Nickel(II), palladium(ii), platinum(ii), and magnesium(ii) fluorene-substituted porphyrinates: Synthesis,structure, and comparative analysis of fluorescence spectra

Using free meso-tetra(2-fluorenyl)porphine (H₂TFP) and nickel(II), palladium(II), and platinum(II) chlorides and an MgBr₂ · Et₂O complex, corresponding metal porphyrinates were synthesized with a high yield. The structures of these new compounds were studied by means of ¹H NMR spectroscopy and electron absorption spectroscopy. The fluorescence spectra of the synthesized compounds in toluene solution were comparatively analyzed. Coordination of Mg²⁺ ion with porphyrinic cycle H₂TFP significantly increases the fluorescence intensity of porphyrinic luminophore; however, the coordination of platinum metal ions (Pt²⁺, Pd²⁺) with tetrapyrrole fragment H₂TPP decreases the fluorescence intensity of porphyrinic cycle and, in the case of nickel ions, fluorescence transitions disappear     

预处理条件对Pt/Al2O3催化氧化NO性能的影响

考察了温度和反应气氛对新鲜态Pt/Al2O3催化剂上NO氧化过程中的degreening效应的影响。利用活性评价实验测试不同条件下NO氧化活性,用H2程序升温还原(H2-TPR)表征了degreening效应过程中催化剂中Pt的价态变化。在degreening效应过程中,新鲜态Pt/Al2O3催化剂中与载体结合较弱的PtOx物种在温度低于300℃时被NO还原为Pt⁰;与载体结合较强的PtOx物种在温度高于400℃时分解成Pt⁰。新鲜态Pt/Al2O3催化剂经过第一次程序升温反应后,NO氧化活性位Pt⁰的增加导致了其NO氧化能力提高。     

Electrodeposition of platinum metal and platinum-rhodium alloy on titanium substrates

A method for application of an adherent platinum (Pt) and platinum-rhodium (Pt-Rh) alloy plate to a titanium (Ti) substrate includes steps of surface pretreatment, anodization, and electrodeposition of Pt and Pt-Rh alloy from their electrolytic baths consisting of H₂Pt₂Cl₆·6H₂O (20 gL⁻¹), and HCl (300 gL⁻¹) for a Pt bath. The Pt-Rh bath consists of H₂Pt₂Cl₆·6H₂O (20 gL⁻¹), and HCl (300 gL⁻¹) and Rh₂ (SO₄)₃ (2 gL⁻¹). At the optimum conditions of electroplating, the Pt and Pt-Rh deposits were formed over the anodized Ti substrates with high adhesion, brightness, and high current efficiency (35.33% for Pt and 70.38% for the Pt-Rh alloy).     

Cathodic inhibition of the corrosion of mild steel in phosphate,tungstate, arsenate and silicate solutions containing Ca2+ions

Abstract

It was found, usinig the potentiokinetic methed of cathodic polarisation of steel and platinum, that in the presence of Ca²⁺ Ions In dilute aerated solutions containing hydrogen-phosphate, -arsenate, -silicate and -tungstate ions, the cathodic reaction of the oxygen reduction is inhibited. This inhibition is due to the formation on the cathode of a layer of sparingly soluble calcium salts. Corrosion rate measurements with steel confirmed the beneficial influence of the addition of Ca²⁺ ions on the inhibitive efficiency of the above solutions. The best results were obtained with calcium phosphate and calcium tungstate.     

Rotating split ring disc electrode study of corrosion of iron in near neutral and alkaline solutions

Abstract

A rotating split ring disc electrode (RSRDE) with a sensitive triple potentiostat was constructed and used for determination of soluble ferrous and ferric species during potentiodynamic polarisation of iron in borate buffer solution (pH 8·4) and in 1 M NaOH at 25°C. The high sensitivity of the RSRDE apparatus enabled determination of these species in both solutions. In the borate solution shielding and blocking effects were observed. The shielding effect on the half ring detecting Fe³⁺ occurred at high cathodic potentials of the disc and was ascribed mainly to atkalisation of the ring due to hydroxyl ions produced on the disc. The blocking effect on the half ring detecting Fe²⁺ was caused by the deposition of solid ferric products; methods are proposed to diminish the inaccuracy associated with this effect.     

Microelectrochemical surface and product investigations during electrochemical machining (ECM) in NaNO3

The structure of the sample surface during electrochemical machining (ECM) of iron in neutral NaNO₃ solutions was investigated. From former experiments, we expected a duplex structure: a solid oxide film of some nm and, above, a meta-stable, highly soluble supersaturated iron nitrate film for ECM in NaNO₃ (current densities up to 100 A/cm², electrolyte flow). The total current (and charge) and the dissolution products during anodic pulses was measured. The formation of Fe³⁺ and Fe²⁺ was monitored by UV-VIS spectroscopy and enabled (for the first time) a quantitative product determination.A transition from predominant oxygen evolution to predominant iron dissolution was found in the range from 5 to 30 A/cm². At current densities >35 A/cm² the oxygen evolution is reduced to some percent of the total current. The Fe³⁺/Fe²⁺ formation ratio increases to 2, corresponding to a dissolution of Fe₃O₄.     

Preparation of nano- and microstructured gold surfaces by application of a square wave potential regime

Gold nanometallic structures have been prepared by application of square wave potential regime to a platinum electrode in a 1.0 × 10^?3 M HAuCl₄ + 0.5 M H₂SO₄ solution. Formation of gold particles onto the platinum surface has been followed by cyclic voltammetry, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. The results indicate that the size, shape, uniformity of distribution of the particles are affected by the selected parameters of the applied square wave potential regime. Parameters of the square wave include the frequency, the lower and the upper limits of the square wave and the time of application of the square wave potential regime. The concentration of HAuCl₄ in the solution is another important factor. The results of the present work indicated that the 100 Hz frequency is the optimal frequency for obtaining gold nanoparticles on platinum surface. Deposition time has been also found to play a critical role in affecting the size, shape and homogeneity of gold nanostructures at the surface. The surface coverage with nanoparticles as calculated from the decrease in the charge of hydrogen adsorption/desorption peaks is found to be directly proportional to the time of application of the square wave. Testing the nanostructured gold/Pt electrode for oxidation of formic acid shows its higher catalytic activity than that of platinum and gold plain electrodes.     

Stabilization of supported platinum nanoparticles on γ-alumina catalysts by addition of tungsten

The thermal stabilization of Al₂O₃ using W⁶⁺ ions has been found useful to the synthesis of Pt/Al₂O₃ catalysts. The simultaneous and sequential methods were used to study the effect of W⁶⁺ upon Pt/γ-Al₂O₃ reducibility, Pt dispersion, and benzene hydrogenation. The W/Pt atomic ratios were from 0.49 to 12.4. In the first method we found that the W⁶⁺ ions delayed reduction of a fraction of Pt⁴⁺ atoms beyond 773 K. At the same time, W⁶⁺inhibited sintering of the metallic crystallites once they were formed on the surface. For the sequential sample with a W/Pt atomic ratio of 3.28 W⁶⁺ did not inhibit the H₂ reduction of Pt oxides even below of 773 K, the Pt oxides were reduced completely. After reduction at 1073 K, sequential samples impregnating Pt on WO_x–γ-Al₂O₃ were more active and stable during benzene hydrogenation. TOF of the reaction did not change when the W/Pt atomic ratio, preparation technique and reduction temperature changed and its value was of 1.1 s⁻¹. W⁶⁺ ions promoted high thermal stability of Pt crystallites when sequential catalysts were reduced at 1073 K and decreased their Lewis acidity_.     

Re-investigation of the phase constitution of the system Pt-Te

The phase relations of the system Pt-Te have been investigated using the conventional sealed-capsule technique. The identification of phases present in the reaction products was made by reflected light microscopy, X-ray diffraction, and electron probe microanalysis. Four binary phases were confirmed to exist in the system: PtTe., Pt₃Te₄, Pt₂Te₃ and PtTe₂. The composition of all these appears to be constant without showing any appreciable compositional range. The Pt₂Te phase was not found in this study. The Te content in platinum and the Pt in tellurium in solid solution are negligible, less than 0.5 at.% up to 1000°C. The eutectic point between Pt and PtTe is near at 40 at.% Te and at 870°C. The Pt₂Te₃ phase is stable up to about 675°C, whereas the melting point of the Pt₃Te₄ phase is apparently above 1000°C. The most part of liquidus curve between PtTe₂ and Te exists above 1000°C. Physico-chemical properties of Pt-Te phases obtained in this study are given. The revised phase diagram of the Pt-Te system is proposed from this study.     

Synthesis and photoactivity of the highly efficient Ag species/TiO2 nanoflakes photocatalysts

Ag species/TiO₂ nanoflakes photocatalysts with different relative contents (Ag⁺, Ag²⁺, Ag⁰) have been successfully synthesized by a simple template-free synthetic strategy. X-ray photoelectron spectroscopy, X-ray diffraction, and UV-vis diffuse reflectance spectra indicated that the dopant ions (Ag⁺ or Ag²⁺) were partly incorporated into the titanium dioxide nanoflakes. Meanwhile, part of the silver ions migrated to the surface after the subsequent calcination and aggregated into ultra-small metallic Ag nanoclusters (NCs) (1-2 nm), which are well dispersed on the surface of TiO₂ nanoflakes. The photocatalytic activities of the Ag species/TiO₂ materials obtained were evaluated by testing the photodegradation of the azo dye reactive brilliant X-3B (X-3B) under near UV irradiation. Interestingly, it was found that the maximum photocatalytic efficiency was observed when Ag species coexisted in three valence states (Ag⁺, Ag²⁺, Ag⁰ NCs), which was higher than that of Degussa P25. The high photocatalytic activity of the Ag species/TiO₂ can be attributed to the synergy effect of the three Ag species.     

Chemical and microstructural organization of graphite intercalated with SbCl5 and SbF5 from 121Sb-Mössbauer spectroscopy

Differently prepared stage-one and stage-two graphite intercalation compounds (GICs) with SbCl₅ and SbF₅ were investigated with the 37.1 keV ¹²¹Sb-Mössbauer resonance and by transmission electron microscopy (TEM). The TEM observation parallel to the graphite c-axis gave insight into the inplane arrangement of various samples. An island structure was clearly imaged in non-stoichiometric samples. The ¹²¹Sb resonance spectra revealed the presence of both Sb⁵⁺ and Sb³⁺ intercalant species, with their relative abundances depending on the preparation conditions. In SbCl₅-graphite, the Sb³⁺ species were identified as neutral SbCl₃ molecules, with their trifold molecular symmetry axes oriented almost parallel to the carbon-layer planes. In undersaturated stage-two SbCl₅-GICs, Sb⁵⁺ and Sb³⁺ intercalant species in Sb⁵⁺:Sb³⁺ ratios varying from 1.4 to 2.2. were found; the former were identified as SbCl₆⁻-like. In saturated stage-one SbCl₅-graphite, the intercalant species were predominantly SbCl₅-like, with only small amounts of SbCl₃. Comparative studies of stage-one and stage-two SbF₅-GICs revealed the dominant presence of Sb⁵⁺ components in these systems, with Sb⁵⁺:Sb³⁺ ratios varying from ⋍4 to 17; two kinds of Sb³⁺ species were identified on the basis of Mössbauer spectra. One species, molecular SbF₃, was shown not to be in an intercalated state, while the other one was intercalated and tentatively assigned to SbF₄⁻ or SbF₅²⁻ molecules. It clearly emerged for all investigated systems that the Sb⁵⁺:Sb³⁺ ratio of intercalated species depended critically on the preparation conditions and hence was not a direct measure of the intercalation-induced charge transfer.     

Adsorption of octanohydroxamic acid at fluorite surface in presence of calcite species

The surface properties of fluorite are often affected by dissolved gangue species (e.g., calcite) during the flotation process. Microflotation testing with and without the addition of calcite supernatant was conducted using octanohydroxamic acid (OHA) as the collector. The results revealed that dissolved calcite species significantly affected the flotation behavior of fluorite. Fourier transform infrared spectra confirmed that the decrease in flotation recovery was linked to lower OHA adsorption. Solution chemistry analysis indicated that CaCO₃ and Ca²⁺ from the calcite supernatant were the most favorably adsorbed species, and X-ray photoelectron spectroscopy analysis confirmed the surface adsorption of calcite species. Density functional theory simulations provided a detailed analysis of the multidentate adsorption configuration of OHA, which was the most favorable for adsorption on the fluorite surface. The adsorption energy calculation showed that the calcite dissolved species were more stably adsorbed on the fluorite surface than OHA. The pre-adsorption of calcite dissolved species hindered the adsorption of OHA due to electrostatic repulsion.     

Effect of the oxidation state of gold on the complete oxidation of isobutane on Au/CeO2 catalysts

Catalysts of highly dispersed gold supported on ceria were prepared by deposition precipitation method. Au is dispersed as Au⁰, Au⁺ and Au³⁺ species on ceria. The content of Au⁺ and Au³⁺ was highest on catalyst prepared on uncalcined ceria, which possess least ordered surface. It is inferred that oxygen vacancy on disordered ceria surface is essential for the preparation of highly dispersed gold catalysts and in stabilizing monolayer surface Au⁺ clusters while cationic vacancies are sites for substitutional Au³⁺. Au/CeO₂ catalysts showed low-temperature isobutane oxidation activity with maximum conversion at 150–180°C. Ex-situ XPS results demonstrated that the low temperature isobutane oxidation activity was closely related to the content of Au⁺ which we interpreted as surface gold oxide formed under reaction conditions. Isobutane oxidation activity associated with ceria at temperature above 300°C was enhanced by substitutional Au³⁺.     

The influence of the microstructure of high noble gold-platinum dental alloys on their corrosion and biocompatibility in vitro

The aim of this work was to compare the microstructures of two high noble experimental Au-Pt alloys with similar composition with their corrosion and biocompatibility in vitro. We showed that Au-Pt II alloy, composed of 87.3 wt.% Au, 9.9 wt.% Pt, 1.7 wt.% Zn and 0.5 wt.% Ir + Rh + In, although possessing better mechanical properties than the Au-Pt I alloy (86.9 wt.% Au, 10.4 wt.% Pt, 1.5 wt.% Zn and 0.5 wt.% Ir + Rh + In), exerted higher adverse effects on the viability of L929 cells and the suppression of rat thymocyte functions, such as proliferation activity, the production of Interleukin-2 (IL-2), expression of IL-2 receptor and activation — induced apoptosis after stimulation of the cells with Concanavalin-A. These results correlated with the higher release of Zn ions in the culture medium. As Zn²⁺, at the concentrations which were detected in the alloy’s culture media, showed a lesser cytotoxic effect than the Au-Pt conditioning media, we concluded that Zn is probably not the only element responsible for alloy cytotoxicity. Microstructural characterization of the alloys, performed by means of scanning electron microscopy in addition to energy dispersive X-ray and X-ray diffraction analyses, showed that Au-Pt I is a two-phase alloy containing a dominant Au-rich α₁ phase and a minor Pt-rich α₂ phase. On the other hand, the Au-Pt II alloy additionally contained three minor phases: AuZn3, Pt₃Zn and Au_1.4Zn_0.52. The highest content of Zn was identified in the Pt₃Zn phase. After conditioning, the Pt₃Zn and AuZn₃ phases disappeared, suggesting that they are predominantly responsible for Zn loss, lower corrosion stability and subsequent lower biocompatibility of the Au-Pt II alloy.     

Transition metal- chalcogen systems XI: the platinum- selenium phase diagram

The platinum-selenium phase diagram was investigated by differential thermal analysis, metallography, and X-ray powder diffraction methods. The two previously known intermediate phases, Pt₅Se₄ and PtSe₂, both melt congruently: Pt₅Se₄ at ∼1070 °C and PtSe₂ (under its own vapor pressure) at 1245 ± 10 °C. Pt₅Se₄ forms a eutectic with Pt at 1065 ± 2 °C and ∼42 at % Se and another one with PtSe₂ at 1067 ± 2 °C and somewhat below 45 at.% Se. On cooling, Pt and PtSe₂ form a metastable eutectic at 1037 ± 2 °C and ∼43 at % Se. Between PtSe₂ and Se, a degenerate eutectic was found at 221 °C, which also indicates negligible solubility of platinum in solid selenium.     

Anion incorporation and migration during barrier film formation on aluminium

Surface analysis, using Auger electron spectroscopy with ion etching, and direct electronoptical examination have been employed to determine the relative contributions to solid film development during anodizing of aluminium, initially supporting a xenon implanted thin alumina film, in individual electrolytes containing phosphate, oxalate and chromate species. Under the anodizing conditions selected, film formation in the phosphate and chromate electrolytes proceeds at the metal/film and film/electrolytes interfaces, by O²⁻/OH⁻ ion ingress and Al³⁺ egress, respectively. In the oxalate electrolyte, little or no contribution to solid film growth is evident at the film/electrolyte interface, migrating Al³⁺ ions being ejected directly into the bulk electrolyte at that interface. Both phosphate and oxalate species are incorporated within the film material and are subsequently mobile inward under the field. Their respective migration rates are lower than that of O²⁻/OH⁻ ions such that a region of film material, free of the anion of the forming electrolyte, is developed adjacent to the metal/film interface.     

Growth and surface properties of new thermoacidophilic Archaea strain Acidianus manzaensis YN-25 grown on different substrates

The growth and surface properties of new thermoacidophilic Archaea strain Acidianus manzaensis YN-25 isolated from an acid hot spring in Tengchong, Yunnan Province, China were investigated cultured on different substrates including soluble substrate ferrous sulfate and nonsoluble solid substrates S^0, pyrite and chalcopyrite. The growth characteristics of the cells in each substrate were characterized with the changes in cell number, pH, Eh, and concentrations of Fe^2＋ or SO4^2- , or ratios of [Fe^2＋] to [Fe^3＋], and the surface properties were characterized and analyzed in terms of Zeta-potential, hydrophobicity, and surface FT-IR spectra of the cells. The results show that the cells grown on solid substrates have higher value of isoelectric points. They are more hydrophobic and express more surface proteins than ferrous sulfate grown cells.     

Adsorption of platinum(IV) by a composite based on silicon dioxide and copolymer of 4-vinylpyridine and 2-hydroxyethylmethacrylate

The adsorption of platinum(IV) solutions by a composite based on silicon dioxide and copolymer of 4-vinylpyridine and 2-hydroxyethylmetacrylate in hydrochloric acid solutions has been studied. The maximum efficiency of extraction of platinum(IV) ions has been detected in a solution of HCl with a concentration of 1 mol L^–1 at a temperature of 338 K (sorption capacity equal to 188 mg g^–1). The interaction of platinum (IV) with the surface of the composite is a result of chemisorption. The models of Langmuir, Freundlich, and Dubinin–Radushkevich have been used to describe the nature of adsorption. Adsorption kinetics was assessed using the models of Boyd–Adamson, pseudofirst and pseudosecond orders, and Elovich.     

嗜酸氧化亚铁硫杆菌（ATCC 23270）浸出黄铜矿过程中的EPS、Cu2+和Fe3+的相互作用机制（英文）

采用超声-离心方法提取嗜酸氧化亚铁硫杆菌(ATCC 23270)胞外多聚物(EPS)、EPS中的Cu2+、Fe3+离子,研究生物浸出黄铜矿过程中Cu2+、Fe3+和EPS的相互作用机制。结果表明:与Fe3+离子相比,Cu2+离子可刺激细菌产生更多的EPS;当Cu2+离子浓度从0.01mol/L增加到0.04mol/L时,EPS中Fe3+/Cu2+质量比从4:1降低到2:1;从1%黄铜矿的无铁9K介质中提取的EPS中铜铁含量是从含0.04mol/LCu2+离子的9K介质中提取的量的2倍。在生物浸出黄铜矿过程中,黄铜矿表面结合黄铁钾钒的EPS层减弱了Cu2+、Fe3+离子的迁移,逐渐成为离子扩散壁垒。     

Effect of metal ions on corrosion inhibition of pimeloyl-1,5-di-hydroxamic acid for steel in neutral solution

The influence of metal ions on the adsorption process and corrosion inhibition of pimeloyl-1,5-di-hydroxamic acid (C7) on carbon steel surface in neutral solutions has been investigated by surface analytical and electrochemical techniques. Effective corrosion inhibition given by C7 in the presence of Zn²⁺ and Ni²⁺ is believed to be associated with the ability of the hydroxamic acid to form stable slightly soluble complexes with these cations. The influence of the metal ions on the inhibition efficiency is primarily related to the stability constants of C7-cation complexes. Magnesium has no effect on the inhibition performance as it has low stability constant with C7. It was found that the inhibition by C7/cation mixtures depends greatly on the molar ratio and immersion time.