Primary and high-intensity maxima “d” and “f” have equivalent positions, 349.3 eV and 352.7 eV, with slight variations (see Table 3) and correspond for the L3 and L2 calcium edges, respectively. Having said that, the main distinction inside the spectra of the samples may be the shape with the “c” and “e” pre-peaks (see Figure 6). In [25,635], it can be specified that a much less structured shape of features “c” and “e” is connected with low symmetry and indicates the amorphous structure in the sample. It is also noted in [63] that the ratio of your “e” pre-peak towards the “f” peak is usually a fantastic indicator with the environment closest for the absorbing Ca atom surrounded by oxygen atoms. The larger the “e”/”f” ratio is, the extra ordered the structure is.Figure 6. Ca L-edge XANES spectra of reference samples, biomimetic composites and natural mineralised tissue (enamel and dentine). Spectra of all-natural enamel, reference enamel, a synthesised biomimetic composite that imitates the properties of tooth enamel and 5-Azacytidine Technical Information stoichiometric and carbonatesubstituted hydroxyapatite hydroxyapatites are in the left part of the figure. Spectra of natural dentine, reference dentine, a synthesised biomimetic composite that imitates the properties of tooth dentine, stoichiometric and carbonate-substituted hydroxyapatite hydroxyapatites are in the proper aspect.Detailed analysis on the experimental data (Figure 6) shows that inside the XANES spectra of all samples, the capabilities “a”, “b” and “c” appear at 347, 347.6 and 348.1 eV, respectively. These data are in excellent agreement with all the final results obtained for Ca phosphates from [61] andNanomaterials 2021, 11,12 ofthe positions of these spectral features are characteristic from the octahedral crystal field [61]. Furthermore, in [25], it’s shown that the functions “a”, “b”, “c” and “e” are additional Resazurin Autophagy prominent inside the spectra of natural enamel, that is linked with larger crystallinity compared to natural dentine. It could be observed (Table 4) that “a”, “b” and “c” are shifted towards reduced energies inside the CD biocomposite.Table four. Positions of functions in the Ca L2,3 -edge XANES spectra. Sample HS H1 H2 H3 Eexp ERef [25] CE Dexp DRef [25] CD Positions of Characteristics, eV a 347.0 347.0 347.2 347.0 347.0 346.8 b 347.5 347.5 347.5 347.2 c 348.1 348.1 348.1 348.two 348.two 348.4 348.two 348.three 348.3 348.0 d 349.three 349.3 349.three 349.3 349.three 349.1 349.3 349.3 349.4 349.three e 351.6 351.six 351.6 351.eight 351.six 351.eight 351.six 351.8 351.7 351.6 f 352.7 352.7 352.7 352.7 352.7 352.7 352.7 352.7 352.7 352.In [64], the calcium L-edge XANES spectra of calcite and aragonite had been investigated. It was shown that in aragonite, which has reduced symmetry than calcite, Ca is bound to nine oxygen atoms and “a”, “b” and “c” possess the positions 347, 347.6 and 348.4 eV, respectively. In the very same time, in calcite with greater symmetry, the Ca is surrounded by six oxygen atoms, as well as the positions of “a”, “b” and “c” correspond for the values 346.eight, 347.two and 348 eV, which correspond towards the outcomes obtained for the biomimetic biocomposite CD (Table 4). In performing so, it was shown [63] that, for calcite, the ratio of intensities for the functions “”/”f” 0.45, whereas for the CD biocomposite, this ratio is 0.3 (Figure 7), which we associated having a unique Ca/P ratio.Figure 7. Relative heights of pre-peak “e” and peak “f” in the calcium L-edge XANES spectrum from the biocomposite CD . BL–baseline.Nanomaterials 2021, 11,13 ofAs was shown earlier by Cosmidis et al. [61], the atomic Ca/P ratio, the fingerprint of Ca-phosphate biological tissues.