Liesegang ring formation

The Liesegang ring formation may be considered as possible example of Turing phenomena. 

FIGURE 6.27 Liesegang ring formation. From Kai et al. (1982) with permission. 

No version of micellar entry theory has been proposed, which is able to explain the experimentally observed leveling off of the particle number at high and low surfactant concentrations where micelles do not even exist. There is a number of additional experimental data that refute micellar entry such as the positively skewed early time particle size distribution (22.), and the formation of Liesegang rings (30). Therefore it is inappropriate to include micellar entry as a particle formation mechanism in EPM until there is sufficient evidence to do so. 

Variety is introduced into the structures which may be formed by chemical reaction and by crystal growth through a special circumstance which leads to a spatial periodicity. It is best illustrated in the formation of what are called Liesegang rings. 

Bard and coworkers described a novel SECM-based surface patterning of fluorescent molecules onto a solid substrate by forming covalent bonds through a click chemistry reaction." Patterned images could be observed by their fluorescence and the formation of Liesegang rings in the diffusion reaction system was also detected. 

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