Structure and Performance Optimization of Co Magnetic Thin Films Deposited by Vacuum Evaporation Coating.

Co magnetic films are widely used in high-frequency magnetic recording and vertical magnetic recording due to their high saturation magnetization and magnetocrystalline anisotropy. In this work, ferromagnetic Co magnetic films were prepared on copper substrate by vacuum evaporation combined with heat treatment (H2 atmosphere), to investigate the impact of film thickness and annealing temperature on microstructure and magnetic properties. The results show that with the increase in annealing temperature, the Co thin film physical phase does not change significantly, the crystallinity increases, and the grain size increases, which is consistent with the results obtained from the SEM morphology map of the sample surface, leading to an increase in coercivity. By annealing experiments (atmospheric atmosphere) on Co magnetic films with and without an Al protective layer, as shown by scanning electron microscopy microscopic characterization results, it was verified that the Al layer can protect the inner Co layer from oxidation. As the film thickness increases from 10 to 300 nm, the magnetic properties of Co films change significantly. The saturation magnetization gradually increases from 0.89 to 5.21 emu/g, and the coercivity increases from 124.3 to 363.8 Oe. The remanence ratio of the 10 nm magnetic film is 0.82, which is much higher than the film remanence ratio of 0.46 at 50 nm. This is because when the thickness of the film is between 10 and 50 nm, the magnetic moments partially deviate from the in-plane direction, and the out-of-plane component reduces the film remanence ratio. This study shows that optimizing annealing temperature and film thickness can effectively control the structure and magnetic properties of Co magnetic films, which is of great significance for the development of the magnetic recording field.

Dissociation of Bipyridine and Coordination with Nitrosyl: Cyclometalated Ruthenium Nitrosyl Complex.

A novel family of ruthenium nitrosyl complexes [Ru(bpy)(C∧N)(MeCN)NO](PF6)2 (2a-2e, bpy = 2,2'-bipyridine, HC∧N = 2-phenylpyridine and its derivatives) has been prepared by reacting cyclometalated ruthenium complexes [Ru(bpy)2(C∧N)][PF6] (1a-1e) with NO+, which were comprehensively characterized by mass, IR, NMR, and UV-vis spectra as well as the single-crystal X-ray structure determinations. Herein, the coordination geometry of Ru atoms in 2a-2e is a distorted octahedron and {RuII-NO+}6 is present in these complexes. Theoretical calculations suggest that the reactions involving dissociation of one bipyridine and coordination with NO+ proceed spontaneously (ΔG < 0) and the transformation from 1a-1e to the intermediates is dominated by substituents (ΔGRI varies from -1.19 to -1.53 eV), which influence the binding energy between Ru(II) and NO+ in complexes 2a-2e (-89.42 to -101.17 kcal/mol) and thus control the photorelease of NO on a certain scale. The weak absorption bands in the visible region could be attributed to the contribution of dπ(RuII) → π*(NO+), which were enhanced greatly under light, indicating the possible release of NO. The photoinduced NO, as well as singlet oxygen (1O2), was then confirmed by EPR spectra, and the amount of NO released from 2a-2e was estimated via Griess reagent assay. The cytotoxicity of these complexes with or without visible light irradiation was also investigated using an MTT assay.

Synergistic Optimization of Electrical-Thermal-Mechanical Properties of the In-Filled CoSb3 Material by Introducing Bi0.5Sb1.5Te3 Nanoparticles.

How to realize the synergistic optimization of electrical-thermal-mechanical properties of thermoelectric materials is a key challenge. Using the Bi0.5Sb1.5Te3 nanoparticle as a mixed agent provides an effective way to address this challenge. Here, Bi0.5Sb1.5Te3/In0.25Co4Sb12 nanocomposites with different contents of Bi0.5Sb1.5Te3 nanoparticles were successfully prepared by ultrasonic dispersion combined with spark plasma sintering. Phase and microstructure characterization presented that Te nanoparticles were precipitated from Bi0.5Sb1.5Te3 during the SPS sintering process. Transport measurement results showed that the electrical conductivity was increased due to the increased carrier concentration induced by the charge transfer between Te nanoparticles and the matrix. The Seebeck coefficient was also increased due to the selected electron scattering and increased scattering factor. The lattice thermal conductivity was dramatically suppressed because of the enhanced phonon scattering induced by the Bi0.5Sb1.5Te3 nanoparticles and in situ-precipitated Te nanoparticles and increased dislocations. As a result, a higher average ZT value of 1 was obtained in the range of 300-700 K by the decoupling of the electrical and thermal transport properties for the nanocomposite with 0.1 wt % of Bi0.5Sb1.5Te3 nanometer suspension. Furthermore, the flexural strength, fracture toughness, and hardness of the nanocomposites were also improved significantly. This work demonstrates that using the Bi0.5Sb1.5Te3 nanoparticle as a mixed agent can realize the synergistic optimization of electrical-thermal-mechanical properties of the In-filled CoSb3 thermoelectric material.

A highly sensitive and selective colorimetric probe based on a cycloruthenated complex: an Hg2+-promoted switch of thiophene coordination.

A cyclometalated ruthenium complex [Ru(pthb)(bpy)2]+ (1, bpy = 2,2'-bipyridine, Hpthb = 3,3-dimethyl-2-(5-pyridylthiophen-2-yl)vinyl-benzo[e]indolium-1-propylsulfonate) could be converted from a C-coordinated structure to non-metallated species with N,S-bonded Hpthb upon treatment with mercury(ii) ions in water. Strikingly, the switch in the coordination mode resulted in a great absorption change along with a change in the solution color of 1 from dark red to light yellow. Therefore, 1 can be used as a colorimetric probe to detect mercury(ii) ions by the naked eye. Although the emission was not observed for 1 in water, it still demonstrated an appreciably low detection limit of 21 nM by using UV-Vis absorption spectroscopy, which was comparable with those of some probes determined by ratiometric fluorescence spectroscopy.

A polymer membrane tethered with a cycloruthenated complex for colorimetric detection of Hg2+ ions.

A new cyclometallated ruthenium complex (Ru1) involving a 2-(2-thienyl)pyridine and a benzo[e]indolium block connected with a hexanoic acid was successfully synthesized and characterized, which exhibited the high sensitivity and selectivity to Hg2+ over other common metal ions with the detection limit of as low as 0.053 µM in aqueous system. Then, it was grafted onto a polymer membrane to afford a Hg2+-sensitive membrane (sensor 1), which was characterized by FT-IR, SEM and XPS spectra, respectively. When sensor 1 was dipped into the aqueous solution of Hg2+ ions, the color of the membrane changed from dark-red to yellow, which could be observed by naked eyes easily. It should be noted that the membrane can absorb Hg2+ ions well in aqueous solution and the adsorption capacity of this polymer membrane for Hg2+ ions was determined by atomic absorption spectroscopy, indicating that it also could be used as a potential material for removal of Hg2+ ions.

Benzo[e]indolium derivatives in aqueous solutions: Reaction with bisulfite and successive interaction with Cu2+ and Hg2.

A new benzo[e]indolium derivative 1 including pyridyl and thienyl groups was synthesized and characterized, which failed to response to Hg2+ or Cu2+ in aqueous system. However, it is interesting that when it reacted with bisulfite in HEPES buffer, the in situ generated ensemble as 1-SO3H displayed dramatic absorption and fluorescence changes after adding Cu2+ or Hg2+, which were contrary to the changes of 1 upon the addition of bisulfite ions. By contrast, the other two derivatives 2 and 3 showed the almost similar trends of spectral changes, which were short of ligating atoms N or S. The further investigation of 1HNMR spectra changes of 1 showed that C-SO3H bond may be interrupted because the good binding capacity of Hg2+ and Cu2+ with O of C-SO3H weaken the binding force of C-SO3H, which resulted in the recovery of ethylene with benzo[e]indolium block. The DFT calculations results further confirmed it.

Cycloruthenated complexes: pH-dependent reversible cyclometallation and reactions with nitrite at octahedral ruthenium centers.

The pH-dependent reversible cyclometallation and reactions with nitrite in a near-aqueous system of a related set of cyclometallated ruthenium(ii) bipyridyl complexes were investigated in detail. These complexes are [Ru(ppy)(bpy)2]PF6 (, bpy = 2,2'-bipyridine, Hppy = 2-phenylpyridine), [Ru(thpy)(bpy)2]PF6 (, Hthpy = 2-(2-thienyl)pyridine), and [Ru(dfppy)(bpy)2]PF6 (, Hdfppy = 2-(2,4-difluorophenyl)pyridine). As expected, reversible UV-Vis spectra of these three complexes in near-aqueous solutions can be achieved by treating with acid or base, which indicates a pH-dependent reversible cyclometallation. However, the addition of nitrite to acidic solutions of these complexes disturbed the reversible pH-dependent processes. Unexpected ruthenium complexes in the aforementioned system were then isolated and characterized using FT-IR, MS, (1)H NMR, and UV-Vis spectra, indicating that two reaction modes occurred at the ruthenium(ii) centers: (1) the insertion of NO into the ruthenium-aryl bond to form a ruthenium C-nitroso complex; and (2) the coordination of NO with the entire dissociation of one bipyridine to form a {Ru-NO}(6) complex, which is the first example involving the cleavage of Ru-N(∧)N bonds in ruthenium bipyridyl complexes.

Multi-localization transport behaviour in bulk thermoelectric materials.

Simultaneously optimizing electrical and thermal transport properties of bulk thermoelectric materials remains a key challenge due to the conflicting combination of material traits. Here, we have explored the electrical and thermal transport features of In-filled CoSb3 through X-ray absorption fine structure, X-ray photoemission spectra, transport measurement and theoretical calculation. The results provide evidence of three types of coexisting multi-localization transport behaviours in the material; these are heat-carrying phonon-localized resonant scattering, accelerated electron movement and increase in density of states near the Fermi level. The 5p-orbital hybridization between In and Sb is discovered in the In-filled CoSb3 compound, which results in a charge transfer from Sb to In and the enhancement of p-d orbital hybridization between Co and Sb. Our work demonstrates that the electrical and thermal properties of filled skutterudite bulk thermoelectric materials can be simultaneously optimized through the three types of coexisting multi-localization transport behaviours in an independent way.

Iron oxide encapsulated by ruthenium hydroxyapatite as heterogeneous catalyst for the synthesis of 2,5-diformylfuran.

Magnetic γ-Fe2 O3 nanocrystallites encapsulated by hydroxyapatite (HAP), HAP@γ-Fe2 O3 , were prepared followed by cation exchange of Ca(2+) on the external HAP surface with Ru(3+) to give the γ-Fe2 O3 @HAP-Ru catalyst. The structure of the as-prepared catalyst was characterized, and its catalytic activity was studied in the aerobic oxidation of 5-hydroxymethylfurfural (HMF). γ-Fe2 O3 @HAP-Ru showed a high catalytic activity for the aerobic oxidation of HMF into 2,5-diformylfuran (DFF). A high DFF yield of 89.1 % with an HMF conversion of 100% was obtained after 4 h at 90 °C. Importantly, the synthesis of DFF from fructose was realized by two consecutive steps. The dehydration of fructose in the presence of a magnetic acid catalyst (Fe3 O4 @SiO2-SO3 H) produced HMF in a yield of 90.1%. Then the Fe3 O4 @SiO2 SO3 H catalyst was removed from the reaction solution with a permanent magnet, and HMF in the resulting solution was further oxidized to DFF with a yield of 79.1% based on fructose. The synthesis of DFF from fructose by two steps avoids the tedious separation of the intermediate HMF, which saves time and energy.