2.7 Silver nanoparticles: a case study in cutting edge research  (Page 2/6)

When we cross from the small scale as in molecules and atoms, to the large scale that we see with our own eyes, we travel through the nanoscale. In that scale we go from quantum physics to classical physics and a lot of very interesting effects can be used to our benefit, and actually nanoparticles are an excellent example of this. Just by virtue of their size they are able to absorb four times more light than is even shone on them! This is very different from the bulk material, it is difficult to understand in one sitting, but let’s just say that there is a coupling between the light energy and the matter of the nanoparticles that is best explained through quantum mechanics, but we won’t go into that now.

When you make something very large, there is lots of room for error, the more parts you have in a system the more chances there are that some of those parts can be faulty. However when you make something in the nanoscale you have far less parts in the system and each part has to be virtually perfect. Material scientists are concerned with the defects that are created in materials, because these are the parts that cause a material to break down often and stop functioning correctly. As you get into the nanoscale there are less defects and you get enhanced effects from the purer material, that don’t occur on the larger scale. One example of this is carbon nanotubes, by virtue of there shape and size they are 6 times lighter than steel, but almost 100 times stronger. There is great potential for using these in new materials in the future that are ultra lightweight and extremely strong.

When we make things with modern technology we have for centuries been using a top down approach, and this brings us down to a fine limit but not as fine as that on which nature works. Nanotechnology is more about understanding the fundamental forces in nature by physics, and seeing their interaction through chemistry, and then making something larger from our engineering skills. And we can always take examples from biology that has been doing this for far longer than we have. So really what we do is take a bottom up approach, so that we can create large materials that we can use, that has every part of the interaction tailored all the way from how the atoms interact and how the molecules are formed and bonded together to make building blocks for new materials and applications. This bottom up approach is a change in the way things have been done and for this reason nanotechnology is a very potent discipline, with an immense capacity for expansion.

In all we have only really begun to scratch the surface of what could be possible when we create things using nanotechnology, and we should be aware of this because nanotechnology is finding its way into every corner of life, from health studies, medicine, robotics, materials and maybe even food and many many more.

What are nanoparticles and how are they made?

A simple way of seeing this is by imagining tennis balls that are squeezed down to a few billionths of a meter. The particles are rounded because they try to minimize the surface energy as much as possible; any edges will make things more energetic since typically nature follows the path of least resistance the particles tend to form colloids, or spheres with as few edges as possible. It is possible though, to direct the growth of nanoparticles into various shapes such as cubes, and tetrahedrons. We will concern ourselves with only colloidal nanoparticles for the moment.