ABSTRACT. CoFe2O4 (CFO)-BiFeO3 (BFO) nanocomposites are an intriguing option for future memory and logic technologies due to the magnetoelctric properties of the system. However, these nanocomposites form with CFO pillars randomly located within a BFO matrix, making implementation in devices difficult. To overcome this, we present a technique to produce patterned nanocomposites through self-assembly. CFO islands are patterned on Nb-doped SrTiO3 to direct the self-assembly of epitaxial CFO-BFO nanocomposites, producing square arrays of CFO pillars.2 Multiferroic nanocomposite films have been heavily studied for their potential applications in magnetoelectric systems. 1 The CoFe2O4-BiFeO3 (CFO and BFO, respectively) system has generated particular interest due to the magnetoelastic properties of CFO 2 and the combination of ferroelectricity and anti-ferromagnetism in BFO 3 . It has been shown that when CFO and BFO are codeposited via physical vapor deposition at high temperatures on a SrTiO3 (001) substrate that the materials will spontaneously phase segregate to produce an epitaxial CFO pillar in an epitaxial BFO matrix, which is referred to as a 1-3 nanocomposite. 4 The CFO pillars form faceted structures with {110}-type interfaces with the BFO matrix and {111}-facets on the surface, protruding above the matrix. 5 The pattern of the CFO pillars in the structure is essentially random, since they are formed through the nucleation of a CFO island on the substrate, while BFO wets the remaining surface. Thus, to control the location of the pillars a means of controlling the nucleation site for the CFO island is needed. CFO-BFO composites have been found to demonstrate magnetoelectric coupling, allowing for electrical control of the magnetic anisotropy of the CFO pillars. 6 , 7 Based on these properties, the composite system has been proposed for both magnetoelectric memory 8 and logic 9 applications. In particular, the reconfigurable array of magnetic automata (RAMA) 9,10 is a nanomagnetic logic system based on the magnetic quantum cellular automata (MQCA) logic architecture 11 which would use a CFO-BFO 1-3 composite with the pillars arranged in a square array to create a reprogrammable logic system. However, in order to make devices using these composites, the ability to place the pillars into pre-determined arrays is required.Previous work in patterning multiferroic nanocomposites has been limited. One method to produce patterned magnetoelectric composites is to use a porous anodic aluminum oxide (AAO) film as a liftoff mask during deposition, which produces a hexagonal array pattern. 12,13 In one approach, a BaTiO3-CoFe2O4 (BTO-CFO) multilayer is deposited onto the AAO film on an STO substrate, which yields a small amount of magnetoelectric response. 12 Another technique is to use the AAO film to form CFO islands and then overcoat the islands with ferroelectric Pb(Zr,Ti)O3 (PZT), which yields a composite that is both ferroelectric and ferromagnetic. 13 Others have used a SiN membrane as a shadow mask to 3 ...

The low-temperature phase transitions of thermoelectric Zn 4 Sb 3 have been characterized using singlecrystal X-ray diffraction, electrical resistance, and thermal conductivity measurements. Room-temperature stable, disordered β-Zn 4 Sb 3 undergoes a phase transition at 254 K to ordered R-Zn 4 Sb 3 , which has an ideal composition Zn 13 Sb 10 . Below 235 K, a second low-temperature phase (R′-Zn 4 Sb 3 ) can be detected. The sequence of phase transitions β-R-R′ is reversible. The R-R′ transformation originates from a slight Zn deficiency with respect to Zn 13 Sb 10 . The actual composition of Zn 4 Sb 3 is Zn 13-δ Sb 10 .

We report a simple one-pot strategy to prepare surface-function-alized, water-dispersible iron oxide nanoparticles. Small organic molecules that have desired functional groups such as amines, carboxylics, and thiols are chosen as capping agents and are injected into the reaction medium at the end of the synthesis. A diversity of functionalities are effectively introduced onto the surface of the nanoparticles with a minimal consumption of solvents and chemical resources by simply switching the capping ligand to form the ligand shell. The resulting nanocrystals are quasi-spherical and narrowly size-distributed. Energy-dispersive X-ray analysis and Fourier transform infrared spectroscopy studies suggest a successful surface modification of iron oxide nanoparticles with selected functionalities. The colloidal stabilities are characterized by dynamic light scattering and zeta potential measurements. The results imply that functionalized nanoparticles are very stable and mostly present as individual units in buffer solutions. The pedant functional groups of the capping ligand molecules are very reactive, and their availabilities are investigated by covalently linking fluorescent dyes to the nanoparticles through the cross-linking of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride. The quenched quantum yield and shortened lifetime of the dyes strongly indicate a direct bonding between the functional group of the nanoparticles and the fluorescent molecules.

Rechargeable zinc–air batteries typically require efficient, durable, and inexpensive bifunctional electrocatalysts to support oxygen reduction/evolution reactions (ORR/OER). However, sluggish kinetics and mass transportation challenges must be addressed if the performance of these catalysts is to be enhanced. Herein, a strategy to fabricate a catalyst comprising atomically dispersed iron atoms supported on a mesoporous nitrogen‐doped carbon support (Fe SAs/NC) with accessible metal sites and optimized electronic metal–support interactions is developed. Both the experimental results and theoretical calculations reveal that the engineered electronic structures of the metal active sites can regulate the charge distribution of Fe centers to optimize the adsorption/desorption of oxygenated intermediates. The Fe SAs/NC containing Fe1N4O1 sites achieves remarkable ORR activity over the entire pH range, with half‐wave potentials of 0.93, 0.83, and 0.75 V (vs reversible hydrogen electrode) in alkaline, acidic, and neutral electrolytes, respectively. In addition, it demonstrates a promising low overpotential of 320 mV at 10 mA cm−2 for OER in alkaline conditions. The zinc–air battery assembled with Fe SAs/NC exhibits superior performance than that of Pt/C+RuO2 counterpart in terms of peak power density, specific capacity, and cycling stability. These findings demonstrate the importance of the electronic structure engineering of metal sites in directing catalytic activity.

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The hydrothermal reactions of NH4VO3 with the aromatic phosphonate ligands 1,4-, 1,3-, and 1,2-phenylenediphosphonic acids (H4L1, H4L3, H4L4, respectively); biphenyl-4,4'-diyldiphosphonic acid (H4L2); and 1,3,5-tris(phenyl)-4,4'-triphosphonic acid (H6L5) yielded materials of the V(x)O(y)/organophosphonate family [VO(H2L1)] (1), [VO(H2L2)] (2), [V2O2(H2O)2(L3)] x 1.5 H2O (3 x 1.5 H2O), [V2O2(H2O)2(L4)] x 2 H2O (4 x 2 H2O), and [V3O3(OH)(H3L5)2] x 7.5 H2O (6 x 7.5 H2O). The reactions were carried out in the presence of HF, and in one case, fluoride was incorporated to provide [V2F(OH)(H2O)3(L4)] x 2.25 H2O (5 x 2.25 H2O). The materials exhibit diverse structural chemistry, including the prototypical buttressed layer architecture for 1 and 2, a complex three-dimensional structure for 3, and unique two-dimensional structures for 4, 5, and 6. The structures of this oxovanadium-arylphosphonate family are quite distinct from those previously described for the V(x)O(y)/alkyldiphosphonate series.

The products of the reactions of copper(II) starting materials with 4-pyridyltetrazole (4-Hpt) in N,N-dimethylformamide (DMF)/methanol solutions are determined by the anion identity and concentration. In the absence of chloride, the 3-D open-framework material [Cu(3)(OH)(3)(4-pt)(3)(DMF)(4)].5DMF.3MeOH (1.5DMF.3MeOH) is isolated, while variations in the chloride concentration yield the 2-D and 3-D materials, 2 and 3, respectively. All three structures exhibit trinuclear copper(II) building blocks: the triangular {Cu(3)(mu(3)-OH)}(5+) core in 1 and {Cu(3)Cl(4)(4-pt)(4)(4-Hpt)(2)}(2-) and {Cu(3)Cl(2)(4-pt)(8)}(4-) chains in 2 and 3, respectively. All three materials display microporosity, which is highly dependent on the method of sample preparation.

The development of rechargeable zinc-air batteries is heavily dependent on bifunctional oxygen electrocatalysts to offer exceptional oxygen reduction/evolution reaction (ORR/OER) activities. However, the design of such electrocatalysts with high activity and durability is challenging. Herein, a strategy is proposed to create an electrocatalyst comprised of copper-cobalt diatomic sites on a highly porous nitrogen-doped carbon matrix (Cu-Co/NC) with abundantly accessible metal sites and optimal geometric and electronic structures. Experimental findings and theoretical calculations demonstrate that the synergistic effect of Cu-Co dual-metal sites with metal-N 4 coordination induce asymmetric charge distributions with moderate adsorption/desorption behavior with oxygen intermediates. This electrocatalyst exhibits extraordinary bifunctional oxygen electrocatalytic activities in alkaline media, with a half-wave potential of 0.92 V for ORR and a low overpotential of 335 mV at 10 mA cm −2 for OER. In addition, it demonstrates exceptional ORR activity in acidic (0.85 V) and neutral (0.74 V) media. When applied to a zinc-air battery, it achieves extraordinary operational performance and outstanding durability (510 h), ranking it as one of the most efficient bifunctional electrocatalysts reported to date. This work demonstrates the importance of geometric and electronic engineering of isolated dual-metal sites for boosting bifunctional electrocatalytic activity in electrochemical energy devices.