Self-construction of Magnetic Hollow La_0.7Sr_0.3MnO₃ Microspheres with Complex Units

Perovskite structure La_0.7Sr_0.3MnO₃ magnetic hollow microspheres with complex units were prepared via the hydrothermal route without hard and soft templates. The formation of hollow microspheres follows the self-construction mechanism involving oriented attachment, dissolution, and recrystallization processes. It exhibits a ferromagnetic behavior at room temperature

Hydrothermal Growth of Centimeter-Scale CuO Plates: Planar Chromium(III) Oligomer as a Facet-Directing Agent

In this work, a simple hydrothermal method was developed to synthesize CuO plates in centimeter scale for the first time. Plates of up to 20 μm thickness and several square millimeters in area have been prepared. The unusual size was obtained under ultrahigh-concentration NaOH and a planar chromium­(III) oligomer, which served as a new kind of inorganic facet-directing agent. The obtained CuO plates were glossy black, free-standing, and crack-free. The chromium­(III) oligomer offered ideal chemically active sites for adsorbing and confining Cu²⁺ ions. They could be adsorbed on the surface of Cu­(OH)₄^2– clusters via hydrogen-bonding interaction, which thus modified the growth orientation. The as-synthesized centimeter-scale CuO plates could possibly serve as substrates and electronic materials with potential applications

Hydrothermal Synthesis of 1‑Butanol from Ethanol Catalyzed with Commercial Cobalt Powder

We reported a highly efficient conversion of ethanol to 1-butanol under hydrothermal conditions with commercial cobalt (Co) metal powder as a recyclable and inexpensive catalyst. The possible reaction pathways were explored. Moreover, it has been found that sodium bicarbonate is better than sodium hydroxide for the Guerbet reaction because the former led to less corrosion of reaction vessels and blocked the oxidation of the ethanol to acetic acid

Synthesis, Structures, and Magnetic Properties of Three Fluoride-Bridged Lanthanide Compounds: Effect of Bridging Fluoride Ions on Magnetic Behaviors

A family of fluoride-bridged lanthanide compounds, [Dy^IIIF­(oda)­(H₂O)₃] (<b>1</b>,<b> oda =</b> oxidiacetate) and [Ln^III₂F₂(oda)₂(H₂O)₂] (Ln = Tb­(<b>2</b>) and Dy­(<b>3</b>)), was synthesized and characterized. To investigate the effects of bridging ligands on magnetic behaviors, two hydroxyl-bridged complexes of formulas [Ln^III₂(OH)₂(oda)₂(H₂O)₄] (Ln = Tb­(<b>4</b>) and Dy­(<b>5</b>)) were also synthesized. Magnetic measurements show that the magnetic behaviors of the compounds are obviously distinct. Compounds <b>1</b>,<b> 2</b>, and <b>3</b> show ferromagnetic interactions, while only antiferromagnetic interactions are observed in compounds <b>4</b> and <b>5</b>. Among these compounds, <b>1</b> and <b>3</b> show frequency-dependent ac-susceptibility indicative of slow magnetic relaxation. Because the structures of Dy₂ cores are very similar in compounds <b>3</b> and <b>5</b>, it may be inferred that the differences of bridging ligands are mainly responsible for the distinct magnetic exchange interactions and relaxation dynamics

Crystal Shape Tailoring in Perovskite Structure Rare-Earth Ferrites REFeO₃ (RE = La, Pr, Sm, Dy, Er, and Y) and Shape-Dependent Magnetic Properties of YFeO₃

Controllable growth of perovskite oxide with tailored shapes is challenging but promising for shape-dependent physical and chemical property studies and probable applications. In this article, we report a general method for tailoring the crystal shape of perovskite structure rare-earth ferrite (REFeO₃) crystals in hydrothermal conditions. By adjusting the ratio of KOH to urea, various shapes of REFeO₃ crystals can be prepared, such as LaFeO₃ truncated cubes, PrFeO₃ perpendicular cross prisms, SmFeO₃ crossed bars with trustum, DyFeO₃ double pyramids on cubes, ErFeO₃ distorted octahedrons, and YFeO₃ long bars and thick hexagonal elongated plates. Detailed shape tailoring conditions for each phase of the crystals have been discussed clearly. The structure-dependent shape growing mechanism for each REFeO₃ is generally discussed by consideration of the variance of reduced unit cell parameters in reference to the ideal cubic ABO₃ perovskite structure. DyFeO₃ was taken as an example to elucidate the crystal shape formation mechanism based on the Bravais–Friedel–Donnay–Harker theory. The magnetic property of the YFeO₃ crystal shows shape dependence: elongated bars have the highest saturated magnetization, while the lowest coercive field, while the tailored polyhedrons are vice versa. This paper not only builds a general technique for tailoring the crystal shape to various shapes of REFeO₃ crystals but also provides many crystals for further study and application of anisotropy either in physical or in chemical properties

δ‑MnO₂–Mn₃O₄ Nanocomposite for Photochemical Water Oxidation: Active Structure Stabilized in the Interface

Pure phase manganese oxides have been widely studied as water oxidation catalysts, but further improvement of their activities is much challenging. Herein, we report an effective method to improve the water oxidation activity by fabricating a nanocomposite of Mn₃O₄ and δ-MnO₂ with an active interface. The nanocomposite was achieved by a partial reduction approach which induced an in situ growth of Mn₃O₄ nanoparticles from the surface of δ-MnO₂ nanosheets. The optimum composition was determined to be 38% Mn₃O₄ and 62% δ-MnO₂ as confirmed by X-ray photoelectron spectra (XPS) and X-ray absorption spectra (XAS). The δ-MnO₂–Mn₃O₄ nanocomposite is a highly active water oxidation catalyst with a turnover frequency (TOF) of 0.93 s^–1, which is much higher than the individual components of δ-MnO₂ and Mn₃O₄. We consider that the enhanced water oxidation activity could be explained by the active interface between two components. At the phase interface, weak Mn–O bonds are introduced by lattice disorder in the transition of hausmannite phase to birnessite phase, which provides active sites for water oxidation catalysis. Our study illustrates a new view to improve water oxidation activity of manganese oxides

Two Metal–Organic Frameworks Constructed from One-Dimensional Cobalt(II) Ferrimagnetic Chains with Alternating Antiferromagnetic/Ferromagnetic and AF/AF/FM Interaction: Synthesis, Structures, and Magnetic Properties

Here, we report two three-dimensional metal–organic frameworks of formula [Co₂(4-ptz)₂(bpp)­(N₃)₂]_n (<b>1</b>) and [Co₃(OH)₂(bdt)₂(bpp)₂(H₂O)₂]_n (<b>2</b>), which were synthesized by hydrothermal reaction from the respective tetrazole ligand (5-(4-pyridyl)­tetrazole (4-H-ptz) for <b>1</b> and 5,5′-(1,4-phenylene)­bis­(1-<i>H</i>-tetrazole) (H₂bdt) for <b>2</b>), long and flexible pyridyl-containing ligand 1,3-bi­(4-pyridyl)­propane (bpp), NaN₃, and CoCl₂. Both <b>1</b> and <b>2</b> consist of well-isolated one-dimensional cobalt­(II) alternating chains further linked by the bpp and/or the tetrazole ligand, while their chain structures are totally different. The chains of <b>1</b> are formed by Co²⁺ ions bridged by single μ-EE-N₃ and triple (μ-EO-N₃)­(μ-tetrazole)₂ alternately, whereas the Co²⁺ ions are bridged by μ₃–OH to form Co₃(OH)₂ chains in compound <b>2</b>. Magnetic measurements demonstrate that compound <b>1</b> contains an alternating antiferromagnetic (AF)/ferromagnetic (FM) ferrimagnetic chain, while compound <b>2</b> exhibits the coexistence of spin canting, slow magnetic dynamics, and finite-size effect, with alternating AF/AF/FM ferrimagnetic chains

Porous Pt Nanotubes with High Methanol Oxidation Electrocatalytic Activity Based on Original Bamboo-Shaped Te Nanotubes

In this report, a facile and general strategy was developed to synthesize original bamboo-shaped Te nanotubes (NTs) with well-controlled size and morphology. On the basis of the as-prepared Te NTs, porous Pt nanotubes (NTs) with excellent property and structural stability have been designed and manufactured. Importantly, we avoided the use of surface stabilizing agents, which may affect the catalytic properties during the templated synthesis process. Furthermore, Pt NTs with different morphology were successfully prepared by tuning the experimental parameters. As a result, transmission electron microscopy (TEM) study shows that both Te NTs and Pt NTs have uniform size and morphology. Following cyclic voltammogram (CV) testing, the as-prepared porous Pt NTs and macroporous Pt NTs exhibited excellent catalytic activities toward electrochemical methanol oxidation reactions due to their tubiform structure with nanoporous framework. Thus, the as-prepared Pt NTs with specific porous structure hold potential usage as alternative anode catalysts for direct methanol fuel cells (DMFCs)

Histidine-Derived Nontoxic Nitrogen-Doped Carbon Dots for Sensing and Bioimaging Applications

Nitrogen-doped (N-doped) photoluminescent carbon dots (CDs) were prepared by a one-pot microwave-assisted hydrothermal treatment using histidine as the sole carbon source in the absence of acid, alkali, or metal ions. With a diameter of 2–5 nm, the synthesized CDs had apparent lattice fringes and exhibited an excitation-dependent photoluminescent behavior. The CDs were highly yielded, well-dispersed in aqueous solution, and showed high photostability in the solutions of a wide range of pH and salinity. They were used as probes to identify the presence of Fe³⁺ ions with a detection limit of 10 nM. With confirmed nontoxicity, these CDs could enter the cancer cells, indicating a practical potential for cellular imaging and labeling

Rational Design and Functionalization of a Zinc Metal–Organic Framework for Highly Selective Detection of 2,4,6-Trinitrophenol

To develop potential metal–organic frameworks (MOFs) for 2,4,6-trinitrophenol (TNP) detection, an amino-functionalized Zn-MOF, [NH₂(CH₃)₂]­[Zn₄O­(bpt)₂(bdc-NH₂)_0.5]·5DMF (where H₃bpt = biphenyl-3,4′,5-tricarboxylate, H₂bdc-NH₂ = 2-aminoterephthalic acid, and DMF = <i>N</i>,<i>N</i>-dimethylformamide), has been designed theoretically and synthesized experimentally. Its structure is composed of Zn₄O­(CO₂)₇ secondary building units linked by mixed ligands, exhibiting a three-dimensional framework. Fluorescence exploration revealed that the amino-functionalized Zn-MOF shows high selectivity and sensitivity for TNP, which agrees well with the predictions of theoretical simulations. This work provides a suitable means to develop new potential MOFs for TNP detection performance with a combination of experimental and theoretical perspectives