Collective properties of neutron-rich Ru, Pd, and Cd isotopes

Collective properties of neutron-rich Ru, Pd, and Cd isotopes are reviewed, combining the original results from the IGISOL β-decay experiments with recent experimental and theoretical progress. The transitional nature of Ru and Pd nuclei is discussed via the low-lying level systematics, including the low-lying 0^?+? states. Although the role of an anharmonic quadrupole vibrator in Cd nuclei was recently questioned, level systematics for the three-phonon quintuplet in ^116,118,120Cd are presented, and an outlook of the spectroscopic methods for the level lifetime or B(E2) values is given.     

Oscillatory oxidation of co over Pd and Ir catalysts

Oscillations in the rate of CO₂ production have been observed for the first time over Pd and Ir catalysts. The experiments were conducted near atmospheric pressure in a clean flow reactor system using polycrystalline Pd or Ir wire. For Pd, sustained oscillations were found over a wide range of gas compositions and temperatures (230 < T_g < 350°C), where P_CO and P_O2 are the respective partial pressures of carbon monoxide and oxygen in the gas stream, and Tg is the temperature of the gas. For Ir, oscillations were found for and 180 < T_g < 250°C. As proposed for CO oxidation over a Pt catalyst, it is believed that the oscillations occur between two branches of a Langmuir-Hinshelwood reaction mechanism, and that the slow formation and removal of subsurface oxygen drives the reaction between these two branches. These experiments suggest that oscillations in surface reactions are more general than previously suspected.     

Asymmetric hydrogenation of ketones: Tactics to achieve high reactivity,enantioselectivity, and wide scope

Ru complexes with chiral diphosphines and amine-based ligands achieve high catalytic activity and enantioselectivity for the hydrogenation of ketones under neutral to slightly basic conditions. The chiral environment is controllable by changing the combination of these two ligands. A concerted six-membered transition state is proposed to be the origin of the high reactivity. The η⁶-arene/TsDPEN–Ru and MsDPEN–Cp*Ir catalysts effect the asymmetric reaction under slightly acidic conditions. A variety of chiral secondary alcohols are obtained in high enantiomeric excess.     

Synthesis,Characterization, DNA Binding Studies,Photocleavage, Cytotoxicity and Docking Studies of Ruthenium(II) Light Switch Complexes

A new ligand 3-(1H-imidazo[4,5-f][1,10]phenanthrolin-2yl)phenylboronic acid and its (IPPBA) three ruthenium(II) complexes [Ru(phen)₂(IPPBA)](ClO₄)₂ (1), [Ru(bpy)₂(IPPBA)](ClO₄)₂ (2) and [Ru(dmb)₂(IPPBA)](ClO₄)₂ (3) have been synthesized and characterized by elemental analysis, UV/VIS, IR, ¹H-NMR,¹³C-NMR and mass spectra. The binding behaviors of the three complexes to calf thymus DNA were investigated by absorption spectra, emission spectroscopy, viscosity measurements, thermal denaturation and photoactivated cleavage. The DNA-binding constants for complexes 1, 2 and 3 have been determined to be 7.9?×?10⁵ M^?1, 6.7?×?10⁵ M^?1 and 2.9?×?10⁵ M^?1. The results suggest that these complexes bound to double-stranded DNA in an intercalation mode. Upon irradiation at 365 nm, three ruthenium complexes were found to promote the cleavage of plasmid pBR322 DNA from super coiled form ? to nicked form ??. Further in the presence of Co²⁺, the emission of DNA–Ru(ΙΙ) complexes can be quenched. And when EDTA was added, the emission was recovered. The experimental results show that all three complexes exhibited the “on–off–on” properties of molecular “light switch”. The highest Cytotoxicity potential of the complex1 was observed on the Human alveolar adenocarcinoma (A549) cell line. Good agreement was generally found between the spectroscopic techniques and molecular docked model which provides further evidence of groove binding.     

利用交流阻抗谱揭示Ir(111)电极在酸性溶液中的氢吸附动力学

本文利用阻抗谱研究Ir(111)电极在HClO₄和H₂SO₄中溶液中的氢吸附行为. 在HClO₄溶液中,随着施加电位从0.2 V降到0.1 V(vs RHE),Ir(111)电极上氢吸附速率从1.74×10^-8 mol·cm^-2·s^-1增大到 3.47×10^-7 mol·cm^-2·s^-1 . 与相同条件下Pt(111)电极上的氢吸附速率相比,Ir(111)上的氢吸附速率要小1∽2个数量级,这是由于Ir(111)电极与H₂O结合能力更强,因此位于水合氢键网络中的氢离子需要克服更高的能垒才能重新定向进而发生欠电位沉积. 在H₂SO₄溶液中,氢吸附电位负移了200 mV,吸附速率也下降了一个数量级,这是由于Ir(111)电极表面强吸附的硫酸根/硫酸氢根物种的阻碍作用. 结果表明,在电化学环境下,位于电极表面附近的水分子的取代和重新定向在很大程度上影响了氢吸附过程.     

Synthesis, crystal structure and thermoelectric properties of IrSn1.5Te1.5 -based skutterudites

The mixed anion skutterudite IrSn_1.5Te_1.5 has been synthesized and characterized by X-ray powder diffraction, thermopower and electrical resistivity measurements. Structural analysis reveals that Sn and Te order in layers perpendicular to the [111] direction of the skutterudite unit cell, and a distortion of the anion sublattice is evident. The thermopower (S) is 160 μV/K at room temperature, while the electrical resistivity (ρ) is . The effects of chemical substitutions on the Ir site (Ru, Pd) and Sn site (In, Sb) have been investigated. The power factor (S²/ρ) was found to improve with In substitution but, at 0.9 μW/K² cm, is too small for this material to be useful for thermoelectric applications.     

Generating Parahydrogen-Induced Polarization Using Immobilized Iridium Complexes in the Gas-Phase Hydrogenation of Carbon–Carbon Double and Triple Bonds

Immobilized iridium complexes synthesized using [Ir(COD)Cl]₂ by anchoring on hydrous and anhydrous silica gels were studied in terms of generating parahydrogen-induced polarization (PHIP) in the gas-phase hydrogenation of propylene and propyne. Distinguishing differences in the hydrogenations of carbon–carbon double and triple bonds were found. It has been shown that in the double bond hydrogenation both catalysts are very active even at 25 °C. The reaction yield in continuous flow experiments is more than 70 %, whereas the obtained PHIP degrees are very low. In the case of the triple bond hydrogenation, a more or less active hydrogenation reaction was observed at relatively high temperatures (≈70–80 °C) for the catalyst immobilized on anhydrous silica, while the catalyst immobilized on hydrous silica was inactive at these temperatures. Contrary to the double bond hydrogenation, the triple bond hydrogenation provided significant signal enhancements observed in ¹H nuclear magnetic resonance spectra for the signals corresponding to protons of vinyl fragments of product propylene in both PASADENA and ALTADENA experiments. The catalyst, however, is not stable under the triple bond hydrogenation reaction conditions, and deactivates within several minutes. It was also found that at higher temperatures (100–120 °C), this catalyst demonstrates a reactivation most likely associated with the reduction of Ir(I) that results in the formation of Ir(0) surface metal nanoparticles.     

Copper ion induced reactions on110-108-106Cd,109-107Ag and110Pd. new rhenium,osmium and iridium isotopes

By⁶³Cu induced reactions on¹¹⁰Cd,¹⁰⁸Cd,¹⁰⁶Cd,¹⁰⁹Ag,¹⁰⁷Ag and¹¹⁰Pd targets, new isotopes were searched in the Ir, Os, Re region. Cross bombardments and excitation function measurements were used to identify newα emitting isotopes:¹⁷⁰Ir (E _α = 6.01 ±0.01 MeV?T _1/2=1.1±0.2s),¹⁶⁹Ir (E _α =6.11±0.01 MeV?T _1/2=0.4±0.1 s),¹⁶⁸Ir (E _α =6.22±0.02 MeV,¹⁶⁸Os (E _α =5.66±0.01 MeV?T _1/2=1.9±0.1 s),¹⁶⁷Os (E _α =5.84 ±0.01MeV ?T ^1/2=0.65±0.15s),¹⁶⁶Os (E _α =6.00±0.02 MeV?T _1/2=0.3 ±0.1 s),¹⁶⁵Os (E _α =6.20±0.02 MeV),¹⁶⁹Re (E _α =5.05±0.01 MeV),¹⁶⁸Re (5.26±0.01 MeV?T ^1/2=5.5 ±0.5 s). Theα-decay measurements are compared to theQ _α values obtained from different mass predictions.     

Excited states of97Pd

The⁹⁷Pd nucleus has been studied from the reaction⁹⁶Ru(³He, 2n)⁹⁷Pd. From in and out beam directγ-spectra andγ-γ coincidences a partial level scheme is proposed. The observed high spin states can be explained by the coupling of the even proton core with the d_5/2 51^st neutron.     

Spin-flipβ − decay of even-even deformed nuclei110Ru and112Ru

Neutron-rich nuclides¹¹⁰Ru and¹¹²Ru produced in symmetric fission of²³⁸U by 20 MeV protons have been studied at the IGISOL facility by means ofβ-ray,γ-ray and conversion electron spectroscopy. A total of 12 and 6γ-transitions were observed in the decays of¹¹⁰Ru and¹¹²Ru, respectively. Multipolarities were determined for a few transitions. The beta decay half-life was determined to be 11.6±0.6 s for¹¹⁰Ru and 1.75±0.07 s for¹¹²Ru. As a side product, a new value of 2.1±0.3 s for theβ half-life of the¹¹²Rh 1⁺ state was obtained. The decay energy measured with the plastic scintillator was 2.81 ±0.05 MeV for¹¹⁰Ru and 4.52 ±0.08 MeV for¹¹²Ru. The beta decay schemes of¹¹⁰Ru and¹¹²Ru isotopes indicate that the main fraction of their beta strength resides in two 0⁺→1⁺ spin-flip transitions with their logf t values between 4.4 and 4.7. The decay energies and the energies of the 1⁺ GT states are compared with the macroscopic-microscopic model calculations. The observed GT-strengths are discussed in the framework of the deformed single-particle model.     

On the assignment of high-spin cascades to98Rh and98Pd isotopes

Isotopic assignment of high-spin cascades in⁹⁸Rh and⁹⁸Pd have unambigously been obtained by a suitable combination of the⁹⁶Ru(α, xn yp) and the⁹⁹Ru(d, xn yp) reactions. As a result the band headed by the 841.3 keV line was assigned to⁹⁸Rh and the one headed by the 862.6 keVγ-ray has been found to belong to⁹⁸Pd. In the case of⁹⁸Rh the band is based on the (2⁺) ground state.     

Nonlinear optical absorption and refraction in Ru, Pd, and Au nanoparticle suspensions

We present the results of studies of the nonlinear optical properties of Pd, Ru, and Au nanoparticles. We studied the nonlinear refraction and nonlinear absorption of suspensions of these nanoparticles at 1064-nm wavelength. A relatively strong nonlinear absorption of the Pd nanoparticles was observed in the case of 1064-nm, 50-ps pulses (β=2×10⁻⁹ m W⁻¹). The Ru and Pd nanoparticles showed weak negative nonlinear refraction (γ∼−(6–8)×10⁻¹⁶ m² W⁻¹) in this spectral range. In the case of the Au nanoparticles, a saturated absorption at 532 nm dominated over other nonlinear optical processes.     

Isomer shifts and changes of the nuclear charge radii in99Ru and101Ru

The recoilless nuclear gamma resonance of the 127 keV γ-rays of¹⁰¹Ru was observed in ruthenium metal, RuO₂ and [Ru(NH₃)₄(HSO₃)₂]. By comparison of the isomer shifts observed in these materials for the 127 keV absorption line with the corresponding shifts of the 90keV γ-rays of⁹⁹Ru one obtains δ〈r ²〉 [127 keV]/ δ〈r ²〉 [90 keV]=1.78±0.26 for the ratio of the changes of the mean square nuclear charge radii between the first excited and the ground states in these nuclei. An estimate of electron density differences based on free-ion relativistic self-consistent field calculations yields δ〈r ²〉[90keV]≈+1.4·10^?3 for⁹⁹Ru and δ〈r ²〉/〈r ²〉 [127 keV]≈+2.4·10^?3 for the¹⁰¹Ru case. These results are discussed in terms of the core excitation model.     

L12 phase formation and giant exchange anisotropy in Mn3Ir/Co–Fe bilayers

The degree of order S of Mn–Ir layers and the exchange anisotropy of Mn–Ir/Co–Fe bilayers were investigated for various chemical compositions of Mn–Ir layers, underlayer materials, and underlayer thicknesses. It was found that: (1) The compositional range over which L1₂-phase Mn₃Ir could be formed is 22–32 at% Ir and giant exchange anisotropy is obtained in this range. (2) Ru is favorable as an underlayer material for avoiding interdiffusion with the Mn–Ir layer during deposition on the temperature elevated substrate. (3) The underlayer thickness could be reduced to 5 nm while maintaining a giant exchange anisotropy in excess of 1 erg/cm².     

The low-lying quadrupole collective excitations of Ru and Pd isotopes

Quadrupole excitations of even-even Ru and Pd isotopes are described within a microscopic approach based on the general collective Bohr model which includes the effect of coupling with the pairing vibrations. The excitation energies and E2 transition probabilities observed in ^104–114Ru and ^106–110Pd are reproduced in the frame of the calculation containing no free parameters. Particularly interesting are ¹⁰⁴Ru and ^106–110Pd where good agreement to very rich information based on Coulomb excitation experiments is achieved.     

Conversion coefficients and E0 transitions in102, 104, 106Pd

In in-beam (p, p′) experiments, electron and γ-spectra were measured in the electron energy range of 500-1840 keV for¹⁰²Pd and¹⁰⁴Pd, and 600–1580 keV for¹⁰⁶Pd. The conversion coefficients of all transitions in this range were obtained with accuracies of about 20%, in some favourable cases 10%. Special attention was given to 0⁺′-0⁺ transitions from the two-phonon triplets to the ground states with the following results for the branching ratios 0⁺′-0⁺ (ground state) to 0⁺′-2⁺ (one-phonon state):¹⁰²Pd:T _k (E0)/T _γ (E2)<(2.1±3.6)·10^{?7 104}Pd:T _k (E0)/T _γ (E2)=(6.0±1.4)·10^{?5 106}Pd:T _k (E0)/T _γ (E2)=(6.0±2.0)·10^?4     

Multiwalled carbon nanotube supported Pt–Sn–M (M = Ru,Ni, and Ir) catalysts for ethanol electrooxidation

In the present study, Pt–Sn–M (M = Ru, Ni, and Ir) nanocatalysts were supported on multiwalled carbon nanotube and their electrocatalytic activity for ethanol oxidation in membraneless fuel cells was investigated. The combination of monometallic Pt/MWCNTs, bi-metallic Pt–Sn/MWCNTs, and tri-metallic Pt–Sn–Ru/MWCNT, Pt–Sn–Ni/MWCNT, and Pt–Sn–Ir/MWCNT nanocatalysts were prepared by the ultrasonic assisted chemical reduction method. Transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) were used for the catalyst characterization. The electrocatalytic activities of the catalysts were investigated in half-cell experiments using cyclic voltammetry (CV), CO stripping voltammetry, and chronoamperometry (CA). During the experiments performed on a single membraneless ethanol fuel cell (MLEFC), the Pt–Sn–Ir/MWCNTs exhibited a better catalytic activity from among all the catalysts prepared, with a power density of 39.25 mW cm^?2.     

Beta delayed proton emission from the 14s 21/2+ spin gap isomer in95Pd

The residual activities of the projectile-target system⁴⁰Ca→⁵⁸Ni have been investigated with gamma and proton multi spectrum analyses,γγ andpγ coincidences. Aβ decaying high-spin isomer in⁹⁵Pd withJ ^π=(21/2⁺), a half-life of 14±1 s and an excitation energy of about 2 MeV has been identified. It has been found that⁹⁵Pd ^m is aβ delayed proton precursor. The totalβ branching to proton emitting states has been determined to be (0.74±0.19)·10^?2. It has been observed that the final state in⁹⁴Ru, populated after proton emission, is dominantly the 8⁺ state. A decay scheme of⁹⁵Pd ^m has been derived.     

Thermoelectric power of Ir(Fe)

Thermoelectric power data between 4.2 and 300°K are presented for Ir containing 0.5 and 1 at.% Fe and for pure Ir. Peaks similar to those found in Pd(Ni) and Rh(Fe) occur in Ir(Fe) at the spin fluctuation temperature T_sf = 28°K, independent of solute concentration. Similarities and differences among the three alloy systems are discussed.