Technology.am (Sept. 14, 2009) — Researchers from the Center for the Environmental Implications of Nano Technology (CEINT), based at Duke University, argues for a new look at the way nanoparticles are selected when studying the potential impacts on human health and the environment.
They have found that while many small particles are considered to be “nano,” these materials often do not meet full definition of having special properties that make them different from conventional materials.
A particle is deemed nano if its diameter is between 1 and 100 nanometers (nm) – about 1/10,000 the diameter of a human hair – and if it has properties that significantly differ from its naturally occurring, or bulk, counterpart.
The special properties of nanoparticles come from their high surface-area-to-volume ratio. They also have a considerably higher percentage of atoms on their surface compared to bulk particles, which can make them more reactive.
These man-made materials can be found in a vast array of consumer products, including paints and sunscreens, as well as in water treatment plants and drug delivery systems.
For most of this decade, discussions of nanoparticles have tended to focus more on their size than their properties.
The Duke-led team focuses on properties of nanoparticles, which are the most likely to represent a threat to the environment or human health.
Mark Wiesner, a Duke professor of civil and environmental engineering said about this very smallest particles (less than 30 nanometers) that should receive the most attention in studying the environmental and human health impacts of nanomaterials.
“There are an infinite number of potential new man-made nanoparticles, so we need to find a way to narrow our efforts to those that have the greatest likelihood of having the unique properties with unique effects,” Wiesner said.
Specifically, the researchers found that nanoparticles approaching the 100 nm end of the size spectrum tend to have fewer special properties when compared to their bulk counterparts. They also found that nanoparticles smaller than 30 nm tend to exhibit the unique properties that enhance how the atoms on their surface interact with the environment,” Wiesner said.
For example, because of the increased surface-area-to-volume ratio, nanoparticles can be highly reactive with other chemicals in the environment and can also disrupt certain activities within cells.