Oscillating Pattern in Nanoparticle Crystallisation
Max Planck researchers in Potsdam demonstrate an oscillating pattern in nanoparticle crystallisation and self-organisation
Scientists are especially interested in oscillating chemical reactions. These occur when reaction products periodically and repeatedly change. Their behaviour is of importance to many fields of study - including chaos research. That is because these reaction systems are always complex and far away from thermodynamic equilibrium. One particularly well-known example is the "Belousov-Zhabotinsky" reaction.
Mathematically, spatially oscillating reactions can be described as "reaction-diffusion systems". This means that it is not just chemical reactions which influence the amount of material at a certain point in space. Diffusion also plays a role - the exchange of material with the surrounding area. In such simulations, we get the typical concentric circle pattern of a Belousov-Zhabotinsky reaction. In the picture above, it is indicated in red-violet.
Researchers from Potsdam have now proven that these oscillating reactions can also apply to multi-phase systems, and even to the self-organisation processes of nanoparticles. What is central is that in a multi-phase reaction system, it is possible to formulate either an autocatalyic or autoinhibiting reaction step. This leads an oscillating system to be constructed, and ultimately a pattern to be formed.
The researchers used a newly synthesized polymer to create the typical concentric circle pattern, via controlled barium carbonate crystallisation. Such patterns correspond quite well to the calculations in a simulation. The researchers also were able to formulate a complex coupled reaction system including crystallisation, complexation, and precipitation reactions and identify the autocatalytic formation of a complex between barium and the polymer.
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