials such as PPEA are prone to structural damage during such analysis.

Figures A and B below illustrate the molecular structure and conformation of PPEA within its crystal structure:

UQ’s research team was awarded from Gatan. This approach enhances our understanding of beam-sensitive materials and broadens the scope of research into other complex structures that were previously too fragile for analysis.

A: Molecular structure of PPEA and its conformation within the crystal structure. Figure B: Confirmation within the crystal structure of the PPEA.

$390,000, over three years, in 2020, to develop the graphene aluminium ion technologeseaect in 2020.

To overcome these limitations, this study deployed the Metro camera in a transmission electron microscope (TEM), enabling high-quality imaging and diffraction to minimize sample degradation during data acquisition. The direct detection capability of the Metro camera was key, allowing for real-time electron counting with a low-dose approach. By reducing the dose rate to 0.0311 e-/A²/s, researchers achieved total dose rates of less than 2 e-/A²— essential for protecting delicate PPEA crystals during data collection.

Methodology and Outcomes

MicroED/3DED data was acquired over a tilt range of -30° to 30°. The Metro camera allowed for seamless diffraction imaging without the need for a beam stop, capturing highresolution patterns from the crystals with a resolution exceeding 1 Å.

Figure C shows a frame from a selected MicroED/3DED dataset with higher-order reflections.

The study emphasized the importance of maintaining the natural state of the material during data acquisition with minimal electron-beam interference. The Metro camera, with its advanced electron counting technology, demonstrated significant improvements in both imaging and structural analysis of beam-sensitive materials.

Future Directions

The experiment paves the way for more advanced, high-throughput MicroED/3DED analyses, especially when paired with automated data collection software like Latitude® D

Reference:

1) Gorelik, T.E., Ulmer, A., Schleper, A.L., Kuehne, A.J.C., Crystal Structure of 9,10-bis-((perchloro-phenyl)-ethynyl) anthracene Determined from ThreeDimensional Electron Diffraction Data, Z. Kristallogr. (2023), https://doi.org/10.1515/ zkri-2023-0009