o The Frog Blog: Guest Post - Nanoscience Part 1

Friday, 3 September 2010

Guest Post - Nanoscience Part 1

This excellent interactive guest post has been produced especially for the Frog Blog by Michael Seery, a lecturer in Physical Chemistry at the Dublin Institute of Technology (DIT). Michael also has his own blog, Is This Going To Be On The Exam?, which contains a wide range of posts surrounding chemistry and education. You can also following Michael on Twitter here. The post will presented in three parts, the first will look at what is nanoscience and why is it important. 

What is Nanoscience?

Nanoscience is the science of very small things. How small? Well before we answer that, see how good you are at thinking about the size of things. The quiz below consists of a lists of things of various sizes - can you rank them in order of size, starting with the biggest?

So how did you get on? It's clear from the list that there are some very big things and some very small things. To help group things into similar sizes, we use a scale. For example, the milliscale is used to group things the size of things based around the size of millimetres - 1 thousandth of a metre. The microscale is the scale of one billionth of a metre, 0.000001 m. When we use a microscope, we can view things on this scale. The next scale down has recently come into view, with new sophisticated instruments and clever ways of making things at this scale - this is the nanoscale - things in the size range below 1 billionth and above 1 trillionth of a metre - one nanometre is 0.000000001 m or more conveniently 10 -9 m. At this scale, we start to see things like viruses, which are 100's of nanometres in size, DNA strands, which are a couple of nanometres wide. However, this scale is bigger than simple molecules such as water - which are only parts of nanometres and atoms which are smaller still.

Why is the nanoscale important?

Things of the nanoscale have always been there, but it's only in the last twenty or so years that scientists have developed the technology to see them clearly. Now that we can see them, we can start some clever science, and even make things on the nanoscale. Why would we want to? There are some very special properties about nanoparticles - two of the most important of which are surface area and shape.

Surface Area:

Imagine we have a cube that has a side of 3 cm. What is its surface area? When you work it out - the area of each side times the number of sides, you should get an area of 54 cm2.

If we now cut the cube up, so that it contains 27 cubes, each with a side of 1 cm, what is the new surface area? When you work it out, you should find that the new surface area is 162 cm2. In other words, just by chopping the cube up into smaller pieces, we have increased the surface area. Imagine we kept doing this, so that the cubes we formed would become smaller and smaller, ending up with sides of the size of a few nanometres. The resulting surface area would increase greatly, to approximately two thousand times the surface area of the original bulk material, so that the nanomaterial would have a much larger surface area. Many chemical reactions occur by molecule's surfaces interacting - thing of the hydrogenation of alkenes in chemistry. Therefore, the greater the surface area, the more reactive a substance generally is. And it is a LOT more reactive! Take something like aluminium metal. In bulk form, it corrodes very slowly to form aluminium oxide, and does not react much with water. Nanoscale aluminium reacts explosively with water, simply because the water is able to reach a lot more of the aluminium surface very quickly. In short, larger surface area means greater reactivity


The next key thing about nanomaterials is their shape. Because we are dealing with molecules on the same size as proteins receptors, and various other biological substances, very small changes in shape mean that we can impact how these molecules interact with biological substances, in designing new ways to tackle viruses or new methods for sensing proteins of different types, for example in a diagnostic test for different diseases. For this reason, nanoscience is considered to be a hybrid of all the traditional sciences, as it brings together chemistry, biology and physics, with engineering in the manufacture of devices.

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