Influence Of Transition Metal Ions Research Articles

Impact of Nitrate and Iron Ions on Uptake Coefficients and Condensed Phase Products From the Reaction of Gaseous NO2 With HULIS Proxies

AbstractHumic‐like substances (HULIS) are a ubiquitous reactive component of atmospheric aerosol. They participate in the formation of secondary organic aerosols via chemical reactions with atmospheric oxidants. Here, we assess the influence of transition metal ions (namely ferric iron, Fe(III)), and nitrate ions () on the heterogeneous reaction of gaseous NO2 with an aqueous film containing gallic acid (GA) or tannic acid (TA) as proxies for HULIS. Using a vertical wetted wall flow tube technique, the uptake coefficients of gaseous NO2 on GA and TA increased nonlinearly with increasing [Fe(III)], in dark and under light irradiation. However, the combined effect of both ions, Fe(III) and , led to a substantial decrease in NO2 uptake in the dark and under simulated near‐UV sunlight irradiation (300 < λ < 400 nm). The lifetime of GA in dilute aqueous phase, which corresponds to cloud water, due to reaction with NO2 would be 6 hr during both nighttime and daytime. However, the lifetime of GA in aerosol particles which contain both ions, that is, Fe(III) and , would increase to 27 hr during nighttime and 11 days and 6 hr due to light‐induced reaction with NO2. Also, we observed, using Fourier transform ion cyclotron resonance mass spectrometry, the formation of nitrocatechols compounds (e.g., methyl‐nitrocatechol), which contribute to brown carbon. Compounds with reduced functional groups such as amines were also observed in the presence of iron and nitrate ions in the dark and under irradiation, indicating that Fe(III) and , can influence the kinetics and product distribution in deliquescent aerosol particles.

Revisiting the HO●-initiated oxidation of L-proline amino acid in the aqueous phase: influence of transition metal ions.

The oxidation of L-proline (Pro) by HO● radical in water and the influence of transition metal ions on this process has been revisited by using the density functional theory (DFT) method at the M05-2X/6-311 + + G(3df,3pd)//M05-2X/6-311 + + G(d,p) level of theory at the temperature of 298.15 K. The main reactive sites of the HO●-initiated oxidation of Pro via hydrogen atom transfer (HAT) reactions are at the β- and γ-carbon, with the branching ratios being 44.6% and 39.5%, respectively. The overall rate constant at 298.15 K is 6.04 × 108 M-1 s-1. In addition, Pro tends to form stable complexes with both Fe and Cu ions via the -COO functional group of dipole-salt form. The most stable Cu(II)-Pro complexes have high oxidant risks in enhancing the HO● formation in the presence of reducing agents. Besides this, the high oxidation state metal complexes, i.e. Fe(III)-Pro and Cu(II)-Pro, may be oxidized by HO● radical via HAT reactions but with a lower rate constant than that of free-Pro. By contrast, the low oxidation state metal complexes (i.e. Fe(II)-Pro and Cu(I)-Pro) have higher oxidation risks than the free ligands, and thus, the complexation enhances the oxidation of Pro amino acid.

The influence of transition metal ions on the oxidation of kraft pulp using hydrogen peroxide under mildly acidic conditions

Abstract Oxidation of kraft pulp using hydrogen peroxide under mild acidic conditions can be applied in order to obtain new functionality of the fibres, in the form of carbonyl groups. The hydrogen peroxide concentration must, however, be higher than consumed by the oxidation reactions meaning that the liquid must be recirculated to fully utilize the hydrogen peroxide. This paper investigates the consequences of recirculation of the oxidation liquor. It was found that recirculation results in an accumulation of ions of transition metals (copper, iron and manganese) in the oxidation liquor. The transition metal ions are known for catalytic decomposition of hydrogen peroxide, producing radicals which may react with carbohydrates, forming carbonyl groups as well as causing carbohydrate degradation. This was confirmed through the recirculation of oxidation liquor as well as through controlled addition of transition metals. At high transition metal ion concentration the reactions were fast and a severe degradation of carbohydrates was observed, accompanied by a rapid hydrogen peroxide consumption. The consequence of this, in an industrial context, is that the concentration of metal ions must be carefully controlled in order to add functionality to the cellulose without causing excessive degradation of carbohydrates or consumption of hydrogen peroxide.

Influence of transition metal ions: Broad band upconversion emission in thermally stable phosphors

Abstract Frequency upconversion (UC) study at different temperatures in Ho3+/Yb3+/Mn4+:SnO2 phosphors, prepared via solid state reaction method has been performed. The prepared phosphors have been characterized via XRD, Raman spectra, FESEM, EDAX, XPS and diffuse reflectance analysis. The decrease in bandgap has been reported due to codoping with Mn4+ ions in the developed phosphors. An enhancement of about 47 and 6 times in the green and red UC emission bands has been observed with the addition of Yb3+ ions. Moreover, incorporation of Mn4+ ions gives broad visible UC emission ranging from 400 nm to 900 nm. The mechanism responsible for the enhancement and broad band UC emission has been discussed on the basis of pump power dependence followed by the photon avalanche energy transfer process.

Enhancing the Electrochromic Properties of Polyaniline through Incorporating Terpyridine Units and Coordination Bonding with Transition Metal Ions

AbstractA novel polyaniline‐terpyridine‐transition metal ions (PANI‐TPY−M (M=Fe (II), Co (II), Ni (II))) hybrid electrochromic materials containing coordination bonds were successfully synthesized in an aqueous medium. The molecular and aggregation structures of PANI‐TPY−M were systematically studied by FTIR (Fourier transform infrared spectroscopy), particle size analysis and Raman spectroscopy. The influence of transition metal ions on the thermal stability of materials was analyzed by TGA (thermogravimetric analysis). The electrochemical behaviors and electrochromic properties of materials were measured by CV (cyclic voltammetry) and UV‐vis (UV‐visible spectroscopy). It can be found that the electrochemical activities of PANI‐TPY and PANI‐TPY−M are both higher than that of PANI. Especially, the electrochromic devices with PANI‐TPY−M (M=Fe (II), Co (II), Ni (II)) as active layer exhibit obvious optical contrast enhancement function. As comparison to PANI, the contrast of PANI‐TPY increases about 57%, the contrast of PANI‐TPY−Fe increases about 76%, the contrast of PANI‐TPY−Co increases by nearly 73%, and the contrast of PANI‐TPY−Ni increases by 54%.

Influence of transition metal ions on multiferroic properties of lead-free NBT–BT ceramics

Using the conventional solid-state reaction method, 0.5[Formula: see text]wt.% of MnO2-, NiO-, Cr2O3-, Fe2O3- and Co2O3-added 0.94[Formula: see text][Formula: see text]TiO3 (NBT)–0.06BaTiO3 (BT) ceramics were prepared. The perovskite nature of the prepared ceramics was analyzed by powder XRD and the surface morphology was studied by means of SEM. The dielectric analysis was carried out from room temperature to [Formula: see text]C at various frequencies and the diffusive transition at the dielectric maxima confirmed the relaxor nature of the ceramics. Creation of oxygen vacancies by the possible substitution of ferromagnetic impurities decreased the dielectric constant and piezoelectric constant ([Formula: see text]. The co-existence of ferromagnetism and the ferroelectricity was observed in the Mn, Ni, Co and Cr-added NBT–BT ceramics. The magnetic force microscopy (MFM) analysis was carried out to study the ferromagnetic domains in the prepared ceramic.

Tuning the optical bandgap of V2O5 nanoparticles by doping transition metal ions

Abstract In this study the influence of transition metal ions doping on optical properties of V2O5 nanoparticles is investigated. The shift in absorption edge caused by the dopant is analyzed from the UV-visible absorption spectra. The absorption edge of Ti doped V2O5 nanocrystals is shifted to longer wavelength region, while that of Zr doped V2O5 showed a blue shift. Ti doped V2O5 nanocrystal in spite of its large crystallite size showed improved optical properties and its optical bandgap (1.96 eV) is less than un-doped V2O5 (2.2 eV). This is attributed to lattice expansion by Ti ion and formation of oxygen vacancies within the bandgap. The oxygen vacancies acts as intermediate energy states and reduce the optical bandgap. However, the PL spectra of Ti-doped V2O5 did not exhibited emission peak corresponding to oxygen vacancies due to high crystallinity. The life time of excitons in excited state is investigated from time resolved PL decay. The excitons in doped sample showed tri-exponential decay whereas in pure sample they exhibited bi-exponential decay. The average lifetime of excitons in doped V2O5 is higher than pure V2O5 sample. This study reveals that by optimizing the concentration of Ti and Zr dopant ions in V2O5 lattice, its energy band structure can be tailored for photovoltaic, catalytic and photoluminescence applications. © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Nanotechnology: Ideas, Innovations & Initiatives-2017 (ICN:3i-2017).

Influence of metal ions on the formation of new metal complexes constructed from tetrachlorophthalic acid

Abstract Reaction of 3,4,5,6-tetrachloro-1,2-benzenedicarboxylyic acid (1,2-H2BDC-Cl4) with transitional metal salts at room temperature in mixed DMF/H2O solvent affords three complexes formulated as [Cu(1,2-HBDC-Cl4)2(DMF)2] (1), {[Cd(1,2-HBDC-Cl4)2(H2O)4]·2DMF} (2), and {[Ni(1,2-BDC-Cl4)(H2O)5]·DMF·H2O} (3) (DMF = N,N-dimethylformamide). All these complexes have been characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, and single-crystal X-ray crystallography. In 1, the CuII ion is four-coordinated with a square-planar geometry formed by two 1,2-HBDC-Cl4 anions and two DMF ligands; in 2, the CdII ion takes an octahedral geometry coordinated by two 1,2-HBDC-Cl4 anions and four aqua ligands; while in 3, the NiII ion is octahedrally coordinated by one 1,2-BDC-Cl4 dianion and five aqua ligands. Intermolecular O–H···O hydrogen bonds and Cl···Cl (or C–H···Cl) interactions provide a significant contribution to stabilizing the three mononuclear structures in the solid state. The results suggest that structural differences among them are attributed to the influence of transition metal ions. The fluorescence of the complexes and of 1,2-H2BDC-Cl4 has been investigated. No significant metal effect has been observed.

The influence of transition metal ions on the catalytic performance of Ru particles during the liquid phase hydrogenation of benzene to cyclohexene

The influence of some transition metal ions including Fe2+, Ni2+, Cr3+, Mn2+, Zn2+, Cd2+ on the catalytic performance of Ru particles during the liquid phase partial hydrogenation of benzene to cyclohexene was investigated in a titanium autoclave and a stainless steel autoclave. The Ru particles were prepared by the precipitation method. The catalysts were characterized using XRD, BET surface area measurement and XPS. The structure configurations and formation enthalpies of the hydrated metal ions, the complexes of the metal ions with benzene and cyclohexene as well as the complexes of hydrated metal ions with benzene and cyclohexene were optimized and evaluated using quantum chemical calculation methods. It was found that the poisoning effect of the transition metal ions on the catalytic activity of Ru particles only partially obeys the “Maxted rule”. The enhancing effect of the transition metal ions on the cyclohexene selectivity is associated with both the interaction of the metal ions with the active sites on Ru surface and with the tendency of metal ions to form hydrated complexes. In the stainless steel autoclave, the Fe2+, Ni2+ and Cr3+ resulted from the corrosion of the stainless steel have a synergetic effect with Zn2+, leading to a higher selectivity to cyclohexene.

Kinetic Study of Decolorization of Methylene Blue with Sodium Sulphite in Aqueous Media: Influence of Transition Metal Ions

The kinetics of decolorization of methylene blue (MB+) with sodium sulphite in aqueous media was investigated over the temperature range 20-40°C. The kinetic studies were carried out as a function of different variables like concentration, pH, and temperature on rate of decolorization. The rate of the reaction was found to be [H+] dependent and first order in both [MB+] and reductant. The empirical rate law conforms to the equation: Where K1 is the protonation constant, and k2 and k3 are overall pseudo-second order rate constants for the decolorization of MB+ with 2 3 SO − . The rate was found to increase linearly with temperature. The rate of decolorization decreased after addition of Co(II), Ni(II), Mn(II) and Zn(II), but increased after addition of Fe(II) and Cu(II). The activation parameters (Ea, ΔG#, ΔH# and ΔS#) of the decolorization reaction of MB+ with 2 3 SO − in absence and in presence of Fe(II) and Cu(II) were calculated.

A perfluorocyclopentene based diarylethene bearing two terpyridine moieties – synthesis, photochemical properties and influence of transition metal ions

The synthesis of a perfluorocyclopentene based diarylethene bearing two terpyridine units is reported. Furthermore studies of the free ligand’s photochromism and investigations regarding the influence of various transition metal ions on the photochromic reaction are presented. The photochromism of the central diarylethene unit is strongly dependent on the transition metal present, vice versa the photochromic reaction seems to influence the MLCT transition of a binuclear Ru(II) complex.

Thin Layer Chromatography of Purines on Silica Gel G Impregnated with Transition Metal Ions; Assay of Caffeine and Theophylline in Pharmaceutical Formulations

AbstractThis study was undertaken to develop thin layers of silica gel G impregnated with transition metal ions for separation, identification and estimation of purines. The influence of transition metal ions and eluting solvents on chromatographic behaviour (hRf) has been studied. The method was applied for qualitative analysis of purines in the mixtures and quantitative analysis of purine bases in the mixture as well as in pharmaceutical formulations. The results were compared statistically with those obtained by official methods. The method is simple, reproducible, and accurate within 1.3 ± 0.6%.

Influence of transition metal ions on the textural properties of alumina and aluminasilicates

Accelerated phase transformations and chemical reactions of metastable aluminas and kaolinite, doped with Cu2+, Mn3+/Mn2+ and Fe3+/Fe2+ ions, are accompanied with accelerated decrease of surface area and pore volume values. The phenomena in metal ion doped samples are explained by a catalytic mechanism, in terms of the Jahn-Teller effect.

Selective alkaline oxidative degradation of mono- and di-saccharides by hydrogen peroxide using borate as catalyst and protecting group

Lactose, maltose, cellobiose, and galactose can be degraded selectively in one step and in high yield into the corresponding next lower aldose and formic acid by H 2O 2 in the presence of borate. The selectivity further improves when a small amount of EDTA is added, in order to suppress the influence of transition metal ions which catalyze the decomposition of H 2O 2 via radical pathways, leading to non-selective oxidative degradation of aldoses. The function of borate in the selective oxidative degradation of aldoses is two-fold: catalysis of the degradation of the starting aldose and protection of the next lower aldose against oxidation.

Influence of metal ions on the electrocatalytic oxygen reduction of carbon materials prepared from pyrolyzed polyacrylonitrile

The influence of transition metal ions during a thermal process in which electrocatalysts are made from polyacrylonitrile is discussed. The electrocatalysts were applied on appropriate carbon supports and used for the cathodic oxygen reduction in acid and alkaline electrolytes. Results concerning the electrocatalitic properties of these materials in self-breathing oxygen electrodes as well as the long-term behaviour and the metal dissolution are compared.

Influence of transition metal ions on the photo-behaviour of BHT in polypropylene: A uv-study

The photo-behaviour of 2,6-di-tert-butyl-4-methylphenol, commercially known as BHT, has been examined in diluent phase and experimental gas phase polypropylene films by uv-derivative spectroscopy. Whilst the lower photolytic stability of BHT in the latter type polymer is associated with the catalytic effect of higher levels of residual titanium and aluminium, an additional reaction due to loss of one or both ortho-tert-butyl groups is more associated with trace levels of iron. The commercial implications of the experimental findings are discussed.