Inclusion/energy transfer/release of L-ascorbate in the interlayer gallery of layered yttrium hydroxide

L-ascorbate (AS, Vitamin C) was intercalated into the interlayer gallery of layered yttrium hydroxide (LYH), a representative member of the layered rare earth hydroxide series (LRHs), through an ion-exchange reaction in an aqueous solution of sodium ascorbate. Based on the expansion of the interlayer space of the resulting AS-LYH hybrid, it is suggested that AS anions vertically oriented to hydroxide layers would be arranged to form a partially interdigitated bilayer in the interlayer space of LYH with a high loading capacity and density of AS. This arrangement is different from the antiparallel monolayer configuration of AS anions that are horizontally or vertically oriented to the layer of classical layered double hydroxides (LDHs). The durability of AS against light and oxidation was sufficiently enhanced in the interlayer gallery of LYH so that no degradation occurred after exposure to simulated sunlight or heating at 60 degrees C for a long time. Practically no release of AS from AS-LYH was observed in a saline solution and simulated sea water, whereas a sustained release of AS occurred selectively in a phosphate buffer solution, with a release process best described by the first-order model. When LYH was doped with Tb3+ activator to give it photoluminescence ability, the UV light energy absorbed for the pi -> pi* transition of AS was efficiently transferred to Tb3+, leading to strong green emission attributed to its 5D4 -> 7F5 transition.

Automated summary

In this study, L-ascorbate was incorporated into layered yttrium hydroxide, resulting in a partially interdigitated bilayer structure with high loading capacity and density of L-ascorbate. This arrangement enhanced the durability of L-ascorbate against light and oxidation. The release of L-ascorbate could be described by a first-order model in a phosphate buffer solution. Furthermore, when yttrium hydroxide was doped with Tb3+ activator, the absorbed UV light energy of L-ascorbate was efficiently transferred to Tb3+, resulting in strong green emission.