Growth and Structure of Single-Crystal ZnO Nanorods Codoped with Fe and Li for Multiferroic Applications

ZnO nanorods codoped with Fe, Li (ZnO:Fe,Li) with a diameter of 50–100 nm and a length of 0.5–5 μm were obtained by thermal growth from salt mixtures. The HAADF-STEM, EDX, and AAS analysis showed that the nanorods grew in the [001] direction as single crystals with a wurtzite structure and contain 2.05% Fe and 1.95% Li. A detailed study of ZnO:Fe,Li nanorods using X-ray diffraction, X-ray absorption, Mössbauer spectroscopy, and cathodoluminescence spectroscopy revealed the incorporation of Fe and Li atoms into the nanocrystal lattice, which can lead to ferroelectric behavior of ZnO multiferroic structures, usually fabricated by codoping with transition metals and lithium

Solution Processing of Methylammonium Lead Iodide Perovskite from γ‑Butyrolactone: Crystallization Mediated by Solvation Equilibrium

The chemical origin of solvents typically used for preparation of hybrid lead halide perovskitesdimethyl sulfoxide (DMSO), dimethylformamide (DMF), and γ-butyrolactone (GBL)strongly influences the process of perovskite crystallization because of the formation of intermediate adducts with different structures and morphology. The composition and crystal structures of the adducts depend on the coordination and binding ability of the solvents and the ratio of the precursors. New adducts of perovskite and GBL with either an unusual cluster structure, (MA)₈(GBL)_<i>x</i>[Pb₁₈I₄₄], or an adduct, (MA)₂(GBL)₂Pb₃I₈, similar to those observed for DMF and DMSO are described for the first time. Complex equilibriums between chemical species existing in perovskite solutions are revealed by Raman spectroscopy. As a result, new features of the perovskite crystallization through intermediate adduct phases are discussed, and effective perovskite deposition pathways are suggested

Solution Processing of Methylammonium Lead Iodide Perovskite from γ‑Butyrolactone: Crystallization Mediated by Solvation Equilibrium

The chemical origin of solvents typically used for preparation of hybrid lead halide perovskitesdimethyl sulfoxide (DMSO), dimethylformamide (DMF), and γ-butyrolactone (GBL)strongly influences the process of perovskite crystallization because of the formation of intermediate adducts with different structures and morphology. The composition and crystal structures of the adducts depend on the coordination and binding ability of the solvents and the ratio of the precursors. New adducts of perovskite and GBL with either an unusual cluster structure, (MA)₈(GBL)_<i>x</i>[Pb₁₈I₄₄], or an adduct, (MA)₂(GBL)₂Pb₃I₈, similar to those observed for DMF and DMSO are described for the first time. Complex equilibriums between chemical species existing in perovskite solutions are revealed by Raman spectroscopy. As a result, new features of the perovskite crystallization through intermediate adduct phases are discussed, and effective perovskite deposition pathways are suggested

Cobalt-Based Single-Ion Magnets on an Apatite Lattice: Toward Patterned Arrays for Magnetic Memories

Single-ion magnets (SIMs) that can maintain magnetization direction on an individual transition metal atom represent the smallest atomic-scale units for future magnetic data storage devices and molecular electronics. Here we present a robust extended inorganic solid hosting efficient SIM centers, as an alternative to molecular SIM crystals. We show that unique dioxocobaltate­(II) ions, confined in the channels of strontium hydroxyapatite, exhibit classical SIM features with a large energy barrier for magnetization reversal (<i>U</i>_eff) of 51–59 cm^–1. The samples have been tuned such that a magnetization hysteresis opens below 8 K and <i>U</i>_eff increases by a factor of 4 and can be further enhanced to the highest values among 3d metal complexes of 275 cm^–1 when Ba is substituted for Sr. The SIM properties are preserved without any tendency toward spin ordering up to a high Co concentration. At a maximal Co content, a hypothetical regular hexagonal grid of SIMs with a 1 nm interspacing on the (001) crystal facet would allow a maximal magnetic recording density of 10⁵ Gb/cm²

Solution Processing of Methylammonium Lead Iodide Perovskite from γ‑Butyrolactone: Crystallization Mediated by Solvation Equilibrium

The chemical origin of solvents typically used for preparation of hybrid lead halide perovskitesdimethyl sulfoxide (DMSO), dimethylformamide (DMF), and γ-butyrolactone (GBL)strongly influences the process of perovskite crystallization because of the formation of intermediate adducts with different structures and morphology. The composition and crystal structures of the adducts depend on the coordination and binding ability of the solvents and the ratio of the precursors. New adducts of perovskite and GBL with either an unusual cluster structure, (MA)₈(GBL)_<i>x</i>[Pb₁₈I₄₄], or an adduct, (MA)₂(GBL)₂Pb₃I₈, similar to those observed for DMF and DMSO are described for the first time. Complex equilibriums between chemical species existing in perovskite solutions are revealed by Raman spectroscopy. As a result, new features of the perovskite crystallization through intermediate adduct phases are discussed, and effective perovskite deposition pathways are suggested

Solution Processing of Methylammonium Lead Iodide Perovskite from γ‑Butyrolactone: Crystallization Mediated by Solvation Equilibrium

The chemical origin of solvents typically used for preparation of hybrid lead halide perovskitesdimethyl sulfoxide (DMSO), dimethylformamide (DMF), and γ-butyrolactone (GBL)strongly influences the process of perovskite crystallization because of the formation of intermediate adducts with different structures and morphology. The composition and crystal structures of the adducts depend on the coordination and binding ability of the solvents and the ratio of the precursors. New adducts of perovskite and GBL with either an unusual cluster structure, (MA)₈(GBL)_<i>x</i>[Pb₁₈I₄₄], or an adduct, (MA)₂(GBL)₂Pb₃I₈, similar to those observed for DMF and DMSO are described for the first time. Complex equilibriums between chemical species existing in perovskite solutions are revealed by Raman spectroscopy. As a result, new features of the perovskite crystallization through intermediate adduct phases are discussed, and effective perovskite deposition pathways are suggested

Cobalt-Based Single-Ion Magnets on an Apatite Lattice: Toward Patterned Arrays for Magnetic Memories

Single-ion magnets (SIMs) that can maintain magnetization direction on an individual transition metal atom represent the smallest atomic-scale units for future magnetic data storage devices and molecular electronics. Here we present a robust extended inorganic solid hosting efficient SIM centers, as an alternative to molecular SIM crystals. We show that unique dioxocobaltate­(II) ions, confined in the channels of strontium hydroxyapatite, exhibit classical SIM features with a large energy barrier for magnetization reversal (<i>U</i>_eff) of 51–59 cm^–1. The samples have been tuned such that a magnetization hysteresis opens below 8 K and <i>U</i>_eff increases by a factor of 4 and can be further enhanced to the highest values among 3d metal complexes of 275 cm^–1 when Ba is substituted for Sr. The SIM properties are preserved without any tendency toward spin ordering up to a high Co concentration. At a maximal Co content, a hypothetical regular hexagonal grid of SIMs with a 1 nm interspacing on the (001) crystal facet would allow a maximal magnetic recording density of 10⁵ Gb/cm²

Highly Flexible Molecule “Chameleon”: Reversible Thermochromism and Phase Transitions in Solid Copper(II) Diiminate Cu[CF₃C(NH)CFC(NH)CF₃]₂

Three thermochromic phases (α, green; β, red; γ, yellow) and six polymorphic modifications (α₁, monoclinic, <i>P</i>2₁/<i>n</i>, <i>Z</i> = 2; β₁, monoclinic, <i>P</i>2₁/<i>c</i>, <i>Z</i> = 4; β₂, triclinic, <i>P</i>1̅, <i>Z</i> = 4; β₃, monoclinic, <i>P</i>2₁/<i>n</i>, <i>Z</i> = 4; γ₁ and γ₂, tetragonal, <i>P</i>4₂/<i>n</i>, <i>Z</i> = 4) have been found and structurally characterized for copper­(II) diiminate Cu­[CF₃C­(NH)CFC­(NH)CF₃]₂ (<b>1</b>). The α phase is stable under normal conditions, whereas the high-temperature β and γ phases are metastable at room temperature and transform slowly into the more stable α phase over several days or even weeks. X-ray diffraction study revealed that the title molecules adopt different conformations in the α, β, and γ phases, namely, staircase-like, twisted, and planar, respectively. The investigation of the α, β, and γ phases by differential scanning calorimetry showed that the three endothermic peaks in the range 283, 360, and 438 K are present on their thermograms upon heating/cooling. The two peaks at 283 and 360 K correspond to the solid–solid phase transitions, and the high-temperature peak at 438 K belongs to the melting process of <b>1</b>. The temperature and thermal effect of all the observed transitions depend on the prehistory of the crystalline sample obtained. A reversible thermochromic single-crystal-to-single-crystal α₁⇌β₁ phase transition occurring within a temperature interval of 353–358 K can be directly observed using a CCD video camera of the X-ray diffractometer. A series of other solid–solid α₁→γ₁, β₂→γ₁, β₃→γ₁, and γ₁⇌γ₂ phase transitions can be triggered in <b>1</b> by temperature. It has been suggested that, under equilibrium conditions, the α₁→γ₁ and β₂→γ₁ phase transitions should proceed stepwise through the α₁→β₁→β₂→β₃→γ₁ and β₂→β₃→γ₁ stages, respectively. The mechanism of the phase transitions is discussed on the basis of experimental and theoretical data

Mild and Regioselective Hydroxylation of Methyl Group in Neocuproine: Approach to an N,O-Ligated Cu₆ Cage Phenylsilsesquioxane

The self-assembly synthesis of Cu­(II)-silsesquioxane involving 2,9-dimethyl-1,10-phenanthroline (neocuproine) as an additional N ligand at copper atoms was performed. The reaction revealed an unprecedented aerobic hydroxylation of only one of the two methyl groups in neocuproine to afford the corresponding geminal diol. The produced derivative of oxidized neocuproine acts as a two-centered N,O ligand in the assembly of the hexacopper cage product [Cu₆(Ph₅Si₅O₁₀)₂·(C₁₄H₁₁N₂O₂)₂] (<b>1</b>), coordinating two of the six copper centers in the product. Two siloxanolate ligands [PhSi­(O)­O]₅ in the cis configuration coordinate to the rest of the copper­(II) ions. Compound <b>1</b> is a highly efficient homogeneous precatalyst in the oxidation of alkanes and alcohols with peroxides

Nanocrystallinity as a Route to Metastable Phases: Rock Salt ZnO

A synthesis route to rock salt zinc oxide (<i>rs</i>-ZnO), high-pressure phase metastable at ambient conditions, has been developed. High-purity bulk nanocrystalline <i>rs</i>-ZnO has been synthesized from wurtzite (<i>w</i>) ZnO nanopowders at 7.7 GPa and 770–820 K and, for the first time, recovered at normal conditions. Structure, phase composition, and thermal phase stability of recovered <i>rs</i>-ZnO have been studied by synchrotron X-ray powder diffraction and X-ray absorption spectroscopy (XANES and EXAFS) at ambient pressure. Phase purity of <i>rs</i>-ZnO was achieved by usage of <i>w</i>-ZnO nanoparticles with a narrow size distribution as a pristine material synthesized by various chemical methods. At ambient pressure, <i>rs</i>-ZnO could be stable up to 360 K. The optical properties of <i>rs</i>-ZnO have been studied by conventional cathodoluminescence in high vacuum at room and liquid-nitrogen temperatures. The nanocrystalline <i>rs</i>-ZnO at 300 and 77 K has shown bright blue luminescence at 2.42 and 2.56 eV, respectively