A new methodology for studying vortex dynamics based on point-contact spectroscopy.

Vortex dynamics has attracted tremendous attention for both fundamental physics and applications of type-II superconductors. However, methods to detect local vortex motion or vortex jump with high sensitivity are still scarce. Here, we fabricated soft point contacts on the clean layered superconductor 2H-NbSe2, which are demonstrated to contain multiple parallel micro-constrictions by scanning electronic microscopy. Andreev reflection spectroscopy was then studied in detail for the contacts. Differential conductance taken at fixed bias voltages was discovered to vary spontaneously over time in various magnetic fields perpendicular to the sample surface. The conductance variations become invisible when the field is zero or large enough, or parallel to the sample surface, which can be identified as the immediate consequence of vortex motion across a finite number of micro-constrictions. These results demonstrate point contact Andreev reflection spectroscopy to be a new potential way with a high time resolution to study the vortex dynamics in type-II superconductors.

Fully Depleted Self-Aligned Heterosandwiched Van Der Waals Photodetectors.

Room-temperature-operating highly sensitive mid-wavelength infrared (MWIR) photodetectors are utilized in a large number of important applications, including night vision, communications, and optical radar. Many previous studies have demonstrated uncooled MWIR photodetectors using 2D narrow-bandgap semiconductors. To date, most of these works have utilized atomically thin flakes, simple van der Waals (vdW) heterostructures, or atomically thin p-n junctions as absorbers, which have difficulty in meeting the requirements for state-of-the-art MWIR photodetectors with a blackbody response. Here, a fully depleted self-aligned MoS2 -BP-MoS2 vdW heterostructure sandwiched between two electrodes is reported. This new type of photodetector exhibits competitive performance, including a high blackbody peak photoresponsivity up to 0.77 A W-1 and low noise-equivalent power of 2.0 × 10-14  W Hz-1/2 , in the MWIR region. A peak specific detectivity of 8.61 × 1010  cm Hz1/2  W-1 under blackbody radiation is achieved at room temperature in the MWIR region. Importantly, the effective detection range of the device is twice that of state-of-the-art MWIR photodetectors. Furthermore, the device presents an ultrafast response of ≈4 µs both in the visible and short-wavelength infrared bands. These results provide an ideal platform for realizing broadband and highly sensitive room-temperature MWIR photodetectors.

Enhanced Electrochemical O2 -to-H2 O2 Synthesis Via Cu-Pb Synergistic Interplay.

Electrocatalytic reduction of oxygen (O2 ) to produce hydrogen peroxide (H2 O2 ) frequently suffers from the low activity and poor selectivity of catalysts owing to the lack of systematic strategies. The resulting enhancement to enable the further design of a new bimetallic catalyst with the synergistic interplay, as exemplified by Cu-Pb catalyst for two-electron oxygen reduction reaction (2e- ORR), is reported here. Critically, in-depth evidence, including density functional theory (DFT) calculations, electrochemical signals, in-situ Raman, and H2 O2 -proof work, allude to a catalytic favor to the 2e- ORR of Cu-Pb.

Nanohybridization of Keggin polyoxometalate clusters and reduced graphene oxide for lithium-ion batteries.

The nanocomposites of reduced graphene oxide (RGO) and polyoxometalates (POMs) have been considered to be effective to boost more Li+ to participate in intercalation/deintercalation process of lithium-ion batteries (LIBs). In this paper, a nanocomposite (PMo12@RGO-AIL) with electrostatic interaction of RGO and Keggin-type [PMo12O40]3- has been fabricated and characterized by XRD, XPS, SEM, and TEM. To prepare PMo12@RGO-AIL, a strategy of covalent modification is developed between amino-based ionic liquid and RGO, helping to achieve the uniform dispersion of [PMo12O40]3-. When the PMo12@RGO-AIL was used as a cathode for LIBs, it could exhibit more excellent reversible capacity, cycle stability, and rate capability than those of samples without modifying by ionic liquids. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11051-020-05108-x.

Biomolecule-Assisted Synthesis and Electro-Catalytic Hydrogen Evolution of Flowerlike Nickel Sulfide Nanostructures.

In this paper, flowerlike nickel sulfide materials are synthesized using a facile solution-phase biomolecule-assisted approach in the presence of L-cysteine (an ordinary and cheap amino acid), which turned out to serve as both the sulfur source and the directing molecule in the formation of nickel sulfide nanostructures. The morphology, structure, and phase composition of the assynthesized nickel sulfide products are characterized using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman. Moreover, the nickel sulfide materials are investigated as electro catalysts for hydrogen evolution reaction (HER) in strongly alkaline media. The electro catalytic performance of as-prepared nickel sulfide is promising for applications as non-noble-metal HER catalysts with water splitting for hydrogen production.

A bimetallic oxide Fe1.89Mo4.11O7 electrocatalyst with highly efficient hydrogen evolution reaction activity in alkaline and acidic media.

Transition-metal Mo-based materials have been considered to be among the most effective hydrogen evolution reaction (HER) electrocatalysts. Regulating the electronic structure of Mo atoms with guest metal atoms is considered as one of the important strategies to improve their HER activity. However, introduction of guest metal elements in the vicinity of Mo sites with atomic-level hybridization is difficult to realize, resulting in the failure of the modified electronic structure of Mo sites. Herein, an Fe1.89Mo4.11O7/MoO2 material is prepared through the thermal treatment of a ferrimolybdate precursor. It exhibits a Tafel slope of 79 mV dec-1 and an exchange current density of 0.069 mA cm-2 in 1 M KOH medium, as well as a Tafel slope of 47 mV dec-1 and an exchange current density of 0.072 mA cm-2 in 0.5 M H2SO4 medium. Compared to original Mo-based oxides, Fe1.89Mo4.11O7 with the regulated Mo electronic structure shows a more suitable Mo-H bond strength for the fast kinetics of the HER process. Density functional theory (DFT) calculations also indicate that the Mo-H bond strength in Fe1.89Mo4.11O7 is similar to the Pt-H bond strength, resulting in the high kinetic activity of Mo-based HER electrocatalysts in alkaline and acidic media.

α-Diimine nickel complexes of ethylene and related alkenes.

A series of nickel mono(alkene) complexes, [LNi(alkene)], which consist of nickel(0) and neutral α-diimine ligand L (L = [(2,6-iPr2C6H3)NC(Me)]2), have been synthesized. The bonding and structures of the complexes were studied by X-ray diffraction, spectroscopic methods, and DFT computations.

[Detection and analysis of ABO Hemolytic disease in newborn].

This study was purposed to investigate the incidence and the model of ABO hemolytic disease in newborn (ABO-HDN) and the results of the three hemolysis test, so as to provide the evidences for clinical diagnosis and therapy. A total of 227 cases of maternal-fetal ABO incompatibility from January 2013 to October 2013 in the First Affiliated Hospital of Xiamen University were enrolled in the study. The ABO blood group of newborn and mother was detemined and three hemolysis tests (direct antiglobulin test, free antibody test, RBC antibody release test) were performed. The results indicated that in 227 cases of ABO incompatible pregnancies,186 cases were ABO-HDN (81.94%). There was no significant difference in the incidence between O-A and O-B incompatible pregnancies (P > 0.05). The positive ratio of direct antiglobulin test, free antibody test and RBC antibody release test were 59.14% (110/186), 84.78% (156/186) and 94.62% (176/186) respectively. It is concluded that the incidence of ABO-HDN is high. The main models of ABO-HDN were O-A and O-B. There was no significant difference in the incidence between O-A and O-B incompatible pregnancies. Three hemolysis tests are high sensitivity and are helpful in early diagnosis and early treatment of HDN.

[Rapid propagation system for tissure culture of Smilax glabra].

OBJECTIVE: Establishing the rapid propagation for plant tissue culture of Smilax glabra in order to rationally protect and utilize the resource. METHODS: The seed, shoot, leaf and rhizome of Similax glabra were cultured as explants. Different media and plant growth regulators at different concerntration were used. RESULTS: The best medium for bud induction was MS + 6-BA 2.0 mg/L + NAA 0.05 mg/L; The optimal medium for proliferation culture was MS +6-BA 2.0 mg/L + NAA 0.5 mg/L; The optimal medium for rooting was H + IBA 0.5 mg/L + NAA 0.5 mg/L; The optimal stroma for seedlings was 50% peat + 50% river sand. CONCLUSION: Different explants except leaf can be induced for tissue culture and rhizome has the optimal bud induction rate. An effective approach for rapid propagation has been provided,which can promote the artificial cultivation of Smilax glabra.

TiO2 nanotube arrays modified with Cr-doped SrTiO3 nanocubes for highly efficient hydrogen evolution under visible light.

In recent decades, solar-driven hydrogen production over semiconductors has attracted tremendous interest owing to the global energy and environmental crisis. Among various semiconductor materials, TiO2 exhibits outstanding photocatalytic properties and has been extensively applied in diverse photocatalytic and photoelectric systems. However, two major drawbacks limit practical applications, namely, high charge-recombination rate and poor visible-light utilization. In this work, heterostructured TiO2 nanotube arrays grafted with Cr-doped SrTiO3 nanocubes were fabricated by simply controlling the kinetics of hydrothermal reactions. It was found that coupling TiO2 nanotube arrays with regular SrTiO3 nanocubes can significantly improve the charge separation. Meanwhile, doping Cr cations into SrTiO3 nanocubes proved to be an effective and feasible approach to enhance remarkably the visible-light response, which was also confirmed by theoretical calculations. As a result, the rate of photoelectrochemical hydrogen evolution of these novel heteronanostructures is an order of magnitude larger than those of TiO2 nanotube arrays and other previously reported SrTiO3 /TiO2 nanocomposites under visible-light irradiation. Furthermore, the as-prepared Cr-doped SrTiO3 /TiO2 heterostructures exhibit excellent durability and stability, which are favorable for practical hydrogen production and photoelectric nanodevices.

Distinct stepwise reduction of a nickel-nickel-bonded compound containing an α-diimine ligand: from perpendicular to coaxial structures.

A nickel-nickel-bonded complex, [{Ni(µ-L(.-))}2] (1; L=[(2,6-iPr2C6H3)NC(Me)]2), was synthesized from reduction of the LNiBr2 precursor by sodium metal. Further controllable reduction of 1 with 1.0, 2.0 and 3.0 equiv of Na, respectively, afforded the singly, doubly, and triply reduced compounds [Na(DME)3]·[{Ni(µ-L(.-))}2] (2; DME=1,2-dimethoxyethane), [Na(Et2O)]Na[(L(.-))Ni-NiL(2-)] (3), and [Na(Et2O)]2Na[L(2-)Ni-NiL(2-)] (4). Here L represents the neutral ligand, L(.-) denotes its radical monoanion, and L(2-) is the dianion. All of the four compounds feature a short Ni-Ni bond from 2.2957(6) to 2.4649(8) Å. Interestingly, they display two different structures: the perpendicular (1 and 2) and the coaxial (3 and 4) structure, in which the metal-metal bond axis is perpendicular to or collinear with the axes of the α-diimine ligands, respectively. The electronic structures, Ni-Ni bonding nature, and energetic comparisons of the two structure types were investigated by DFT computations.

Reactivity of Dialumane and "Dialumene" Compounds toward Alkenes.

The reactions of dialumane [L(thf)Al-Al(thf)L] (1, L=[{(2,6-iPr2C6H3)NC(Me)}2](2-)) with stilbene and styrene afforded the oxidation/insertion products [L(thf)Al(CH(Ph)-CH(Ph))AlL] (2) and [L(thf)Al(CH(Ph)-CH2)Al(thf)L] (3), respectively. In the presence of Na metal, precursor 1 reacted with butadienes, possibly through the reduced "dialumene" or the "carbene-like" :AlL species, to yield aluminacyclopentenes [LAl(CH2C(Me)=C(Me)CH2)Na]n (4 a) and [Na(dme)3][LAl(CH2C(Me)=CHCH2)] (4 b, dme=dimethoxyethane) as [1+4] cycloaddition products, as well as the [2+4] cycloaddition product 1,6-dialumina-3,8-cyclodecadiene, [{Na(dme)}2][LAl(CH2C(Me)=C(Me)CH2)2AlL] (5). The possible mechanisms of the cycloaddition reactions were studied by using DFT computations.

Synthesis and reactivity of nickel hydride complexes of an α-diimine ligand.

Reaction of L(0)NiBr(2) with 2 equiv of NaH yielded the Ni(II) hydride complex [(L(•-))Ni(µ-H)(2)Ni(L(•-))] (1) (L = [(2,6-iPr(2)C(6)H(3))NC(Me)](2); L(0) represents the neutral ligand, L(•-) is its radical-anionic form, and L(2-) denotes the dianion) in good yield. Stepwise reduction of complex 1 led to a series of nickel hydrides. Reduction of 1 with 1 equiv of sodium metal afforded a singly reduced species [Na(DME)(3)][(L(•-))Ni(µ-H)(2)Ni(L(•-))] (2a) (DME = 1,2-dimethoxyethane), which contains a mixed-valent core [Ni(µ-H)(2)Ni](+). With 2 equiv of Na a doubly reduced species [Na(DME)](2)[L(2-)Ni(µ-H)(2)NiL(2-)] (3a) was obtained, in which each monoanion (L(•-)) in the precursor 1 has been reduced to L(2-). By using potassium as the reducing agent, two analogous species [K(DME)(4)][(L(•-))Ni(µ-H)(2)Ni(L(•-))] (2b) and [K(DME)](2)[L(2-)Ni(µ-H)(2)NiL(2-)] (3b) were obtained. Further treatment of 3b with 2 equiv of K led to a trinuclear complex [K(DME)(THF)](2)K(2)[L(2-)Ni(µ-H)(2)Ni(µ-H)(2)NiL(2-)] (4), which contains one Ni(II) and two Ni(I) centers with a triplet ground state. When 1 and 3a were warmed in toluene or benzene, respectively, three reverse-sandwich dinickel complexes, [(L(•-))Ni(µ-η(3):η(3)-C(7)H(8))Ni(L(•-))] (5) and [Na(DME)](2)[L(2-)Ni(µ-η(3):η(3)-C(6)H(5)R)NiL(2-)] (6: R = CH(3); 7: R = H), were isolated. Reaction of 1 with Me(3)SiN(3) gave the N(3)-bridged complex [(L(•-))Ni(µ-η(1)-N(3))(2)Ni(L(•-))] (8). The crystal structures of complexes 1-8 have been determined by X-ray diffraction, and their electronic structures have been fully studied by EPR/NMR spectroscopy.

Alkali metal and zinc complexes of a bridging 2,5-diamino-1,4-benzoquinonediimine ligand.

Two alkali metal complexes of a bridging 2,5-diamino-1,4-benzoquinonediimine ligand (dipp-dabqdiH(2)), [(thf)(2)Li(µ-dipp-dabqdi)Li(thf)(2)] (1) and [(dme)(1.5)Na(µ-dipp-dabqdi)Na(dme)(1.5)](n) (2, dme = 1,2-dimethoxyethane), have been synthesized by the reaction of dipp-dabqdiH(2) with Li(n)Bu or sodium metal. In addition, treatment of 1,2,4,5-tetrakis(2,6-diisopropylamino)benzene (dipp-tabH(4)) with potassium metal in dme afforded the complex [(dme)(2)K(µ-dipp-tabH(2))K(dme)(2)] (3). X-ray crystal diffraction analyses revealed that complexes 1 and 3 have dinuclear structures, while the sodium complex 2 aggregates to a one-dimensional polymer through bridging dme ligands. With increasing ion radius, the coordination number of the alkali metal (Li, Na, and K) increases from four to five to six, while the coordination geometry changes from distorted tetrahedral to square pyramidal and further to octahedral in 1, 2, and 3, respectively. The salt metathesis reactions of 1 and 2 with anhydrous ZnCl(2) yielded the ion-contacted zinc complexes [(thf)(3)Li(µ-Cl)ClZn(µ-dipp-dabqdi)ZnCl(µ-Cl)Li(thf)(3)] (4), [(dme)(2)Li(µ-Cl)ClZn(µ-dippdabqdi)ZnCl(µ-Cl)Li(dme)(2)] (5), and [(dme)(2)Na(µ-Cl)(2)Zn(µ-dipp-dabqdi)Zn(µ-Cl)(2)Na(dme)(2)] (6), respectively. The ligand exists as the dianionic form in compounds 1-6 upon double deprotonation, and a complete electronic delocalization (except for 3) of the quinonoid π-system is observed between the metal centers over the two N═C-C═C-N halves of the ligand. The electronic structures of the complexes were studied by density functional theory (DFT) computations.

[Evaluation on germplasm resources of main production area of Artemisia annua in China].

OBJECTIVE: To evaluate and select excellent germplasm resources of Artemisia annua L., providing basic data for data base and breeding of A. annua. METHOD: Seventy-two germplasms of A. annua, which were collected from main production areas, were planted in germplasm resources garden in Jingxi and Nanning under the same conditions. The samples were gathered in the squaring stage. Artemisinin was extracted by supersonic wave and determined by ultraviolet spectrophotometry. RESULT: The leaf's yield and the content of artemisinin in the samples of different germplasms were varied significantly. Effect of environment on artemisinin content was more than that of hereditary factors. The content of artemisinin was different when the same material of A. annua grew in different place. The content of artemisinin in next year's plant was decreasing. CONCLUSIONS: Seven germplasms from south of China have been selected, their content of artemisinin was above 0.9% and calculated yield was more than 2250 kg x hm(-2). The content of artemisinin has been affected by hereditary factors and variation of the growth environment.