Periodically ordered nanoscale islands and mesoporous films composed of nanocrystalline multimetallic oxides

Abstract

Innovative strategies to produce well-defined nanoparticles and other nanostructures such as nanofibres, quantum wells and mesoporous materials have revitalized materials science for the potential benefit to society. Here, we report a controlled process, involving soft-chemistry-based deposition, template-assisted mesostructured growth, and tuned annealing conditions that allows the preparation of ordered mesoporous crystalline networks and mesostructured nano-island single layers, composed of multicationic metal oxides having perovskite, tetragonal or ilmenite structures. This strategy to obtain meso-organized multi-metal-oxide nanocrystalline films (M(3)NF) bridges the gap between conventional mesoporous materials and the remarkable properties of crystalline ternary or quaternary metallic oxides. Nanocrystalline mesoporous films with controlled wall thickness (10-20 nm) of dielectric SrTiO(3), photoactive MgTa(2)O(6) or ferromagnetic semi-conducting Co(x)Ti(1-x)O(2-x) were prepared by evaporation-induced self-assembly (EISA) using a specially designed non-ionic block-copolymer template. A tuned thermal treatment of the mesoporous films permits the transfer of the wall structure into nanocrystallites, with all tectonic units being tightly incorporated into mechanically stable ordered tri- or bidimensional nanocrystalline networks. This methodology should allow multifunctionalization, miniaturization and integration during development of devices such as smart sensors and actuators, better-performing photocatalysts, and fast electrochromic devices. On the other hand, organized arrays of dispersed ferromagnetic or ferroelectric nanoparticles are promising materials for spintronics and for cheap, non-volatile 'flash' memories.

Morphology, Microstructure, and Magnetic Properties of Ordered Large-Pore Mesoporous Cadmium Ferrite Thin Film Spin Glasses

“…[3,8,18] During this research, we found that the use of hydrated cadmium and ferric nitrate salts gives the best results in terms of pore structure and material homogeneity. Synthesis carried out using other precursor combinations such as chlorides and acetylacetonates failed or produced illdefined materials (not shown) likely due to both the different sol-gel behavior and interactions with the KLE diblock copolymer.…”

“…We note that this type of polymer has been shown to produce materials with comparatively thick walls that typically allow for uniform nucleation and growth of the crystalline phase in such way that the pore-solid architecture is only affected to a limited extent. [3,8,18] Cadmium ferrite belongs to the spinel-type oxides with space group 3 ̅ ( magneto-optical devices and as semiconducting sensing material. [19][20][21] In general, spinel ferrites exhibit a variety of interesting electrical, optical, and magnetic properties which is why they are widely used in applications such as magnetic recording.…”

“…[1][2][3][4][5] Advances in both polymer templating and processing of sol-gel derived coatings have enabled the preparation of a range of different metal oxides with ordered pore cavities ranging from a few nanometers to almost 40 nanometers in diameter. [5][6][7][8][9][10] Their formation relies on the coassembly of molecular precursors with an amphiphilic polymer using an evaporation-induced self-assembly (EISA)…”

Nanoarchitectonics for Mesoporous Materials

“…171 Sanchez and co-workers reported the preparation of ordered mesoporous crystalline networks composed of multicationic metal oxides having perovskite, tetragonal, or ilmenite structures through evaporationinduced self-assembly (EISA). 172 This method was applied to synthesize nanocrystalline mesoporous films of dielectric SrTiO 3 174176 Zhou et al reported very simple preparation of hierarchically macro-mesoporous titania and alumina by simple dropwise addition of titanium and aluminum alkoxides to an ammonia solution in the presence or absence of surfactant molecules, CTAB. 177 The addition of CTAB does not direct the formation of macropores, but significantly affects the mesopore size, the surface area, and the pore volume.…”

Effective use of flexible low-dimensional colloidal particles and colloidal crystals for the control of hierarchically porous materials

“…14) Mesoporous Ta 2 O 5 with crystalline walls show high activity for photocatalytic water splitting. 15) Because the shrinkage of metal oxide frameworks by crystallization at high temperature causes destruction of mesostructures, several researchers reinforced the frameworks with stable block copolymer template, 16) siloxane materials, 17) and carbon. 18) Fig.…”