Mo–Bi Bimetallic Chalcogenide Nanoparticles Supported on CNTs for the Efficient Electrochemical Reduction of CO2 to Methanol

The electrochemical reduction of CO2 to methanol is a promising strategy, which currently suffers from the poor catalytic activity, selectivity, and stability of the electrode. Here, we report a simple one-pot hydrothermal strategy to fabricate Mo–Bi BMC@CNT nanocomposites, in which Mo–Bi bimetallic chalcogenide nanoparticles were in-situ decorated on carbon nanotubes. The Mo–Bi BMC nanoparticles with an average particle size of 12 nm were uniformly supported on the surface of CNTs without aggregation into larger clusters. The Mo–Bi BMC@CNT nanocomposites exhibited a relatively good catalytic performance for the electrochemical reduction of CO2 to methanol in a 60 wt.% 1-ethyl-3-methylimidazolium tetrafluoroborate aqueous electrolyte. Among them, the Mo–Bi BMC@CNT-15% nanocomposite showed the highest Faradaic efficiency of 81% for methanol at −0.3 V vs. a saturated calomel reference electrode (SCE) and a stable current density is 5.6 mA cm−2 after a run time of 12 h. The excellent catalytic properties are likely attributed to its nanostructure and fast electron transfer. These derive from the synergistic effect of Mo–Bi and the high conductivity of CNTs. This work opens a way to provide an efficient catalytic system for the electroreduction of CO2 to methanol in industrial applications.

Ion Release and Galvanic Corrosion of Different Orthodontic Brackets and Wires in Artificial Saliva

ABSTRACT Introduction To investigate the galvanic corrosion of brackets manufactured by four different companies coupled with stainless steel (SS) or nickel–titanium (NiTi) wires in an artificial saliva solution. Materials and methods A total of 24 mandibular central incisor Roth brackets of four different manufacturers (American Orthodontics, Dentaurum, Shinye, ORJ) were used in this experimental study. These brackets were immersed in artificial saliva along with SS or NiTi orthodontic wires (0.016”, round) for 28 days. The electric potential difference of each bracket/ wire coupled with a saturated calomel reference electrode was measured via a voltmeter and recorded constantly. Corrosion rate (CR) was calculated, and release of ions was measured with an atomic absorption spectrometer. Stereomicroscope was used to evaluate all samples. Then, samples with corrosion were further assessed by scanning electron microscope and energydispersive X-ray spectroscopy. Two-way analysis of variance was used to analyze data. Results Among ions evaluated, release of nickel ions from Shinye brackets was significantly higher than that of other brackets. The mean potential difference was significantly lower in specimens containing a couple of Shinye brackets and SS wire compared with other specimens. No significant difference was observed in the mean CR of various groups (p>0.05). Microscopic evaluation showed corrosion in two samples only: Shinye bracket coupled with SS wire and American Orthodontics bracket coupled with NiTi wire. Conclusion Shinye brackets coupled with SS wire showed more susceptibility to galvanic corrosion. There were no significant differences among specimens in terms of the CR or released ions except the release of Ni ions, which was higher in Shinye brackets. How to cite this article Tahmasbi S, Sheikh T, Hemmati YB. Ion Release and Galvanic Corrosion of Different Orthodontic Brackets and Wires in Artificial Saliva. J Contemp Dent Pract 2017;18(3):222-227.

Improved current collection in WO3:Mo/WO3 bilayer photoelectrodes

We report on the incorporation of molybdenum into tungsten oxide by co-sputtering and its effect on solar-powered photoelectrochemical (PEC) water splitting. Our study shows that Mo incorporation in the bulk of the film (WO3:Mo) results in poor PEC performance when compared with pure WO3, most likely due to defects that trap photo-generated charge carriers. However, when a WO3:Mo/WO3 bilayer electrode is used, a 20% increase of the photocurrent density at 1.6 V versus saturated calomel reference electrode is observed compared with pure WO3. Morphological and microstructural analysis of the WO3:Mo/WO3 bilayer structure reveals that it is formed by coherent growth of the WO3:Mo top layer on the WO3 bottom layer. This effect allows an optimization of the electronic surface structure of the electrode while maintaining good crystallographic properties in the bulk.

Enhanced Photoelectrochemical Activity of 120 MeV Ag9+ Irradiated Nanostructured Thin Films of ZnO for Solar-Hydrogen Generation via Splitting of Water

This paper deals with a study on 120 MeV Ag9+ irradiated thin films of zinc oxide (ZnO), obtained by sol-gel – spin coating onto TCO glass plates. Films irradiated at fluence 5×1011, 3×1012, 5×1012 and 2×1013 ions cm-2, were optically characterized for band gap determination. XRD analysis revealed polytypism as both wurtzite and zincblend phases co-evolved. Scherrer’s calculations indicated grain size in nanodimensions, while SEM analysis indicated smooth surface morphology of films. Flat band potentials and donor densities were evaluated by Mott-schottky calculations. For PEC studies, thin films of ZnO were employed as working electrode in conjunction with Platinum Counter electrode, Saturated Calomel Reference electrode, 13 pH aqueous solution of NaOH as electrolyte and 150W Xenon Arc light source for illumination. A significant gain in photoelectrochemical current was recorded on SHI irradiation. The films irradiated at fluence 3×1012 ions cm-2 yielded maximum increase in photocurrent that was nearly five times compared to unirradiated samples.

Thiophenophane–metal complexes. I. Preparation, X-ray structure, and cyclic voltammetry of 2,5,8-trithia[9](2,5)thiophenophane, L, and of its metalcomplexcation bis(2,5,8-trithia[9](2,5)thiophenophane-S2,S3]copper(I),[CuL2]+1

Preparation of the thiophenophane C10H14S4, (L), and syntheses of its copper(I) complex [CuL2]ClO4 or [CuL2]BF4 are described. The 13C and 1H nmr spectra of L and the ir spectra (4000–200 cm−1) of [CuL2]ClO4 and [CuL2]BF4 are reported. The molecular structures of L and [CuL2]ClO4 have been determined. For L: space group P21/a, a = 7.9347(2) Å, b = 18.7479(3) Å, c = 8.8596(2) Å, β = 108.446(2)°, Z = 4, Rf = 0.048, and Rw = 0.034. For [CuL2]ClO4: space group P21/c, a = 9.4363(1) Å, b = 18.2768(3) Å, c = 16.2157(3) Å, β = 96.520(2)°, Z = 4, Rf = 0.056, and Rw = 0.037. The Cu(I) complex has distorted tetrahedral coordination geometry; its perchlorate anion is non-coordinating and disordered. The Cu—S bond lengths lie in the range 2.301–2.392 Å and the S—Cu—S angles in the range 92.43—150.26°. Cyclic voltammetry of [CuL2]ClO4 (10−3 mol/L in dimethylsulfoxide, 0.1 mol/L Et4NClO4, glassy carbon working electrode, platinum counter electrode, aqueous saturated calomel reference electrode against which the ferrocenium/ferrocene potential under similar conditions was 400 mV) shows a quasi-reversible oxidation (E1/2 = 0.150 V, ΔEp = 170 mV at 50 mV/s). Thiophene's effect as a sub-unit in a small macrocycle upon properties of the latter is discussed.

Free Calcium in Serum. I. Determination with the Ion-Specific Electrode, and Factors Affecting the Results

Free (ionic) calcium in human serum was measured with a commercially available ion-specific electrode, together with a saturated-KCl salt bridge, a saturated-calomel reference electrode, and a direct-reading electrometer. Effects of sodium, potassium, and magnesium on the electrode values for calcium were assessed and a rationale demonstrated for the use of calcium standards containing 140 mmol of NaCl, 5 mmol of KCl, and 0.55 mmol of MgCl2 per liter. Trypsin, triethanolamine, and heparin bind calcium; therefore, their use is to be avoided. Variability is greatly decreased if the serum is from a fasting subject and if the collection tube is completely filled, transported on ice, and handled anaerobically. The range for free calcium for 86 apparently healthy adults was 1.175-1.375 mmol/liter when measured at 25°C. The precision (coefficient of variation) of duplicates was 0.6%; the long-term precision ≃2.0%.

Polarographic Determination of Piperazine in Animal Feeds

A simple and rapid polarographic method has been developed for the analysis of piperazine in animal feeds. A polarographically reducible condensation product of piperazine dihydrochloride is formed in the presence of excess formaldehyde in pH 5 buffer solution; the diffusion current of the product is measured at —0.98 v vs. a saturated calomel reference electrode.

THE CHEMISTRY OF IRIDIUM IN BASIC AQUEOUS SOLUTION: A POLAROGRAPHIC STUDY

The polarographic behavior of iridium(IV) has been studied in basic solutions at 25 °C at an ionic strength maintained with sodium chloride at 0.50 M. Between pH 11.3 and 13.0, a reversible, diffusion-controlled, one Faraday per mole reduction wave was obtained. The E1/2 was −0.60 V versus a saturated calomel reference electrode at pH 12.0; a shift of −57 mV per pH unit indicated that one hydrogen ion is involved in the reduction. With basic solutions of iridium(III), the corresponding oxidation wave was obtained, but the metal was easily air oxidized. The basic iridium(IV) species gave an absorption peak at 313 mμ. The rate of formation of the basic iridium(III) complex from an acid iridium(III) solution was found to be more rapid than that of the basic iridium(IV) complex from an acid iridium(IV) solution. The reaction of iridium (IV) with ethylenediaminetetracetate was also studied.