Electron Microscopy Proves its Worth in Nanoscale Applications
Laboratory Equipment - July 2012
Field emission scanning electron microscopes (FESEM) have been around for years and have applications across many fields. These high-resolution microscopes can be used in biology, chemistry and physics to study materials from cell organelles to microchip coatings. Now, recent improvements in electron optics make FESEM appropriate for nanoscale applications, including new product research and development. Recently, the technique has aided the development of two such products: an antimicrobial wound dressing and anti-hypersensitivity toothpaste.
The nitty gritty
All scanning electron microscopes (SEM) have common features, but they vary in their degree of complexity. Images are formed by scanning a beam over the sample (like reading a book) while collecting the electron signals generated in synchronized fashion. Secondary electrons and backscattered electrons are the two commonly detected types of electron signals. However, the greatest information is available when images from both signal types are acquired with exactly the same conditions, and then compared with matched image sets acquired at different beam conditions.
While SEM is good for broad analysis of samples, it has a usable spatial resolution limit of approximately 300 nanometers at magnifications of 10 to 300,000x. On the other hand, FESEM supports magnifications of one million times with the ability to resolve the distance between two objects spaced only one nanometer apart. Because FESEM has much higher resolution, researchers are able to investigate samples as large as those that can be held in your hand without resorting to the need of preparing samples, as is the case with transmission electron microscopy. Therefore, samples can be analyzed much faster and without adulteration by sample preparation processes.