In this article, we discuss the benefits of using benchtop scanning electron microscopy for nanoscale analysis.
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The high spatial resolutions of scanning electron microscopy (SEM) have proved invaluable in nanomaterial development, with the ability to resolve even single atoms on a surface.1 The spatial resolving powers of electron microscopy are unmatched by other techniques for nanoscience, and for samples where electron beam damage is not a concern, SEM is often the characterization technique of choice.2
However, a major challenge that has been associated with the family of electron microscopy techniques is the cost of the equipment and the stability requirements for the microscopy environment. One of the most important developments in the more widespread adoption of SEM-based methods has been a reduction in the costs associated with instrumentation, including more affordable detectors and electron sources as well as an increasing number of consultancy services and electron microscopy facilities being available.3
As the hardware technology for electron microscopes has matured, there has also been the development of a number of benchtop SEM instruments that are suitable for nanoanalysis.
Smaller footprint instruments have made electron microscopy methods available for a number of new fields, including histopathology and medical diagnosis,4 as well as educational and outreach tools for students and the wider public.5
What Are the Advantages of Benchtop Instruments?
Many of the advantages of benchtop instruments come down to accessibility and cost. While achieving the ultimate resolution or contrast is still perhaps more readily achievable with large footprint instrumentation, recent work comparing the nanoanalysis of a series of nanomaterials and colloids has demonstrated that a low voltage benchtop electron microscopy instrument could achieve similar spatial resolutions without much compromising on the accuracy of the particle sizing.6
The availability of benchtop instruments and reduced cost also offer a significant advantage to industry, which is that an in-house instrument can be obtained without a significant infrastructure and equipment investment.
For quality control or manufacturing nanoanalysis applications, getting fast or close to real-time feedback for process optimization or development is very important and is only achievable if the instrumentation can be run in-house with good availability. With the right support, staff training and measurement protocols, benchtop instruments can also be used to achieve very high throughput measurements.
Another advantage of greater amounts of instrument access is that it also provides an opportunity to optimize scanning and image acquisition parameters.7 While SEM is a relatively standard technique now, there still must be some consideration of the imaging conditions used, particularly where it concerns electron beam damage.
The amount of electron beam damage caused during imaging is related to the intensity of the electron beam and the radiation dose but can be somewhat difficult to predict.8 Small and delicate nanostructures can be complex to work with as there are a number of different mechanisms by which they can be damaged by the electron beam.
While cryogenic cooling can help and there are an increasing number of protocols advising on optimal imaging conditions in the scientific literature,8 often the only way is simply to do testing with the nanomaterials to be measured. Here, easier access to a benchtop instrument can be highly beneficial.
Examples of Benchtop SEM for Nanoanalysis
Nanostructure imaging with benchtop SEM has been used to look at the silicon structures extracted from a variety of plant materials.9 For this study, the benchtop instrumentation was invaluable as it was easy to combine it with a custom sample preparation scheme compatible with the microwave digestion methods used.
While a conventional SEM was also used for higher resolution imaging of the finer nano and microstructures present in the plant material, the benchtop instrumentation was essential in allowing a large number of samples to be studied.
With nanomaterials becoming more and more commonly used in next-generation sensor technologies, photovoltaic applications and pharmaceuticals, nanoscale imaging and characterization tools are more important than ever.
Benchtop instrumentation is a key part of standardizing nanomaterial characterization approaches and interfacing with a series of benchtop test platforms designed to expose the nanomaterials to environmental conditions and observe their stability and breakdown products.10
Standardized benchtop instrumentation makes it easy to share protocols between research laboratories and facilities, mainly where standard digital operating procedures are being developed.
Results from projects looking at developing and establishing standard protocols show benchtop instrumentation can achieve comparable performance for all but the smallest of particles.10 However, the degree of interfacing between test environments and chambers would not be possible with a full laboratory-sized SEM.
SEM is a powerful, robust and well-developed method for materials characterization. With benchtop instruments now also capable of achieving nanometer-scale resolution, it is likely that the cost and space savings associated with smaller-footprint SEM instruments will mean they become more commonplace.
A greater user community for SEM will also further accelerate the development of standard operating protocols and mean that SEM can be considered as a technique for standard analysis and quality control in a number of different scientific fields.
References and Further Reading
Smith, D. J. (2008). Ultimate resolution in the electron microscope? Materials Today, 11, pp. 30–38. doi.org/10.1016/S1369-7021(09)70005-7
Rydz, J., et al. (2019). Scanning Electron Microscopy and Atomic Force Microscopy: Topographic and Dynamical Surface Studies of Blends, Composites, and Hybrid Functional Materials for Sustainable Future. Advances in Materials Science and Engineering, 2019. doi.org/10.1155/2019/6871785
Chua, E. Y. D., et al. (2022). Better , Faster , Cheaper : Recent Advances in Cryo – Electron Microscopy. Annual Review of Biochemistry, 91, pp. 1–32. doi.org/10.1146/annurev-biochem-032620-110705
Cohen Hyams, T., et al. (2020). Scanning electron microscopy as a new tool for diagnostic pathology and cell biology. Micron, 130, p. 102797. doi.org/10.1016/j.micron.2019.102797
Harvey, K., & Edwards, G. (2022). Using Benchtop Scanning Electron Microscopy as a Valuable Imaging Tool in Various Applications. Microscopy Today, 30(5), pp. 32–35. doi.org/10.1017/s155192952200110
Dazon, C., et al. (2019). Comparison between a low-voltage benchtop electron microscope and conventional TEM for number size distribution of nearly spherical shape constituent particles of nanomaterial powders and colloids. Micron, 116(July 2018), pp. 124–129. doi.org/10.1016/j.micron.2018.09.007
Wang, L. L., et al. (2014). Full‐Field Measurements on Low‐Strained Geomaterials Using Environmental Scanning Electron Microscopy and Digital Image Correlation: Improved Imaging Conditions. Strain, 50, pp. 370–380. doi.org/10.1111/str.12076
Karuppasamy, M., et al. (2011). Radiation damage in single-particle cryo-electron microscopy: Effects of dose and dose rate. Journal of Synchrotron Radiation, 18(3), pp. 398–412. doi.org/10.1107/S090904951100820X
Guerriero, G., et al. (2020). Visualising Silicon in Plants: Histochemistry, Silica Sculptures and Elemental Imaging. Cells, 9(1066), pp. 1–19. doi.org/10.3390/cells9041066%0A. https://pdfs.semanticscholar.org/c6a7/0ce0d4da8871fe626ff05f2591d59e0d04e3.pdf
Radnik, J., et al. (2022). Automation and Standardization—A Coupled Approach Towards Reproducible Sample Preparation Protocols for Nanomaterial Analysis. Molecules, 27(3). doi.org/10.3390/molecules27030985