Abstract
We have developed pillared layered rare earth hydroxides showing the reversible photoluminescence switching via reducing–oxidizing processes. An air-stable Ce3+-based host, Ce2(OH)4SO4·2H2O, was successfully synthesized via a homogeneous alkalization protocol to precipitate Ce3+ ions from a solution of the relevant salt. Structural analysis revealed that the compound consists of cationic layers of {[Ce(OH)2(H2O)]+}∞, linked by sulfate bidentate ligands to construct a layered framework architecture. Tb3+ ion was incorporated into this host lattice to form a solid solution across the full compositional range. At an optimized doping of ∼30%, the characteristic green emission was enhanced by ∼20 times, being promoted by the efficient energy transfer from Ce3+ to Tb3+. The emission could be drastically diminished upon the action of the KMnO4 oxidizing reagent, which induced the transformation of Ce3+ to Ce4+. Characterizations by X-ray diffraction and X-ray photoelectron spectroscopy showed that the oxidation of Ce3+ occurs without degradation of the crystalline framework. The emission could be recovered to its original intensity by the reduction treatment with ascorbic acid. This photoluminescence switching behavior was detectable by the eye and exhibited high reversibility.
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