Large oriented mesoporous self-supporting Ni–Al oxide films derived from layered double hydroxide precursors

Abstract

Large (~1 cm 2 ) transparent highly (111)-oriented mesoporous self-supporting Ni-Al oxide films of uniform small nanoparticles have been prepared using an Ni 2 Al(OH) 6 (NO 3 )$2.1H 2 O layered double hydroxide (LDH) as a single precursor. The monodisperse small LDH nanoparticles (about 20 nm in diameter) are first cast as an oriented assembly on a glass substrate to form large transparent self-supporting (00l)-oriented LDH films. Subsequent heating in air affords (111)-oriented mesoporous Ni-Al oxide films preserving the shape, dimensions and optical transparency of the films. The process involves a topotactic transformation from the LDH (00l) facet to the NiO and NiAl 2 O 4 spinel (111) facets, demonstrated here for the first time, and does not require any template, structure-directing agent, or lattice-matched single crystal substrate. The nanostructures of the resulting mixed metal oxide films can be controlled by changing the calcination temperature: Al-doped NiO and composite NiO/NiAl 2 O 4 films of uniform small nanoparticles have been obtained at 500 C and 900 C respectively. The pore size and pore size distribution increase monotonically with temperature due to the increased sintering of the nanoparticles at higher temperatures. The resulting large transparent Ni-Al oxide films have a narrow distribution of mesopores (<10 nm) and high thermal stability, suggesting their potential application as catalysts or catalyst supports, in sensors, and as ultrafiltration membranes in harsh environments.

Exchange-biased NiFe2O4/NiO nanocomposites derived from NiFe-layered double hydroxides as a single precursor

“…We suggest that this can account for the marked difference in the magnetic stabilities (as shown by the T B values) of the NiFe 2 O 4 /NiO nanocomposites synthesized from the LDH precursor and by the chemical coprecipitation method. In the case of the LDH, during the early stages of the transformation, oxide nucleation occurs on its (00l) planes where the packing of cations is the densest, giving the lowest nucleation energy, and resulting in the formation of the (111) [20] of the decomposition of the LDH accounts for the close structural dependence of the resulting NiFe 2 O 4 and the NiO matrix and the much better quality of the interface between the NiO matrix and the NiFe 2 O 4 nanoparticles. Moreover, it can be seen from the TEM results that the sizes of the nanoparticles derived from the LDH precursor are much smaller than those obtained from the precursor prepared by the coprecipitation method and are strongly clustered with each other, giving a larger effective AFM NiO phase "thickness" around the NiFe 2 O 4 nanoparticles.…”

“…level [19], and the mechanism of the transformation from the LDH precursor to the final composites has been investigated in detail [20][21][22]. The structure of the LDH precursor belongs to the hexagonal group, and the cations on the (00l) facets are arranged in an ordered "hexagon" formation.…”

Stoichiometric synthesis of Fe/Ca x O catalysts from tailored layered double hydroxide precursors for syngas production and tar removal in biomass gasification

“…[21]. The increase in d-spacing as the Ca/Fe ratio increased can be attributed to the decreased electrostatic interaction between the positively charged layers and the negatively charged interlayer anions [22].…”

Layered Double Hydroxide Materials: Assembly and Photofunctionality

“…For example, alkoxideintercalated LDHs have been synthesized in a nonaqueous media (methanol), and the hydrolysis of these LDH derivatives resulted in a colloidal LDH suspension which can be used as a precursor for the formation of continuous transparent films via solvent evaporation [18,19]. For another example, the fabrication of oriented LDHs films without organic solvents has been attempted, and separate nucleation and aging steps (SNAS) were adopted as a main method [20]. Due to the uniform and small crystal size (about 40 nm) of the LDH platelets, both the face-to-face and edge-to-edge interactions occur between individual LDH platelets, which facilitate the formation of densely packed c-oriented LDH film [21].…”

“…This composite UTF was illustrated as (BTBS/LDH) 12 (QD-530/ LDH) 20 (QD-620/LDH) 7 , composed of three chromophores: red-emission and green-emission QDs and blue-emission organic compound BTBS. Due to the different excitation and emission spectra of these three chromophores, it can be concluded that BTBS can be excited at 360 nm while photon energy above 500 and 600 nm can efficiently excite QD-530 and QD-620.…”