Polycationic disorder in [Bi6O4(OH)4](NO3)6: Structure determination using synchrotron radiation and microcrystal X-ray diffraction

Dimorphism of [Bi2O2(OH)](NO3) - the ordered Pna21 structure at 100 K

The re-investigation of [Bi2O2(OH)](NO3), dioxidodibismuth(III) hydroxide nitrate, on the basis of single-crystal X-ray diffraction data revealed an apparent structural phase transition of a crystal structure determined previously (space group Cmc21 at 173 K) to a crystal structure with lower symmetry (space group Pna21 at 100 K). The Cmc21 → Pna21 group-subgroup relationship between the two crystal structures is klassengleiche with index 2. In contrast to the crystal structure in Cmc21 with orientational disorder of the nitrate anion, disorder does not occur in the Pna21 structure. Apart from the disorder of the nitrate anion, the general structural set-up in the two crystal structures is very similar: [Bi2O2]2+ layers extend parallel to (001) and alternate with layers of (OH)- anions above and (NO3)- anions below the cationic layer. Whereas the (OH)- anion shows strong bonds to the BiIII cations, the (NO3)- anion weakly binds to the BiIII cations of the cationic layer. A rather weak O-H⋯O hydrogen-bonding inter-action between the (OH)- anion and the (NO3)- anion links adjacent sheets along [001].

Bismuth gallate coordination networks inspired by an active pharmaceutical ingredient

The effect of solvent has been investigated for the synthesis of bismuth gallate compounds, of which the water-based bismuth subgallate has been used as an active pharmaceutical ingredient (API) for...

Effects of Oxidizing/Reducing Agent Ratio on Phase Purity, Crystallinity, and Magnetic Behavior of Solution-Combustion-Grown BiFeO3 Submicroparticles

Fabrication of phase-pure well-crystalline BiFeO₃ submicroparticles in large scale is of great importance for the utilization of this rhombohedrally distorted perovskite material in applications such as memory storage and spintronic devices and visible photocatalyst for the degradation of organic pollutants. In fact, because of the narrow temperature range of phase stabilization, the fabrication of phase-pure BiFeO₃ in large scale remained elusive. We present the synthesis of phase-pure BiFeO₃ particles of submicrometric dimensions (246-330 nm average size) through the adjustment of oxidizing/reducing agent ratio in solution combustion process utilizing glycine as reducing agent and nitrate precursors as oxidizing agent. Utilizing X-ray diffraction and Raman spectroscopy, we demonstrate that the BiFeO₃ submicroparticles synthesized at equivalence ratio (Φ_e) close to 0.5 do not contain undesired impurities such as Bi₂Fe₄O₉ and Bi₂₄Fe₂O₃₉. Moreover, the submicroparticles are highly crystalline, possessing high room temperature magnetic moment and stable antiferromagnetic behavior across a wide temperature range. The superparamagnetic behavior at low magnetic field manifested by impurities attached to the BiFeO₃ submicroparticles might lead to their use as effective magnetically separable photocatalysts.

Synthesis and photocatalysis performances of bismuth oxynitrate photocatalysts with layered structures

A new type of layered oxy-acid salt of bismuth oxynitrate was synthesized by a simple hydrothermal method. The obtained bismuth oxy-nitrates consist of a Bi2O2(2+) layered module inserted into the interlamellar anion modules of NO3(-) and OH(-). Varying amounts of NO3(-) and OH(-) complexes on the surface of the bismuth oxynitrate were also obtained by adjusting the precursor pH before hydrothermal treatment. It was found that the sample prepared with the precursor pH = 5.00 presented the highest photocatalytic activity, with a rate constant of 0.05 min(-1), which is 2 and 6.7 times higher than those presented by the samples with the precursor pH = 7.00 and 1.22, respectively. The largest cathodic to anodic photocurrent switching was also presented by the sample with the precursor pH = 5.00, which can be reasonably attributed to NO3(-) complexes on the surface of the bismuth oxynitrate. The NO3(-) complexes could efficiently migrate the photo-induced holes to the surface of the semiconductor.

A facile strategy to adjust the density of planar triangle units in lead borate–nitrates

Three novel lead(ii) borate–nitrates were obtained through a facile hydrothermal reaction by adjusting the concentrations of the starting materials.

Discovery of a new crystalline phase: BiGeO2(OH)2(NO3)

A new crystalline phase, BiGeO₂(OH)₂(NO₃), has been synthesized from a homogeneous aqueous solution. This new phase is found to possess a layered structure consisting of BiO₆polyhedra, GeO₅trigonal bipyramids and nitrate ions.

Easy synthesis of high-purity BiFeO3 nanoparticles: new insights derived from the structural, optical, and magnetic characterization

Synthesis of high-purity BiFeO3 is very important for practical applications. This task has been very challenging for the scientific community because nonstoichiometric Bi(x)Fe(y)O(z) species typically appear as byproducts in most of the synthesis routes. In the present work, we outline the synthesis of BiFeO3 nanostructures by a combustion reaction, employing tartaric acid or glycine as promoter. When glycine is used, a porous BiFeO3 network composed of tightly assembled and sintered nanocrystallites is obtained. The origin of high purity BiFeO3 nanomaterial as well as the formation of other byproducts is explained on the basis of metal-ligand interactions. Structural, morphological, and optical analysis of the intermediate that preceded the formation of porous BiFeO3 structures was accomplished. The thorough characterization of BiFeO3 nanoparticles (NPs) included powder X-ray diffraction (XRD); scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM); thermogravimetric analysis (TGA); UV-vis electronic absorption (diffuse reflectance mode), Raman scattering, Mössbauer, and electron paramagnetic resonance (EPR) spectroscopies; and vibrating sample magnetometry (VSM). The byproducts like β-Bi2O3 and 5 nm Bi2Fe4O9 NPs were obtained when tartaric acid was the promoter. However, no such byproducts were formed using glycine in the synthesis process. The average sizes of the crystallites for BiFeO3 were 26 and 23 nm, for tartaric acid and glycine promoters, respectively. Two band gap energies, 2.27 and 1.66 eV, were found for BiFeO3 synthesized with tartaric acid, obtained from Tauc's plots. A remarkable selective enhancement in the intensity of the BiFeO3 A1 mode, as a consequence of the resonance Raman effect, was observed and discussed for the first time in this work. For glycine-promoted BiFeO3 nanostructures, the measured magnetization (M) value at 20,000 Oe (0.64 emu g(-1)) was ∼5 times lower than that obtained using tartaric acid. The difference between the M values has been associated with the different morphologies of the BiFeO3 nanostructures.

Bismuth hexagons: facile mass synthesis, stability and applications

A unique direct electrodeposition technique involving very high current densities, high voltages and high electrolyte concentrations is applied for highly selective mass synthesis of stable, isolable, surfactant-free, single-crystalline Bi hexagons on a Cu wire at room temperature. A formation mechanism of the hexagons is proposed. The morphology, phase purity, and crystallinity of the material are well characterized by FESEM, AFM, TEM, SAED, EDX, XRD, and Raman spectroscopy. The thermal stability of the material under intense electron beam and intense laser light irradiation is studied. The chemical stability of elemental Bi in nitric acid shows different dissolution rates for different morphologies. This effect enables a second way for the selective fabrication of Bi hexagons. Bi hexagons can be oxidized exclusively to α-Bi(2)O(3) hexagons. The Bi hexagons are found to be promising for thermoelectric applications. They are also catalytically active, inducing the reduction of 4-nitrophenol to 4-aminophenol. This electrodeposition methodology has also been demonstrated to be applicable for synthesis of bismuth-based bimetallic hybrid composites for advanced applications.