Iron is an element that, in its bulk form, is used in such everyday settings as stair railings and the structural beams in cars or buildings. Iron is also present in water and in our bloodstream, where it helps to transport oxygen. Iron is one of the materials that we can use to make magnets due to the way electrons orbit each atom. And, as we all know, iron rusts when you combine iron and oxygen to form iron oxide. It turns out that nanoparticles of both iron and iron oxide can be quite useful.
If iron is left in the rain it will rust, and rust is composed of iron oxide, a molecule that contains three atoms of iron and four atoms of oxygen. Like iron, iron oxide has magnetic properties. Iron has four unpaired electrons, whereas iron oxide has only two unpaired electrons. Because the unpaired electrons make a material magnetic, iron oxide is less magnetic than iron. Iron oxide is therefore called a paramagnetic material. The paramagnetic properties of iron oxide nanoparticles are not changed from the bulk material except that these tiny particles can go where larger particles never could.
For example, in magnetic resonance imaging (MRI), you get a better image if paramagnetic nanoparticles are attached to the object you’re taking an image of. For that reason, researchers are functionalizing iron oxide nanoparticles by coating them with molecules that are attracted to cancer tumors to provide a better MRI image. We discuss how nanotechnology is improving medical diagnostics here.
Making nanoparticles that have a core made of iron oxide nanocrystals surrounded by nanoporous silica can improve not only the MRI images of tumors but also give researchers control over the release of therapeutic drugs. We discuss how nanotechnology is improving drug delivery here.
A problem for tens of millions of people around the world is the presence of arsenic, a naturally occurring substance in soil that can dissolve in water, including well water. Robert Bunsen, the developer of the Bunsen burner, which most of us encountered in our high school science labs, determined in the 1830s that when you mix ferric oxide with arsenic, you get a potion that both the fluids in your body and water cannot break down. Based on Bunsen’s discovery, scientists started using iron oxide in filters to remove arsenic from water. We discuss how nanotechnology is improving water quality here.