A novel electrochemical deposition route for the preparation of Zn1−xCdxO nanorods with controllable optical properties

Here we explored a novel and facile electrochemical route for the preparation of Zn_1?xCd_xO (x is atomic percentage of Cd) nanorods with controllable optical properties. The Zn_1?xCd_xO nanorods can be routinely obtained when the electrochemical deposition was carried out in solution of Zn(NO₃)₂ + Cd(NO₃)₂ + citric acid at ?1.0 V (vs SCE). EDS results demonstrated that Cd, Zn, and O elements existed in the deposits, and ternary Zn_1?xCd_xO compounds were obtained. XRD results showed that Zn_1?xCd_xO nanorods were pure ZnO wurtzite structures. HRTEM and SAED analyses confirmed that Zn_1?xCd_xO nanorods were single-crystalline. The optical properties of Zn_1?xCd_xO nanorods were investigated in this paper.     

Mesoporous TiO2−xAy (A = N,S) as a visible-light-response photocatalyst

Mesoporous TiO_2?xA_y (A = N, S) thin films were fabricated using thiourea as a doping resource by a combination of sol-gel and evaporation-induced self-assembly (EISA) processes. The results showed that thiourea could serve two functions of co-doping nitrogen and sulfur and changing the mesoporous structure of TiO₂ thin films. The resultant mesoporous TiO_2?xA_y (A = N, S) exhibited anatase framework with a high porosity and a narrow pore distribution. The formation of the O–Ti–N and O–Ti–S bonds in the mesoporous TiO_2?xA_y (A = N, S) were substantiated by the XPS spectra. A new bandgap in visible light region (520 nm) corresponding to 2.38 eV could be formed by the co-doping. After being illuminated for 3 h, methyl orange could be degraded nearly completely by the co-doped sample under both ultraviolet irradiation and visible light illumination. While pure mesoporous TiO₂ could only degrade 60% methyl orange under UV illumination and showed negligible photodegradation capability in the visible light range. Furthermore, the photo-induced hydrophilic activity of TiO₂ film was improved by the co-doping. The mesoporous microstructure and high visible light absorption could be attributed to their good photocatalytic acitivity and hydrophilicity.     

A family of porous magnets, [M3(HCOO)6] (M = Mn,Fe, Co and Ni)

A family of porous magnets of [M₃(HCOO)₆] (M = Mn, Fe, Co and Ni) with open diamond framework based on M-centred MM₄ tetrahedral nodes, can be prepared by conventional solution chemistry method. They display permanent porosity, stability for thermal treatment, guest removal, and guest inclusion for a wide spectrum of both polar and non-polar guests of different size. The porous magnets show 3D long-range magnetic ordering and guest-modulated magnetic properties due to the subtle structure change of the magnetic framework that conforms to the guests and the nature of host–guest interaction. The dilution of [Fe₃(HCOO)₆] framework by diamagnetic zinc ion results in a mixed-metal porous [Fe_xZn_3−x(HCOO)₆] series showing gradual evolution from 3D long-range ordering to spin glass then superparamagnet and finally paramagnet.     

The effect of transition metals on the structure of h-BN intercalation compounds

In this study, hexagonal boron nitride (h-BN) were synthesized by the modified O’Connor method in the presence of various metal nitrates [M(NO₃)_x, M=Cr, Mn, Fe, Co, Ni, Cu, Zn, and Ag]. The composites were analyzed by FTIR, XRF, XRD, and SEM techniques. XRD results indicated a change in the interlayer spacing due to the intercalation of Cr, Mn, Fe and Ag. SEM analyses illustrated the grain growth upon metal intercalation even at a temperature of 1320 K.     

Copper,cobalt and manganese: Modified hydrotalcite materials as catalysts for the selective catalytic reduction of NO with ammonia. The influence of manganese concentration

Hydrotalcites containing Cu, Co and Mn with varying manganese contents were prepared by co-precipitation. Manganese was also introduced into the catalysts via adsorption of an Mn–EDTA complex from an aqueous solution. The obtained samples were characterized by room- and high-temperature XRD, low-temperature nitrogen sorption, and FT–IR. Calcination of the catalysts at 500 °C resulted in the formation of mixed oxides with specific surface areas of 166–187 m²/g. The calcined samples were tested as catalysts for selective catalytic reduction of NO_x with ammonia. It was found that the Mn content strongly influences the product selectivity in SCR–NH₃. Mn–EDTA modified samples exhibited higher selectivity towards N₂ than Mn hydrotalcites obtained by the co-precipitation method. A hydrotalcite sample containing 5.4 wt% of manganese showed the highest catalytic activity and the lowest selectivity to N₂ at the same time.     

Structural and optical properties of sprayed Zn1−xMnxO films

In recent years the dilute magnetic semiconductors have received much attention due to the complementary properties of semiconductor and ferromagnetic behaviour. Zn_1−xMn_xO thin films have been synthesized by chemical spray pyrolysis at a substrate temperature of 400 °C with different manganese compositions that vary in the range, 0.0 ≤ x ≤ 0.25, on Corning 7059 glass substrates. The X-ray diffraction studies revealed that all the films were strongly oriented along the (002) orientation corresponding to the hexagonal wurtzite structure. The crystalline quality of the layers was found to decrease with the increase of x, however, no structural changes were observed over the ‘Mn’ composition range investigated. The optical absorption studies revealed that the energy band gap of the films followed the Vegard's law. The optical band gap of the films prepared at x = 0.15 was found to be ∼3.35 eV. The photoluminescence characteristics of Zn_1−xMn_xO films showed an emission peak at around 390 nm with a broad band about 530 nm. The details of these results were reported and discussed.     

Chimie douce preparation of CuxZn3−xV2O7(OH)2·yH2O isostructural to trigonal zinc pyrovanadate

New Cu_xZn_3−xV₂O₇(OH)₂·yH₂O (0 < x ≤ 1.5) isostructural to zinc pyrovanadate Zn₃V₂O₇(OH)₂·2H₂O, were successfully prepared by using a chimie douce technique. The method consists in mixing zinc nitrate and copper nitrate with a boiling solution of vanadium oxide (obtained by reacting V₂O₅ with few millilitres of 30 vol.% H₂O₂ followed by addition of distilled water). When ammonium hydroxide NH₄OH 10% was added (pH ≈ 6), a precipitate was obtained. Using powder X-ray diffraction data, the crystal structures of as-prepared samples were determined by Rietveld refinement. Copper substitutes zinc in the zinc pyrovanadate lattice and is found to introduce distortion in the structure, which is mainly due to the Jahn–Teller effect. Distortion becomes more pronounced when the amount of copper is increased. This restricts the amount of copper which can be incorporated in the hexagonal zinc pyrovanadate lattice.     

Coordination polymers incorporating copper(II) and manganese(II) centers bridged by pyridinedicarboxylate ligands: Structure and magnetism

Two heterobimetallic coordination polymers, [Cu(2,4-pydc)₂Mn(H₂O)₄]_x (1) and [Cu(2,5-pydc)₂Mn(H₂O)₂]_x · 4xH₂O (2), have been synthesized and structurally characterized by single crystal X-ray diffraction. Both compounds have extended 2-D sheet structures. In 1 the copper centers are linked in chains by double ligand bridges and these chains are cross-linked through the manganese coordination spheres and O–C–O bridges to form polymeric sheets. In 2 separate O–C–O bridged Cu and Mn chains are connected in an alternating array by additional ligand bridging to generate the overall 2-D structure. Analysis of magnetic data of 1 reveals that ferromagnetic exchange between the O–C–O bridged copper and manganese centers dominates the magnetic properties of this system. The magnetic data for 2 fit well to a model incorporating antiferromagnetic exchange in independent S = 1/2 and S = 5/2 linear chains with J(Cu) = −0.073 cm⁻¹ and J(Mn) = −0.32 cm⁻¹. Unlike the situation in 1, there is no evidence for heterometallic exchange. In both 1 and 2 the significant exchange occurs via O–C–O bridges. To study the effect of thermal dehydration on the magnetic properties of these systems, the compounds Cu(2,4-pydc)₂Mn · H₂O (1d) and Cu(2,5-pydc)₂Mn · H₂O (2d) were synthesized and studied.     

Synthesis and characterization of three Cu(II), Zn(II), Cd(II) supramolecular complexes bridged by biphenyl 2,2′-dicarboxylate

Three complexes, M₂(bpy)₂(bpdc)₂·xH₂O [M = Cu, x = 0; M = Zn or Cd, x = 2], have been hydrothermally synthesized by 1,1′-biphenyl-2,2′-dicarboxylic acid (H₂bpdc) with 2,2′-bipyridine (bpy) to form binuclear molecules. In each, the two bpdc groups align the two opposing planar [M(bpy)]²⁺ cations. The molecules are connected by C–H⋯O hydrogen bonds, π–π stacking, and C–H⋯π interactions to form three dimensional supramolecular networks. Furthermore, at room temperature, complex 3 exhibits strong photoluminescence.     

Synthesis and spectroscopic characterization of new tetradentate Schiff base and its coordination compounds of NOON donor atoms and their antibacterial and antifungal activity

New Schiff base (H₂L) ligand is prepared via condensation of o-phthaldehyde and 2-aminobenzoic acid in 1:2 ratio. Metal complexes are prepared and characterized using elemental analyses, IR, solid reflectance, magnetic moment, molar conductance, ¹H NMR, ESR and thermal analysis (TGA). From the elemental analyses data, the complexes were proposed to have the general formulae [MCl(L)(H₂O)]·2H₂O (where M = Cr(III) and Fe(III)); [M(L)]·yH₂O (where M = Mn(II), Ni(II), Cu(II) and Zn(II), y = 1–2) and [M(L)(H₂O)_n]·yH₂O (where M = Co(II) (n = y = 2), Co(II) (n = y = 1), Ni(II) (n = 2, y = 1). The molar conductance data reveal that all the metal chelates were non-electrolytes. IR spectra show that H₂L is coordinated to the metal ions in a bi-negative tetradentate manner with NOON donor sites of the azomethine-N and carboxylate-O. The ¹H NMR spectral data indicate that the two carboxylate protons are also displaced during complexation. From the magnetic and solid reflectance spectra, it was found that the geometrical structure of these complexes are octahedral (Cr(III), Fe(III), Co(II) and Ni(II)), square planar (Cu(II)), trigonal bipyramidal (Co(II)) and tetrahedral (Mn(II), Ni(II) and Zn(II)). The thermal behaviour of these chelates showed that the hydrated complexes losses water molecules of hydration in the first step followed immediately by decomposition of the ligand molecule in the subsequent steps. The biological activity data show that the metal complexes to be more potent/antibacterial than the parent Shciff base ligand against one or more bacterial species.     

Metal complexes of gliclazide: Preparation,spectroscopic and thermal characterization. Biological potential study of sulphonylurea gliclazide on the house fly,Musca domestica (Diptera – Muscidae)

Metal complexes of gliclazide (GLZ; HL) drug are prepared and characterized based on elemental analyses, IR, diffused reflectance, magnetic moment, molar conductance and thermal analyses (TG and DTG) technique. From the elemental analyses data, the complexes are proposed to have the general formulae [M(HL)Cl₃(H₂O)]·3H₂O (M = Cr(III) and Fe(III)), [M(HL)Cl₂(H₂O)₂]·yH₂O (M = Co(III), Ni(II) and Cu(II), y = 0–2) and [M(HL)Cl₂]·yH₂O (M = Mn(II) and Zn(II), y = 0–1). The molar conductance data reveal that all the metal chelates are non-electrolytes. IR spectra show that GLZ is coordinated to the metal ions in a neutral bidentate manner with ON donor sites of the amide-O and sulphonamide-OH. From the magnetic and solid reflectance spectra, it is found that the geometrical structures of these complexes are octahedral (Cr(III), Fe(III), Co(II), Ni(II) and Cu(II)) and tetrahedral (Mn(II) and Zn(II)). The thermal behaviour of these chelates is studied using thermogravimetric analysis (TG and DTG) techniques. The results obtained show that the hydrated complexes lose water molecules of hydration followed immediately by decomposition of the anions and ligand molecules in the successive unseparate steps. The activation thermodynamic parameters are calculated using Coats–Redfern method. The GLZ drug, in comparison to its metal complexes also is screened for their biological activity against house fly, Musca domestica (Diptera – Muscidae). Dose of 5 μg/insect of gliclazide is typically applied against 3 days-old larval instar of M. domestica. Survival of pupal and adult stages has been affected by the complexes of gliclazide more than larval instars. Morphogenic abnormalities of larvae, pupae and adults are studied. On the other hand, pupation and adult emergence program is deteriorated by the effect of different chemicals.     

Solid solutions: An efficient way to control the temperature of spin transition in heterospin crystals MxCu1 − x(hfac)2L (M = Mn,Ni, Co; L = nitronyl nitroxide)

A series of mixed-metal solid solutions M_xCu_1 − x(hfac)₂L (M = Mn, Ni, and Co) liable to undergo thermally induced spin transitions have been synthesized. The structure and magnetic properties of the compounds have been investigated. By varying the metal to be incorporated in the complex (Mn, Ni, or Co) and the value of x, one can control the character of the magnetic anomaly.     

Synthesis and characterization of A-site deficient rare-earth doped BaZrxTi1−xO3 perovskite-type compounds

A-site deficient rare-earth doped BaZr_xTi_1?xO₃ (BZT) ceramics were prepared from a soft-chemistry route and by solid-state reaction (SSR). Perovskite-like single-phase diagrams for the BaTiO₃–La_2/3TiO₃–BaZrO₃ system were constructed for each method of synthesis. Infrared spectroscopy on (Ba_1?yLa_2y/3)Zr_xTi_1?xO₃ solid solution revealed a dramatic stress on the M–O (M = Ti, Zr) bonds due to the combined effect of A-site vacancies and the lower ionic radius of La³⁺ than that of Ba²⁺. A relationship between the M–O stretching vibration (υ) and the tolerance factor (t) was determined. (Ba_1?yLn_2y/3)Zr_0.09Ti_0.91O₃ (Ln = La, Pr, Nd) samples synthesized by SSR were selected for detailed studies. X-ray diffraction data were refined by the Rietveld method. Scanning electron microscopy on sintered compacts detected abnormal crystal growth and grain sizes in the range of about 1 μm up to 10 μm when the dopant concentration is 6.7 at. %. Impedance measurements exhibited that ferroelectric to paraelectric phase-transition temperature shifted to lower values as increasing rare-earth content. (Ba_1?yLn_2y/3)Zr_0.09Ti_0.91O₃ system showed a diffuse phase transition with a relaxor-like ferroelectric behaviour. Furthermore, the dielectric constant was enhanced with respect to non-doped BZT system.     

Preparation and photocatalytic activity of visible light-active sulfur and nitrogen co-doped SrTiO3

Nitrogen and sulfur co-doped SrTiO₃ was prepared by high energy grinding of the mixture of SrTiO₃ and thiourea. A new band gap in visible light region (522 nm) corresponding to 2.37 eV could be formed by the co-doping. The photocatalytic activity for nitrogen monoxide oxidation of SrTiO₃ in visible light region especially in the long wavelength range (λ > 510 nm) could be improved greatly. Under the irradiation of light with wavelength larger than 510 nm, the photocatalytic activity of nitrogen and sulfur co-doped SrTiO₃ was 10.9 times greater than that of pure SrTiO₃. The high visible light photocatalytic activity of this substance may be due to the formation of a new band gap that enables to absorb visible light effectively.     

Structural investigation of the Zn1−xCdxSb solid solution by density-functional theory approach

A peculiar behaviour was already reported in literature from experimental investigations in the Zn_1?xCd_xSb solid solution around x = 0.5. This behaviour was assumed to be linked to an ordering in the phase; however this assumption was never confirmed. The aim of this work was to understand this behaviour from a theoretical point of view. DFT calculations were performed to calculate the energy and the lattice parameters for all the possible structures of Zn_1?xCd_xSb with several compositions (x = 0.125, 0.25, 0.375, 0.5, 0.625, 0.75, 0.875, 1.0). The results show that an ordering appears in the most stable structure for x = 0.5. This ordering consists in stacked planes each containing only one chemical species.     

Structural,morphological and magnetic properties of nano-crystalline zinc substituted cobalt ferrite system

Nano-crystalline zinc-substituted cobalt ferrite powders, Co_1−xZn_xFe₂O₄ (x = 0, 0.25, 0.5, 0.75 and 1), have been synthesized by the combustion route. The structural, morphological and magnetic properties of the products were determined and characterized in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and vibrating sample magnetometer (VSM). X-ray analysis showed that the samples were cubic spinel. The increase in zinc concentration resulted in an increase in the lattice constant, unit cell volume, X-ray density, ionic radii, the distance between the magnetic ions and bond lengths on tetrahedral sites and octahedral sites of cubic spinel structure. Opposite behavior was observed for the average crystallite size of the as synthesized solids. The variation of saturation magnetization (M_s) value of the samples was studied. The maximum saturation magnetization value of the Co_o.25Zn_0.75Fe₂O₄ sample reached 76.87 emu/g. The high saturation magnetization of these samples suggests that this method is suitable for preparing high-quality nano-crystalline magnetic ferrites for practical applications.     

Photocatalytic activity of nitrogen and copper doped TiO2 nanoparticles prepared by microwave-assisted sol-gel process

Cu and N-doped TiO₂ photocatalysts were synthesized from titanium (IV) isopropoxide via a microwave-assisted sol-gel method. The synthesized materials were characterized by X-ray diffraction, UV-vis diffuse reflectance, photoluminescence (PL) spectroscopy, SEM, TEM, FT-IR, Raman spectroscopy, photocurrent measurement technique, and nitrogen adsorption–desorption isotherms. Raman spectra and XRD showed an anatase phase structure. The SEM and TEM images revealed the formation of an almost spheroid mono disperse TiO₂ with particle sizes in the range of 9-17 nm. Analysis of N₂ isotherm measurements showed that all investigated TiO₂ samples have mesoporous structures with high surface areas. The optical absorption edge for the doped TiO₂ was significantly shifted to the visible light region. The photocurrent and photocatalytic activity of pure and doped TiO₂ were evaluated with the degradation of methyl orange (MO) and methylene blue (MB) solution under both UV and visible light illumination. The doped TiO₂ nanoparticles exhibit higher catalytic activity under each of visible light and UV irradiation in contrast to pure TiO₂. The photocatalytic activity and photocurrent ability of TiO₂ have been enhanced by doping of the titania in the following order: (Cu, N) - codoped TiO₂ > N-doped TiO₂ > Cu-doped TiO₂ > TiO₂. COD result for (Cu, N)-codoped TiO₂ reveals ∼92% mineralization of the MO dye on six h of visible light irradiation.     

Diels-Alder reaction with cyclopentadiene and electronic structures of (η5-cyclopentadienyl)M(CO)x(η1-N-maleimidato) (M = Fe,Mo, W,x = 2 or 3)

Diels-Alder reaction of (η⁵-cyclopentadienyl)M(CO)_x(η¹-N-maleimidato) complexes (M = Fe, Mo, W, x = 2 or 3) with cyclopentadiene has been studied. The observed order of reactivity was: N-ethylmaleimide > W complex > Mo complex > Fe complex. The X-ray structures of the adducts have been determined for M = W and Fe. DFT calculations on the starting complexes have been performed to explain the observed reactivity order.     

Structural and magnetic properties of metal telluromolybdates MxM′1−xTeMoO6 (M,M′ = Mn,Co, Cd)

Synthesis, crystal structures and magnetic properties of metal telluromolybdates M_xM′_1?xTeMoO₆ (M, M′ = Mn, Co, Cd) have been investigated. Their crystal structures have two-dimensional arrays of M and M′ atoms. From the powder X-ray diffraction measurements, Mn_xCo_1?xTeMoO₆ adopt an orthorhombic structure throughout the composition range (x = 0.0–1.0). On the other hand, Mn_xCd_1?xTeMoO₆ and Co_xCd_1?xTeMoO₆ adopt two types of structures corresponding to their end members (orthorhombic for Mn- or Co-rich solid solutions; tetragonal for Cd-rich ones). In the intermediate compositions, it was found that two phases coexist with different metal components. Magnetic properties of these solid solutions were investigated. All the Mn_xCo_1?xTeMoO₆ exhibits an antiferromagnetic transition at ～23 K. The antiferromagnetic transition was also observed in Mn_xCd_1?xTeMoO₆ and Co_xCd_1?xTeMoO₆. However, the Néel temperature rapidly decreases with increasing the concentration of Cd and disappeared below x = 0.6, which is characteristic for two-dimensional magnetic system.     

Electronic structure of lanthanum transition-metal oxyarsenides LaMAsO (M = Fe,Co, Ni) and LaFe1−xM′xAsO (M′ = Co,Ni) by X-ray photoelectron and absorption spectroscopy

The electronic structures of the quaternary oxyarsenides LaMAsO (M = Fe, Co, Ni) were examined with X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectroscopy (XANES). Interpretation of the metal 2p_3/2 and arsenic 3d_5/2 binding energies, as well as a satellite feature in the Co 2p XPS spectrum, suggests charges that are much less extreme than expected (i.e., not M²⁺ and As^3?) because of the strong covalent character within the M–As bonds. As M is varied, the differing degrees of charge transfer from M to As atoms within these bonds are manifested by shifts in the As 3d_5/2 binding energies and changes in the As K-edge intensities. This charge transfer is isolated within the [MAs] layer and does not influence the O 1s and La 3d XPS spectra. Fitting the experimental valence band spectra of these oxyarsenides LaMAsO yielded electron populations of states that support the formal charge assignment [La³⁺O^2?][M²⁺As^3?]. The mixed-metal series LaFe_1?xM′_xAsO (M′ = Co, Ni) was examined by XANES; analysis of the metal K- and L-edges, as well as of the Co 2p XPS satellite feature, revealed that no metal–metal charge transfer takes place.