Flexibly transparent luminescent organic-inorganic-polymer composite films: Intense full-color emissions at a single excitation wavelength

Abstract

A versatile method utilizing organic-inorganic-polymer composite materials has been developed for the fabrication of both white-converting films and flexibly transparent full-color luminescent films. In this study, a single organic UV-harvester, salicylate (sal), was intercalated into the gallery of Eu3+-doped layered terbium hydroxide (LTbH:Eu), Tb3+-doped layered yttrium hydroxide (LYH:Tb), and layered yttrium hydroxide (LYH), to create three primary color emitting hybrids, sal-LTbH:Eu, sal-LYH:Tb, and sal-LYH. By adopting an identical organic sensitizer, its S0 → S1 (π, π*) transition was able to produce characteristically intense 5D0 → 7FJ Eu3+ red-emissions, as well as 5D4 → 7FJ green-emissions of Tb3+, through energy transfer to host matrices without a change in excitation wavelength. Despite a considerable energy difference between the 5D0 resonance energy level of Eu3+ and the lowest triplet state of salicylate, the energy transfer of Tb3+ to Eu3+ in the LTbH:Eu matrix resulted in the intense red-emission observed for Eu3+. In contrast, when the salicylate was included into the interlayer gallery of LYH (containing no activator ions), its typical blue-emission was found preserved at the same excitation wavelength. Moreover, these salicylate-intercalated hybrids, prepared by a facile aqueous solution route at room temperature, were well dispersed in water to form luminescent colloidal solutions. By mixing individual hybrid colloids at certain specific ratios, an intense white-light and full-color emission was successfully achieved at a low excitation energy (λ = 365 nm) using a commercial UV-lamp. Polyvinyl alcohol (PVA) was also employed to produce flexibly transparent luminescent composite films via simple casting of desired hybrid-dispersed solutions. Full-color generation and white-light converting behavior was demonstrated using the as-synthesized organic-inorganic-polymer composite films.