X-ray spectroscopic analysis of stochastic, periodic precipitation in Co–Fe-Based Prussian blue analogues

Abstract

Stochastic, ripening-induced, periodic precipitation of Co–Fe-based Prussian blue analogues in water-glass gels was analyzed by XRF and XANES spectroscopies.

An Electrochemical System for Forming Periodic Precipitation Bands of Cu-Fe-Based Prussian Blue Analogues

“…(3) The spaces between the adjacent bands were within 0.30 ± 0.25 mm after removing unreacted ions (details will be discussed later). (4) The positions of the periodic bands were maintained over the observation time, similar to the unusual Liesegang bands previously found in a Co-Fe PBA system [30]. (5) After removing unreacted ions, several periodic bands became blue instead of reddish-brown, strongly suggesting the presence of Cu(OH)2 precipitates (as already suggested in Figures 4 and 7).…”

“…After subtracting the constant background from the Fe Kα peak, the integrated intensities over 6214-6647 eV were used to determine the Fe Kα intensity distribution. In situ time-resolved Fe Kα distributions as the precipitation patterns evolved (as reported in previous studies [25][26][27][28][29][30]) were not measured because the Fe Kα intensity from the unreacted [Fe(CN)6] 3-ions was too strong to allow the examination of the distribution of Cu-Fe PBA formed in the tube.…”

Low-Cost, High-Performance Sample Cell for X-Ray Spectroscopy of Solutions and Gels Made from Plastic Straw

“…The relative XRF intensity, where the Fe Kα intensity at the bottom of the samples in the initial stages (∼1 h after the addition of the outer electrolyte sols; not shown here for simplicity), was set to 1, according to the procedure used in previous studies. [13][14][15] In Gel-1 ( Fig. 6(a)), a peak in the Fe Kα distribution at the gel boundary (X ≈ 0 mm), similar to one previously found, 10 was observed, suggesting Fe accumulation near the boundary.…”

“…The combined use of X-ray fluorescence (XRF) spectroscopy and X-ray absorption near-edge structure (XANES) spectroscopy was experimentally proven to be useful for obtaining such in situ, elemental-selective information, 9 particularly for selforganized, discrete precipitation banding of Prussian blue analogs (PBA) in water-glass gels. [10][11][12][13][14][15] In previous X-ray spectroscopic studies on self-organized systems, [9][10][11][12][13][14][15] quartz capillary tubes have been employed as sample cells. These have also been widely used for X-ray diffraction measurements of protein, liquids, liquid crystals, and single crystals and powder specimens that can be degraded by air and moisture.…”

Spontaneous precipitation pattern formation by crystallites of Mn–Fe-based Prussian blue analogues in agarose gel

“…In other words, the phase boundaries of the diagram are not unambiguously dened. 10 The ve types of characteristic precipitation patterns are denoted as A, B, C, D, and E in the phase diagram. The concentrations tested experimentally are indicated as squares in region A (continuous patterns in the inner electrolyte gel), triangles in region B (continuous patterns in the outer electrolyte gel), inverted triangles in region C (a very short band close to the gel boundary), circles in region D (periodic band patterns in the inner electrolyte gel), and diamonds in region E (lament-like patterns in the inner electrolyte gels).…”