مجله دانش آزمایشگاهی ایران
سال هفتم شماره 1 (پیاپی 25، بهار 1398)

Scanning electron microscope is one of the best methods of analysis that is widely used in various fields. The microscope provides the possibility of examining the surface and microstructure in micron and nano dimensions. Today, one of the most specialized areas of interest is biological and living tissue. The observation of these samples and the investigation of their microstructures by scanning electron microscope require special preparation. Due to the high sensitivity of the samples, if any of the steps in the preparation are not carefully performed, it will cause shrinkage, collapse, or damage to the sample structure and will affect the quality of the final images, so it is very important that the conditions and procedures for tissue preparation carefully done with the standard method. There are many different techniques for preparing and analyzing various types of tissue that vary according to the type of tissue and structure. This paper study the general methods for the preparation of biological samples and living tissues including: a) various fixations (chemical fixtaion and physical fixation), (b) dehydration with different percentages of alcohol, and (c) different drying methods In air, critical point dryers, freeze dryers and chemical dryers), in order to view the biological structures in the closest to their living structure in a high resolution SEM is discussed.

A comprehensive background information concerning underlying basis of final image formation procedure inside an Energy-Filtering Transmission Electron Microscope (EFTEM) has been provided in our previous article titled “Introduction to Energy-Filtering Transmission Electron Microscope fundamental principles” (published in Iranian Journal of Laboratory knowledge; Volume 6; Issue 4; Winter 2019; No. 24). In this article, structures of two widely used commercial energy filters have been reviewed in detail, namely, In- Column Filters and Post-Column Filters. . In-Column Filters and Post-Column Filters are located inside and beneath a Conventional Transmission Electron Microscope (CTEM), respectively. It is very important that users in various fields know when to use this piece of valuable equipment to get the desired results. For this purpose, applications of Energy-Filtering Transmission Electron Microscope in various fields like: Biology, Polymer science, Semiconductors, and Carbon nanotubes has been explained with simple examples in order to obtain a better comprehension of the unique operations and advantages of this equipment.

Scanning tunneling microscope is considered as the first member in the scanning probe microscope family, which it can sense the smallest height and pitch in the surface (nanometer scale) due to the very small size of tip. Development of nanostructured detection methods lead to increase the resolution of this microscopic method in order to investigate smaller structures and identify magnetic nanostructures. For this purpose, Spin-Polarized Scanning Tunneling Microscopy (Sp-STM) has become a powerful tool for examining magnetic nanostructures in recent years. The basis of the polarized spin scanning tunneling microscope is the improvement of magnetic studies in nanometer scale.