Effect Of Transition Metal Cations Research Articles

Characterization of Blue Tourmaline from Madagascar for Exploring Its Color Origin

In the research, spectroscopic studies of tourmaline for color origin were performed by X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, and X-ray photoelectron spectroscopy. The research work emphasized the analysis of transition metal atoms, including their valence state and coordination number, in order to better understand the effect of transition metal cations on the color origin. The results showed that the blue color of the crystal is caused by the strong absorption at 725 nm in the red spectrum, which generates a symmetrical and wide absorption band. The absorption band at 725 nm is caused by charge transfer between Fe2+ at the Y site and Fe3+ at the Z site. Other ions in the crystal did not generate absorption lines in the visible spectral range. Besides position, its valence state and coordination number were clarified to reveal color variation and the origin of tourmaline. Most importantly, this spectroscopic analysis method makes the coloration mechanism of charge transfer that is difficult to be uncovered to be clearly revealed, which will provide an available material and chemical method to investigate the structure-property relationship for gems as well as reveal the genesis of beautiful colors.

Spectroscopic Characteristics and Color Origin of Red Tourmaline from Brazil

In the present paper, I report on the spectroscopic study for tourmaline color origin, performed red samples from Minas Geras State, Brazil, by gemological routine testing, X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, and X-ray photoelectron spectroscopy. The main goal was the analysis of the optical absorption spectra and the chemical states of transition metal cations in order to better understand the effect of transition metal cations on color of tourmaline. The results showed that the red color was confirmed by the symmetric broad absorption at 527 nm and the narrow absorption at 400 and 450 nm, and the above three absorption bands were caused by the d-d electron transition of Mn3+, which occupied the Y site in the crystal structure and coordinated with F to form bonds. In addition, in principle, the chemical states of the chromogenic ions in tourmaline and their influence on coloration were confirmed, which would be beneficial to assessing the color change and identifying the origin of tourmaline.

Effect of transition metal cations on the local structure and lithium transport in disordered rock-salt oxides.

Lithium-excess oxides Li1.2Ti0.4Mn0.4O2 and Li1.3Nb0.3Mn0.4O2 with a disordered rock-salt structure and Mn3+/Mn4+ as a redox couple were compared to analyze the effect of different d0 metal ions on the local structure and Li+ ion migration. These cathode materials were obtained by mechanochemically assisted solid-state synthesis. Using XRD, 7Li NMR and EPR spectroscopy and transmission electron microscopy it was shown that the Mn ions are prone to form clusters, while d0 metal ions are evenly distributed in the crystal lattice. The presence of Nb5+ ions contributes to the formation of noticeably larger Mn clusters and larger gaps in the Li+ migration maps as compared to Ti4+. These results were confirmed by the geometrical-topological method, BVSE simulation and DFT calculations, and are in good agreement with the Li diffusion coefficient determined by GITT, which is 1.5 orders of magnitude higher in Li1.2Ti0.4Mn0.4O2 than that in Li1.3Nb0.3Mn0.4O2.

The Chemical States of Color-Induced Cations in Tourmaline Characterized by X-Ray Photoelectron Spectroscopy

In order to better understand the effect of transition metal cations on color of tourmaline, X-ray photoelectron spectroscopy was used to investigate the species, chemical state, site occupancy, and chemical environment of color-induced metal cations in colorful tourmaline samples from Minas Gerais State, Brazil. Our results showed that the colorful tourmalines usually contained a small amount of transition metal elements, and a colorful tourmaline sample had several transition metal cations; however, the color of tourmaline resulted from the transition metal cations in the Y site of the crystal structure. The pink color of tourmaline was associated with Mn2+ in the Y site coordinating with F; the yellow color was derived from Ni2+ in the Y site binding to O; the green color was associated with Fe3+ in the Y site coordinating with O, OH, and F; the rose red color originated from Mn2+ and Ni2+ in the Y site in which Mn2+ coordinated with O and F, and Ni2+ coordinated with O; and the blue color was derived from Fe3+ and Mn2+ in the Y site in which Fe3+ binded to O, OH, and F and Mn2+ binded to F. Additionally, other transition metal cations were also observed in colorful tourmalines, but all these species occupied the Z site of the structure. In the pink and yellow samples, Fe and Cr were observed in Fe3+ and Cr3+; in the rose red sample, Fe was also found in Fe3+; in the blue sample, Cr was present in Cr3+; in the green sample, Mn, Ni, and Cu were found in Mn2+, Ni2+, and Cu2+, respectively. The color of tourmaline was induced from the absorption of the d-d transition of transition metals in the crystal structure, as charge transfer tended to occur between cations occupying different coordination positions.

Effect of Transition Metal Cations on Assembly of Highly Ordered 2D Multiporphyrin Arrays on Liquid and Solid Substrates

Effect of Transition Metal Cations on Assembly of Highly Ordered 2D Multiporphyrin Arrays on Liquid and Solid Substrates

Enhancement effect of transition metal cations on the electrochromic properties of nanostructure tiron doped polypyrrole film

Herein, the electrochemical polymerization of pyrrole on the surface of FTO electrode is described in the presence of tiron as doping anion with the aim of producing uniform, adherent, conducting and electroactive films. The use of tiron promoted charge transfer during electropolymerization and allowed reduced electropolymerization potential of polypyrrole (PPy). The resultant polymer was characterized via scanning electron microscopy (SEM), electrochemical and spectroelectrochemical methods. SEM study indicates that the PPy–tiron has a spherical morphology with primary particles size of 40–60nm. The spectroelectrochemical analysis revealed the PPy–tiron has distinct electrochromic properties in the presence of different transition metal salts (CoCl2, NiCl2, CuCl2, FeCl2, MnCl2 and ZnCl2) as supporting electrolyte compared to conventional electrolyte solutions. Results showed that the electrochromic properties of PPy–tiron such as optical contrast, switching time, film stability and coloration efficiency were greatly enhanced in the presence of transition metal cations. PPy–tiron exhibited a switching time of 1.5s and the maximum transmittance contrast (ΔT%) and coloration efficiency calculated 62% and 136.7cm2C−1 at 800nm in the presence of Ni2+ ion, respectively.

Effect of transition metal cations on commensurate freezing of n-hexane confined in micropores of ZSM-5

Besides its importance concerning fundamental studies on gas adsorption in narrow pores, investigation of commensurate freezing of fluid within the zeolite is of practical importance in application of zeolite in the process of adsorption, separation and catalysis. In this work the adsorption of n-hexane on HZSM-5 and its transition metal ion-exchanged modified forms was studied at 303 K by means of microcalorimetry. The thermal molar entropies of adsorption were calculated and thus, the freezing like behaviour of n-hexane inside the structure of zeolite as a confinement media was noticed. This effect is governed by the attractive interactions between n-hexane molecules and the pore walls, and is also influenced by the length of the pores and the nature of charge-balancing cations. Among the investigated zeolites, solid like phase of n-hexane in the pores of zeolites with Fe2+ ions is the most like a solid n-hexane bulk, while the presence of Cu2+ ions contribute to the lowest ordering obtained solid like phase of n-hexane.

Metal ion influence on eumelanin fluorescence and structure

Melanin has long been thought to have an unworkably weak and complex fluorescence, but here we study its intrinsic fluorescence in order to demonstrate how metal ions can be used to control the rate of formation, constituents and structure of eumelanin formed from the well-known laboratory auto-oxidation of 3,4-dihydroxy-L-phenylalanine (L-DOPA). The effect on eumelanin absorption and fluorescence of a range of solvated metal ions is reported including Cu, Zn, Ni, Na and K. Monovalent cations and Zn have little effect, but the effect of transition metal cations can be considerable. For example, at pH 10, copper ions are shown to accelerate the onset of eumelanin formation, but not the rate of formation once it commences, and simplify the usual complex structure and intrinsic fluorescence of eumelanin in a way that is consistent with an increased abundance of 5,5-dihydroxyindole-2-carboxylic acid (DHICA). The presence of a dominant 6 ns fluorescence decay time at 480 nm, when excited at 450 nm describes a distinct photophysical species, which we tentatively assign to small oligomers. Copper is well-known to normally quench fluorescence, but increasing amounts of copper surprisingly leads to an increase in the fluorescence decay time of eumelanin, while reducing the fluorescence intensity, suggesting copper modification of the excited state. Such results have bearing on diverse areas. The most accepted morphology for melanin is that of a graphite-like sheet structure, and one which readily binds metal ions, an interaction that is thought to have an important, though as yet unclear bearing on several areas of medicine including neurology. There is also increasing interest in bio-mimicry by preparing and labelling sheet structures with metal ions for new electronic and photonic materials.

ChemInform Abstract: Aerobic Oxidation of Alcohols over Hydrotalcite‐Supported Gold Nanoparticles: The Promotional Effect of Transition Metal Cations.

AbstractHydrotalcite, with all Al3+ replaced by Cr3+, shows strong synergy with Au‐nanoparticles in achieving highly efficient catalysts for the aerobic oxidation of alcohols.

Aerobic oxidation of alcohols over hydrotalcite-supported gold nanoparticles: the promotional effect of transition metal cations

Chromium (III)-containing hydrotalcites show strong synergy with gold nanoparticles in achieving high activity in the aerobic oxidation of alcohols.

Effect of Transition-Metal Cations on the Adsorption of H2S in Modified Pillared Clays

Sodium montmorillonite was intercalated with the Keggin ion (hydroxyaluminum polycation) and calcined at 400 °C. Then, doping with Fe3+, Cu2+, or Zn2+ was carried out. On the obtained samples, H2S breakthrough capacity tests were carried out under wet conditions. Doping with metals significantly improved the capacity of adsorbents, despite a noticeable decrease in microporosity. The sample doped with copper showed the best performance as a hydrogen sulfide adsorbent. The reason for this is likely the affinity of the metal to bind hydrogen sulfide, the degree of metal dispersion, and the accessibility of small pores.

Effect of transition metal cations on the production of citric acid using mixed cultures of Aspergillus niger and Candida gulliermondii

Mixed culture technique was applied to citric acid production. Selected transition metal ions, namely, cadmium, lead, chromium and molybdenum were added in calculated quantities during fermentaion and their effect on the metabolic path followed by the microbes was studied. Cadmium was dragged inside the cell across the membrane to balance the proton motive force and was found to increase considerably the citric acid production. Lead was found to suppress the transport pump by strengthening cell wall cross links, whereas chromium activated the pump thereby inducing production. The possible reasons are discussed.

Rules governing the effect of transition metal cations on structuring of liquid rubbers

The effect of transition metal cations on the complex formation in liquid butadiene rubbers carrying CN, COOH, OH, and Cl end groups was investigated. An equation has been derived which relates the relative viscosity of the structured rubber to a quantity which characterizes the complex-forming ability of individual ions. Composition of the metal-polymer complexes formed in the liquid rubbers was studied by viscometry, IR spectroscopy and light scattering, and their dissociation constants were determined by analytical methods. Since the complexes formed in the rubbers and in low-molar-mass analogs have the same composition and the tendency to their formation is also identical in the two instances, one may use published data for predicting the effect of transition metal cations on structuring processes proceeding in oligobutadienes containing functional groups of various nature.