Synthesis of Fe<Superscript>3+</Superscript> doped ordered mesoporous TiO<Subscript>2</Subscript> with enhanced visible light photocatalytic activity and highly crystallized anatase wall

Fe³⁺ doped mesoporous TiO₂ with ordered mesoporous structure were successfully prepared by the solvent evaporation-induced self-assembly process using P123 as soft template. The properties and structure of Fe³⁺ doped mesoporous TiO₂ were characterized by means of XRD, EPR, BET, TEM, and UV–vis absorption spectra. The characteristic results clearly show that the amount of Fe³⁺ dopant affects the mesoporous structure as well as the visible light absorption of the catalysts. The photocatalytic activity of the prepared mesoporous TiO₂ was evaluated from an analysis of the photodegradation of methyl orange under visible light irradiation. The results indicate that the sample of 0.50%Fe–MTiO₂ exhibits the highest visible light photocatalytic activity compared with other catalysts.     

Thermodynamics of citrate complexation with Mn<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> ions

Isothermal titration calorimetry has been used to determine the stoichiometry, formation constants and thermodynamic parameters (ΔG ^o, ΔH, ΔS) for the formation of the citrate complexes with the Mn²⁺, Co²⁺, Ni²⁺ and Zn²⁺ ions. The measurements were run in Cacodylate, Pipes and Mes buffer solutions with a pH of 6, at 298.15 K. A constant ionic strength of 100 mM was maintained with NaClO₄. The influence of a metal ion on its interaction energy with the citrate ions and the stability of the resulting complexes have been discussed.     

Vacuum activation-induced Ti<Superscript>3+</Superscript> and carbon co-doped TiO<Subscript>2</Subscript> with enhanced solar light photo-catalytic activity

Ti³⁺ and carbon co-doped TiO₂ photocatalysts were prepared hydrothermally to introduce the carbon, and followed by simple vacuum activation to achieve the Ti³⁺ self-doping. The prepared co-doped photocatalysts were characterized by XRD, TEM, UV–Vis absorption spectra, EPR, and XPS. It was found that the co-doped TiO₂ has dispersed nanoparticles and a narrower band-gap compared with the un-doped TiO₂ and single-doped TiO₂. The experimental results displayed that the coke carbon generated on the surface of co-doped TiO₂ acts as a photosensitizer and has the photosensitization effect under solar light irradiation. Except for the carbon sensitization effect, the Ti³⁺ self-doping modification has a synergistic effect which is the reason for the effective photo-degradation of methyl orange under simulated solar light irradiation.     

Preparation of graphene oxide and its application in Ni<Superscript>2+</Superscript> removal

Graphene oxide (GO) has been prepared by the modified Hummers method using graphite as starting material. The product was studied by the X-ray diffraction (XRD), Raman spectroscopic, transmission electron microscopic (TEM), and scanning electron microscopic (SEM) analyses. Adsorption capacity of GO for heavy metal ions was studied for the example of the Ni²⁺ ions and the adsorption kinetics and adsorption isotherm were determined. It was shown that the adsorption equilibrium curves are adequately described by the Langmuir equation.     

Hydrothermal synthesis and characterization of In<Superscript>3+</Superscript> modified BiVO<Subscript>4</Subscript> nanoparticles with enhanced photocatalytic activity

In³⁺-doped BiVO₄ nanoparticles with enhanced visible light activity have been successfully synthesized by a hydrothermal method. The synthesized materials were characterized by X-ray diffraction, Raman, X-ray photoelectron spectroscopy, scanning electron microscopy, BET surface areas analysis, and ultraviolet–visible diffuse reflectance spectra. In comparison with pure BiVO₄, the In³⁺-doped BiVO₄ displayed greater photocatalytic activity in the degradation of methyl blue under visible light illumination. All samples possessed a single monoclinic structure. The introduction of In ions resulted in structural distortion and the decreased band gap energy, producing more electrons and holes for photocatalytic reaction. In the meantime, the doping In ions entails a red shift in the absorption edge and an increase in the intensity of light absorption. The best photocatalytic performance was obtained with the BiVO₄ sample containing 5.0 mol% In ions.     

Complex formation of maleic acid with the Zn<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, Cu<Superscript>2+</Superscript> in aqueous solution

The process of complex formation of maleic acid (H₂L) with the ions Zn²⁺, Ni²⁺, Co²⁺, Cu²⁺ was studied by potentiometric titration in a wide range of concentration ratios at 298 K and I = 0.1 mol/l (NaNO₃). The moieties ZnL, CoL, NiL, NiL ₂ ^2? , CuL, and CuL ₂ ^2? were detected and their stability constants were determined.     

Extraction of metal ions (Fe<Superscript>3+</Superscript>, Co<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript>, Cu<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript>) using immobilized-polysiloxane iminobis(n-2-aminophenylacetamide) ligand system

A new insoluble solid functionalized ligand system bearing chelating ligand group of the general formula P-(CH₂)₃-N[CH₂CONH(C₆H₄)NH₂]₂, where P represents [Si–O] _n polysiloxane network, was prepared by the reaction of the immobilized diethyliminodiacetate polysiloxane ligand system, P-(CH₂)₃N(CH₂CO₂Et)₂ with 1,2-diaminobenzene in toluene. ¹³C CP-MAS NMR, XPS and FTIR results showed that most ethylacetate groups (–COOEt) were converted into the amide groups (–N–C=O). The new functionalized ligand system exhibits high capacity for extraction and removal of the metal ions (Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺) with efficiency of 95–97% after recovery from its primary metal complexes. This functionalized ligand system formed 1:1 metal to ligand complexes.     

Synthesis,characterisation and photocatalytic activity of Ag<Superscript>+</Superscript>- and Sn<Superscript>2+</Superscript>-substituted KSbTeO<Subscript>6</Subscript>

Ag⁺- and Sn²⁺-substituted KSbTeO₆ were prepared by a facile ion-exchange method at ambient temperature. All the samples were characterised by scanning electron microscopy, energy-dispersive spectra, thermogravimetric analysis, powder X-ray diffraction, Raman spectra and UV-VIS diffuse reflectance spectra. Both Sn²⁺- and Ag⁺-substituted KSbTeO₆ were crystallised in a cubic lattice with the \(Fd\bar 3m\) space group. The band-gap energy of all the samples was deduced from their UV-VIS diffuse reflectance spectral profiles. The visible light-induced photocatalytic oxidation of the methylene blue (MB) dye was examined in the presence of all the as-prepared materials. The Ag⁺- and Sn²⁺-substituted KSbTeO₆ exhibited a higher photocatalytic activity than the parent KSbTeO₆ in degradation of the MB dye under visible light irradiation.     

Difference of Electron Capture and Transfer Dissociation Mass Spectrometry on Ni<Superscript>2+</Superscript>-, Cu<Superscript>2+</Superscript>-, and Zn<Superscript>2+</Superscript>-Polyhistidine Complexes in the Absence of Remote Protons

Electron capture dissociation (ECD) and electron transfer dissociation (ETD) in metal-peptide complexes are dependent on the metal cation in the complex. The divalent transition metals Ni²⁺, Cu²⁺, and Zn²⁺ were used as charge carriers to produce metal-polyhistidine complexes in the absence of remote protons, since these metal cations strongly bind to neutral histidine residues in peptides. In the case of the ECD and ETD of Cu²⁺-polyhistidine complexes, the metal cation in the complex was reduced and the recombination energy was redistributed throughout the peptide to lead a zwitterionic peptide form having a protonated histidine residue and a deprotonated amide nitrogen. The zwitterion then underwent peptide bond cleavage, producing a and b fragment ions. In contrast, ECD and ETD induced different fragmentation processes in Zn²⁺-polyhistidine complexes. Although the N–C_α bond in the Zn²⁺-polyhistidine complex was cleaved by ETD, ECD of Zn²⁺-polyhistidine induced peptide bond cleavage accompanied with hydrogen atom release. The different fragmentation modes by ECD and ETD originated from the different electronic states of the charge-reduced complexes resulting from these processes. The details of the fragmentation processes were investigated by density functional theory.

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Enhancement of 2-chlorophenol photocatalytic degradation in the presence Co<Superscript>2+</Superscript>-doped ZnO nanoparticles under direct solar radiation

The performance of Co²⁺-doped ZnO nanoparticles, prepared using the sol–gel method, for 2-chlorophenol degradation under direct solar radiation was investigated. Various parameters were investigated during the degradation process, namely solar intensity, Co²⁺ ion concentration, loading concentrations of Co²⁺-doped ZnO, and pH. The photocatalytic degradation efficiency increased when the initial concentration of 2-chlorophenol decreased; the optimum concentration was 50 mg/L under similar experimental conditions. Moreover, optimum values, established on a sunny day, were 0.75 wt% of Co²⁺, a 1 g/L loading concentration, and a pH of 6.0, respectively. The highest degradation efficiency observed was 95 %, after only 90 min of solar light irradiation. The mechanism of visible photocatalytic degradation using Co²⁺-doped ZnO was explained as a strong electronic interaction between Co²⁺, Co³⁺ and ZnO, and a promotion in the charge separation, which enhanced the degradation performance. The fragmentation of 2-chlorophenol under the optimal conditions was investigated using HPLC, comparing standards of all intermediate compounds. The pathway of the fragmentation was proposed as involving hydroxyhydroquinone, catechol, and phenol formation, which were then converted to non-toxic compounds such as oxalic acid and acetic acid with further decomposition to CO₂ and H₂O.     

Preparation, characterization, and photocatalytic activity of sulfate-modified titania for degradation of methyl orange under visible light

Hydrated titania was prepared by a sol-gel method, taking tetraisopropyl orthotitanate as starting material, and then promoted with different weight percentages of sulfate by an incipient wetness impregnation method. The materials were characterized by various advanced techniques such as PXRD, BET surface area, N(2) adsorption-desorption measurements, FTIR, and SEM. Analytical results demonstrated that TiO(2) is mesoporous in nature, and sulfate modification could inhibit the phase transformation and enhance the thermal stability of TiO(2). It was also found that sulfate modification could reduce the crystallite size and increase the specific surface area of the catalysts. The degradation of methyl orange under solar radiation was investigated to evaluate the photocatalytic activity of these materials. Effects of different parameters such as pH of the solution, amount of catalyst, additives, and kinetics were investigated. At 2.5 wt% sulfate loading, the average percentage of degradation of methyl orange was nearly two times than that of neat TiO(2). The photocatalytic degradation followed first-order kinetics.     

Thermodynamic characteristics of formation reactions of Zn<Superscript>2+</Superscript> and Ni<Superscript>2+</Superscript> complexes with succinic acid in aqueous solutions

The heat effects of complex formation between zinc(II) and nickel(II) ions and succinic acid were determined calorimetrically at 298.15 K and several ionic strength values against the background of NaNO₃. The standard thermodynamic characteristics of complex formation in aqueous solution were calculated.     

Incorporation of Mg<Superscript>2+</Superscript>, Sr<Superscript>2+</Superscript>, Ba<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> into aragonite and comparison with calcite

We have investigated the presence of foreign ions into the bulk structure and the external surfaces of aragonite using periodic ab-initio methods. Four cations isovalent to Ca²⁺ were studied: Mg²⁺, Sr²⁺, Ba²⁺ and Zn²⁺. The calculations were performed at structures (bulk, surface) that contain four and eight CaCO₃ units. Our results, at the Hartree-Fock level, show that the incorporation of those ions into aragonite depends strongly on their size. Mg²⁺ and Zn²⁺, due to their smaller size, can substitute Ca²⁺ ions in the crystal lattice while the incorporation of Sr²⁺ and Ba²⁺ into aragonite is energetically less favoured. Examination of the [011], [110] and [001] surfaces of aragonite revealed that the surface incorporation reduces the energetic cost for the larger ions. These systems provide challenging examples for most shape analysis methods applied in Mathematical Chemistry.     

Thermal behavior of Cd<Superscript>2+</Superscript> and Co<Superscript>2+</Superscript> phenyl-vinyl-phosphonates under non-isothermal condition

The thermal behavior of Cd²⁺ and Co²⁺ phenyl-vinyl-phosphonates was studied using two different experimental strategies: the coupled TG-EGA (FTIR) technique by decomposition in nitrogen respectively air, and the kinetic analysis of TG data obtained in dynamic air atmosphere at four heating rates. In nitrogen two decomposition steps were observed: the loss of crystallization water, respectively the decomposition of the phenyl-vinyl radical. In air, the same dehydration was observed as the first step, but the second one is a thermooxidation of the organic radical with formation of the pyrophosphoric anion. The kinetic analysis of the TG non-isothermal data was performed by the isoconversional methods suggested by Friedman and Flynn, Wall and Ozawa, as well as by the non-parametric (Sempere-Nomen) method. All processes put in evidence in TG curves exhibit strong changes of the activation energy values with the conversion degree, which mean that these processes are complex ones. Assuming that each of these processes consists in two steps, the application of non-parametric method leads to average values of the activation energy close to the average values of this parameter obtained by isoconversional methods.     

Crystal structures of a family of layered coordination polymers containing divalent metal ions (Mn<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript>) and the 3-amino 4-methyl benzoate ion

The syntheses and crystal structures of the layered coordination polymers M(C₈H₈NO₂)₂ [M = Mn (1), Co (2), Ni (3) and Zn (4)] are described. These isostructural compounds contain centrosymmetric trans-MN₂O₄ octahedra as parts of infinite sheets; the ligand bonds to three adjacent metal ions in μ³-N,O,O′ mode from both its carboxylate O atoms and its amine N atom. In each case, weak intra-sheet N–H?O and C–H?O hydrogen bonds may help to consolidate the structure. Crystal data: 1, C₁₆H₁₆MnN₂O₄, M _r = 355.25, monoclinic, P2₁/c (No. 14), a = 10.6534(2) Å, b = 4.3990(1) Å, c = 15.5733(5) Å, β = 95.1827(10)°, V = 726.85(3) ų, Z = 2, R(F) = 0.026, wR(F ²) = 0.067. 2, C₁₆H₁₆CoN₂O₄, M _r = 359.24, monoclinic, P2₁/c (No. 14), a = 10.6131(10) Å, b = 4.3374(4) Å, c = 15.3556(17) Å, β = 95.473(4)°, V = 703.65(12) ų, Z = 2, R(F) = 0.041, wR(F ²) = 0.091. 3, C₁₆H₁₆N₂NiO₄, M _r = 359.02, monoclinic, P2₁/c (No. 14), a = 10.6374(4) Å, b = 4.2964(2) Å, c = 15.2827(8) Å, β = 95.9744(14)°, V = 694.66(6) ų, Z = 2, R(F) = 0.028, wR(F ²) = 0.070. 4, C₁₆H₁₆N₂O₄Zn, M _r = 365.68, monoclinic, P2₁/c (No. 14), a = 10.6385(5) Å, b = 4.2967(3) Å, c = 15.2844(8) Å, β = 95.941(3)°, V = 694.89(7) ų, Z = 2, R(F) = 0.038, wR(F ²) = 0.107.     

Synthesis,characterization, and photocatalytic properties of La<Superscript>3+</Superscript>-doped BiPO<Subscript>4</Subscript> photocatalysts

La³⁺-doped BiPO₄ photocatalysts were prepared via a hydrothermal process. Their morphologies, structures, and light absorption properties were evaluated. A small amount of La-doping (optimized at 2 mol %) could significantly improve the activity of BiPO₄ in the degradation of methylene blue under ultraviolet irradiation. After five recycles, the La³⁺-doped BiPO₄ did not exhibit any apparent loss in activity, confirming its stability despite recycling.     

Studies of surface properties of pure and modified by Mn<Superscript>2+</Superscript> and Ni<Superscript>2+</Superscript> ions of aluminium oxide samples using complex methods

Complex studies of physicochemical properties of pure and modified of aluminia oxides samples are presented. The presence of Mn²⁺ and Ni²⁺ modifiers on the aluminium oxide surface causes increase in water adsorption capacity and decrease in benzene and n-octane adsorption. This is due to decrease of specific surface area, volume and radius of pores as a result of surface impregnation and microcrystal formation during modification with manganese and nickel chlorides. Microcrystal formation on the surface and porosity decrease as confirmed by AFM, EDX and powder diffraction studies using automated diffractometer by step scanning. From the Q-TG and Q-DTG data, the energies of liquid desorption from the surface of the samples and the functions of desorption, energy distribution were calculated. High degree of nonlinearity of the functions resulting from great heterogeneity of the studied surface was found. Adsorption of cations creates more homogeneous surface in aluminium oxide, and it is responsible for the change in adsorbate molecule interaction energy and changes mechanism of adsorption and desorption as well as thickness and structure of the adsorbed film. From the experimental data some parameters characterizing adsorption properties and porosity of the studied samples were determined using the complex measuring methods (thermal analysis, sorptometry, porosimetry, AFM and EDX).     

Thermochemistry of complex formation of Ni<Superscript>2+</Superscript> with glycyl-L-asparagine in aqueous solutions

The heats of formation of complexes in the glycyl-L-asparagine—Ni²⁺ system were determined by calorimetry in an aqueous solution at ionic strengths of 0.5, 1.0, and 1.5 (KNO₃) and a temperature of 298.15 K. The thermodynamic characteristics of the formation of nickel complexes with dipeptide were determined. The influence of the ligand structure on the complexation thermodynamics in solutions was discussed.Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 2, 2005, pp. 143–148.Original Russian Text Copyright © 2005 by Zelenin, Kochergina.