Rights: The University of Waikato Published 30 May 2008 Download

Prof Richard Haverkamp, of Massey University, outlines why he uses plants to make gold nanoparticles. There are also views of Dr Aaron Marshall and the electrolysis equipment used to test catalysts.



The standard way to make gold particles is by a precipitation reaction where we take a gold salt and we add a component to cause it to reduce – so it goes from a gold salt to be a gold metal and then those gold metal atoms glue together into a little particle. So it’s important to control how fast that reaction takes place, the rate of nucleation of particles and the rate of growth of those so you control the size of the particles.

With a lot of catalytic materials it’s not just the one material required. Often when you've got a reaction that you want to make happen you've got a starting material and an end material that you want, but often there’s some intermediate steps and sometimes these steps have to happen in tandem with each other or together so one compound’s made unstable it has to immediately be converted into something else. So you often need two catalysts together in the right form, so right beside each other, so its almost like its a synergetic effect.

So with the process we are looking at, it was believed that we need some sort of carbon material in there as well. So the trick is then to get gold nanoparticles associated with carbon in a way that’s not fully understood, but some aspects of it are. So that the reaction that takes place will react on the gold and then something else will happen on the carbon and then you will get your product. The challenge then is to make gold nano particles that are connected up with carbon. So we thought well we could use plants to take up the gold, because we knew it made gold nanoparticles in the plant, and plants is a carbon based material, so it would be associated with carbon. So the hope was we could make gold nanoparticles widely dispersed within the plants so they are not all clumped together and they are all connected up with carbon, so that we might have a plant do all the complicated stuff of making a catalyst for us. So the hope was it would be an environmentally friendly way of doing it, because its not involving any particularly nasty chemicals, and its a clever way to do it. The plant can do all the clever stuff for us and we just have to go and take advantage of it.

Dr Aaron Marshall