The measurement of Cs adsorption by the precipitation bands of Mn-based Prussian blue analogues (PBAs), Co-based PBAs, and Prussian blue (PB), which were spontaneously formed in agarose gel, was carried out using in situ X-ray fluorescence (XRF) spectroscopy.

The adsorption of Cs+ ions by the precipitation bands of a Mn–Fe based Prussian blue analogue that form spontaneously in agarose gel was investigated by XAFS spectroscopy coupled with SEM and XRF distribution analysis.

Low-cost tube-type sample cells for X-ray spectroscopy of solutions, sols, and gels were made from plastic straws. Energy-dispersive X-ray fluorescence (XRF) experiments showed that the X-ray transparency of the straw cells is ∼50% superior to that of quartz capillary cells for 6-7 keV XRF and is almost uniform over the entire range, allowing its use for position-dependent measurements. Wavelength-dispersive XRF experiments showed that the difference in the surface curvature between the straw cells and pellet samples leads to an apparent ∼1.5 eV shift of the Fe Kβ1,3 peak; however, chemical effects of Fe Kβ1,3 spectra can be studied if all the samples (including standards) are evenly set in the straw cells. Additionally, the application of the straw cell in studying precipitation band formation in gels was shown on two gel samples containing 0.004 M [Fe(CN)6] 3-/[Fe(CN)6] 2in 2 mass% κ-carrageenan and 0.040 M Fe 2+ /Fe 3+ in 1 mass% agarose, respectively.

Mn Kβ spectra of Mn, MnO, MnSO4•H2O, KMnO4, 0.50 M MnSO4 aqueous solution, and the precipitation bands of Mn-Fe-based Prussian blue analogs formed in 2.4 wt.% agarose gel ("Gel") were measured using a laboratory-use X-ray setup with ∼2.6 eV instrumental resolution, which comprises a cylindrically bent Si (400) crystal monochromator and a spherically bent Ge (440) crystal analyzer. The oxidation-state dependent shift of the Mn Kβ1,3 peak (∼1 eV) was clearly observed for Mn, MnO, and KMnO4, confirming that the employed setup can acquire the key features of Mn Kβ spectra. The Mn Kβ spectra of MnSO4•H2O, the 0.50 M solution, and Gel exhibited small but distinguishable differences, whereas the spectra acquired at two positions in Gel were almost the same. These results suggest that highly resolved Mn Kβ spectra can be helpful for assessing ligand coordination around Mn atoms in gels and solutions.