Magnetic-Field-Induced Painting-Out of Precipitation Bands of Mn–Fe-Based Prussian Blue Analogues in Water–Glass Gels

Abstract

The effect of magnetic fields on the precipitation patterns of Mn-Fe-based Prussian blue analogues in water-glass gels was studied 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.