Using ferretin protein to aliquot nano-quantities of iron oxyhydroxide, Temple University nanotechnologist Daniel Strongin is investigating whether nano-amounts of iron can clean up the environment better than bulk iron.
Strongin is one of a handful of researchers who uses proteins to help investigate the properties of nanoparticles — tiny molecules between one and 100 nanometers in size that are of interest because they have properties that are different from their bulk counterparts.
“Nanotechnologies are a hot field now; people are trying to find out whether nanoparticles in certain cases can be used to do things that you can’t do with bulk materials,” said Strongin. “Our own interest is in finding unique chemistry. We’re looking for non-scalable properties such as electrical or structural properties that all of a sudden change when you get down to nano-quantities.”
Iron in bulk quantities can be used to convert Chromium-6, a carcinogen that is very mobile in groundwater, to Chromium-3, a particle that is less mobile in groundwater and less likely to find its way into drinking water. Using funding from the US Environmental Protection Agency, Strongin and his research team are investigating whether nano iron oxy-hydroxide particles can clean up Chromium more effectively than iron in bulk.
“What we want to do is investigate whether you can do it better with nanoparticles (than with bulk iron),” said Strongin. “We’re doing exploratory research to find out whether nano-size particles exhibit reactivity that is better in terms of environmental remediation. The work is still in its infancy.”
Though nano-aliquots can be created using solution techniques, Strongin prefers to use ferritin to isolate nano-quantities because using the protein is easier. Ferritin is designed to assemble isolated particles of iron oxy-hydroxide inside of its hollow, porous sphere, Strongin explained. It is like a mini-container designed especially to hold the particle.
Strongin uses ferritin from horse spleens, which is commercially available. In the past he and his research team have also used ferritin from the bacteria listeria. The listeria ferritin is smaller and isolates even smaller amounts of iron oxy-hydroxide.
“It’s sometimes difficult to assemble well-defined metal-oxide and metallic nanoparticles and to make homogeneous nanoparticles,” said Strongin. “This protein does a good job where it can allow us to assemble well-defined nanoparticles in the lab.”
Aside from isolating nanoparticles of iron, Strongin’s research group is also using ferritin to isolate nanoparticles of manganese and cobalt. The team is investigating to see if the managese and cobalt nanoparticles have different properties than the same materials in bulk.
“They might have different properties. That’s something we’re looking into right now,” said Strongin.
With metallic particles, sometimes good conductors act like semi-conductors when the particles get down to nano-size, Strongin explained. With gold, nanoparticles of the substance oxidize carbon monoxide to carbon dioxide — something that bulk gold does not do.
In the case of iron oxy-hydroxide, the band gap, or amount of energy that the particle needs to become excited, might change when the particle gets down to nano-size, Strongin said.
“It’s intriguing,” said Strongin. “That’s one of the reasons why I got into the area — to see if we could find some materials that show a reactivity in the nanoregime that is superior to bulk materials.”
Aside from chemical reactivity properties, other properties that can change when particles get down to nano-size include optical properties, magnetic properties and thermo or electrical conductivity. Cadmium sulfide is an example of a material that absorbs and gives off light differently when it is isolated in nano-quantities.
“I think there are a lot of unanswered questions,” said Strongin. “This field is really early in its development, and I think it’s fun being in an area where there’s really a lot to learn.”