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Gold nanoparticles

20 nm diameter, OD 1, stabilized suspension in citrate buffer

Au NP, Gold Colloid
Linear Formula:
Molecular Weight:
MDL number:
PubChem Substance ID:

Quality Level




Proprietary Surfactant as stabilizer


~6.54E+11 particles/mL




20 nm


518-522 nm



storage temp.


SMILES string




InChI key


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General description

Gold nanoparticles (AuNPs) are versatile materials widely used in biomedical sciences and electrochemical sensor based applications. AuNPs are tunable nano-materials with excellent thermo-mechanical properties, high surface area, and low toxicity.


Citrate stabilized AuNPs can be used for a variety of applications such as:
  • neutrophil labeling for monitoring the effect of different drugs
  • immobilization of proteins for biosensor applications
  • nano-carrier for drug delivery system for the release of hydrophobic drugs.

Ideal for adsorption of thiolated ligands such as oligonucleotides and polyethylene glycols. Also, due to the increased stability, these gold nanoparticles are ideal for use in physical and optical applications. Note: This product is not ideal for protein adsorption. For gold nanoparticles suitable for adsorption of proteins and other ligands for conjugate development, please see our gold nanoparticles stabilized in PBS.

This material is highly monodisperse (<12% variability in size and shape), and provides significantly improved surface reactivity. Applications include Surface Enhanced Raman Lables, Sensing/Detection, Biological Targeting, Plasmonics and Electronics.


25, 100 mL in glass bottle

Legal Information

Product of CytoDiagnostics, Inc.

Storage Class Code

12 - Non Combustible Liquids



Flash Point(F)

Not applicable

Flash Point(C)

Not applicable

Certificate of Analysis

Enter Lot Number to search for Certificate of Analysis (COA).

Certificate of Origin

Enter Lot Number to search for Certificate of Origin (COO).

More Documents

Quotes and Ordering

  1. How does the storage temperature relate to shipping conditions?

    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. See Shipping and Storage for more information.

  2. Which document(s) contains shelf-life or expiration date information for a given product?

    If available for a given product, the recommended re-test date or the expiration date can be found on the Certificate of Analysis.

  3. How do I get lot-specific information or a Certificate of Analysis?

    The lot specific COA document can be found by entering the lot number above under the "Documents" section.

  4. How do I find price and availability?

    There are several ways to find pricing and availability for our products. Once you log onto our website, you will find the price and availability displayed on the product detail page. You can contact any of our Customer Sales and Service offices to receive a quote.  USA customers:  1-800-325-3010 or view local office numbers.

  5. What is the Department of Transportation shipping information for this product?

    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. 

  6. What is the shape of the gold nanoparticles?

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

  7. Can the Gold nanoparticles be frozen?

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

  8. Which gold nanoparticle size should I choose for my application?

    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.

  9. My gold nanoparticles 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 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.

  10. Why does my gold nanoparticle solution turn violet when I add salt containing buffer?

    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.

  11. Do I need to 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.

  12. How do you attach gold nanoparticles to glass?

    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

  13. How do you attach gold nanoparticles to oligos?

    To attach gold nanoparticles to oligos please view the information in the attached reference - Bioconjug Chem. 2011 Apr 20;22(4):794-807. Epub 2011 Mar 28. 

  14. How do you attach gold nanoparticles to peptides and peptide conjugates?

    To view information on how to attach gold nanoparticles to peptides and peptide conjugates, please view the information in the reference - Rosenthal, S. J. and Wright, D. W. (Eds.). (2005), p. 91-92. NanoBiotechnology Protocols. New Jersey. Humana Press.

  15. My question is not addressed here, how can I contact Technical Service for assistance?

    Ask a Scientist here.

Enhanced thermomechanical properties of a nematic liquid crystal elastomer doped with gold nanoparticles
Montazami R, et al.
Sensors and actuators A, Physical, 178(11), 175-178 (2012)
Design of hybrid multimodal poly (lactic-co-glycolic acid) polymer nanoparticles for neutrophil labeling, imaging and tracking
Qiu Y, et al.
Nanoscale, 5(24), 12624-12632 (2013)
Nanomaterials based electrochemical sensors for biomedical applications
Chen A and Chatterjee S
Chemical Society Reviews, 42(12), 5425-5438 (2013)
Toxicity and cellular uptake of gold nanoparticles: what we have learned so far?
Alkilany AM and Murphy CJ
Journal of Nanoparticle Research, 12(7), 2313-2333 (2010)
Gold-Organic-Inorganic High-Surface-Area Materials as Precursors of Highly Active Catalysts
Budroni G and Corma A
Angewandte Chemie (International ed. in English), 45(20), 3328-3331 (2006)


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Gold Nanoparticles: Properties and Applications

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