By Jack Mason
Small Times Correspondent
May 6, 2003 -- One scientist calls them the ball bearings of the 21st century. Yet quantum dots -- semiconductor nanocrystal particles that confine electrons in their cores -- tend to get less attention than carbon nanotubes or even bulk nanoparticles.
They are, however, the stuff of which future flat panel displays, lasers, lighting and even optical "fingerprints" may be made.
The potential for the quantum dot (QD) field ''is wide open," said Michael Brelle, author of a report from Business Communications Corp. (BCC) due in July. New companies are aiming to commercialize QDs, from Oxonica Inc. and NanoCo. Inc. in England, to Energenius Inc. in Toronto and Zia Lasers in Albuquerque, N.M.
Production challenges include making larger quantities of QDs at uniform sizes that won't break down over time. The challenge for electronics applications such as solar cells is connecting the ultrasmall structures with larger-scale circuitry.
QDs can be made two ways: through a "wet" process of colloidal chemistry that produces nanocrystals in a solution; or through molecular beam epitaxy (MBE), in which dots grow as tiny islands on a semiconducting surface.
For applications such as cellular probes, quantum dots can be "tuned" to emit a precise color across a broad spectrum by controlling their size -- generally between 2 and 20 nanometers -- during production. Indeed, the largest market for QDs now is as customizable tags for cell or tissue analysis. They can be tailored to glow a particular color in the presence of, for example, a genetic marker for breast cancer.
Quantum Dot Corp., in Hayward, Calif., controls some of the key patents for biotech applications. Its QDots come in various sizes and compositions that offer advantages over existing dye technologies.
Such fluorescent dyes and proteins are available in a limited range of colors that fade relatively quickly. By comparison, QDs can shine longer, brighter and in many more colors. Different QDs can be stimulated by a single laser, enabling more complex testing to be done.
Evident Technologies recently announced the opening of its QD production facility in Troy, N.Y. Steve Talbot, Evident's director of business development, said that the company is producing grams of QDs for prospective customers. The immediate goal is "demonstrating the benefit of what the materials can do and how they can be integrated into products."
Palo Alto, Calif.-based Nanosys Inc. is focusing on applications including solar energy and computer displays. NanoSys recently announced a partnership with Matsushita Electric to market solar roofing tiles embedded with the company's photovoltaic nanorods by 2006 or 2007. Stephen Empodocles, director of business development for Nanosys, said the nanorods are a kind of elongated quantum dot that can direct a flow of electrons. Developed by quantum dot pioneer Paul Alivisatos at the University of California, Berkeley, each nanorod acts like a tiny solar cell.
Nanosys' goal, said Empodocles, is to produce inexpensive, solar-power films that can be applied to a variety of large surfaces. "Our aim is to equal the performance of semiconductor solar cells, but at a significantly lower cost," he said.
Nanosys is also working on quantum dot technology for display screens. At the Massachusetts Institute of Technology, Professor Moungi Bawendi has integrated quantum dots into an organic light-emitting device that could challenge LCDs in flat-panel displays for consumer electronics. Universal Display Corp. of Ewing, N.J., is one of the funders of the research.
Empodocles said that Nanosys is even looking at ways quantum dots could work as light sources, or in combination with solid-state LED lights. Solid-state lights, such as those already in many traffic signals, last longer and use less energy than conventional incandescent light bulbs.
Zia Laser Inc. in Albuquerque, N.M., is one of the few companies growing quantum dots on semiconducting surfaces via molecular beam epitaxy. Founded in 2000, the company recently closed a second round of financing for $5.4 million. Zia's management said that the prototype lasers it has built with quantum dots will be field tested by potential telecom customers in the next six months.
Paul O'Brien, founder of NanoCo. in Manchester, England, said his company is developing QDs as security tags for currency or other valuable objects. A unique color code of a few quantum dots could serve as an "optical fingerprint" for an individual object. O'Brien, who is selling batches of QDs in quantities from milligrams to grams, said "the question to ask is how much product companies are actually selling right now." Very little, in his estimate. He pegs the current world market at "about a hundred kilos a year, maybe a thousand in a few years."
"It's a potential commercial market today, so now is the time to establish a reputation," he said. "But it's a field of dreams market. If we can make [valuable QDs], buyers will come."