Modification of Layered Double Hydroxides Using First-Row Transition Metals for Superior UV-Vis-NIR Absorption and the Influence of the Synthesis Method Used

Layered double hydroxides (LDHs) with high and tailorable UV-Vis-NIR absorption were prepared through transition
metal (TM) modification. The synthesis method used and amount of TM present were found to influence the UV-Vis-
NIR absorption intensity, -range, and the optical bandgap.
It was found that the incorporation of TMs in MgAl-LDH results in the existence of a "UV-Vis-NIR absorption fingerprint", the intensity of which can be tuned by the amount of TM present. There also exist differences in the UV-Vis-NIR absorption spectra and bandgaps obtained for MgAl-LDH synthesised using different synthesis conditions and methods, but these are not as visible when including transition metals. Further, the materials exhibit very complex spectra for which adequate explanation is lacking in literature. Finally, standard methods to determine the bandgap of materials, did not give conclusive results for all materials, only for some, and indicate that some of the materials might have multiple different transition types.