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

07 February 2020, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

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.

Keywords

layered double hydroxides
visible light absorption
bandgap analysis
co-precipitation
urea hydrolysis
nanomaterials
UV-vis-NIR spectrum
transition metal modification
quintinite
LDH compounds
Material properties
optical properties

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