Quantitative nanoscale mapping of the Mn redox states in silicates by scanning transmission X-ray microscopy at the Mn L2,3-edges

We present a novel analytical protocol for quantifying and mapping Mn oxidation states in silicates at the nanoscale. Based on X-ray Absorption Near Edge Structure spectra of the Mn L 2,3 -edges (630–660 eV) acquired thanks to a Scanning transmission X-ray microscope available at various Synchrotron facilities, we calibrate two equations using reference Mn-bearing samples to precisely determine the Mn mean valence. We detail the spectra processing and the methodology for deriving quantitative Mn redox maps from the proposed calibrations, with a high spatial resolution (20–30 nm). Furthermore, we explore the potential for coupling Mn and Fe L 2,3 -edge redox calibrations over the 630–730 eV energy range. The effectiveness of these calibrations, the coupling of Mn Fe results, and the subsequent redox mapping are evaluated through two case studies, showcasing the benefits of this non-destructive approach. • A novel approach for quantifying Mn oxidation states in silicates is proposed. • The protocol is based on Mn L 2,3 -edge X-ray Absorption Near Edge Structure spectra. • The mapping of Mn oxidation states is feasible on ultrathin foils or powders. • Spatial resolution for quantification and mapping is a few tens of nanometers. • Through study cases, Mn and Fe oxidation state quantification protocols are coupled.