Quantifoil^® Micromachined Holey Carbon Grids

An Introduction to Quantifoil® Holey Carbon Films Quantifoil is a perforated support foil with a precisely pre-defined hole size, shape, and arrangement. The use of these support foils as "support films" on TEM grids offers a number of advantages not only for conventional transmission electron microscopy (TEM), but also for low-energy point source (LEEPS) microscopy when compared with conventional holey carbon support films. The quantitatively defined geometry of the Quantifoil holey film facilitates the use of automation in TEM, something that with conventional carbon films would probably not be possible.

Quantifoil holey mesh carbon film for TEM

In other words, the product is a superior type of holey carbon film, one that costs more than the conventional holey carbon filmed grids offered by SPI Supplies, and it surely does cost more money, however for a select group of users, the Quantifoil supported grids do offer some very real advantages and in some instances permit the conduct of certain types of work that just otherwise could not be done.

In summary, the Quantifoil support film exhibits a high percentage of open area and is used to minimize the total specimen thickness and to minimize object distortions arising from interactions with a support film.

Quantifoil holey carbon film for TEM

Thus the perforated foil is used to bear an ultra-thin carbon support foil or to directly support a large sample object, such as µm sized powder particle, which could be important when doing either electron diffraction (ED), electron energy loss spectroscopy (EELS) and electron spectroscopic and dark field imaging. The foil finds applications when nano-sized features are to be studied, such as biomacromolecular complexes, are studied in a free hanging layer of sustaining medium.

For use with Cryo-TEM:

The surface properties of Quantifoil holey carbon supported grids, specifically the wetting properties, may have to be adapted according to one's particular requirements. Untreated Quantifoil, like all carbon films, especially with ageing, tends to be hydrophobic (freshly made foils tend to be more hydrophilic). Before shipment, SPI Supplies can "treat" the grids in our SPI Plasma Prep II plasma etcher for an additional charge. The effect of the plasma treatment (glow discharge) can be expected to "last" typically for 30-45 days.

Main Applications Areas for Quantifoil Holey Carbon Supported Grids

• Cryo-electron tomographic reconstruction
• Automated image acquisition
• Low-dose electron microscopy
• Low-energy point source (LEEPS) microscopy

Standard Quantifoil Products:

Quantifoil holey carbon supported TEM grids are offered with "holes" that are either circles or squares, but in both cases, the support films are regular meshes of precisely defined hole size or square size. The support films are available in our different hole sizes and bar widths.

A Few Words about Packaging:

All shipments of Quantifoil holey carbon grids are shipped in SPI Supplies Slide-A-Grids storage boxes with the holey carbon film on the dull side of the grid. The carbon film side always faces the center of the grid box.

Custom Products:

If you have the need for holey films with other geometric parameters, let us know your requirements. In addition, the material making up the foil, which is usually carbon, can be any material that can be deposited by vacuum evaporation. The standard carbon films are made to the minimum thickness that they will be stable in a normal TEM beam environment, on a grid that is 200 mesh or finer. If a larger hole mesh is required, the carbon thickness has to be slightly thicker. If very high mesh numbers, e.g. 2000 mesh, grids are used, in theory, we can make the foils with thinner carbon layers. However the very thinnest that can be made would be 10 nm.

Need help deciding which Quantifoil holey film is for you?

Try the new Quantifoil "Sampler" kit. It was designed for that very purpose.

Circular Holes:

Quantifoil with circular holes is preferred for cryo-TEM. The roundness of the holes is advantageous with respect to the formation of an ice layer of constant thickness. The hole size spacing that is selected depends on the magnification being contemplated, and also, whether one wishes to include or exclude evidence of the support film in the final image. Assessment of the image quality is easier when the foil is included in the final image, since the power spectrum of a foil is stronger than that of unsupported ice.

Quantifoil R 2/1	Quantifoil R 2/2	Quantifoil R 2/4

Quantifoil R 1.2/1.3	Quantifoil R 1/4	Quantifoil R 3.5/1

Quantifoil holey films with 2 and 1.2 µm circular holes are used with magnifications in the range of 30,000X to 40,000X. Quantifoil R 2/4 is probably recommended over R 2/2 when an increased tolerance with respect to position of the beam, and a larger beam diameter is desired, such as in the case of automated image acquisition.

Square Holes: Quantifoil with square holes, or which is in the form of a square mesh, with relatively thin "bars" can be used in conjunction with TEM work, where the carbon film being used is too thin to span the distance between grid bars or to support sections from which EDS is being done.

Quantifoil S 7/2

Square Mesh Film The square mesh film is also available on the SPI Multi-Slot TEM grid, in both copper and nickel. Often times one does not know which size slot will be the optimum for their work, and this style grid permits the selection of the one that is the best for that particular application.

Square Mesh Film Note: The fine smoothness of the "bars" and the complete absence of any protruberances.

"Multi A" Holey Films Quantifoil Multi A is a holey support film in which a pattern of various hole sizes, shapes and arrangements are repeated. In addition to circular holes, of three different diameters, there are also different hole spacings, including an oval hole which at high tilt angles would appear round (this would occur at ~ 70°).

Multi A

Standard Quantifoil Products: Quantifoil holey carbon supported grids, circular holes R 2/1 Hole size: 2 µm; Space between holes: 1 µm; Center to center: 3 µm; R 2/2 Hole size: 2 µm; Space between holes: 2 µm; Center to center: 4 µm; R 2/4 Hole size: 2 µm; Space between holes: 4 µm; Center to center: 6 µm; R 1.2/1.3 Hole size: 1.2 µm; Space between holes: 1.3 µm; Center to center: 2.5 µm; R 3.5/1 Hole size: 3.5 µm; Space between holes: 1 µm; Center to center: 4.5 µm; R 1/4 Hole size: 1 µm; Space between holes: 4 µm; Center to center: 5 µm R 0.6/1 Hole size: 0.6 µm; Space between holes: 1 µm; Center to center: 1.6 µm; - hole size might be as large as 1 µm R5/20 Hole size: 5 µm; Space between holes: 20 µm; Center to center: 25 µm;

Quantifoil holey carbon supported grids, square holes S 7/2 Hole size: ~7 µm; bar width ~2 µm Repeat distance: 9 µm

Quantifoil holey carbon supported grids, Multiple hole sizes/shapes Multi A

QUANTIFOIL® with hexagonal geometry Hexagonal geometry (HEX 15) A foil with hole size of 26 µm (diameter of inscribed circle) and a repeating distance of 41 µm, the side length of the holes and the bar width are 15 µm.