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Frequently Asked Questions (FAQs)
SMART TEM Grid Selection and Design
How do I choose which grid surface functionalization is right for me?
To achieve maximum performance, the grid surface functionalization should be matched to the surface properties of the sample that you are depositing. For example, if you have citrate-stabilized nanoparticles, the citrate carries a negative charge, so one would select our PLUS grids to electrostatically bond the nanoparticles. For more specific bonding, such as for biomolecules, our epoxy-functionalized BioLysine grids will covalently bond to primary amines on the surface of the molecule. Our LinkedON kits enable one to covalently tether to amines, carboxyl, or sulfhydryl groups. If you would like assistance in selecting the right functionalization, please contact us.
What if I don’t know anything about the surface properties of my sample?
Dune Sciences sells variety packs for both its NanoGrids and BioGrids with three surface functionalities so you can experimentally determine which grid is best suited for your sample.
Which membrane type should I choose for my imaging?
Dune currently offers three membrane types: low stress Si3N4, thermal SiO2, and carbon. Both the nitride and oxide membranes are ultra-clean and the surface functionalization has a long shelf life. The nitride membranes tend to be less susceptible to charging than the SiO2 and are recommended for nanomaterials. The SIO2 membranes behave much like glass slides and are amenable to processing as one would a glass slide. For low contrast samples such as biomolecules, the carbon grids provide the lowest background.
Which grid geometry is right for me?
In general, for our nitride and oxide grids, our grids with 50um x 50um windows are the most durable and are generally recommended. However, depending on your sample or analysis method, other grids may be preferred. Our 2mm x 50um windows are recommended for tomography, while our 100 um x 100um windows provide a greater viewing area. We currently only offer our functionalized carbon grids with 400 mesh copper. If you would like a different geometry, please contact us.
Why are your TEM grids shaped like octagons?
Dune’s unique grid design is a product of our microfabrication process that produces the octagonal shapes. The flat sides of the grid improve your ability to hold with tweezers.
Why do your nitride or oxide membrane grids have some many windows?
Silicon nitride or SiO2 membranes can be fragile especially when they are extremely thin. The large number of windows ensures that you have the maximum opportunity to achieve success when handling your samples.
Can Dune produce custom substrate geometry or surface functionalization for my application?
Yes. Dune provides a variety of services for its customers including custom grid geometries, custom surface chemistries, as well as complete characterization. Contact us today to help solve your problems.
Why choose Si half grids for FIB sample preparation?
Si Half Grids from Dune 1) are metal-free which eliminates interference for metal analysis using EDX; 2) are rigid which simplifies handling and will not bend; 3) are ultra-clean for reduced contamination; 4) can be easily shaped without redeposition; and 5) reduce the currents required for bonding.
Why are your TEM grids SMART?
SMART Grids are smart because they have active functionalized surfaces that create affinity for your sample to improve the uniformity of coverage and eliminate preparation artifacts when compared to legacy grids that have no such features.
SMART TEM Grid Usage and Handling
Will SMART TEM grids fit in my TEM holder?
SMART TEM grids will fit in nearly all standard TEM holders. The silicon grids have standard 3 mm geometry and are 100 um thick. The carbon grids are 15 um thick and offer a familiar grid format, but with superior performance.
Do I need to preclean or glow discharge SMART TEM grids?
No, SMART Grids should be used directly out of the box. Glow-discharge will adversely affect the surface functionalization. For our Si-based NanoBasic Grids (that don’t have functionalization), it is possible to clean using a variety of protocols including plasma cleaning, acid cleaning and solvent rinses. Strong bases are not recommended for these grids.
CAN I use SMART Grids for scanning electron microscopy (SEM) or atomic force microscopy (AFM)?
Yes. Our Si-based grids are ultra-flat and conductive which enables them to be used with SEM, AFM, STM, and a variety of surface analytical techniques in addition to TEM. Since the space between the windows is also functionalized, these areas are ideal for AFM.
Can I reuse SMART TEM grids?
In general, this is not recommended since TEM is extremely sensitive to “seeing” contamination. Also, cleaning protocols can damage the surface functionalization.
What is the shelf-life for SMART TEM Grids?
Our Si-based grids with nitride or oxide membranes have a shelf-life of 1-2 years if they are stored in a closed container free of dust and exposure to airborne contaminants. Our functionalized C membrane grids have a shelf life from 3-6 months.
How should I store SMART TEM Grids?
In general SMART Grids should be stored under ambient conditions in the grid boxes sealed inside the reclosable plastic bag included with the grids. In some cases, we recommend special storage conditions which will be included in the instructions with the grids.
What is the protocol for producing publication quality images and data?
Dune Sciences provides a variety of protocols in both video format that show the handling and usage of the grids as well as written documents is the User guides & Tutorials section. If you have specific questions, please contact us.
How do I remove the nitride or oxide membrane grids from the Gel-Pak grid boxes without damaging them?
The grids are most easily removed by grabbing the grids on two sides and gently twisting in the plane of the grid case. A more detailed description can be found at: http://www.dunesciences.com/files/Smart%20Grid%20Usage%20and%20Handling.pdf
Are SMART TEM Grids compatible with my solvents/solutions?
In most cases, yes. The Si grids are compatible with nearly all solvents with the exception of strong alkaline solutions. The copper grids will react with some buffer solutions.
Does the concentration of my sample matter?
Yes. Samples can be either too concentrated which will result in a high density of coverage that may be difficult to analyze or, less frequently, too dilute. SMART Grids have the effect of concentrating the sample on the grid. For nanomaterials, a general recommendation is to use 1 mg/ml, although concentrations much high and much lower will also work. For biomolecules, concentrations as low as 10^4 particles/ml can be used.
Can I sonicate SMART TEM Grids?
No. The energy imparted from sonicating will destroy the membranes of the grids.
What if I get aggregation of my sample on the grid?
Aggregation can be a result of numerous factors including a poorly matched substrate, a too highly concentrated solution, or the particles are actually aggregated in solution. For nanoparticle solutions, we recommend a 15 sec sonication prior to sample preparation to break up any weekly bound aggregates in solution. For well-matched substrates and well-dispersed solutions, aggregation will not occur. You can actually use SMART Grids to determine if you have aggregation in solution. Contact us to learn more.
How I store prepared grids for long-term storage?
Once you have prepared a sample, the grids can be stored inside the grids boxes for long term storage. The enclosed index card allows you to identify each sample.
Can I reduce the handling required for preparing samples using SMART TEM grids?
Yes, Dune offers a variety of sample handling aids including our tack strips that simplify/reduce grid handling. A video showing the use of Tack Strips can be found at the bottom of the User guides & Tutorials page.
How do I analyze my images?
There are a variety of software packages that can aid in the analysis of your images. Dune has published a protocol for analysis of particulate materials.
Where can I buy SMART Grids?
SMART Grids can be purchased directly through our website, through purchase orders directly to Dune, or through one of our worldwide distributors.
What is the standard turnaround time for shipping?
In general SMART Grids are shipped in 1-2 days from receipt of order. After placing an order, we will provide you with a specific estimate for the product you have ordered.
Is it possible to get a sample of SMART TEM Grids?
In some cases, it is possible to receive a sample for your evaluation. We request feedback and images from any samples that we provide for evaluation so we can ensure that they meet your expectations.
Do you offer discount for bulk purchases?
Yes, we have introduced a new pricing schedule that can be found on the purchasing page for each grid type that give up to a 40% discount off our list price for order of 100 or more grids of the same type.
Can I become a distributor of SMART TEM Grids?
Yes, we are always looking for new outlets for distributing our grids. Please contact us.