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Scanning Electron Microscopy

Scanning Electron Microscopy

A scanning electron microscope (SEM) is used to study the surface features of a sample by using an electron beam that scans the sample surface in a two-dimensional manner. Typically, areas between ~1 centimeter to 5 micrometers in width can be imaged. SEM can be used to image bacteria, viruses, tissues as well as larger samples like insects. Conventional SEM gives a magnification ranging from 20X to 30,000X and spatial resolution of 50 to 100 nanometers.
Fundamental Principles
Accelerated...

Overview of Electron Microscopy

Overview of Electron Microscopy

The wavelengths of visible light ultimately limit the maximum theoretical resolution of images created by light microscopes. Most light microscopes can only magnify 1000X, and a few can magnify up to 1500X. Electrons, like electromagnetic radiation, can behave like waves, but with wavelengths of 0.005 nm, they produce significantly greater resolution up to 0.05 nm as compared to 500 nm for visible light. An electron microscope (EM) can create a sharp image that is magnified up to 2,000,000X.

Electron Microscope Tomography and Single-particle Reconstruction

Electron Microscope Tomography and Single-particle Reconstruction

Transmission electron microscopy (TEM) can be used to determine the 3D structure of biological samples with the help of techniques such as electron microscope tomography and single-particle reconstruction. While single-particle reconstruction can examine macromolecules and macromolecular complexes in vitro conditions only, tomography permits the study of cell components or small cells in vivo.
Electron Tomography
Electron tomography can be performed either in TEM or STEM (scanning transmission...

Transmission Electron Microscopy

Transmission Electron Microscopy

In 1931, physicist Ernst Ruska—building on the idea that magnetic fields can direct an electron beam just as lenses can direct a beam of light in an optical microscope—developed the first prototype of the electron microscope. This development led to the development of the field of electron microscopy. In the transmission electron microscope (TEM), electrons are produced by a hot tungsten element and accelerated by a potential difference in an electron gun, which gives them up to 400 keV in...

Preparation of Samples for Electron Microscopy

Preparation of Samples for Electron Microscopy

To be visualized by an electron microscope, either transmission or scanning, biological samples need to be fixed (stabilized) so the electron beam does not destroy them and dried thoroughly (desiccated/dehydrated) so the vacuum does not affect them. Fixation needs to be done as quickly as possible because the sample properties will start changing as soon as it is removed from its natural environment. For example, in a tissue sample, the oxygen levels begin decreasing, causing an altered...

Cryo-electron Microscopy

Cryo-electron Microscopy

Conventional electron microscopy (EM) involves dehydration, fixation, and staining of biological samples, which distorts the native state of biological molecules and results in several artifacts. Also, the high-energy electron beam damages the sample and makes it difficult to obtain high-resolution images. These issues can be addressed using cryo-EM, which uses frozen samples and gentler electron beams. The technique was developed by Jacques Dubochet, Joachim Frank, and Richard Henderson, for...

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Related Experiment Video

Updated: May 13, 2026

Preparation of Nanoparticles for ToF-SIMS and XPS Analysis

Preparation of Nanoparticles for ToF-SIMS and XPS Analysis

Published on: September 13, 2020

Characterisation of Co@Fe3O4 core@shell nanoparticles using advanced electron microscopy.

Benjamin R Knappett¹, Pavel Abdulkin, Emilie Ringe

¹Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.

|March 7, 2013

Summary

This study details the core@shell structure of iron oxide-coated cobalt nanoparticles. Researchers identified metallic cobalt cores, magnetite shells, and a novel carbon residue layer.

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Synthesis, Characterization, and Functionalization of Hybrid Au/CdS and Au/ZnS Core/Shell Nanoparticles

Synthesis, Characterization, and Functionalization of Hybrid Au/CdS and Au/ZnS Core/Shell Nanoparticles

Published on: March 2, 2016

Area of Science:

Materials Science
Nanotechnology
Chemistry

Background:

Previous research focused on thermal alloying of cobalt-iron oxide nanoparticles.
A detailed understanding of the core@shell structure and composition is lacking.

Purpose of the Study:

To fully elucidate the composition and core@shell structure of iron oxide-coated cobalt nanoparticles.
To investigate the presence and origin of any intermediate layers within the nanoparticles.

Main Methods:

Synthesis of cobalt nanoparticles via thermal decomposition of Co2(CO)8.
Coating with iron oxide using Fe(CO)5.
Advanced electron microscopy techniques including energy-filtered transmission electron microscopy (EFTEM) and electron energy loss spectroscopy (EELS).
Multivariate statistical analysis (MSA) for enhanced elemental mapping.

Main Results:

Confirmed core@shell structure with an oxidatively stable metallic cobalt core.
Identified the shell as magnetite (Fe3O4).
Observed and identified a novel layer of trapped carbon residue between the core and shell, originating from organic capping agents.

Conclusions:

The study provides a comprehensive characterization of cobalt-iron oxide core@shell nanoparticles.
The metallic cobalt core and Fe3O4 shell are stable.
The identification of a carbon residue layer offers new insights into nanoparticle synthesis and processing.