Identification and optical features of the Pb4Ln2O7 series (Ln = La, Gd, Sm, Nd); genuine 2D-van der Waals oxides
Résumé
We report on the identification and survey of the Pb 4 Ln 2 O 7 series (Ln = La, Gd, Sm and Nd) which turn out to be real van der Waals 2D oxides. In the neutral layers, strong covalent Pb-O bonds together with external stereoactive Pb 2+ lone pairs, which act as sensitizers, lead to an ideal matrix for enhanced and tunable luminescence by lanthanide emitters, tested here for Sm 3+ and Eu 3+ doping. DFT calculations and preliminary ex-solution experiments validate the weak bonding between the layers separated by 3.5 Å and suggest a indirect to direct crossover realized by isolating the layers.
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