Gold nanoparticles

It is best to store the particles in the buffer solution provided. The particles can be dried down and reused, but there are important considerations to keep in mind. Drying gold nanoparticles can lead to aggregation, which may affect their size, shape, and overall functionality. The citrate ions help stabilize the nanoparticles in solution, and removing the solvent can disrupt this stabilization. If dried, the nanoparticles need to be re-dispersed in ultra-pure water. If drying is necessary, consider storing the nanoparticles in a controlled environment (e.g., desiccator) to minimize moisture and humidity, which can lead to aggregation.

The storage conditions that a Sigma-Aldrich catalog and label recommend for products are deliberately conservative. For many products, long-term storage at low temperatures will increase the time during which they are expected to remain in specification and therefore are labeled accordingly. Where short-term storage, shipping time frame, or exposure to conditions other than those recommended for long-term storage will not affect product quality, Sigma-Aldrich will ship at ambient temperature. The products sensitive to short-term exposure to conditions other than their recommended long-term storage are shipped on wet or dry ice. Ambient temperature shipping helps to control shipping costs for our customers. At any time, our customers can request wet- or dry-ice shipment, but the special handling is at customer expense if our product history indicates that the product is stable for regular shipment.

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 is 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.

To view the procedure on how to attach gold nanoparticles to glass please view information in the reference - Journal of Atomic, Molecular, and Optical PhysicsVolume 2012 (2012). Article ID 683830, 6 pagesdoi:10.1155/2012/683830

No, the Gold nanoparticles should not be frozen.  If frozen, the gold nanoparticles will irreversibly aggregate, turning the solution clear.

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.

The majority (>95%) of the gold nanoparticles are spherical.

The size of gold nanoparticle to use is very depandent upon the intended application. Generally, smaller particles offer better sensitivity in applications such as immunogold labeling due to less steric hindrance and the ability to bind more gold nanoparticles to the desired target. Small gold nanoparticles are less visible than larger particles, however, which must also be taken into account.As an application example, particles with a size between 30-50nm are particularly useful for the development of rapid tests such as lateral flow assays.

Settling of gold nanoparticles on the bottom of the storage flask is completely normal and is especially common for larger sized particles, which settles at 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 obtain a homogenous solution.

Transportation information can be found in Section 14 of the product's (M)SDS.To access the shipping information for this material, use the link on the product detail page for the product.