Combining sol-gel chemistry with polymer templating strategies enables production of CuFe 2 O 4 thin films with both an ordered cubic network of 17 nm diameter pores and tunable spinel domain sizes. These nanocrystalline materials contain only minor structural defects with k = 0.85 AE 0.02 and exhibit multiple functionalities, including superparamagnetic behavior (T B E 310 K) and redox-and photoactivity.Transition metal ferrites with the general formula MFe 2 O 4 (M = Cu, Co, Ni, etc.) constitute an important class of spinel oxides that exhibit a broad range of interesting physical properties. Therefore such materials are used in applications, such as magnetic recording, high-frequency devices, and so forth.In recent years, it has been shown that MFe 2 O 4 ferrites can adopt normal, inverse, and partially inverted or even mixed spinel structures. 1 As a result, the magnetic, optical, and electronic properties can be tailored through the variation of cations on the tetrahedral and octahedral coordination sites. However, it is also known that physical properties can be tailored by controlling both the grain size and the material morphology itself. Many materials have therefore seen benefits from structuring at the nanoscale in that they were able to outperform their bulk counterparts.Among the existing transition metal ferrites, copper ferrite (CuFe 2 O 4 ) plays an important role. As opposed to most MFe 2 O 4 ferrites that crystallize in a cubic Fd % 3m spinel structure, CuFe 2 O 4 is characterized by a tetragonal I4 1 /amd structure (Jahn-Teller effect) at room temperature. 2 In the present work, we specifically focus on mesoporous CuFe 2 O 4 spinel thin films, materials that as we show here can be readily produced with both a 3D honeycomb structure and tunable nanocrystalline domain sizes. We use these spinel materials as model systems both to study the cation distribution, relative to bulk versions of CuFe 2 O 4 , and to examine the magnetic properties.In the past decade, it has been shown that polymer templating strategies are efficient routes to produce nanocrystalline metal oxides with mesoporous morphologies. 3 The formation of these materials relies on the solution phase coassembly of inorganic sol-gel precursors with an organic structure-directing agent, in particular amphiphilic polymers. The corresponding thin films can be achieved by the same coassembly methods but using an evaporation-induced self-assembly (EISA) process. 4 The mesoporous CuFe 2 O 4 thin films were produced using an EISA process. In this work, we incorporated a KLE-type diblock copolymer (here H[(CH 2 CH 2 ) 0.67 (CH 2 CHCH 2 CH 3 ) 0.33 ] 89 -(OCH 2 CH 2 ) 79 OH)) as the structure-directing agent and hydrated copper and ferric nitrate salts as the precursors (see the Experimental procedure in ESIw). 5 To probe the nanoscale structure, both transmission (TEM) and scanning electron microscopy (SEM) were used. Fig. 1 shows TEM and SEM data of KLE-templated CuFe 2 O 4 spinel thin films heated to 650 1C. The top view SEM images in panel...

In this paper, we report on ordered mesoporous NiFe(2)O(4) thin films synthesized via co-assembly of hydrated ferric nitrate and nickel chloride with an amphiphilic diblock copolymer, referred to as KLE. We establish that the NiFe(2)O(4) samples are highly crystalline after calcination at 600 °C, and that the conversion of the amorphous inorganic framework comes at little cost to the ordering of the high quality cubic network of pores averaging 16 nm in diameter. We further show that the synthesis method employed in this work can be readily extended to other ferrites, such as CoFe(2)O(4), CuFe(2)O(4), MgFe(2)O(4), and ZnFe(2)O(4), which could pave the way for innovative device design. While this article focuses on the self-assembly and characterization of these materials using various state-of-the-art techniques, including electron microscopy, grazing incidence small-angle X-ray scattering (GISAXS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), X-ray photoelectron spectroscopy (XPS), as well as UV-vis and Raman spectroscopy, we also examine the electrochemical properties and show the benefits of combining a continuous mesoporosity with nanocrystalline films. KLE-templated NiFe(2)O(4) electrodes exhibit reasonable levels of lithium ion storage at short charging times which stem from facile pseudocapacitance.

Monodisperse, monocrystalline magnesium ferrite (MgFe2O4) nanoparticles were synthesized phase purely by fast nonaqueous microwave-assisted solution-phase synthesis. Colloidal stabilization of the nanocrystals in nonaqueous media was realized either in-situ during synthesis or postsynthetically by surface capping with oleylamine and oleic acid. Phase transfer to aqueous media was performed employing citric acid and betaine hydrochloride, resulting in agglomerate-free dispersions of citrate- or betaine-functionalized MgFe2O4 nanocrystals. Furthermore, a one-step synthesis of highly stable, water-dispersible colloids of MgFe2O4 was achieved using polyvinylpyrrolidone as stabilizer. Characterization of the as-synthesized and functionalized nanoparticles was performed employing X-ray diffraction, UV–vis and infrared spectroscopy, thermogravimetry, dynamic light scattering, and transmission electron microscopy. Special focus was laid on phase purity, which was thoroughly monitored using Raman microscopy/spectroscopy. Photocatalytic reactions were performed to evaluate the use of such highly stable ferrite colloids for solar energy conversion.

Thermally stable, ordered mesoporous thin films of 8 mol % yttria-stabilized zirconia (YSZ) were prepared by solution-phase coassembly of chloride salt precursors with an amphiphilic diblock copolymer using an evaporation-induced self-assembly process. The resulting material is of high quality and exhibits a well-defined three-dimensional network of pores averaging 24 nm in diameter after annealing at 600 °C for several hours. The wall structure is polycrystalline, with grains in the size range of 7 to 10 nm. Using impedance spectroscopy, the total electrical conductivity was measured between 200 and 500 °C under ambient atmosphere as well as in dry atmosphere for oxygen partial pressures ranging from 1 to 10(-4) bar. Similar to bulk YSZ, a constant ionic conductivity is observed over the whole oxygen partial pressure range investigated. In dry atmosphere, the sol-gel derived films have a much higher conductivity, with different activation energies for low and high temperatures. Overall, the results indicate a strong influence of the surface on the transport properties in cubic fluorite-type YSZ with high surface-to-volume ratio. A qualitative defect model which includes surface effects (annihilation of oxygen vacancies as a result of water adsorption) is proposed to explain the behavior and sensitivity of the conductivity to variations in the surrounding atmosphere.