Trade.Information

Topic Name: Silver Now Draw Star Attraction in a Series of Products from Socks to Bandages to Washing Machine

Category: Nanobiotechnology

Research persons: Paul Westerhoff, Troy M. Benn

Location: American Chemical Society (ACS), United States

Details

Nanotechnology is now available in a store near you. Valued for it’s antibacterial and odor-fighting properties, nanoparticle silver is becoming the star attraction in a range of products from socks to bandages to washing machines. But as silver’s benefits propel it to the forefront of consumer nanomaterials, scientists are recommending a closer examination of the unforeseen environmental and health consequences of nanosilver.

“The general public needs to be aware that there are unknown risks associated with the products they buy containing nanomaterials,” researchers Paul Westerhoff and Troy M. Benn said in a report scheduled for the 235th national meeting of the American Chemical Society (ACS).

Westerhoff and Benn report that ordinary laundering can wash off substantial amounts of the nanosilver particles from socks impregnated with the material. The Arizona State researchers suggest that the particles, intended to prevent foot odor, could travel through a wastewater treatment system and enter natural waterways where they might have unwanted effects on aquatic organisms living in the water and possibly humans, too.

“This is the first report of anyone looking at the release of silver from this type of manufactured clothing product,” said the authors.

Behind those concerns lies a very simple experiment. Benn and Westerhoff bought six pairs of name brand anti-odor socks impregnated with nanosilver. They soaked them in a jar of room temperature distilled water, shook the contents for an hour and tested the water for two types of silver — the harmful “ionic” form and the less-studied nanoparticle variety.

“From what we saw, different socks released silver at different rates, suggesting that there may be a manufacturing process that will keep the silver in the socks better,” said Benn. “Some of the sock materials released all of the silver in the first few washings, others gradually released it. Some didn’t release any silver.” The researchers will present the specific brands they studied at their ACS presentation.

If sufficient nanosilver leeches out of these socks and escapes waste water treatment systems into nearby lakes, rivers and streams, it could damage aquatic ecosystems, said Benn. Ionic silver, the dissolved form of the element, does not just attack odor-causing bacteria. It can also hijack chemical processes essential for life in other microbes and aquatic animals.

“If you start releasing ionic silver, it is detrimental to all aquatic biota. Once the silver ions get into the gills of fish, it’s a pretty efficient killer,” said Benn. Ionic silver is only toxic to humans at very high levels. The toxicity of nanoparticle silver, said Westerhoff, has yet to be determined.

Westerhoff and Benn did not intend to establish the toxicity of silver. “The history of silver and silver regulation has been set for decades by the U. S. Environmental Protection Agency — we’re not trying to reexamine or reinvent that,” said Westerhoff.

They do hope to spark a broader examination of the environmental and health consequences of nanomaterials, as well as increasing awareness of nanotechnology’s role in everyday consumer goods.

Silver has been used historically since ancient roman times, though its nanoparticle form has only recently appeared in consumer products. Beyond socks, nanosilver appears in certain bandages, athletic wear and cleaning products. Benn suggested that most consumers are unaware of these nano-additions.

“I’ve spoken with a lot of people who don’t necessarily know what nanotechnology is but they are out there buying products with nanoparticles in them. If the public doesn’t know the possible environmental disadvantages of using these nanomaterials, they cannot make an informed decision on why or why not to buy a product containing nanomaterials,” said Benn.

To that end, the researchers suggest that improved product labeling could help. Westerhoff proposes that clothing labels could become like the back of a food packaging, complete with a list of “ingredients” like nanosilver.

Westerhoff and Benn expect to expand their leeching experiments to other consumer products imbued with nanomaterials. They hope to find the moment in each product’s lifecycle when nanomaterials could be released into the environment, as well as developing better detection methods to characterize nanoparticles in water and air samples.

“Our work suggests that consumer groups need to start thinking about these things,” said Benn. “Should there be other standards for these products"”

Note for Nanotechnology
Nanotechnology refers broadly to a field of applied science and technology whose unifying theme is the control of matter on the atomic and molecular scale, generally 100 nanometers or smaller, and the fabrication of devices with critical dimensions that lie within that size range.

Nanotechnology is a highly multidisciplinary field, drawing from fields such as applied physics, materials science, interface and colloid science, device physics, supramolecular chemistry (which refers to the area of chemistry that focuses on the noncovalent bonding interactions of molecules), self-replicating machines and robotics, chemical engineering, mechanical engineering, biological engineering, and electrical engineering. Much speculation exists as to what may result from these lines of research. Nanotechnology can be seen as an extension of existing sciences into the nanoscale, or as a recasting of existing sciences using a newer, more modern term. Grouping of the sciences under the umbrella of "nanotechnology" has been questioned on the basis that there is little actual boundary-crossing between the different sciences that operate on the nano-scale. Instrumentation is the only area of technology common to all disciplines; on the contrary, for example pharmaceutical and semiconductor industries do not "talk with each other". Corporations that call their products "nanotechnology" typically market them only to a certain industrial cluster.

Two main approaches are used in nanotechnology. In the "bottom-up" approach, materials and devices are built from molecular components which assemble themselves chemically by principles of molecular recognition. In the "top-down" approach, nano-objects are constructed from larger entities without atomic-level control. The impetus for nanotechnology comes from a renewed interest in Interface and Colloid Science, coupled with a new generation of analytical tools such as the atomic force microscope (AFM), and the scanning tunneling microscope (STM). Combined with refined processes such as electron beam lithography and molecular beam epitaxy, these instruments allow the deliberate manipulation of nanostructures, and lead to the observation of novel phenomena.

Examples of nanotechnology in modern use are the manufacture of polymers based on molecular structure, and the design of computer chip layouts based on surface science. Despite the great promise of numerous nanotechnologies such as quantum dots and nanotubes, real commercial applications have mainly used the advantages of colloidal nanoparticles in bulk form, such as suntan lotion, cosmetics, protective coatings, drug delivery, and stain resistant clothing.

Note for Nanomaterial
Nanomaterials is the study of how materials behave when their dimensions are reduced to the nanoscale. It can also refer to the materials themselves that are used in nanotechnology.

A unique aspect of nanotechnology is the vastly increased ratio of surface area to volume present in many nanoscale materials which opens new possibilities in surface-based science, such as catalysis. A number of physical phenomena become noticeably pronounced as the size of the system decreases. These include statistical mechanical effects, as well as quantum mechanical effects, for example the “quantum size effect” where the electronic properties of solids are altered with great reductions in particle size. This effect does not come into play by going from macro to micro dimensions. However, it becomes dominant when the nanometer size range is reached. Additionally, a number of physical properties change when compared to macroscopic systems. One example is the increase in surface area to volume of materials. Novel mechanical properties of nanomaterials is the subject of nanomechanics research. Their catalytic activity reveals novel properties in the interaction with biomaterials.

Nanotechnology can be thought of as extensions of traditional disciplines towards the explicit consideration of these properties. Additionally, traditional disciplines can be re-interpreted as specific applications of nanotechnology. This dynamic reciprocation of ideas and concepts contributes to the modern understanding of the field. Broadly speaking, nanotechnology is the synthesis and application of ideas from science and engineering towards the understanding and production of novel materials and devices. These products generally make copious use of physical properties associated with small scales.

Materials reduced to the nanoscale can suddenly show very different properties compared to what they exhibit on a macroscale, enabling unique applications. For instance, opaque substances become transparent (copper); inert materials become catalysts (platinum); stable materials turn combustible (aluminum); solids turn into liquids at room temperature (gold); insulators become conductors (silicon). Materials such as gold, which is chemically inert at normal scales, can serve as a potent chemical catalyst at nanoscales. Much of the fascination with nanotechnology stems from these unique quantum and surface phenomena that matter exhibits at the nanoscale.

Nanosize powder particles (a few nanometres in diameter, also called nanoparticles) are potentially important in ceramics, powder metallurgy, the achievement of uniform nanoporosity and similar applications. The strong tendency of small particles to form clumps ("agglomerates") is a serious technological problem that impedes such applications. However, a few dispersants such as ammonium citrate (aqueous) and imidazoline or oleyl alcohol (nonaqueous) are promising additives for deagglomeration.

Nanoparticles or nanocrystals made of metals, semiconductors, or oxides are of interest for their mechanical, electrical, magnetic, optical, chemical and other properties. Nanoparticles have been used as quantum dots and as chemical catalysts.

Nanoparticles are of great scientific interest as they are effectively a bridge between bulk materials and atomic or molecular structures. A bulk material should have constant physical properties regardless of its size, but at the nano-scale this is often not the case. Size-dependent properties are observed such as quantum confinement in semiconductor particles, surface plasmon resonance in some metal particles and superparamagnetism in magnetic materials.

Nanoparticles exhibit a number of special properties relative to bulk material. For example, the bending of bulk copper (wire, ribbon, etc.) occurs with movement of copper atoms/clusters at about the 50 nm scale. Copper nanoparticles smaller than 50 nm are considered super hard materials that do not exhibit the same malleability and ductility as bulk copper. The change in properties is not always desirable. Ferroelectric materials smaller than 10 nm can switch their magnetisation direction using room temperature thermal energy, thus making them useless for memory storage. Suspensions of nanoparticles are possible because the interaction of the particle surface with the solvent is strong enough to overcome differences in density, which usually result in a material either sinking or floating in a liquid. Nanoparticles often have unexpected visible properties because they are small enough to confine their electrons and produce quantum effects. For example gold nanoparticles appear deep red to black in solution.

Note for Silver Nano
Silver Nano (Silver Nano Health System) is a trademarked name of an anti-bacterial technology which uses silver nano particles in washing machines, vacuum cleaners, air conditioners and refrigerators introduced by Samsung in 2003.

Samsung maintains that the silver nano technology sterilises over 650 types of bacteria. and a "Samsung WM1245A Washing Machine releases over 400 billion silver ions which penetrate deep into fabrics of any kind and create a coat of sterilizing protection for a maximum of 99.99% disinfection and an added antibacterial effect of up to 30 days after washing"

According to Paul Lipscomb, Product Manager, White Goods, Samsung Australia: “The Silver Wash system means that it’s no longer necessary to soak clothes in additives or wash at extremely high temperatures in order to sanitise them. This, combined with Samsung front loading washing machine’s industry leading water efficiency ratings of up to 5A, creates a major saving on the long term cost of running the washing machine.”

Concerns have been raised over the use and marketing of washing mashines using the silver nano technology. The German branch of Friends of the Earth, Bund für Umwelt und Naturschutz Deutschland (BUND) has warned consumers not to buy a new type of washing machine that uses silver nanoparticles. BUND criticized that considerable amounts of silver could enter sewage plants and seriously trouble the biologic purification process of the waste water. In addition, silver nanoparticles were blaimed to have a toxic effect on different kinds of cells. Samsung countered that only an accumulated amount of 0.05 grams of silver are released per machine and year, while the released silver-ions quickly bind to non-nano-sized structures in the water.

In 2005 the Korean Consumer Protection Board, published test results according to which Samsung’s Silver Wash technology has no superior sterilization effect, as the company claims in advertisements, when compared with similar drum-type washers of LG Electronics, Daewoo Electronics and Whirlpool.