Lattice solvent- and substituent-dependent spin-crossover in isomeric iron(II) complexes.

Spin-state switching in iron(II) complexes composed of ligands featuring moderate ligand-field strength-for example, 2,6-bi(1-pyrazol-1-yl)pyridine (BPP)-is dependent on many factors. Herein, we show that spin-state switching in isomeric iron(II) complexes composed of BPP-based ligands-ethyl 2,6-bis(1-pyrazol-1-yl)isonicotinate (BPP-COOEt, L1) and (2,6-di(1-pyrazol-1-yl)pyridin-4-yl)methylacetate (BPP-CHOCOMe, L2)-is dependent on the nature of the substituent at the BPP skeleton. Bi-stable spin-state switching-with a thermal hysteresis width (Δ) of 44 K and switching temperature () = 298 K in the first cycle-is observed for complex 1·CHCN composed of L1 and BF counter anions.

Optimization of Magnetic Cobalt Ferrite Nanoparticles for Magnetic Heating Applications in Biomedical Technology.

Using magnetic nanoparticles for extracorporeal magnetic heating applications in bio-medical technology allows higher external field amplitudes and thereby the utilization of particles with higher coercivities (H). In this study, we report the synthesis and characterization of high coercivity cobalt ferrite nanoparticles following a wet co-precipitation method. Particles are characterized with magnetometry, X-ray diffraction, Mössbauer spectroscopy, transmission electron microscopy (TEM) and calorimetric measurements for the determination of their specific absorption rate ().

2-Propanol interacting with Co3O4(001): A combined vSFS and AIMD study.

The interaction of 2-propanol with Co3O4(001) was studied by vibrational sum frequency spectroscopy and ab initio molecular dynamics simulations of 2-propanol dissolved in a water film to gain an insight, at the molecular level, into the pathways of catalytic oxidation. The experimental study has been performed under near ambient conditions, where the presence of water vapor is unavoidable, resulting in a water film on the sample and, thereby, allowing us to mimic the solution-water interface. Both experiment and theory conclude that 2-propanol adsorbs molecularly.

Spray-Flame Synthesis of LaFeCoO ( = 0.2, 0.3) Perovskite Nanoparticles for Oxygen Evolution Reaction in Water Splitting: Effect of Precursor Chemistry (Acetates and Nitrates).

The product properties of mixed oxide nanoparticles generated via spray-flame synthesis depend on an intricate interplay of solvent and precursor chemistries in the processed solution. The effect of two different sets of metal precursors, acetates and nitrates, dissolved in a mixture of ethanol (35 Vol.%) and 2-ethylhexanoic acid (2-EHA, 65 Vol.

Solvent Influence on the Magnetization and Phase of Fe-Ni Alloy Nanoparticles Generated by Laser Ablation in Liquids.

The synthesis of bimetallic iron-nickel nanoparticles with control over the synthesized phases, particle size, surface chemistry, and oxidation level remains a challenge that limits the application of these nanoparticles. Pulsed laser ablation in liquid allows the properties tuning of the generated nanoparticles by changing the ablation solvent. Organic solvents such as acetone can minimize nanoparticle oxidation.

Rare-earth doped BiFeMnO nanoparticles for potential hyperthermia applications.

Ionic engineering is exploited to substitute Bi cations in BiFeMnO NPs (BFM) with rare-earth (RE) elements (Nd, Gd, and Dy). The sol-gel synthesized RE-NPs are tested for their magnetic hyperthermia potential. RE-dopants alter the morphology of BFM NPs from elliptical to rectangular to irregular hexagonal for Nd, Gd, and Dy doping, respectively.

Spin-Polarized Photoemission from Chiral CuO Catalyst Thin Films.

The chirality-induced spin selectivity (CISS) effect facilitates a paradigm shift for controlling the outcome and efficiency of spin-dependent chemical reactions, for example, photoinduced water splitting. While the phenomenon is established in organic chiral molecules, its emergence in chiral but inorganic, nonmolecular materials is not yet understood. Nevertheless, inorganic spin-filtering materials offer favorable characteristics, such as thermal and chemical stability, over organic, molecular spin filters.

Laser Ablation of NiFeO and CoFeO Nanoparticles.

Pulsed laser ablation in liquids was utilized to prepare NiFeO (NFO) and CoFeO (CFO) nanoparticles from ceramic targets. The morphology, crystallinity, composition, and particle size distribution of the colloids were investigated. We were able to identify decomposition products formed during the laser ablation process in water.

Phase Segregation in Cobalt Iron Oxide Nanowires toward Enhanced Oxygen Evolution Reaction Activity.

The impact of reduction post-treatment and phase segregation of cobalt iron oxide nanowires on their electrochemical oxygen evolution reaction (OER) activity is investigated. A series of cobalt iron oxide spinel nanowires are prepared via the nanocasting route using ordered mesoporous silica as a hard template. The replicated oxides are selectively reduced through a mild reduction that results in phase transformation as well as the formation of grain boundaries.

Ferrimagnetic Large Single Domain Iron Oxide Nanoparticles for Hyperthermia Applications.

This paper describes the preparation and obtained magnetic properties of large single domain iron oxide nanoparticles. Such ferrimagnetic particles are particularly interesting for diagnostic and therapeutic applications in medicine or (bio)technology. The particles were prepared by a modified oxidation method of non-magnetic precursors following the green rust synthesis and characterized regarding their structural and magnetic properties.

Magnetic response of CoFeO nanoparticles confined in a PNIPAM microgel network.

The paper addresses coupling of magnetic nanoparticles (MNPs) with the polymer matrix of temperature-sensitive microgels and their response to magnetic fields. Therefore, CoFeO@CA (CA = citric acid) NPs are embedded within -isopropylacrylamid (NIPAM) based microgels. The volume phase transition (VPT) of the magnetic microgels and the respective pure microgels is studied by dynamic light scattering and electrophoretic mobility measurements.

Structural Insights into Hysteretic Spin-Crossover in a Set of Iron(II)-2,6-bis(1H-Pyrazol-1-yl)Pyridine) Complexes.

Bistable spin-crossover (SCO) complexes that undergo abrupt and hysteretic (ΔT ) spin-state switching are desirable for molecule-based switching and memory applications. In this study, we report on structural facets governing hysteretic SCO in a set of iron(II)-2,6-bis(1H-pyrazol-1-yl)pyridine) (bpp) complexes - [Fe(bpp-COOEt) ](X) ⋅CH NO (X=ClO , 1; X=BF , 2). Stable spin-state switching - T =288 K; ΔT =62 K - is observed for 1, whereas 2 undergoes above-room-temperature lattice-solvent content-dependent SCO - T =331 K; ΔT =43 K.

The Effect of Water on the 2-Propanol Oxidation Activity of Co-Substituted LaFe Co O Perovskites.

Perovskites are interesting oxidation catalysts due to their chemical flexibility enabling the tuning of several properties. In this work, we synthesized LaFe Co O catalysts by co-precipitation and thermal decomposition, characterized them thoroughly and studied their 2-propanol oxidation activity under dry and wet conditions to bridge the knowledge gap between gas and liquid phase reactions. Transient tests showed a highly active, unstable low-temperature (LT) reaction channel in conversion profiles and a stable, less-active high-temperature (HT) channel.

The Roles of Composition and Mesostructure of Cobalt-Based Spinel Catalysts in Oxygen Evolution Reactions.

By using the crystalline precursor decomposition approach and direct co-precipitation the composition and mesostructure of cobalt-based spinels can be controlled. A systematic substitution of cobalt with redox-active iron and redox-inactive magnesium and aluminum in a cobalt spinel with anisotropic particle morphology with a preferred 111 surface termination is presented, resulting in a substitution series including Co O , MgCo O , Co FeO , Co AlO and CoFe O . The role of redox pairs in the spinels is investigated in chemical water oxidation by using ceric ammonium nitrate (CAN test), electrochemical oxygen evolution reaction (OER) and H O decomposition.

On the structure-property relationships of (Al, Ga, In)-doped spinel cobalt ferrite compounds: a combined experimental and DFT study.

We report a combined experimental and theoretical study of pure and doped cobalt ferrite where 25% of Fe ions were replaced by Al, Ga, and In ions, respectively, i.e., CoFeXO (X = Al, Ga, and In).

Towards laser printing of magnetocaloric structures by inducing a magnetic phase transition in iron-rhodium nanoparticles.

The development of magnetocaloric materials represents an approach to enable efficient and environmentally friendly refrigeration. It is envisioned as a key technology to reduce CO emissions of air conditioning and cooling systems. Fe-Rh has been shown to be one of the best-suited materials in terms of heat exchange per material volume.

Magnetic Properties and Mössbauer Spectroscopy of FeO/CoFeO Nanorods.

FeO/CoFeO nanorods were obtained via a simple seed-mediated synthesis. Nanorods were used as seeds to grow CoFeO by thermal codecomposition of the cobalt(II) and iron(III) acetylacetonate precursors. The growth process was monitored by electron microscopy (SEM, TEM), and the resulting nanorods were characterized by powder X-ray diffraction analysis and IR and Raman spectroscopy.

In-Field Orientation and Dynamics of Ferrofluids Studied by Mössbauer Spectroscopy.

By studying the response behavior of ferrofluids of 6-22 nm maghemite nanoparticles in glycerol solution exposed to external magnetic fields, we demonstrate the ability of Mössbauer spectroscopy to access a variety of particle dynamics and static magnetic particle characteristics at the same time, offering an extensive characterization of ferrofluids for in-field applications; field-dependent particle alignment and particle mobility in terms of Brownian motion have been extracted simultaneously from a series of Mössbauer spectra for single-core particles as well as for particle agglomerates. Additionally, information on Néel superspin relaxation and surface spin frustration could be directly inferred from this analysis. Parameters regarding Brownian particle dynamics, as well as Néel-type relaxation behavior, obtained via Mössbauer spectroscopy, have been verified by complementary AC-susceptometry experiments, modulating the AC-field amplitude, and using an extended frequency range of 10 to 10 Hz, while field-dependent particle alignment has been cross-checked via magnetometry.

Effect of substrate orientation on local magnetoelectric coupling in bi-layered multiferroic thin films.

In this study we explore the prospect of strain-mediated magnetoelectric coupling in CoFe2O4-BaTiO3 bi-layers as a function of different interfacial boundary conditions. Pulsed laser deposition fabricated thin films on Nb:SrTiO3(100) and Nb:SrTiO3(111) single crystal substrates were characterized in terms of their peculiarities related to the structure-property relationship. Despite the homogeneous phase formation in both films, transmission electron microscopy showed that the bi-layers on Nb:SrTiO3(100) exhibit a higher number of crystallographic defects when compared to the films on Nb:SrTiO3(111).

Adjusting the catalytic properties of cobalt ferrite nanoparticles by pulsed laser fragmentation in water with defined energy dose.

Highly active, structurally disordered CoFeO/CoO electrocatalysts are synthesized by pulsed laser fragmentation in liquid (PLFL) of a commercial CoFeO powder dispersed in water. A partial transformation of the CoFeO educt to CoO is observed and proposed to be a thermal decomposition process induced by the picosecond pulsed laser irradiation. The overpotential in the OER in aqueous alkaline media at 10 mA cm is reduced by 23% compared to the educt down to 0.

Topotactic Synthesis of Porous Cobalt Ferrite Platelets from a Layered Double Hydroxide Precursor and Their Application in Oxidation Catalysis.

Monocrystalline, yet porous mosaic platelets of cobalt ferrite, CoFe O , can be synthesized from a layered double hydroxide (LDH) precursor by thermal decomposition. Using an equimolar mixture of Fe , Co , and Fe during co-precipitation, a mixture of LDH, (Fe Co ) Fe (OH) (CO ) ⋅m H O, and the target spinel CoFe O can be obtained in the precursor. During calcination, the remaining Fe fraction of the LDH is oxidized to Fe leading to an overall Co :Fe ratio of 1:2 as required for spinel crystallization.

A new (Ba, Ca) (Ti, Zr)O3 based multiferroic composite with large magnetoelectric effect.

The lead-free ferroelectric 0.5Ba(Zr0.2Ti0.

Molecular Design for Tailoring a Single-Source Precursor for Bismuth Ferrite.

Nearly phase-pure bismuth ferrite particles were formed by thermolysis of the single-source precursor [Cp(CO)2FeBi(OAc)2] (1) in octadecene at 245 °C, followed by subsequent calcination at 600 °C for 3 h. In contrast, the slightly modified compound [Cp(CO)2FeBi(O2C(t)Bu)2] (2) yielded only mixtures of different bismuth oxide phases, revealing the distinctive influence of molecular design in material synthesis. The chemical composition, morphology, and crystallinity of the resulting materials were investigated by X-ray diffraction, transmission electron microscopy, and energy-dispersive X-ray spectroscopy.