Electron microscopy grids support the observation of nanoparticles and biological molecules. Supports are built up from layers of decreasing rigidity and increasing inertness.
Once the more rigid layers are sacrificed in a chemical bath, a final ultrathin film is left for the attachment of nanoparticles of interest, which are studied under an electron microscope. Thinness is particularly important to resolution in transmission electron microscopy (TEM) as electrons must pass through the support and scattering of electrons as a result of the support degrade image quality.
Recently, graphene and graphene oxide supports have become commercially available as examples of thin supports down to one atom of thickness. However, these supports are often contaminated with carbon from either the preparation process or storage in air. Carbon contamination adds noise to the image due to its random nature.
Furthermore, the thinness of graphene compromises its strength during sample deposition and electron beam analysis. As an alternative, ultrathin (UT) carbon with an additional sacrificial film of amorphous carbon is often employed to image nanometer size samples. While more durable, UT carbon has limitations in that it cannot be readily cleaned. And, like graphene, UT carbon is susceptible to carbon contamination.
To address the above deficiencies in TEM supports, Dr. David Kidwell of the Naval Research Laboratory has developed new robust and flexible TEM supports functionalized to immobilize nanoparticles.
The new supports are made by atomic layer deposition of alumina (or SiN, SiOx, BN, and mixtures thereof) onto a TEM grid of gold or copper supported by a carbon film. (A thermoplastic resin support such as Formvar may also be used in the buildup.) After the ALD deposition, the sacrificial layers are removed by suitable techniques.
These new TEM supports can be cleaned by plasma treatment, which allows removal of residual carbon contamination leaving only the nanoparticles of interest functionally fixed to the alumina. They can be made carbon-less, which avoids deposition of carbon from conventional ultra-thin carbon supports.
- Thin, durable, and contamination resistant grids produced by atomic layer deposition of alumina
- Grids can be coated with nanoparticles in the normal manner by dipping into aqueous or organic solutions or drop drying of the solutions onto the surface
- Grids can be easily cleaned by plasma treatment and heat leaving only the nanoparticles of interest in their immobilized and non-coagulated state
- Support can have functionalities present for immobilization of nanoparticles or biomolecules to avoid coagulation under the electron beam
- Grids are amorphous or contain amorphous areas for tuning the TEM
- US Patent 9,646,803 is available for license from the Navy
- Potential for collaboration with Navy researchers