In Mn XAS of PS II, the presence of Fe in the sample places an inherent limit on the resolution of Mn distances by limiting the data length.
Additional file 1: S1 Calculation of the possible Cu-Mn distance of BB.
The Cu-Mn distance in this mode is approximately in the range of 2.73 to 3.98 Å (Additional file 1: S1).
As aforementioned, the mean Mn-Mn distance is 11.4 nm, thus, all the characteristic lengths, e.g., wire diameter and mean distances, are of the same order of magnitude.
Table 1 shows that the Cu-Mn distance of the sample pH6.0-Cu0.4 pH6.0-Cu0.4ish a coordination number of 1.7 (0.3.37nd that of the sample pH6.0-Cu4.0 is 3.44 Å with a coordination number of 0.7 (0.3).
This means that in bulk material, the temporal PL behavior is determined by the interplay of two characteristic length scales, i.e., the mean Mn-Mn distance and the mean distance between Mn ions and killer centers.
In a density functional theory study, Kown et al. [39] showed that the theoretical values of Cu-Mn distance in incorporation mode are 2.84 Å, 2.95 Å and 2.98 Å.
Though the biogenic Mn oxide (Bixbyite) in this study differs in structure with birnessite, the Cu-Mn distance (3.37 Å and 3.44 Å) in the two sorption samples should be unlikely in incorporation mode.
Based on the Cu-Mn distance, the sorbed Cu II) on the two samples could be in Cu-TCS complexes, but the coordination numbers of the two sorption samples are far less than 3. Additionally, there is no report of cation vacancy site in the structure of bixbyite [31].
The Cu-Mn distance in this edge-sharing mode is approximately 2.80 Å, which is much shorter than the Cu-Mn distances in the two samples (3.37 Å, 3.44 Å), implying that the possibility of a face-sharing and an edge-sharing linkage can be excluded.
