The production and use of silver nanomaterials as antibacterial agents in consumer products, ranging from washing machines to hair dryers, has attracted a good deal of media coverage in recent months. However, it is not widely known that gold, traditionally used in large quantities by the electronics and dental industries, is also being applied as a nanomaterial by manufacturers confirming the growing importance of the technical uses of gold in modern day society.
Why Nano-gold?
Gold nanoparticles exhibit unique chemical and physical properties, quite different from the properties of bulk gold. For example, gold particles that are 20 nanometers in diameter are red-colored, a fact exploited in a number of medical diagnostic products. The gold particles are non-toxic, can easily be attached to other biomolecules and they also show unique optical properties. Additionally, they are now known to be catalytically active for a range of commercially important reactions and they also show useful surface chemistry which permits the "bottom-up" assembly of interesting and useful structures. Based on these unique properties, exciting new applications utilizing gold are being developed, which in turn is requiring the manufacture and supply of a range of gold nanomaterials.
Applications: Biomedical Leads the Way
Four types of nanoparticle materials, including gold, accounted for more than 90% of the market in 2006 according to a report, "Nanostructured Materials for the Biomedical, Pharmaceutical and Cosmetic Markets," from BCC Research. Titanium dioxide, zinc oxide, and calcium phosphate were the other dominant materials. The global market for these nanoparticles in biomedical, pharmaceutical and cosmetic applications was worth $204.6 million in 2006. This sector looks set to increasingly use gold with clinical trials using gold nanoparticles to deliver anticancer drugs already underway.
Gold nanoparticle formulations are also being used in the tableware industry which uses the gold for decorative purposes and in the electronic industry where specialized gold nanoparticle inks are used to provide metalized gold tracks. New uses envisaged in the electronics industry include gold nanomaterials to enhance solar cells, liquid crystal displays and even flash memory devices, although these have yet to emerge from the research laboratories working on them.
Leading Manufacturers
Recognizing the business opportunities presented, a number of companies have developed commercial supplies of gold nanomaterials. One of the most successful, BBInternational based in the UK, claims to have a unique recipe for the manufacture of high quality gold nanoparticles. This enables the production of spherical, aggregate-free gold nanoparticles, which can then be attached to specific antibodies or antigens for use in biomedical applications. BBInternational is now recognized globally for the production of these gold nanomaterials which are used within lateral flow rapid diagnostic tests for the 'Point of Care' (POC) market, such as pregnancy testing kits. Established precious metals companies like Tanaka who are based in Japan and Swiss company Metalor are also now manufacturing these nanomaterials for customers, and Johnson Matthey in the UK is one of the leading manufacturers of the gold nanoparticle formulations used by the decorative tableware industry.
A much younger company called Nanopartz Inc, based in Salt Lake City, is innovating in the gold nanomaterials market with its work on gold nanorods (rectangular rather than spherical-shaped particles). Nanopartz's gold nanorods are designed specifically for use in diagnostic applications, biomedical imaging, and photothermal therapy. Gold nanorods have long been sought for their potential in detection and therapy for cancer and Nanopartz was the first known commercial source for these materials.
Support From the Mining Industry
One group keen to see the markets for nanomaterials develop is the gold mining industry. Through the industry's marketing body, the World Gold Council, supports research into new applications for these materials. At the recent NSTI Nanotech 2008 event, WGC partnered with a number of organizations to exhibit some of the uses for gold nanomaterials. The World Gold Council believes that even if the amount of gold used in each application is small, new high-volume consumer-based uses of these materials, for example in electronics, can generate significant quantities of new gold demand in the future.
Although the market for gold nanomaterials is still developing, it is clear that gold's unique properties will make it an important part of nanotechnology in the future.
Richard Holliday is Head of Industrial Applications for the World Gold Council. www.gold.org
