Transmission electron microscopy (TEM) utilizes an electron beam to produce high resolution images of nanoparticles. The interaction of the electron beam with the sample produces amplitude and phase variations that yield contrast due to the mass thickness (the amount of material that the electron beam pass through) and atomic number of the atoms (heavier atoms scatter electrons to a greater degree than lighter atoms). Using TEM images, particle grain size, size distribution, and morphology can be directly measured. Sizing accuracy is typically within 3% of the actual value.

Successful imaging of nanoparticles with a TEM depends on the contrast of the material that you are analyzing compared to the background.  TEM grids are prepared by drying nanoparticles on a copper grid that is coated with a thin layer of carbon.  Materials that have different electron densities than the amorphous carbon film are easily imaged (for example, silver and gold) whereas polymers or biomolecules that have similar electron densities to amorphous carbon are difficult to image.

High Contrast / Easily Imaged:

• Most metals: gold, silver, copper, aluminum
• Most oxides: silica, aluminum oxide, titanium oxide
• Particles made from polymers
• Carbon nanotubes, quantum dots, magnetic nanoparticles

Low Contrast / Difficult to Image

• Biomolecules / Dendrimers
• Some polymers

If you're unsure whether your sample is appropriate for imaging please contact us.

To obtain high quality TEM images often requires optimization of sample preparation techniques that are specific to each material that is being analyzed.  There are many factors that can influence the quality of the image.  The more information that you can provide on your sample the higher the chance that our first pass at imaging your sample will be successful.  We highly suggest that you perform the following steps when preparing your sample for TEM imaging:

• Provide the nanomaterial in a pure state. The grid preparation involves the drying of your sample onto a grid and all residual salts, polymers, biomolecules, or other particulates will be dried and imaged along with your nanoparticles.   Highest quality images will be obtained when you can isolate the nanomaterial from all residual reactant components using centrifugation/wash steps, filtration, or dialysis.
• Provide as much information as possible with your sample.  Details on the size, shape, material, and concentration as well as the solvent and the concentration of residual reactants will help us determine if the sample needs additional processing before images can be obtained.

For questions about sample preparation please contact us.

Our Transmission Electron Microscopy is a 100 kV JEOL 1010 with an AMT XR41-B 4-megapixel (2048 x 2048) bottom mount camera.  The camera's finite-conjugate optical coupler provides high resolution and flat focus with less than 0.1% distortion. Sample images captured with the system are here. <add link to Phoca gallery>

In some cases, the images will be different from what you are expecting. This can be due to a wide range of reasons including sample preparation, residual reactants, or low concentration or low contrast of the particles.

Options for next steps:

Re-imaging:

In some cases, simply re-imaging the sample at a lower/higher dilution or capturing additional images will provide the data that you need. Send an email to service@nanocomposix.com describing what you would like to achieve. A new sample will be prepared and an additional TEM analysis charge will be billed to your order.

New Preparation:

Preparation optimization can be extremely challenging for TEM samples. Typically, nanoparticles are dispersed in a compatible solvent and drop cast on a carbon coated TEM grid. Residual chemicals in solution can coat the nanoparticles during the drying process. A number of different techniques can be tried to improve the sample quality image. Contact service@nanocomposix.com to set up a time to discuss your sample and the potential for achieving better images. We’ll provide a quote for the preparation optimization.

Sample Processing:

Depending on your sample, it may not be possible to obtain high quality images in the as received form. Washing the nanoparticles may be necessary to isolate the nanoparticles from other residual reactants. Contact service@nanocomposix.com to set up a time to discuss sample processing that may generate improved images.