Magnetic-Field-Induced Painting-Out of Precipitation Bands of Mn−Fe-PBAs in Water−Glass Gels

What is it about?

This article shows the effect of magnetic fields on the precipitation patterns of Mn−Fe-based Prussian blue analogues in water−glass gels using X-ray fluorescence and X-ray absorption near-edge structure spectroscopies. Three sets of two glass tubes, A, B, and C, were prepared using 1.20 M Mn2+/0.24 M [Fe(CN)6]3−, 0.60 M Mn2+/0.12 M [Fe(CN)6]3−, and 0.30 M Mn2+/0.06 M [Fe(CN)6]3− solutions, respectively. From each of these sets, one tube was subjected to a magnetic field of 0.5 T, whereas the other was not. The magnetic field barely affected the Liesegang bands in the tube from Set A, but there were noticeable differences in the tubes from sets B and C, where (1) the amounts of electrolytes were small, (2) the dominant Mn species was [Mn(H2O)6]2+, and (3) there was stochasticity of the band formation. In these regions, the magnetic field painted out the spaces between the precipitation bands, even enhancing the formation of additional bands.

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Why is it important?

We demonstrated that a static 0.5 T magnetic field can be an independent parameter that can change the precipitation patterns in gels, even in the classical setups employed for Liesegang band studies. Our results not only provide an insight and better understanding of the precipitate band formation but also exhibit the potential for the application of magnetic fields to the control and engineering of precipitate structures of functional Mn−Fe PBAs in future self-organization processes.

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