Self-assembled hierarchical architecture of tetragonal AgLa(MoO4)2 crystals: hydrothermal synthesis, morphology evolution and luminescence properties

Abstract

Tetragonal AgLa(MoO₄)₂ microcrystals with novel discal hierarchical architectures were successfully synthesized via a one-step hydrothermal route. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and photoluminescence (PL) spectral analysis as well as decay lifetimes were employed to characterize the prepared products. It was found that various hierarchical architectures were obtained by altering the amount of MoO₄²⁻, pH values and surfactants, respectively. In particular, the pH value had a large influence not only on the morphology, but also on the size and crystallinity. The formation mechanism of discal hierarchical architectures was proposed on the basis of the self-assembly growth of nanosheets. The AgLa(MoO₄)₂ microcrystals exhibited excellent down/up-conversion (DC/UC) multicolor emissions after doping different Ln³⁺ ions. For DC luminescence, AgLa(MoO₄)₂:Ln³⁺ (Ln = Eu, Tb, Sm, Dy) exhibited characteristic red emission, green emission, orange emission and yellow emission, respectively. The energy transfer of MoO₄²⁻ → Ln³⁺ (Ln = Tb, Sm, Dy) markedly enhanced the characteristic emissions of Tb³⁺, Sm³⁺ and Dy³⁺. For UC luminescence, AgLa(MoO₄)₂:Yb³⁺/Ln³⁺ (Ln = Er, Tm, Ho) exhibited intense green (²H_11/2 → ⁴I_5/2 of Er³⁺), blue (¹G₄ → ³H₆ of Tm³⁺), yellow (⁵F₅ → ⁵I₈ of Ho³⁺) emissions, respectively. Therefore, the as-prepared AgLa(MoO₄)₂:Ln³⁺ microcrystals may have potential application to serve as fluorescent lamps, field emission display devices, sensors and biological imaging agents.