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Frequently Asked Questions

Below are answers to the most frequently asked questions about our products and services. If you have a question that is not answered feel free to contact us. Our technical specialists are happy to help with any questions you might have about our products.

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Gold Nanoparticles


How do I wash my gold nanoparticles?

For most applications our gold nanoparticles can be used without any additional washing steps. If you have a sensitive application that requires additional washing the best way to do so is by either centrifugation or filtration. For recommended centrifugation speeds and times please refer to Storage & Handling of gold nanoparticles - Tech Note #101.


What gold nanoparticle size should I choose for my application?

The size and the surface chemistry of gold nanoparticle to use is very dependent upon the intended application. Please see our Gold Nanoparticle Product Selection Guide to find the most optimal product for your particular application.


My gold nanoparticle settle out of solution upon storage. Is this normal?

Settling of gold nanoparticles on the bottom of the storage flask is completely normal and is especially common for larger sized particles, which settle at a greater speed. Settling does not affect the performance of the particles. Prior to use, simply swirl the solution to properly disperse your gold nanoparticles and generate a homogenous solution.


What is the shelf life of gold nanoparticles?

Our standard gold nanoparticles are stable for at least 1 year if stored unopened and as specified at 4 degrees Celsius. Do NOT store our non-functionalized standard gold nanoparticles in the freezer since this cause irreversible aggregation, see our gold nanoparticles handling and storage tech note.


The gold nanoparticle solution turns violet when I add salt containing buffer. Why is that?

Due to repulsive forces arising from the surface charge of gold nanoparticles, an energy barrier must be overcome for individual particles to interact. When no (or small) amounts of electrolytes such as NaCl are present, this energy barrier is too strong for interaction to occur between particles. However, upon addition of NaCl this energy barrier is reduced allowing the gold nanoparticles to interact and aggregate. This aggregation causes a phenomenon called surface-plasmon coupling which changes the adsorption maximum of light to a higher wavelength resulting in a change in color of the solution.


What happens if I accidentally freeze my non-functionalized gold nanoparticles?

Freezing of our non-functionalized gold nanoparticles causes irreversible aggregation and can be observed by a clear change in color of the solution, see our gold nanoparticles handling and storage tech note for more information and examples.


Fluorescent Nanocrystals (Quantum Dots)


The amount of your fluorescent nanocrystals are given in mg. How many particles does this correspond to?

The number of nanocrystals per mg is 1.2x1015.


What is the molecular weight of your quantum dots?

All of our quantum dots have the same size with a molecular weight of 650,000 Da.


What is the quantum efficiency of your quantum dots?

The quantum efficiency of our quantum dots is 55-65% (alkyl functional fluorescent nanocrystals compared to laser dyes). Our water soluble quantum dots have 15% lower quantum efficiency compared to the alkylated fluorescent nanocrystals.


Ordering and Shipping


How much do you charge for shipping?

For information regarding our shipping policy and costs please read our shipping policy page.


Can I place an order using a credit card?

We are happy to accept orders placed with VISA and Mastercard, as well as standard purchase orders. For more information please refer to our ordering information page.