Richard Robinson makes new nanoparticle materials for alternative energy devices. 

At the nanoscale, the energetics, electronic states, and even color of materials differ from their bulk counterparts. “When you get down to about 50 nanometers, everything changes,” says Robinson.

Robinson uses colloidal synthesis to make different shapes and compositions of metal and metal oxide nanoparticles. Colloids are suspensions of particles in a liquid, like paint. Under the right conditions, the particles will assemble themselves into desirable structures as the liquid evaporates. “One of the cheapest, and possibly the best, ways to move nanoscale materials from the laboratory into production is through wet chemistry,” he says, “because you can make large batches and you can use different solution-based processing techniques, which make manipulating these particles much easier.”

By identifying the specific reactive properties of nanoparticles based on their size, Robinson hopes to produce better fuel cell catalysts. “You can stabilize the reactive edge sites, and come up with different nanoparticle geometries that are much more reactive,” he says. “Or you can use less material by using a hollow particle, or you can control the amount of diffusion by having a particle inside a particle.”

Robinson also hopes to create more efficient thermoelectric materials, which can create electricity from heat or, conversely, use electricity to remove heat. Known as Peltier coolers, they have found few commercial applications beyond 12 volt coolers and heat pumps for CPUs because they are only 10-15 percent efficient. A conventional refrigerator is 30-40 percent efficient.

“It’s been around for 50 years and they haven’t really increased in efficiency,” says Robinson. “If you bring it down to the nanoscale, you get more efficient materials and you can start to realize the efficiency needed to replace what we have now.”

Robinson’s group will make prototype devices from the materials in order to test their efficiency. “One of our goals is to make better materials based on that testing,” he says. “We’re not just coming up with the science, but we’re also hoping to use that science to re-engineer our initial product.”

Robinson is also working on a new instrument for testing the vibrational properties of nanostructured materials. The lattice structure of crystals vibrate at specific frequencies called phonons. Robinson is trying to create a monochromatic phonon source that can test materials one frequency at a time. “We don’t have a good way of testing that now,” he says. “We just heat something up like a ball of fire and there’s a whole bunch of wavelengths that come out.”

A material’s thermal properties depend on its lattice vibrations, and at about 200 nanometers or less, these properties change because the vibrational waves start to interact with the surface of the nanoparticles. “This phonon source will be a better way of testing thermoelectric materials and understanding the fundamental science behind them,” says Robinson. “And that will feed directly into our thermoelectrics research.”

Beyond the thrill of discovery, Robinson is motivated by a desire to help avert global climate change. “My goal is to come up with an alternate energy source so that we can turn all this waste heat directly into power,” he says. “If I can get just an inch closer with my science then I should definitely try that. It gives what I do a purpose.”