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Real World Nano: Why does nano matter? Surface area.

authored by Clark Miller, Arizona State University

Thanks, everyone, for your great comments to the first RWN post! Keep 'em coming. I'll respond there and in future posts. The question for today is: why does nano matter?

At the 2009 NISE Net annual meeting, evaluators noted that museums were doing a great job of teaching core nanoscience concepts, and they’d also managed to make nano modestly interesting (admittedly, not as interesting as Star Wars, but more interesting than many other things museums are doing). But, no matter how they were asked, visitors couldn’t explain to evaluators the importance of learning about nano.

One of my goals in Real World Nano is to try to figure this out.

Let me start with one possible answer: surface area.

For many areas of nanoscience, the primary reason that nano matters is that it allows scientists to create materials with new properties. These properties can be exploited to make new products that benefit people in exciting ways. And these properties can also have unanticipated consequences that impact people’s lives in not so exciting ways.

One application where surface area is key is the antibacterial properties of silver nanoparticles. Because nanoparticles are very small, the ratio of their surface area to their volume is higher than for larger particles. As a result, smaller particles make more of their material available to react chemically with other nearby molecules. The result, in this case, is that silver nanoparticles in the range of 1-10 nm have been shown to be the most effective form of silver for antibacterial purposes.

Another application is touted by BreatheBetterAir.com. They have created a nano-based air filter for your home. This product can be found on the Woodrow Wilson Project for Emerging Nanotechnologies Consumer Product Inventory. Here, the increased surface area of nanoparticles is used to enhance the reactivity of the air purifier’s catalyst. As a result, it does a better job of removing dust, bacteria, viruses, and other contaminants from your home’s air. Many engineers and companies are seeking to use the surface area of nanoparticles to enhance the effectiveness of air and water filtration systems so that we can breathe cleaner air and drink cleaner water.

Greater reactivity can also be a problem, however. Both the Environmental Protection Agency and Food and Drug Administration are concerned that greater surface area will increase the risks posed by nanoparticles interacting with the environment. EPA, in particular, has been pursuing research on ultrafine particulate matter (called PM10 and PM2.5) that shows that nanoparticles are risky when breathed into the lungs. People exposed to high levels of PM10 and PM2.5 tend to experience more asthma and greater numbers of heart attacks.

So why does nano matter? The first answer is that nano matters because nanoparticles behave differently than larger particles of the same material. As a result, we need to know where nanoparticles are and what they’re doing. If they’re where we want them, they’re likely to help us solve important problems like clean air and clean water. But if they’re where we don’t want them, they may create unanticipated and undesirable risks.

 

The NISE Net catalog of programs has different options for exploring surface area with the public.

  • Intro to Nano cart demo explores surface area along with a number of surprising properties at the nanoscale.
  • The Surface Area demo is all about surface area (of course!) and includes a variety of different activities.