How does the final product compare with biological nacre, and what characteristics does it have? To answer these questions, three main techniques for the structural identification of the final product from the lab mineralisation process are used. Professor Kate McGrath, director of the MacDiarmid Institute, explains each of these techniques.
PROFESSOR KATE MCGRATH
But how do we know what it is that we’ve got? So we want to know several things about the final material. Structurally, does it compare with biological nacre? What polymorph has the calcium carbonate mineralised in? Does it start to have characteristics and similarity to the native nacre?
To look at it, we have to use something that allows us to go to very high magnifications. We use a scanning electron microscope. That allows us to see the structure of the system, but how do we know for example whether we’ve got calcite or aragonite forming? So in order to determine that, we have to use either Raman spectroscopy, and in particular, we use micro-Raman because that allows us to look at a particular crystal in the nanometre to micrometre length scale range and determine its structure.
We use X-ray diffraction to determine what’s the relationship between the calcium and the carbonate. So that tells us, do I have calcite or do I have aragonite? And so I can work out for the entire structure, do I have 100% calcite or do I have 50% calcite and 50% aragonite?
Dr Natasha Munro