Nanotechnology raises big concerns

Nanotechnology is grabbing headlines these days and the growing prospects of its use is spurring increasing attention to safety issues. This article examines the worldwide reaction to burgeoning popularity of the technology and what safety concerns are legit.

By Mike Spear, editor at large

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BASF is not new to nanotechnology, of course. It already markets nanomaterials such as Ultradur thermoplastic and the Col. 9 binders (Figure 2) for coatings. Among the potential products the Singapore researchers will investigate are biocide-free nanostructured coatings to tackle the problem of biofouling on marine surfaces.

Nanocomposite binders

Figure 2. Binders that feature a dispersion of inorganic nanoparticles in an organic polymer are now on the market.

Arkema, Paris and Philadelphia, Pa., which first launched a research and development project for the production of carbon nanotubes in 2003, also is interested in coatings. At the beginning of this year, the company inaugurated the first plant in Europe capable of producing semi-industrial amounts (around 10 metric tons per year) of the material. Located at Arkema’s Lacq Research Center in France, the plant operates a patented catalysis process designed to produce carbon nanotubes at a lower cost than those manufactured today in the laboratory. The company expects output to serve growing demand from converters in the thermoplastics, epoxy, elastomer and coatings sectors.

Producing nanomaterials like carbon nanotubes is only half the story, of course. Putting them to use is the other half — and where the money is. This certainly is the view of Air Products, Allentown, Pa., which recently announced that it is consolidating its efforts in nanotechnology. “We are focused on developing and marketing the high-value-added step of integrating nanomaterials into end-user systems by leveraging our unique dispersion technology and related know-how,” says Larry Thomas, business director for advanced materials.

To that end Air Products has bought nanoparticle-dispersion production facilities in Saarbrücken, Germany, from Nanogate Advanced Materials (NAM), its German joint venture partner. The initial products include zinc oxide, silver, and indium and antimony tin oxides in a variety of organic, aqueous and 100%-solids systems. With additional nanoparticle-dispersion production capabilities in the U.S., Air Products already is serving several markets for nanoformulated systems, such as coatings, adhesives, inks and composites.

Catalyst for change

Potentially one of the biggest application areas for metallic nanopowders and alloys is in consumer electronics. According to nanopowder producer QuantumSphere, Santa Ana, Calif., these materials could eventually replace platinum as the main catalyst in a variety of fuel cells and batteries. “The fuel cell industry and OEMs are confronted with a fundamental problem,” says the company’s CEO Kevin Maloney. “It is well-known that direct methanol fuel cells (DMFCs) should offer a clear replacement advantage for traditional battery technology. DMFCs have more energy density. They operate for far longer periods of time. But they require an excessive amount of platinum to produce the energy required to power consumer electronics and other devices that require portable power.”

QuantumSphere’s solution comes in the form of its proprietary QSI-Nano Cobalt nanomaterials, which it claims cuts the cost of DMFC catalyst materials by at least 30%. “Prior to the nano-cobalt product,” says Maloney, “the business case for a DMFC replacement solution, on a cost per watt basis, just wasn't there.”

The nano-cobalt is produced in QuantumSphere’s “bottom-up” process that combines conventional gas-phase condensation methods with the firm’s own technology. Capable of producing a wide range of nanopowders such as nickel, silver, copper and alloys, the process delivers particles with a tightly controlled particle size, uniform distribution and “custom-tailored” oxide shell thickness. There are four vapor condensation reactors in use for all the QSI products; the latest and largest one went online at the end of last year. It has production rates of between 100 kg to 200 kg/month for the likes of copper and silver, with lower rates for cobalt and nickel because of their higher boiling points. QSI-Nano is available from stock in amounts up to 500 g, and available to order in quantities above that.

Controlling the morphology of nanopowders is key to their use in catalysis, as a joint U.S./U.K. research team has found with its work on heterogeneous catalysis. Led by Graham Hutchings of Cardiff University, Cardiff, Wales, along with Chris Kiely from Lehigh University, Bethlehem, Pa., and researchers from Johnson Matthey, London and Houston, Texas, the team has found that gold nanoparticles can catalyze partial oxidations without solvents. Useful for a wide range of agrochemical and pharmaceutical syntheses, in which a key step is converting unsaturated hydrocarbons to epoxides and ketones, the carbon-supported nanoparticle clusters could replace the conventional oxidation routes involving chlorine or organic peroxides. The catalysts offer better selectivity, which can be fine-tuned by adding trace amounts of bismuth, as well as environmental benefits by potentially replacing the use of chlorine and peroxides. “The key points are that supported gold and gold/palladium alloys are very active oxidation catalysts,” Hutchings says. “They are showing great promise in green oxidations since they can be used with oxygen (rather than environmentally unsound stoichiometric oxygen donors) and without solvents under very mild conditions.”

The nanoparticles are 2 nm to 15 nm wide, and have to be distributed evenly across a large surface area. But they also have to be prevented from coalescing, as larger particles have a much weaker catalytic effect. “We’re trying to determine the size, distribution and shape of the gold nanoparticles,” says Kiely, “and see how these parameters relate to the measured catalytic properties. We’re also interested in the interaction of gold with other promoter elements such as bismuth.” Current research is focusing on selective oxidation — e.g., of hydrogen to form hydrogen peroxide and of bio-renewable feedstocks like glycerol. The emphasis at Lehigh at the moment is on catalyst preparation and characterization using X-ray photoelectron and other spectroscopic techniques. “Perhaps the leading application in the future will be hydrogen peroxide synthesis, where we have shown that gold palladium alloys are very effective for the direct oxidation of hydrogen with oxygen under safe conditions,” Hutchings says.

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