NIST Issues Silver Nanoparticle Test Material

Nanoparticulate silver is, by some estimates, the most common nanomaterial being used in consumer products, according to the Commerce Department agency.

The National Institute of Standards and Technology (NIST) announced March 3 that it has issued a new silver nanoparticle reference material to support researchers studying potential environmental, health, and safety risks associated with these nanoparticles, which are widely used because of their antimicrobial properties. "The new NIST test material is believed to be the first of its kind to stabilize the highly reactive silver particles in a freeze-dried, polymer coated, nanoparticle cake for long-term storage," Michael Baum wrote in a release posted on NIST's website.

Nanoparticulate silver is, by some estimates, the most widely used nanomaterial in consumer products, including in socks, shoe liners, stain-resistant fabrics,, coatings for handrails and keyboards, and more, Baum explained.

"Silver nanoparticles transform, dissolve, and precipitate back into nanoparticles again, combine, or react with other materials—our understanding of these processes is limited," NIST chemist Vince Hackley told him. "However, in order to study their biological and environmental behavior and fate, one needs to know one is starting with the same material and not some modified or oxidized version. This new reference material targets a broad range of research applications."

The same practice of coating and freeze-drying is used in the pharmaceutical industry to preserve blood products and protein-based drugs, according to his article, which adds, "The NIST material uses polyvinylpyrrolidone (PVP), a polymer approved by the Food and Drug Administration for many uses, including as a food additive. The freeze-dried PVP-nanosilver cakes are flushed with an inert gas and sealed under a vacuum. Mixing the cake with water reconstitutes the original suspension. NIST reference materials are designed to be homogeneous and stable. NIST provides the best available estimates for key properties of reference materials. In this case those include the mean silver particle size measured by four different methods, the total silver mass per vial, and the percentage distribution of nanoparticle sizes. The particles have a nominal diameter of 75 nanometers. NIST expects the material to be stable indefinitely when properly stored and handled, but will continue to monitor it for substantive changes in the reported values."

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