General Synthesis of Layered Rare-Earth Hydroxides (RE = Sm, Eu, Gd, Tb, Dy, Ho, Er, Y) and Direct Exfoliation into Monolayer Nanosheets with High Color Purity

Abstract

Layered rare-earth hydroxides (LREHs) are promising optical and magnetic materials, while it is hard to obtain monolayer nanosheets through a direct exfoliation. In this study, organic dodecyl sulfate (C12H25SO4 –, DS–) was used to prepare LREHs. In-plane lattice parameters of the LREHs decreased from Sm3+ to Er3+, correlating well with the monotonically decreasing ionic radius. Conversely, the interlayer spacing slightly increased with the increase of host layer charge density and corresponding intercalated DS– contents. By a direct sonication of the LREHs in formamide, nanosheets were obtained with a thickness of ∼1 nm and size of ∼500 nm. Compared to the bulk crystals, exfoliation resulted in a slight elongation of in-plane lattice constants and a more asymmetric coordination environment. The suspension of europium hydroxide nanosheets exhibited a remarkably high red-light emission purity (91.4%). This work demonstrated an important strategy toward an efficient synthesis of well-defined LREH nanosheets with high color purity.

High-Entropy Layered Rare Earth Hydroxides

“…Layered RE hydroxides (LREH) are a class of compounds constructed from positively charged RE hydroxide layers and anions located in the interlayer space . The unique properties of RE elements make it possible to obtain advanced luminescent and magnetic materials based on LREH. − High-temperature thermal decomposition of LREH leads to the formation of individual and multicomponent RE oxides. ,− As a rule, annealing takes place at 950–1100 °C in an oxygen flow , or in air. , …”

Efficient dispersion of organic fluorophores by size matching with a new di-functionalized spacer interleaved into layered double hydoxide

“…Thus, the general formula of LDH can be written [M 2+ 1-xM 3+ X(OH)2][A n-]x/n.m H2O, where M 2+ is the divalent cation (Ca 2+ , Zn 2+ , Fe 2+ , Mg 2+ …), M 3+ is the trivalent cation (Al 3+ , Fe 3+ , Cr 3+ , Mn 3+ …), A nis the interlayered counterion and m is the number of water molecules present between and at the surface of the LDH layers. Various studies have been carried out in the lighting field and have consisted in hosting phosphors in LDH in order to exploit their luminescence properties, such as rare-earth elements [38][39][40] or quantum dots [41][42][43]. Some organic dyes have been interleaved in a LDH structure, such as fluorescein [44,45], perylenes [46][47][48] or rhodamines [24,49].…”

“…However, these surfactants suffer from a relatively low thermal stability, which leads to their degradation and to the subsequent delamination of the LDH layers at high temperatures. While many applications are based on this delamination [40,52,53], in the field of the intercalation of dyes in LDH this phenomenon must be absolutely avoided in order to guarantee the confinement of the molecules and avoid their migration and mutual aggregation. Thermally resistant spacers are able to prevent such potential delamination and are therefore of great interest in addressing this issue.…”

Delamination of Layered Double Hydroxide in Ionic Liquids under Ambient Conditions

“…The delamination of layered materials into unilamellar nanosheets has attracted considerable interest in both basic and applied disciplines due to the growing importance of such low-dimensional nanomaterials. − These 2D nanosheets offer very interesting properties such as unique electronic, structural, and mechanical properties as well as high specific surface area. , These properties are important for various applications such as catalysis, sensing, , and energy storage . Although graphene is probably the most studied 2D material, , other inorganic compounds (e.g., aluminosilicates, clays, , metal oxides, and chalcogenides) are becoming increasingly common due to their advantageous properties and the availability of the starting materials on a large scale .…”

“…The delamination of layered materials into unilamellar nanosheets has attracted considerable interest in both basic and applied disciplines due to the growing importance of such low-dimensional nanomaterials. 1 − 3 These 2D nanosheets offer very interesting properties such as unique electronic, structural, and mechanical properties as well as high specific surface area. 1 , 4 These properties are important for various applications such as catalysis, 5 sensing, 6 , 7 and energy storage.…”