The 2006 Industrial Physics Forum has ended, and sadly, I didn't get a chance to blog about every single one of the fascinating topics featured by the slate of speakers -- there were just too many. Here's a few of the remaining things I would have blogged about, had time (and wireless access!) permitted:

* I mentioned Paul Alivisatos' work on nanocrystal-based solar cells in the previous post. He's also exploring the possibility of inorganic colloidal nanocrystals as an alternative to quantum dots in fluorescent biological labeling applications. Alivisatos found that these types of structures (particle plasmons, in this case), when coupled -- a property that is strongly dependent on distance between the particles -- exhibit distinctly different properties than in the single state.

Specifically, the Berkeley group measured the light scattering of such coupled plasmon pairs in DNA cutting experiments, and found that the intensity goes up right before the cutting, then drops rapidly afterwards. (It happens because the enzyme used as a cutting tool bends the DNA slightly right before cutting it.) This produces very different light scattering patterns, thereby providing a unique "signature." Alivisatos calls his technique a "plasmon ruler," and believes it could offer advantages over the use of quantum dots/fluorescent dyes, since it can make masurements over a larger length scale: between 1 and 70 nanometers, compared to between 1 and 10 nanometers using the conventional FRET technique.

* Concerns about environmental and health risks aside, nanoparticles can help clean up soil and groundwater contamination. Wei-xian of Lehigh University talked about his work with zero-valent iron nanoparticle technology, which is proving quite popular for remediation and treatment applications: everything from chlorinated organic solvents and organochlorine pesticides, to PCBs, perchlorate and hexavalent chromium. Recent advances have made these nanoparticles much more cost effective for large-scale applications. (Related side note: The New York Times ran an interesting article on November 10 about Rice University researchers who are using rust-like particles to clean up arsenic contamination.)

* During the Frontiers in Physics session, Wim Leemans, who heads the LOASIS program at Lawrence Berkeley National Laboratory, gave an overview and a few recent achievements in the area of laser-plasma wakefield accelerators -- basically a tabletop version of the gigantic particle accelerators found at Fermilab and (very soon!) at CERN, among other locations. Leemans' group has achieved high-quality 1 GeV electron beams in a plasma channel based structure similar to an optical fiber (called a plasma capillary discharge waveguide, if you want to get all technical about it), and are now experimenting with the generation of intense terahertz and X-ray radiation.

And finally, here's a few more potentially useful nano-links for those seeking more information, courtesy of the Nanotechnology Project:

Project on Emerging Nanotechnologies

Managing the Effects of Nanotechnology (by J. Clarence Davies)

An inventory of nanotechnology consumer products

An inventory of nanotechnology impact research

Happy future exploring, and thanks for joining us in Cyberspace (if not at the meeting itself) .

Posted by Jennifer Ouelette at 5:19 PM | Permalink | TrackBacks (0)

Energy. There's never enough of it, at least in terms of our ability to harness it to produce useful work. And right at the center of our solar system, taunting us by being so near, and yet so far, is the Sun -- a big, powerful nuclear generator that produces enough nuclear reactions in a single day to pretty much meet any energy needs we could imagine well into the future. It's just so darned difficult to turn that raw solar energy into a kind of energy we can use.

That's why photovoltaics (solar cells, solar panels and similar technologies) is such an active area of research, attracting sharp minds like Paul Alivisatos, a professor of physics at the University of California, Berkeley, and one of the featured speakers at the 2006 Industrial Physics Forum. Such devices perform quite well in a laboratory setting, but the cost per unit and overall efficiency just don't scale up to sufficient performance levels to make them useful for anything more than select niche energy applications. After all, the US is a major energy hog: we need between 1 and 3 Terawatts of energy just to go about our daily lives. There is no solar technology currently in existence that can generate energy at that enormous scale while still being affordable and efficient.

What to do? If you're Alivisatos, you find a useful analogy in a jewelry store. Economically speaking, diamonds obey a fundamental scaling law that places constraints on what the buyer can afford: the bigger the diamond, the more it will cost. (We'll leave aside questions of quality, etc. for simplicity's sake.) So Alivisatos thought, instead of trying to make large crystals for solar cell applications, why not try to make them as small as possible instead? In fact, why not look to nanotechnology, specifically, colloidal nanocrystals?

Ten years ago, this wouldn't have been a viable solution, but Alivisatos pointed out that there have been many significant advances in our ablity not only to grow colloidal inorganic nanocrystals, but also to control their size, shape, and even branching (called interconnection), as well as their topology (they need to be hollow and nested to achieve the desired properties). Like most nanoscale materials, many of their unique properties are size dependent, but colloidal nanocrystals are also quite stable and can be processed in solution, just like polymers. Alivisatos thinks this makes them an attractive candidate for solar cell components.

He's working on a project (dubbed HELIOS) that seeks to turn solar energy into a usable transport fuel. It's brand new -- they submitted the proposal to DOE earlier this week -- but the concept is to convert photon energy into the energy found in the chemical bonds in gasoline. The goal is to go from the current dismal 1% efficiency of most solar cells to around 6% efficiency. There's some significant challenges, of course: it's really, really hard to control a material's properties and behavior at the nanoscale to a suitable level of precision. We've heard about solar's potential (and the pitalls) before, and it's true at the nanoscale as well: if those challenges can be met -- admittedly a substantial "if" -- nanoscale photovoltaic technology would combine very high efficiency with good scalability, making it a highly desirable energy source.

Alivisatos is interesting in building a type of hybrid solar cell out of the usual polymers paired with randomly oriented, self-assembling nanorods. Over the past few years, his research group has succeeded in controlling the growth of these nanosctructures to achieve very precise multiple branching, resulting in something that resembles a model of a carbon atom -- "tetrapods" of CdTe.

They've also managed to incorporate these nanostructures into hybrid solar cels to achieve a slight improvement in efficiency: currently around 3%. It's still far short of the target 6% efficiency, and Alivisatos admits his team is struggling with controlling material behavior at the crucial interfaces. But he believes they're on the right track, and that nanocrystal based solar cells will be a perfectly viable commercial technology in the future.

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