As I mentioned yesterday, a big area of research in chemistry is controlling the size and shape of different materials. I talked about materials for water purification but that’s just one possible application. By controlling the size and shape of particles of a material you can do some really amazing things. You might have come across the example of gold already. It’s a really unreactive metal in the bulk state – that’s why people have used it for millennia in jewellery after all! But reduce gold down to nanoparticles and it can do amazing things like purify car exhaust.[i]
Size and shape is most important for a class of materials called catalysts. These speed up chemical reactions and they are fundamental to many aspects of our lives. They will also be crucial in many future applications such as hydrogen-powered cars and capturing solar energy. There are many ways that scientists can control how catalysts are formed, but maybe the most exciting way is to copy nature!
Living organisms have been controlling size and shape of materials for millions of years. Mammals generate bones out of a hard mineral called calcium phosphate. Bones have a microscopic honeycomb structure that allows incorporation of cells and blood vessels and also keeps the bones from being too heavy. Sea creatures create a spectacular range of shells that become even more amazing when you view them under the microscope![ii] The best thing about this ‘biomineralization’ is that living organisms create these structures under ambient conditions and from water. In this sense, they have designed the ultimate green materials chemistry.
There are many ways that we can copy nature and control the microscopic architecture of materials. It’s a huge field of research and there are a lot of books on the subject. One way is to use the natural materials themselves as a template.
For example, by coating a leaf skeleton in a solution of iron and heating, we were able to replicate the microscopic vessels of the leaf in a magnetic material called iron carbide (an important catalyst for a range of processes).[iii] Another possibility is to use some of the remarkable polymers (long molecules) that nature produces. Seaweed is a particularly nice example. Brown seaweeds produce a polymer called alginate and this can be used to make nanowires of superconductors. The polymer is able to control how the crystals of the superconductor grow.[iv]
This method of using natural materials to create useful materials is the main area of research in my group.[v] It’s maybe not the conventional idea of a chemistry lab! We have boxes of sawdust (that we’re using to make water filtration materials) alongside tubs of gelatin (to make materials for fuel cells).[vi] As well as being interesting, this type of science is becoming increasingly attractive to industry. Waste materials from industry and agriculture often have very low value. In fact with increasing taxes on landfill and burning, waste materials now often have negative value – the represent a cost to the producer. So if we can take a waste material such as sawdust and create a useful material like a water filter it is not only attractive in terms of sustainability, but may generate valuable income.
Dr Zoe Schnepp is a Birmingham Fellow in the School of Chemistry at the University of Birmingham.
Image source: Dr Zoe Schnepp