The study of nanoparticles is a growing field relevant to nanotechnology. Nanoparticles – tiny particles of a material, anywhere between 1 and 2500 nanometres in diameter – are particularly interesting because they can have different properties than the same material in larger quantities. They have size-dependent properties, because the proportion of atoms on a particle’s surface is non-negligible compared to the atoms inside the particle, unlike with larger objects.
For example, from Wikipedia:
Nanoparticles often possess unexpected optical properties as they are small enough to confine their electrons and produce quantum effects. For example gold nanoparticles appear deep red to black in solution. Nanoparticles of usually yellow gold and gray silicon are red in color. Gold nanoparticles melt at much lower temperatures (~300 °C for 2.5 nm size) than the gold slabs (1064 °C). And absorption of solar radiation in photovoltaic cells is much higher in materials composed of nanoparticles than it is in thin films of continuous sheets of material.
However, the unusual properties of nanoparticles means, naturally, that they could be harmful to human health in some way. This has been a worry for some time now as nanotechnology has risen to prominence. In what seems like a big relief, a new study shows that we may actually be exposed to nanoparticles all the time, so if they have any dangerous effects, we should already know about them.
Since the emergence of nanotechnology, researchers, regulators and the public have been concerned that the potential toxicity of nano-sized products might threaten human health by way of environmental exposure.
Now, with the help of high-powered transmission electron microscopes, chemists captured never-before-seen views of miniscule metal nanoparticles naturally being created by silver articles such as wire, jewelry and eating utensils in contact with other surfaces. It turns out, researchers say, nanoparticles have been in contact with humans for a long, long time…
Using a new approach developed at [the University of Oregon] that allows for the direct observation of microscopic changes in nanoparticles over time, researchers found that silver nanoparticles deposited on the surface of their SMART Grids electron microscope slides began to transform in size, shape and particle populations within a few hours, especially when exposed to humid air, water and light. Similar dynamic behavior and new nanoparticle formation was observed when the study was extended to look at macro-sized silver objects such as wire or jewelry.
“Our findings show that nanoparticle ‘size’ may not be static, especially when particles are on surfaces. For this reason, we believe that environmental health and safety concerns should not be defined — or regulated — based upon size,” said James E. Hutchison, who holds the Lokey-Harrington Chair in Chemistry. “In addition, the generation of nanoparticles from objects that humans have contacted for millennia suggests that humans have been exposed to these nanoparticles throughout time. Rather than raise concern, I think this suggests that we would have already linked exposure to these materials to health hazards if there were any.”
Any potential federal regulatory policies, the research team concluded, should allow for the presence of background levels of nanoparticles and their dynamic behavior in the environment.
So that’s good news. Nanotechnologists, nanotechnology away!